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1 EVALUATING ORNAMENTAL SPECIALTY CUT PRODUCTION USING A SUSTAINABLE AGROFORESTRY APPROACH By EDWARD HENTZ FLETCHER III A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULLFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2009
2 2009 Edward Hentz Fletcher III
3 To my Mother, Sandra Fletcher Whetstone
4 ACKNOWLEDGEMENTS I thank my mother, Sandra Fletcher Whetst one, and my sister, Libby Fletcher Duffy, for their support during the writing of this thesis. Also, I thank my advisors, Mack Thetford and Jyotsna Sharma, for their guidance and patience. I am grateful to William Graves for his advice concerning Hoaglands solution recipes, and I must also mention Barry Ballard who assisted me with data collection and weed control. I would like to ex tend my thanks to my friend John Charles Harnett for allowing me to stay with him during my long trips between Gainesville and my various research sites. Lastly, I thank my late stepfather, Woodrow Whetstone, for allowing me the use of his lake house as I completed da ta collection at the North Florida Research and Education Center in Quincy, Florida.
5 TABLE OF CONTENTS Page ACKNOWLEDGEMENTS....4 LIST OF TABLES......6 LIST OF FIGURES....7 ABSTRACT.......8 CHAPTER 1 INTRODUCTION....10 2 EFFECT OF ROOT COMPETITION A ND SHADE ON SURVIVAL AND GROWTH OF NINE WOODY PL ANT TAXA WITHIN A PECAN ( Carya illinoinensis K. Koch) ALLEY CROPPING SYSTEM.....15 Introduction. Materials and Methods........16 Results and Discussion.... Conclusions.....28 3 NITROGEN AND IRRADI ANCE AFFECT PHOTOSYNTHESIS AND PLANT GROWTH OF TWO NATIVE FLORIDA SHRUBS..... Introduction........37 Materials and Methods...........38 Results and Discussion.......42 Callicarpa americana............. Morella pumila .......45 Conclusions........47 4 CONCLUSION......57 LIST OF REFERENCES....... BIOGRAPHICAL SKETCH ........
6 LIST OF TABLES Table page 2-1 Initial survival (%), height (c m), width (cm), and growth index of Callicarpa americana L. grown in sun or shade with and without root competition ..........................29 2-2 Initial survival (%), height (c m), width (cm), and growth index of Callicarpa americana F.J. Muell. var. Lactea grown in sun or shade with and without root competition ................................................................................................................... .....30 2-3 Initial survival (%), height (c m), width (cm), and growth index of Crataegus marshalii Eggl. grown in sun or shade with and without root competition .......................31 2-4 Initia l survival (%), Hydrangea paniculata Siebold Tardiva grown in sun or shade with and without root competition.. ...................................................................................32 2-5 Initial survival (%), height (c m), width (cm), and growth index of Hydrangea quercifolia Bart. grown in sun or shade w ith and without root competition .....................33 2-6 Initial survival (%), height (c m), width (cm), and growth index of Ilex glabra L. grown in sun or shade with and without root competition.. ...............................................34 2-7 Initial survival (%), height (c m), width (cm), and growth index of Salix matsudana Koidz. f. tortuosa grown in sun or shade with and without root competition ...................35 3-1 Main effect of nitrogen was observed on means for selected growth parameters and concentration of selected nutrients in Callicarpa americana L .....................................48 3-2 Interactive effect of time and irradiance on mean photosynthesis (mol m-2 s-1) for Callicarpa americana L.. ...................................................................................................49 3-3 Main effect of nitrogen was observed on means for selected growth parameters and concentration of nitrogen and phosphorus in Morella pumila Mich.. ...............................50
7 LIST OF FIGURES Figure page 2-1 Rainfall for 2005 and 2006 (inches) for Jay, FL, USA with five-year average included. .................................................................................................................... ........36 3-1 Effect of nitrogen and time on mean photosynthesis (Ps) (mol m-2 s-1) for Callicarpa americana. ......................................................................................................51 3-2 Interaction of nitrogen and time was observed on mean plant height (cm) for Callicarpa americana. ......................................................................................................52 3-3 Effect of time and nitrogen on mean stomatal conductance (molH20 m-2s-1) for Callicarpa americana. ......................................................................................................53 3-4 Mean stomatal conductance (molH20 m-2s-1) for C. americana was affected by an interaction of time and irradiance. .....................................................................................54 3-5 Effect of nitrogen and time on mean plant height (cm) for Callicarpa americana ...........55 3-6 Interactive effect of nitrogen and irradiance on mean plant height (cm) for Morella pumila ..............................................................................................................................56
8 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science EVALUATING ORNAMENTAL SPECIALTY CUT PRODUCTION USING A SUSTAINABLE AGROFORESTRY APPROACH By Edward Hentz Fletcher III May 2009 Chair: Mack Thetford Major: Interdisciplinary Ecology Two experiments were conducted in order to examine the performance of shrubs with potential for use as woody cuts. In the fi rst study, shrubs were established in a Carya illinoinensis (pecan) grove to quantify the effects of i rradiance and root competition on survival and initial growth. Treatments included partial shade without r oot competition (using trenched plots with root barriers), partia l shade with root competition (without barriers), and full sun (no tree/root competition). Species with greater th an 50% survival at the end of year 2 were considered to have potential for inclusion in an agroforestry system for the production of woody cuts. Of the nine shrub species, only Callicarpa americana L., Callicarpa americana F.J. Muell var. lactea Crataegus marshalii Eggl., and Salix matsudana Koidz. F. tortuosa Rehd. maintained high rates of survival throughout both years of the study. Callicarpa americana and Crataegus marshalii performed equally well irrespective of irradiance or root competition. S. matsudana had the highest rates of survival in fu ll sun. The remaining five shrub species suffered high mortality from drought stress in spite of supplemental watering thereby preventing evaluation of the effects of exposure and root competition in the pecan alleycropping system.
9 Additionally, greenhouse experiments were conducted to evalua te the effects of irradiance and nitrogen and photosynthes is and growth of two plant taxa ( Callicarpa americana L. and Morella pumila Mich. Suwannee elf). Plants were grown in a simple hydroponic system by using a modified Hoaglands solution amended with 0, 70, and 210 mgL-1 nitrogen (NH4NO3). Irradiance treatments included full irra diance within the greenhouse and 50% of full irradiance. For both species, mean photosynthesi s was greater for plants under 100% irradiance and for plants given 70 mgL-1 nitrogen. Nitrogen had a greater e ffect than irradiance on growth of C. americana. Application of 210 mgL-1 nitrogen did not increas e plant growth and photosynthesis proportionally compar ed to application of 70 mgL-1 nitrogen for either species, indicating the higher application rate is unn ecessary and may inhibit plant growth.
10 CHAPTER 1 INTRODUCTION Smallholder farmers have long been an important part of Floridas historical and cultural landscape. Over the last half-century, these fa rmers have faced serious competition from large industrial farming operations. Large operations have greater access to both farming subsidies and other forms of capital and can afford to purchase expensive equipment, chemicals, and genetically modified crops that make modern ro w crop agriculture practi cable. Additionally, the environmental problems that are caused by th e pollution of groundwater and surface water by excess nutrients from agricultural operations (alo ng with residential lawns, dairy farms and golf courses) constitute one of the greatest threats to environmental quality in the state (Nair and Graetz 2004). In order to main tain profitability in a changing economy, smallholder farmers need to find ways to reduce their dependence on conventional row crop agri culture, while at the same time finding ways to mitigate the environm ental pollution generated by their operations. Agroforestry is defined as the deliberate grow ing of a tree crop and an agricultural or horticultural crop on the same plot of land (Power s and McSorley 2000). Agroforestry systems, which combine an economically valuable tree or sh rub crop with an agricultural or horticultural crop on the same plot of land, coul d be a viable altern ative for some smallholder farmers (Ellis 2001). The market for specialty forest products th at are useful for the florist trade is expanding, and there is a demand for new varieties of plants with interesting foliage, fruits, and flowers for use in arrangements (Bachmann 2002). Many of Fl oridas native shrubs ha ve these qualities, and a sustainable agroforestry system combini ng certain of these species in an alley cropping arrangement with valuable tree species like Pinus palustris or Carya illinoinensis could provide a farmer with a sustainable, low maintenance crop year after year. Also, a farmer could establish these shrubs in a marginal area unsuitable for crop production, or as part of a riparian buffer.
11 Of critical concern when considering the use of an agroforestry system are the interactions between the tree crop and the agricultural or horticultu ral crop for resources such as water, light and nitrogen (Rao et al. 1998). These interactions ha ve been characterized in many tropical agroforestry systems, but research in temperate agroforestry systems has begun in earnest only in the past two decades. Even so, the vast majority of research in temperate agroforestry systems up to this point in time has focused on characterizing the interactions between trees and agricultural crops (Jose et al. 2000a, 2000b, 2004; Gillespie et al. 2000). Systems combining a tree crop with a horticultural crop are not common, but citrus growers in Florida have had success with intercropping of or namental plants within young citrus orchards (Workman and Allen 2003, Bachmann 2002). Biophysical interactions between tree crops and agricultural crops in agroforestry systems are characterized in several ways. First, there is the traditional system of classifying interactions between living things using such terms as commensalism, mutualism, amensalism, and parasitism/predation (Begon, Townsend, and Harper 2006). Within agroforestry systems, the interspecific interactions can be classified as complimentary (positive) or as competitive (negative) (Jose et al. 2004). Competitive interactions betw een tree and crop are complex, and recent research suggests that the resourceratio hypothesis (Tilman 1985, 1990) is most appropriate when characterizing inte ractions in agroforestry system s. This hypothesis states that species that have different resource requireme nts can co-exist because competitive exclusion does not occur (Tilman 1985). Furthermore, when the right combin ation of tree crop and agricultural crop is determined, more biomass can be accumulated when the two are grown together (Jose et al. 2004).
12 Studies that focused on characterizing competition for light within temperate agroforestry systems have found that despite the evidence th at for C4 species like maize net photosynthetic rates decrease as photosynthetically active radiation (PAR) decreases, there is littl e evidence that crop yields decrease in temper ate alley cropping systems (Jose et al. 2004). This was supported by a study where maize was grown in an alley cropping system with both Juglans nigra L. and Quercus rubra L. (Gillespie et al. 2000). The study confirmed that other interactions, mainly below ground interactions like competition for wa ter and nitrogen were more important than above ground interactions for light as a determining factor in cr op yields. However, while total crop yields were not reduced de spite lower levels of photosynthe tically active ra diation (PAR), there was some spatial variation in yield for crop rows closest to the tree rows (Jose et al. 2004). This was also seen in an alley cropping system in India where below ground interactions were observed to have a greater impact on yields th an light competition (Rao et al. 1998). Competition for light may even represent a positive interactio n for some tree/crop combinations (Jose et al. 2004). This finding is important when considering wh ich plants are suitable for inclusion in an alley cropping system for horticultural production. Since many shrubs used in landscaping and for cut foliage production are forest understory sp ecies within their native ranges, it seems likely that shade could provide a benef it and might increase yields when they are grown in an alley cropping system. Aside from the impact shade has on rates of photosynthesis, temperature is also moderated under shade (Jose et al. 2004). Many understory plants expe rience heat stress under full sun conditions, which can inhibit photosynthes is (Taiz & Zeiger 2002; Jose et al. 2004). In tropical climates, many of the tree species used in agroforestry systems are nitrogenfixing legumes but in temperate zones, trees ar e most often selected based on their economic value as timber or fruit/nut producers (Jose et al 2004). In temperate ag roforestry systems the
13 tree crop and agricultural crop therefore must comp ete for limited nitrogen resources. In an experiment conducted by Jose et al. (2000), th e competition for nitrogen between the tree crop and agricultural crop in an alley cropping sy stem in the Midwestern United States was characterized. This experiment was similar in structure to other experiments by the same authors, which characterized the competition for wa ter within a similar agroforestry system (Jose et al. 2000). Treatments were se t up with and without root barrier s and others were trenched to prune tree roots. Nitrogen fer tilizer was applied and the root tissues of both tree and crop were analyzed to determine the percen tage of nitrogen derived from fertilizer (Jose et al. 2000). Along with percentage of nitrogen derived from fertilizer, the fertilizer use efficiency was determined (Jose et al. 2000). The results of the study revealed that the competition between Juglans nigra and Zea maiz for nitrogen supplied by fertilizer is not signi ficant because the two species do not take up nutrients at the same time during the growing se ason. However, the competition for mineralized soil nitrogen was significant in treatments without root barriers or trenches in place (Jose et al. 2000). In the treatments without root barriers or trenches, competition for soil moisture was also significant (Jose et al. 2000), so it is reasonable to expect the rates of nitrogen uptake by crops to be reduced along with reduced water uptake becau se nutrients such as nitrogen are taken up along with soil moisture by the plants root system (Jose et al. 2000). Agroforestry systems can also be useful in reducing the amount of excess nutrient input into surface and groundwater due to improved nutrient cycling. Ce rtain tree/crop combinations are more efficient than others, as demonstr ated by findings suggesti ng that systems using Populus deltoides Bartram ex. Marsh were highl y efficient in cycling nitrogen within the system, requiring less nitrogen input though fertili zer (Das and Chaturvedi 2005). While P. deltoides
14 does not fix nitrogen in its r oots, the leaf litter has a higher proportion of available nitrogen, which is cycled back into the soil during d ecomposition (Das and Chat urvedi 2005). Nair and Graetz (2004) investigated the role agroforestry systems can play in reducing the input of phosphorus and nitrogen into water supplies. While the root systems of both tree and agricultural crop can occupy the same soil strata at shallow dept hs, the trees root system extends much deeper into the soil profile. This allo ws the tree crop to inte rcept more nitrogen and phosphorus as it leaches out of the surface laye rs of the soil (Nair and Graetz 2004). In an experiment conducted in a pecan ( Carya illinoinensis )cotton ( Gossypium hirsutum ) alley cropping system in Jay, Florida where both organic and inorganic n itrogen fertilizers were applied to both trenched (to remove root inter action between tree and crop ) and untrenched plots, more nitrate was taken up in the untrenched plots where the root systems of tree and crop interacted freely (Nair and Graetz 2004). All of the work cited above was in agroforest ry systems combining trees with agricultural crops, but it provides a good guide for systems th at combine trees with horticultural crops. Horticultural crops, specif ically those species with potential for use as specialty woody cuts can be incorporated into agroforestry systems such as alleycropping arrangemen ts, riparian buffers or wind/snow breaks such that they not only provide a source of profit to the grower, but an ecological benefit by increasing biological diversity at both the ecosystem and landscape scale (Josiah, St-Pierre, and Brott 2004).
15 CHAPTER 2 EFFECT OF ROOT COMPETITION AND SHADE ON SURVIVAL AND GROWTH OF NINE WOODY PLANT TAXA WITHIN A PECAN ( CARYA ILLINOINENSIS K. KOCH.) ALLEY CROPPING SYSTEM Introduction The market for specialty forest products that are useful for the florist trade is expanding, and there is a demand for attractiv e plant cultivars that have attractive flowers, foliage, berries and seedpods for use in arrangements (Bach mann 2002). Farmers who wish to increase production on marginal lands or within tree plan tations could benefit fr om including woody cuts production in a sustainable agroforestry system. Studies carried out in Nebraska, USA and Saskatchewan, Canada have shown that temperate agroforestry systems that include w oody ornamentals can be a profitable alternative for small farmers, producing up to $15 of inco me per meter (Josiah, St-Pierre, and Brott 2004; Josiah, Brott, and Brandle 2004). In order to recommend plant species for inclusion in an agroforestry system for the production of sp ecialty woody ornamentals, evaluation of plant growth and survival of various species under fiel d conditions is needed. An ideal plant choice for producing woody cuts in an environmentally benign alleycropping system would be a species that produces attractive stems and that is able to survive and grow with minimal input of fertilizer and water. In agroforestry systems, yields are sometimes reduced due to the below ground interactions of the tree crop and agricultural crop as they comp ete for water and nitrogen (Jose et al. 2000). Light is the most limiti ng factor of plant growth only if there is sufficient water and nitrogen available to the cr op (Montieth et al. 1991; Zamo ra et al. 2008). Below ground interactions, particularly the competition for wa ter resources and nutrien ts are more likely to occur when the root systems of the plant species in question grow into th e same area of the soil
16 profile (Gillespie et al. 2004). Large trees often have the majority of their root systems in the top 30 cm of soil, the same depth as the root system s of most agricultural cr ops and shrubs (Brady & Weil 2002). The tree canopy will expand over time, and tree roots will extend in to the root zone of the horticultural crop, so any tree/crop comb ination must be supported by proper management techniques including pruning of tree roots (Thevathasan and Gordon 2004). In this study, nine shrub species were established in a Carya illinoinensis K. Koch (pecan) grove in northwest Florida. The objectives of this experiment were to determine which shrub species would survive, grow, and produce high quality st ems under the conditions present at the study site. Treatments included a full sun treatment (uninterrupted daily irradiance without tree competition) and two partial shade treatments (with and without root competition from the tree crop). At the study site irradiance was never reduced to less than 50% of the full sun treatment by the tree canopy, and the topsoil was enriched with nutrients due to de position of leaf litter from the pecan trees over many years (Allen et al. 2004). As a result, competition for water was expected to be the most limiting factor in determining plant survival and growth. A previous study carried out in the same location as this st udy found that growth of Gossypium hirsutum L. (cotton) was greatest when competition from tree roots was inhibited by a root barrier (Wanvesraut et al. 2004). We hypothesized that plants grown in the partial shade without root competition treatment (which included a root barrier) would have the highest rate of survival and would grow larger than plants grown with root competition or in full sun. Materials and Methods Shrubs were established in a 54-year-old Carya illinoinensis (pecan) alley cropping system at the University of Florid a Jay Research Farm in Jay, Florida (30 46 20N; 8709 00W). Soils at the study site are classified as Red Bay sa ndy loam (Wanvestraut et al.
17 2004). Rainfall data were recorded at the Jay Research Farm (weather station on site)(Figure 21). The shrub species chosen for evaluation were Callicarpa americana L. (American beautyberry), Callicarpa americana L. var. lactea F.J. Muell. (white beautyberry), Crataegus marshallii Eggl. (parsley haw), Ilex glabra L. (inkberry), Ilex myrtifolia Walt. (myrtle-leaf holly), Hydrangea paniculata Seibold var. Tardiva (panicle hydrangea), Hydrangea quercifolia Bart. (oakleaf hydrangea), Lyonia lucida (Lam.) K. Koch (fetterbush), and Salix matsudana Koidz. f. tortuosa Rehd. (corkscrew willow). Callicarpa americana L. (American beautyberry) is a deciduous, multi-stemmed shrub with a range extending from Texas to Florida and as far North as Maryland (Austin 2005). It is deciduous throughout most of its ra nge although some plants keep their leaves all year in the southernmost populations. It prefers full sun to pa rtial shade and moist soils in a wide variety of habitats. This shrub is fast gr owing and is often an early colo nizer of disturbed sites (Austin 2005). It can grow up to 2m in height and up to 2m in width (Nelson 2003). Callicarpa americana is commonly used in landscapes and gard ens for its attractive foliage and bright purple fruits that are borne in clusters along the stems at the leaf axils. Leaves are opposite and slightly pubescent, and are aromatic when crushe d (Nelson 2003). The fruits tend to persist on the stems into the winter months, and this give s this species good poten tial for use as a woody cut. Foliage is not persistent on cut stems and should be removed at harvest prior to shipping. Fruiting stems may be harvested wh en fruits at mid-stem are fully colored (Bachmann 2002). If the stems are harvested at this point, the risk of discoloration of the fruits from frost damage can be avoided (Bir and Connor 1997).
18 Callicarpa americana L. var. lactea F.J. Muell (white beautyberry ) is a naturally occurring variety of Callicarpa americana which bears white fruits. It is uncommon in the wild but is produced commercially by the nursery indust ry and is most often en countered as a garden specimen. Flowering and fruiting are typical of the species with fruits in late summer and early autumn. Fruits persist on the stems well into wi nter and often develop brown blemishes as time passes which can reduce their visual appeal, so it may be appropriate to harvest the stems earlier in the season than for C. americana (Nelson 2003). Crataegus marshallii Eggl. (Parsley Haw) is a shrub or sm all tree that is found across the southeastern United States as far west as Texas a nd as far north as Virgin ia. In Florida, it is found primarily in the Panhandle region but is k nown to grow as far south as Marion County (Austin 2005). It typically gr ows in wetland or floodplain habita ts but is equally adapted to upland areas (Nelson 2003). Un like many species in the genus, C. marshallii is easily distinguished by its deeply lobed and toothed leaves, which resemble the leaves of parsley, hence the common name of the species. It has straight thorny stems, attractiv e foliage, white or pink flowers borne in spring, and bright red fruit borne on the stems in the late summer. The stems could be harvested in spring to take advantage of the flowers or in late summer or early autumn to take advantage of the fruits. Hydrangea paniculata Siebold var. Tardiva (panicle hydrangea) is native to temperate areas of East Asia, but has been intr oduced to the United States as an ornamental shrub. It can grow as tall as 3 meters from a single main stem and has a treelike growth habit. Clusters of white flowers are borne at the end of long, straight branches in late summer and persist on the branches into early autumn. Stems may be harvested for the fresh flower market in August or September or may be harvested as a dried product in late September or October. After
19 harvesting the stems in autumn, cutting back the plant allows for re-growth of long, straight stems for the following season (Leeson et al. 2004). Hydrangea quercifolia Bart. (Oakleaf hydrangea) is a st oloniferous, deciduous, multistemmed shrub native to the south eastern United States, from Louisiana to Florida and as far north as Tennessee and North Carolina (Austin 2005). This species is most commonly found on slopes and in ravines and is tole rant of shady conditions (Nels on 2003). Plants typically have multiple stems with shaggy bark and large leaves with multiple lobes (Nelson 2003). H. quercifolia has become a popular native plant in lands capes in North Florida for use in both sunny and shaded areas due to its attractive foliage autumn color and clusters of white flowers born on terminal panicles. Like H. paniculata this species could pr ovide stems for both the fresh and dried stem markets. However, this species generally blooms somewhat earlier than H. paniculata so harvesting could begin in late summer (Nelson 2003). Ilex glabra L. (Inkberry) is a common evergreen shrub native to the Atlantic and Gulf Coastal Plain from Texas to Maine. It can gr ow up to 3 meters tall and has multiple upright stems that bear small black fruits (Austin 2005). This species bears small white flowers in spring and the black fruits are a ttractive and persist on stems into winter (Halls 1977). This species has potential for season-long harvesting of stems. The leafy stems may be used as filler in arrangements while spring flowers and fall fruits may provide additional uses for the stems. This species is stoloniferous and col onial, forms large thickets and sp reads vegetatively (Thetford et al. 2006). New stems are also produced in re sponse to burning or pruning (Tobe 1998). I. glabra is often used in landscapes as a hedge and there are several cultivars available commercially. Most commonly fou nd in moist flatwoods habitats, I. glabra is tolerant of both full sun and partial shade but is not particularly tolerant of dry condi tions (Nelson 2003).
20 Ilex myrtifolia Walt. (Myrtle-leaf holly) is native to th e Atlantic and Gulf Coastal Plain from Texas to North Carolina and is found almost exclusively in wet habitats such as cypress domes (Tobe 1998) but is tolerant of seasonally dry conditions (Nel son 2003). This species is a shrub or small tree and can grow up to approximately 8 meters tall with small leaves and bright red or yellow fruits which ripen from December to January (Nelson 2003). Fruits persist on the stems for a month or more after ripening, so the be st time to harvest stems for use as a woody is in late September or early October. Non-fruiting stems could be harvested but this may diminish future availability of fruiting stems. Lyonia lucida (Lam.) K. Koch (fetterbush) is a common u nderstory shrub in flatwoods and wetlands throughout the coastal pl ain of the Southeastern United States. It can grow up to 2 to 3 meters tall and forms large colonies by means of underground runners (Osorio 2001). Pink to white blooms appear in late winter and early spring and are borne in showy clusters along the branches (Nelson 2003). These blooms can persis t on the stems for up to a month. In addition to flowers, the stems have a characteristic angular pattern of growth providing additional visual interest. Stems may be harvested in early spring when in flower or throughout the remainder of the year if harvested for the foliage. Salix matsudana Koidz. f. tortuosa Rehd. (Corkscrew willow) is a shrub or small tree up to 9 meters tall native to East Asia introduced to North America as a landscaping plant for its attractive foliage and yellow fall color (Gillm an and Watson 1994). Branches grow in a spiraling, twisting shape, giving th is species visual appeal in winter. Stems are also used by florists as woody cuts (Kuz ovkina and Quigley 2005). Salix matsudana f. tortuosa is particularly suited for this purpose because it has been shown to be capable of ample stem production after repeated coppi cing (Douglas et al. 1996, Kuzovkina and Quigley 2005).
21 Callicarpa americana and Ilex myrtifolia were grown in a 100% composted pinebark (0.5 inch screened) nursery production mix at the We st Florida Research and Education center production area from cuttings collected from priv ate land in Santa Rosa County, Florida. One year old Ilex glabra and Hydrangea quercifolia (3.9L containers), and 2 year old Crataegus marshallii (19L containers) were purchased from Superi or Trees, Inc. (P. O. Box 9325 Lee, FL). Plants of all species aside from Crataegus marshallii and Lyonia lucida were planted on December 22, 2004. Crataegus marshallii were planted June 5, 2005, and Lyonia lucida were planted March 1, 2006. Plants were fertilized with controlled-release fertilizer (18N-2.6P-9.9K Osmocote 18-612, 8-9 months; The Scotts Co., Marysville, Ohio) at the time of establishment. The study site had no permanent irrigation system, but plants were supplied with supplemental irrigation via tanker truck (4L per plant per week) during the summ er months of 2005 and 2006. The experimental design was a randomized comp lete block with three blocks and three treatments. Treatments were full sun (uninterrupt ed daily irradiance without root competition), partial shade with root competition and partial sh ade without root competition. Root competition from the tree crop was eliminated by trenching th e margins of the plots to a depth of 1.2 meters and inserting black plastic to form a barrier to su bsequent root growth (Gillespie et al. 2004). All plants were spaced 3 meters apart within and be tween rows. The shaded treatments consisted of plots situated beneath the canopy of the pecan grove that provided approximately a 50% reduction in irradiance at 12 o clock noon local time. The shad e provided was irregular as a result of hurricane Ivan having damaged the tree s within the grove. Mowing and application of herbicides Glyphosate (N-(phosphonomethyl) glycin e) (Monsanto Corp., Saint Lois, MO, USA)
22 and Oryzalin (3,5-dinitro-N4, N4-dipropylsulfan ilamide) (DowElanco, Indianapolis IN, USA ) was used to manage weeds. Plant survival and shoo t growth were recorded once per month in May, June, and July of 2005 and 2006 by measuring plant height (cm), a nd two perpendicular widths (cm). These widths were averaged to provide one value for mean width for each plant. In order to provide a measure of plant growth, a gr owth index was calculated for each plant using the following formula: [(Height x mean widt h)/2] (Norcini and Knox 1989). The data collected during the study were an alyzed using SAS Mixed Procedure (SAS Institute Inc., Cary, NC, USA). Differences am ong treatments were determined using the LS Means procedure (alpha=0.01). Results and Discussion The study site experienced drought conditions during 2006 (Figure 2-1). In December of 2004, when the plants were transp lanted into the alley cropping sy stem, there was a total of 132 mm of rainfall, which is very close to the aver age rainfall (127mm) in December for the years 2002-2006. Total rainfall for 2005 (1.97m) was above the average for 2002-2006 (1.5m) due to tropical storm Arlene (June 11) and Hurricane Dennis (July 10), but during 2006 the total rainfall for the year was down 44% from 2005 and was 26% below the 2002-2006 average. The performances of the plant species used in the study are detailed below. Plant survival (%) and consistent growth were the primary criteria by wh ich a species was judged to be suitable for inclusion in either a full sun woody cu ts production system or an agroforestry system for production of woody cuts. Callicarpa americana had 100% survival in all treatm ents at the end of summer 2006, the highest rate of survival in all treatments for any species in this study (Table 2-1). Mean plant heights decreased over the course of the study an d were similar for all treatments while mean
23 width increased over time as a result of stems becoming more plagiotropic. There was a significant interaction between treatment and m onth (p<0.0001). Plants in the partial shade treatments showed a 32% increase in width fr om May 2005 to July 2006, while mean width for plants in full sun increased by 23% over the sa me time period. Growth indices were similar among all treatments (Table 2-1). Callicarpa americana produced stems, survived equally well in sun or shade and grew well even in drought conditions. Although not sufficient to warrant harvest or measurement, this species did produce a minor crop of fruit in year two indicating a minimum of two years to establish sufficient vi gor for fruit production in both the open field and alley cropping production systems. With the high ra te of survival and consistent growth in full sun and shade both with and without competition and early fruiting, Callicarpa americana should be considered as a component of both a full sun and an agroforestry system for the production of woody cuts. Callicarpa americana var. lactea had high rates of survival for all treatments, losing only one plant in partial shade without root compe tition and two in full sun by the end of the second growing season (Table 2-2). Mean plant height decreased over the cour se of the study, while mean width increased over time as a result of stems becoming more plagiotropic. From May 2005 to July 2006, mean width increased by 39% in partial shade without root competition and by 37% in partial shade with root competition as compared to a 27% increase in mean width in full sun over the same time period. There was a significant difference in growth index among treatments (p<0.0001). Plants in partial shade without root co mpetition showed a 30% increase in growth index from May 2005 to July 2006, compared to an 18% increase in growth index in partial shade with root competition and an 8% increase in growth indices for plants in full sun. These results show that while Callicarpa americana var. lactea has high rates of survival in both
24 shade and sun, plants grew larger and showed an greater percent increase in size in partial shade and therefore could be considered as a component of an agrofo restry system for the production of woody cuts. Crataegus marshallii had high rates of survival ( 92%-100%) under all treatments, losing only two plants, one plant in partial shad e without root competition and one plant in the full sun treatment (Table 2-3). There was a si gnificant difference in mean plant height among the treatments over the course of the study (p<0.0013). Plants in partial shade showed a slight decrease in plant height (5% for pl ants in partial shade without root competition; 2% for plants in partial shade with root competition) from May 2005 to July 2006, while plants in full sun showed a 1% increase in mean he ight over the same time period. While these differences were statistically significant, they were not large enough to be considered biologically significant. No significant differences were found among treatment s for mean width and growth index. These results demonstrate that C. marshallii can survive equally well in s un or shade, and that despite the lack of growth in partial shade this species may be considered as a component of an agroforestry system for the production of woody cuts No plants of this species flowered during the course of the study. Survival of Hydrangea paniculata decreased dramatically for all treatments after June 2005 with only 50% of plants surviving in the partial shade without root competition treatment, 25% of plants surviving in the pa rtial shade with root competition treatment, and 42% of plants surviving in the full sun treatment by July 2005 (T able 2-4). Drought stress and deer browse were the primary causes of mortality (Personal observation). Although H. paniculata shows moderate drought resistance (Gillman and Wa tson 1993), plants in this study frequently displayed symptoms of drought stress. Deer browse was contributed significantly to plant death in all three treatments for Hydrangea paniculata during 2005. Damage from deer browse killed
25 41% of the Hydrangea paniculata plants in the full sun treatment and partial shade without root competition treatments, respectively, compared to 16% mortality in the partial shade with root competition treatment. Overall, out of the 36 Hydrangea paniculata plants included in this study, 12 individuals (33%) were killed by deer browse. A study from Japan showed that H. paniculata was preferentially browsed by Sika deer in its native range (Takatsuki 1986), so it is unsur prising that it would be palatable to deer in Florida especially during a time of below normal rainfall. The low survival and vulnerability to deer limit the potential for this species to be included in woody cuts production systems in Florida without supplemental irriga tion and some measures to exclude deer from the plots. Plant survival for Hydrangea quercifolia decreased between 2005 and 2006 (Table 2-5). By July 2005, survival was 83% or less and in 2006 survival dropped below 50%. Plant height, width and growth index showed no significant di fference in plant size among sun and shade or competition treatments (Table 2-5). As with H. paniculata low survival and vulnerability to deer browse limit the potential for H. quercifolia to be included in woody cuts production systems in Florida without supplemental irrigation and some measures to exclude deer. Deer browse contributed significantly to Hydrangea quercifolia mortality 16% mortality in both the in the full sun and partial shade with root compet ition treatments, compared with 8% mortality in the partial shade without root competit ion treatment. Overall, 14% of the Hydrangea quercifolia plants in this study were killed by damage caused by deer browse. Survival of Ilex glabra ranged from 75% to 83% by July 2005 (Table 2-6) and decreased to 20% in April 2006 (data not shown). Mean pl ant height, mean width, and growth index did not differ among treatments by July 2005 (Table 2-6). After May of 2006, survival of Ilex glabra dropped below 50% in all treatments. Drought stress during the second year of the study
26 was likely the cause of mo rtality. In a study where I. glabra plants grown in differently sized containers were planted in a coastal dune envi ronment (sandy, dry and saline soil conditions), those plants grown in standard one -gallon pots had similarly low rates of survival (50% and less) over a similar time span (Thetford et al. 2005) More study is needed to determine if I. glabra plants grown in deeper pots or the use of a temporary irrigation system to assist with establishment would contribute to higher rates of survival before this species could be recommended for inclusion in an agroforest ry system for the production of woody cuts. Rates of survival for Ilex myrtifolia were high in July 2005, with 100% survival for plants in partial shade without r oot competition. Only two plants were lost in 2005, one in partial shade with root competition and one in full sun. Rates of survival dropped drastically during the summer of 2006, with only four plants of this species alive by July 2006, two in partial shade with root competition and two in the full sun. This species shows a great deal of drought tolerance in its native ha bitat and in landscape plantings (Nels on 2003). The plants used in this study were 3 years old at the time of transplanting. Larger transp lanted plants generally require longer establishment times compared to smaller plants because of the longer time required for root growth to reach a level similar to non-tran splanted plants of the same size (Watson 2005). The water stress experienced by the plants du ring their establishment was compounded by drought conditions during 2006, resulting in the precipitous drop in survival during that year. As with I. glabra, the use of a temporary irrigation system to assist with establishment of I. myrtifolia may contribute to higher rates of survival. Lyonia lucida had very low survival (25% and less) for all treatments. Plants received supplemental water at the time of transplanting a nd periodically thereafte r (one gallon per week per plant). This species was transplanted dur ing March of 2006 during a period of particularly
27 low rainfall (about 50% below the 2002-2006 average). Also, the root system of this species is very fibrous and extends into the native soil very slowly which along with drought stress may have contributed to the high rates of mo rtality experienced in this trial. For Salix matsudana a treatment by year interaction (p= 0.0004) was present indicating the effects of treatment on survival differed between 2005 and 2006. Initially exposure and competition had no impact on survival, which was high with only a single plant lost during 2005. However, continued mortality was evident each mont h in 2006, with the greatest losses in shaded treatments (Table 2-7). Survival for S. matsudana f. tortuosa was highest in the full sun. Although survival in full sun decreased from 92 % in April to 75% in July sufficient plants survived to consider S. matsudana f. tortuosa for full sun woody cuts pr oduction. There is some evidence that growth of S. matsudana f. tortuosa is enhanced under full sun and suppressed under shade (He and Dong 2001). Since survival wa s low under both partial shade treatments is not likely that mortality under shade was solely the result of below-ground competition for water. In its native range, this species is noted for its fast growth ra te and its preference for sunny sites (He and Dong 2001). Most species in the genus Salix are early succession species and are not tolerant of shade, and full sun condi tions have been cited as a main requirement for the establishment of Salix spp. (Kuzovkina and Quigley 2005). Because of its preference for full sun, this species could be established in an alleycropping system along with a young tree crop. S. matsudana f. tortuosa could be replaced with more shade tolerant species as the tree canopy grows and develops. More study is needed to assess the performance of this species in an alleycropping system with young trees in order to fully understand the role of root competition in a scenario where light is not the limiting factor.
28 Conclusion High rates of survival were evident among Callicarpa americana Callicarpa americana var. lactea Crataegus marshallii in both full sun and partial shade and for Salix matsudana f. tortuosa in full sun. Based on survival and growth under partial shade conditions C. americana C. americana var. lactea and C. marshallii have potential for inclus ion in a low input pecan ( Carya illinoinensis ) alleycropping system like the one in this trial. Of these, C. americana and C. marshalii survived and grew equally well in sun or shade and neither experienced a reduction in growth due to root competition. C. americana var. lactea had the greatest increase in growth in the partial shade treatments, although the reason why this speci es performed differently from C. americana despite their similarity is not clear. No plants produced saleable woody cuts as part of the two y ear long study. Although many of the plants were old enough to ha ve produced flowers and fruits, only Callicarpa americana produced flowers and fruits during the course of the study. The poor survival and growth performance of many of thes e species is most likely related to drought stress. In order to reduce mortality of plants vulnerable to drought during establishment, it may be appropriate to install a temporary or portable irrigation system. Herbi vory (deer browse) had an impact on plant survival during this study, so installing fen ces or other measures to exclude deer may be appropriate where economically feasible.
29zGrowth index = (height + mean of two witdths)/2 Table 2-1. Initial survival (%), hei ght (cm), width (cm), and growth indexz of Callicarpa americana grown in sun or shade with and without root competition 152, 183, 214, 579, 610, and 640 da ys after planting on December 24, 2004. Survival (%) Mean Height (cm) Mean Width (cm) Growth Index Shade Sun Shade Sun Shade Sun Shade Sun Competition Competition Competition Competition Date no yes no no yes no no yes No no yes no May 2005 100 100 100 71.1 71.8 73.9 58.0 54.3 58.1 64.5 63.1 66.0 June 2005 100 100 100 75.2 68.9 66.7 76.3 77.0 72.4 75.7 69.1 70.4 July 2005 100 100 100 64.3 66.0 63.6 77.0 72.4 77.3 70.6 69.2 70.5 May 2006 92 100 100 68.5 70.9 73.7 79.4 75.3 79.5 73.9 73.1 76.6 June 2006 100 92 100 66.5 71.1 71.8 74.5 80.7 74.1 70.5 75.9 72.9 July 2006 100 100 100 65.5 67.2 70.0 84.9 79.6 75.7 75.2 73.4 72.9 Significance Year Month Month*year Treatment Treatment*year Treatment*month Treatment*month*year ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns <0.0001 ns ns ns ns ns ns ns ns yFor each variable, means within a row fo llowed by the same letter do not differ, = 0.01.
Table 2-2. Initial survival (%), hei ght (cm), width (cm), and growth indexz of Callicarpa americana L. var. lactea F.J. Muell. grown in sun or shade with and without root competition 1 52, 183, 214, 579, 610, and 640 days after planting on December 24, 2004. Survival (%) Mean Height (cm) Mean Width (cm) Growth Index Shade Sun Shade Sun Shade Sun Shade Sun Competition Competition Competition Competition Date no yes no no yes no no yes no no yes no May 2005 92 92 100 73.3a y 30zGrowth index = (height + mean of two widths)/2 67.1b 62.3c 52.1a 43.3b 41.8c 62.7a 55.2b 52.3c June 2005 100 92 100 73.0a 66.7b 61.0c 64.3a 55.9b 46.5c 68.7a 61.3b 53.8c July 2005 100 92 100 71.2a 61.5b 58.3c 65.4a 56.2b 50.5c 68.3a 58.8b 54.4c May 2006 100 92 100 76.3a 64.8b 54.5c 79.7a 65.3b 54.2c 78.0a 65.1b 54.4c June 2006 100 92 83 77.3a 67.3b 57.1c 77.8a 66.6b 57.5c 77.9a 67.0b 57.4c July 2006 100 92 83 78.7a 66.0b 56.6c 84.8a 68.4b 57.4c 81.7a 67.2b 57.0c Significance Year Month Month*year Treatment Treatment*year Treatment*month Treatment*month*year ns ns ns ns ns ns ns ns ns ns <0.0001 ns ns ns <0.0001 0.0016 ns <0.0001 ns ns ns <0.0001 ns ns <0.0001 ns ns ns yFor each variable, means within a row fo llowed by the same letter do not differ, = 0.01.
Table 2-3. Initial survival (%), hei ght (cm), width (cm), and growth indexz of Crataegus marshalii Eggl. grown in sun or shade with and without root competition 152, 183, 214, 579, 610, and 640 days after planting on December 24, 2004. Survival (%) Mean Height (cm) Mean Width (cm) Growth Index Shade Sun Shade Sun Shade Sun Shade Sun Competition Competition Competition Competition Date no yes no no yes no no yes no no yes no June 2005 100 100 100 165.3b y 31zGrowth index = (height + mean of two widths)/2 182.5a 175.7a 84.6 92.3 89.6 124.9 137.3 132.5 July 2005 100 100 100 152.2b 168.5a 162.5a 102.5 87.7 88.6 127.3 128.1 125.5 May 2006 100 92 92 155.1b 178.8a 179.8a 104.0 95.9 89.4 129.5 136.8 134.1 June 2006 100 92 92 156.0b 171.5a 180.0a 96.8 85.1 89.1 126.4 128.3 134.5 July 2006 100 92 92 157.0b 179.5a 178.3a 99.0 87.7 85.5 128.1 133.6 131.9 Significance Year Month Month*year Treatment Treatment*year Treatment*month Treatment*month*year ns ns ns ns ns ns ns ns ns ns 0.0013 ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns yFor each variable, means within a row fo llowed by the same letter do not differ, = 0.01.
32Table 2-4. Initial Survival (%) of Hydrangea paniculata var. Tardiva grown in sun or shade with and wi thout root competition 152, 183, and 214 days after planting on December 22, 2004. Date Survival (%) Shade Sun Competition no yes no May 2005 92ay 92a 92a June 2005 100a 83a 67a July 2005 50b 25b 42b Significance Month Treatment Treatment*month <0.0001 ns ns y For each variable, means within a row followed by the same letter do not differ, = 0.01.
Table 2-5. Initial survival (%), height (cm), width (cm), and growth indexz of Hydrangea quercifolia Bart. grown in sun or shade with and without root competition 152, 183, a nd 214 days after planting on December 24, 2004. Survival (%) Mean Height (cm) Mean Width (cm) Growth Index Shade Sun Shade Sun Shade Sun Shade Sun Competition Competition Competition Competition Date no yes no no yes no no yes No no yes no May 2005 100 92 83 26.1ay zGrowth index = (height + mean of two widths)/2 27.8a 28.7a 21.6a 17.0b 15.6b 23.8 22.4 22.1 June 2005 92 83 67 32.5a 35.3a 34.0a 30.4a 20.9b 19.6b 31.4 28.1 26.8 July 2005 75 83 67 29.8a 38.6a 32.8a 35.4a 21.7b 22.2b 32.6 30.2 27.5 Significance Month Treatment Treatment*month ns ns ns ns ns ns ns ns ns ns ns ns yFor each variable, means within a row followed by the same letter do not differ, = 0.01. 33
zGrowth index = (height + mean of two widths)/2 Table 2-6. Initial survival (%), height (cm), width (cm), and growth indexz of Ilex glabra L. grown in sun or shade with and without root competition 152, 183, and 214 days after planting on December 24, 2004. Survival (%) Mean Height (cm) Mean Width (cm) Growth Index Shade Sun Shade Sun Shade Sun Shade Sun Competition Competition Competition Competition Date no yes no no yes no no yes no no yes no May 2005 100 100 100 42.1 40.1 44.0 25.5 24.9 27.7 33.8 32.5 35.9 June 2005 100 75 92 47.5 48.2 43.6 30.1 33.0 29.4 38.8 40.6 36.4 July 2005 75 67 83 48.6 44.6 48.4 36.6 34.1 32.8 42.6 39.4 40.6 Significance Month Treatment Treatment*month <0.0001 ns ns ns ns ns ns ns ns ns ns ns yFor each variable, means within a row followed y the same letter do not differ, =0.01. 34
3 5 zGrowth index = (height + mean of two widths)/2 Table 2-7. Initial survival (%), hei ght (cm), width (cm), and growth indexz of Salix matsudana Koidz. f. tortuosa Rehd. grown in sun or shade with and without root competition 1 52, 183, 214, 579, 610, and 640 days after planting on December 24, 2004. Survival (%) Mean Height (cm) Mean Width (cm) Growth Index Shade Sun Shade Sun Shade Sun Shade Sun Competition Competition Competition Competition Date no yes no no Yes no no yes no no yes no May 2005 100a y 100a 100a 83.3a 74.7a 91.1a 41.5a 39.3a 39.8a 62.4a 57.0a 65.4a June 2005 100a 100a 100a 97.7a 91.7a 101a 57.8a 56.0a 62.0a 77.8a 73.9a 81.5a July 2005 100a 92a 100a 98.0a 98.5a 110a 72.3a 67.3a 96.0a 85.1a 82.9a 103.0a May 2006 58b 83ab 92a 121ab 102a 134b 78.0a 72.6a 104b 99.4a 87.1a 119b June 2006 50b 67ab 83a 134ab 110a 150b 102ab 83.6a 113b 118ab 96.8a 131b July 2006 33b 42a 75a 145ab 139a 152b 122b 117b 97.9a 133b 128b 125b Significance Year Month Month*Year Treatment Treatment*year Treatment*month Treatment*month*year <0.0001 ns ns 0.0004 0.0004 ns ns <0.0001 <0.0001 ns <0.0001 ns ns ns <0.0001 <0.0001 ns ns ns ns ns <0.0001 <0.0001 ns 0.0002 ns ns ns yFor each variable, means within a row fo llowed by the same letter do not differ, = 0.01.
3 0 2 4 6 8 10 12 14 16 18 20 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 2005 Monthly 2006 Monthly 2002-2006 Average Figure 2-1. Rainfall for 2005 and 2006 (inches) for Jay, FL, USA with five year average (2002-2006). 6
CHAPTER 3 NITROGEN AND IRRADIANCE AFFECT PHOTOSYNTHESIS AND GROWTH OF TWO NATIVE FLORIDA SHRUBS Introduction Changes in plant community structure due to changes in nitrogen avai lability have been attributed to differences in growth response to nitrogen among plant speci es (Padgett and Allen 1998). A study was conducted to investigate the role of interactions of irradiance and nitrogen supply on growth and photosynthesis of shrubs nativ e to Florida that have potential for use as woody cuts. We chose Callicarpa americana L., a fast growing early succession species (Gillman 1999), and Morella pumila Mich. Suwannee elf, a slower growing understory taxon (De la Garza 1999). The two most important factors in determini ng the successful establishment of shade-tolerant shrub species (where water is not limiting) are irradiance and mineral nutrient supply (Grubb et al. 1996). Of these two factors, studies have s hown that growth of shrubs and tree seedlings is more limited by nitrogen s upply than by light availability (Osmund 1983; Clough et al. 1983). Likewise in Impatiens parviflora DC., a shade tolerant species, growth rate responds to variation in nitrogen supply at both low and high irradiance levels (Peace and Grubb 1982). Fast-growing early succession species tend to show a greater photosynthetic response to nitrogen supply under a range of light conditions than understory plants (Riddoch et al. 1991; Grubb et al. 1996; Fetc her et al. 1996). Based on these findings, we hypot hesized that amount of nitr ogen would have a greater influence than irradiance on photosynthesis and growth of C. americana and M. pumila. Quantifying the effects of nitrogen and irradian ce for these two species can aid growers to produce higher quality plants using less fertilizer and can help growers make better use of field space by growing the shrubs under shade or in marginal areas. Similarly, this information could be useful when choosing low maintenance, shade tolerant plants to include in a landscape design. 37
Materials and Methods For each of the two species, Callicarpa americana and Morella pumila a experiment utilizing a randomized complete block design (RCBD) with a factorial arrangement of two irradiance treatments: high irradiance (full expos ure to sunlight within the greenhouse) and low irradiance (50% reduction of full exposure to sunl ight within the greenhou se), and three nitrogen (NH4NO3) concentrations (0 mgL-1, 70 mgL-1, 210 mgL-1) was established by using four blocks and three pseudoreplicates per block. This arrangement resulted in 12 pseudoreplicates (experimental units) for each of the six treatment combinations for a total of 72 plants for each species. One plant planted within a single contai ner was considered an experimental unit. Because the ambient conditions can vary from lo cation to location within greenhouses, we used four separate greenhouse benches as four bloc ks. Mean daytime temperature inside the greenhouse from April to September 2007 was 27 C, and mean nighttime temperature over the same period was 20C. C. americana plants were purchased as <1 year old liners (150ml) from Ornamental Plants and Trees, Inc. (Hawthorne, FL). Plants of M. pumila were asexually reproduced from cuttings and were purchased from Panhandle Grower s, Inc. (Milton, FL) as 1-year-old plants in 3.79L plastic containers. Fifty percent shade was provided for the lo w irradiance treatment by constructing four individual frames to cover half of each of the f our benches. Frames were constructed by using inch (19mm) diameter polyvinyl chloride (PVC) tubes with th e following dimensions: frames 1.52m wide x 1.83m x long x 1.37 m high. Black polyethylene shade cloth (B&T Growers Supply, Inc., Forest Hills, LA) was placed on th e frames such that it covered the top and hung down each of the four sides. 38
Production substrates were washed free from the roots of each plan t with tap water and the plants were placed in 5.68L plastic containe rs (Lerio Corp., Kissimmee, FL) using coarse perlite (The Schindler Compa ny, Methuchen, New Jersey) as th e growing medium. Plants within containers were arranged on the benches su ch that there were 36 plants per bench, with 18 plants of each species. Nine plants of each spec ies were placed in a random arrangement in the shaded and unshaded portion of each bench such that there were three plants of each species for each of the three nitrogen treatments. To precisely control the nutrient input for each plant, a simple drip-through inorganic medium hydroponic system was used and the nutri ent solutions were applied by top irrigation (Jones 2005). A modified Hoaglands solution (Hoagland 1920) was used to supply the three nitrogen concentrations (0, 70, or 210 mg L-1). The nitrogen-free solution was assembled from six stock solutions. Stock solution #1 was made by dissolving one half of the molecular weight of potassium sulfate into one liter of deionized (DI) water. Stock solutions #2, #3, and #4 were made by dissolving one molecular weight wort h each of calcium chloride, potassium acid phosphate, and magnesium sulfate to one liter of DI water. St ock solution #5 was a blend of different micronutrients and was made by adding the following in the amounts shown to one liter of DI water: 2.86g boric acid, 1.81g manganese chlorate, 0.22g zinc sulfate, 0.08g copper sulfate, and 0.02g molybdic acid. Stock solution #6 was made by disso lving 3.67g of Fe-EDTA into one liter of DI water. For this experiment a 25% strength Hoaglands solution was used. Each plant received 400 ml of solution per applicati on, so that a total of 20L wa s needed per application. In order to make 20L of 25% strength solution for the 0 mg L-1 treatment, the following was added to 500ml DI water: 25ml Stock solu tion #1, 25ml of Stock solution #2, 2.5 ml Stock 39
solution #3, 5ml Stock solution #4, 50ml stock so lution #5, and 5ml stock solution #6. For the treatments that included Nitrogen, Ammonium nitrate was completely dissolved into the DI water before adding the stoc k solutions. For the 70 mg L-1 nitrogen treatment, 4g ammonium nitrate (0.2g x 20 b/c making 20L ) was added, and for the 210 mg L-1 treatment 12g (0.6g x 20 b/c making 20L) was added. Each plant received 400ml of 25% strength Hoaglands solution with the appropriate Nitrogen concentration at 48-hour interv als for the duration of the study. Callicarpa americana received solution for sixteen weeks, and Morella pumila received solution for ten weeks. Data were recorded every two weeks and included measuring photosynthesis, stomatal conductance, and photosynthetically active radiation (PAR ) by using the Li-Cor Li 6400 Portable Photosynthesis System (Li-Cor Inc, Lincoln NE). Plant height (cm) was recorded for both species. The number of stems sprouting from the ba se that were at least one half the length of the main stem was recorded (Callicarpa only). HOBO dataloggers (Onset Computer Corp., Pocasset, MA) were suspended above the benches to gather temperature and relative humidity data during the study. At the end of the data collection period, the leaves were removed from each individual plant and placed in a reclosable plastic bag that was pr e-labeled with the plants individual observation number. A moist paper towel was placed in with the leaves to prevent drying. Leaf area (cm2) was measured using a Li-3100 Leaf Area Meter (L i-Cor Inc, Lincoln NE) and recorded for each plant and the leaves from each plant were placed in pre-labeled paper bags. The paper bags containing the leaves were placed in a dryer at 65C for 72 hours and the dry weight (g) for all the leaves of each plant was recorded. The frui ts (from those individual plants which had them) 40
were also placed in pre-labeled paper bags, dr ied at 65C for 72 hours, and dry weights were recorded after this time. While the leaves and fruits were drying, the stems and roots of each plant were removed from their pots and the roots were carefully wash ed to remove all perlite medium. The roots and stems were separated by severing the stem at the root collar. All stems from each plant were placed in pre-labeled paper bags, dried for 72 hours at 65C and weighed (g). Roots were passed through an area meter and the root area (cm2) for each plant was recorded, along with the length (cm) of the longest root. The roots from each plant were then placed in pre-labeled paper bags and placed in a dryer at 65C for 72 hours prior to weighing (g). After drying, the stems, fruits, a nd leaves from each plant were weighed together and placed in paper bags pre-labeled with the individual obser vation number and marked shoot. The combined shoot tissues from each plant were gr ound in a mill (2mm sieve) and placed in prelabeled reclosable plastic bags. The root tissu es from each plant were also ground after drying and placed in pre-labeled reclosab le plastic bags. After grinding, there were 288 samples, with one root sample and one shoot sample from each of the 144 plants. The samples were then sent to Quality Analytical Laboratories (2355 St. Andrews Blvd. Panama City FL 32405) for full plant tissue analysis. The analys is provided data on the concentra tion of the nutrients nitrogen (%), potassium (%), phosphorus (%), calcium (%), magnesium (%) sulfur (%), iron (ppm), manganese (ppm), boron (ppm), copper (ppm), zinc (ppm), molybdenum (ppm), sodium (ppm) and aluminum (ppm) in both the root and shoot tissues of each plant. The data collected during the study were an alyzed using SAS Mixed Procedure (SAS Institute Inc., Cary, NC, USA). Differences am ong treatments were determined using the LS Means procedure (alpha=0.05). 41
Results and Discussion Callicarpa americana The Main effect of nitrogen on photosynthesi s was significant (p=0.0085) but there was also an interaction between ni trogen and time on photosynthesis for Callicarpa americana (p<0.0001) Mean photosynthesis for Callicarpa americana was higher in plants receiving 70 mgL-1 and 210 mgL-1 nitrogen than for plants receiving no nitrogen on every date except 9 April, 3 July, and 17 July (Figure 3-1). The much higher values for mean photosynthesis on 23 April may have been the result of a total lack of cloud cover on that date. Mean photosynthesis was higher in plants receiving 70 mgL-1 (5.8 mol m-2s-1) and 210 mgL-1 (5.7 mol m-2s-1) nitrogen as compared to plants receiving 0 mgL-1 nitrogen (4.0 mol m-2s-1). Mean photosynthesis for Callicarpa americana on the first two dates was almost twice as high (10.5 mol m-2s-1) as the means on the last two data collection dates (5.11 mol m-2s-1). Interactive effects of time and irradiance were found on mean photosynthesis (p <0.0001). Mean photosynthesis for plants in the high irradiance treatment was higher on all dates except 7 May and 17 July (Figure 3-2). Main effect of irradiance on mean photosynthesi s was significant (p<0.0001), with higher means for plants under high irradiance (5.4 mol m-2s-1) compared to means for plants under low irradiance (4.8 mol m-2s-1). This supports a finding by an earlier study that found significant differences in mean photosynthesis between fertilized and unfertilized Impatiens parviflora grown under high irradiance (Peace and Grubb 1982). St udies that examined growth and survival of seedlings of the early succession species Betula alleganiensis under varying levels of irradiance found that growth was enhanced unde r higher irradiance (Walters and Reich 1996). Results for C. americana, another early successional sp ecies support this finding. 42
Main effects of nitrogen concentration and of irradiance on stomat al conductance were significant (p<0.0001). Stomatal conductance was si gnificantly higher for nitrogen treated plants than for plants receivi ng no nitrogen (0.08 mol H20 m-2s-1) (p<0.0001), but values for mean stomatal conductance in the 70 mgL-1 (0.14 mol H20 m-2s-1) and 210 mgL-1 (0.13 mol H20 m-2s-1) treatments were not significantl y different from each other (LSD( -0.05)=.02). Stomatal conductance was also higher for plants in the low irradiance treatment (0.13 mol H20 m-2s-1) compared to plants in the high irradiance treatment (0.10 mol H20 m-2s-1) (p<0.0001)(LSD( 0.05)=.02). Significant interactions were found of time a nd nitrogen concentra tion and of time and irradiance on stomatal conductance for C. americana (p<0.0001). Mean stomatal conductance was higher for nitrogen treated plants on every date aside from April 9, July 3, and July 17 (Figure 3-3). Mean stomatal conductance was higher for plan ts under 50% irradiance on all dates aside from April 23 (Figure 3-4). Mean plant height for C. americana was affected by a two-way interaction of nitrogen and time (p<0.0001). After 7 May, mean height (c m) for plants receiving nitrogen was much greater on all dates than mean height for plants receiving no nitrogen (Figur e 3-5). Mean height for plants receiving 70 mgL-1 and 210 mgL-1 nitrogen were similar. Nitrogen concentration did influence the number of stems per plant (p<0.0001) with plants receiving 70mgL-1 nitrogen having the greatest mean number of stems (1.7). Plants receiving 0mgL-1 and 210mgL-1 had similar mean number of stems (1.4 and 1.5, respectively). Means for selected growth parameters such as leaf area, leaf dry weight, stem dry weight, shoot dry weight, root dry weight, and root area were consistently higher for the plants receiving 70 mgL-1 nitrogen (Table 3-1). Th e plants receiving 210 mgL-1 nitrogen had means that were 43
approximately half as large as the means for the plants receiving 70 mgL-1 nitrogen, which suggests that application of 210 mgL-1 nitrogen had reached a level su fficient to inhibit growth. Main effect of N on Root:Shoot ratio was significant (p< 0.0001). Root:shoot ratio was significantly higher for pl ants receiving 0 mgL-1 nitrogen (1.23) as oppos ed to root:shoot ratio for plants receiving nitrogen (70 mgL-1: 0.51; 210 mgL-1: 0.64). There was no significant difference in root/shoot ratios between the 70 mgL-1 treatment and the 210 mgL-1 nitrogen treatment (Table 3-2). A study involving two Er icaceous species grown under varying levels of irradiance and three nitrogen application rate s showed a similar tre nd in root:shoot ratio (Hawkins and Gordon 2004). Eric aceous species suffer increased rates of mortality under the highest nitrogen application rates because the su rplus nitrogen inhibits root growth, leaving the plants vulnerable to drought stress (Hawki ns and Gordon 2004). While root:shoot ratio decreased in nitrogen treated C. americana plants, there was no mortality associated with higher nitrogen rate. The mortality seen in Ericaceous species was the result of water stress, which was not a factor in this experiment (Hawkins and Gordon 2004). Based on the results of the earlier study, it is possible that the inhibition in growth of C. americana at 210 mgL-1 nitrogen could lead to plant mortality under water stress. Mean concentration of nitrogen (in both root and shoot tissues) was highest in plants receiving 210 mgL-1 nitrogen. However, mean concentrations of phosphorus and iron were higher in plants receiving 0 mgL-1 nitrogen (Table 3-1). This is likely because the metabolic processes by which plants utili ze these nutrients were inhibited by the lack of nitrogen supply in the 0 mgL-1 nitrogen treatment (Marschner 1995). Amount of nitrogen had a greater effect than irra diance on plant growth of C. americana. There were no significant diffe rences in growth parameters between the two irradiance 44
treatments, whereas plants that received 70 mgL-1 nitrogen showed the greatest growth response and the highest rate of photosynt hesis under both irradiance treatments. Plants supplied with 210 mgL-1 nitrogen did not show a three-fold increa se in photosynthetic rate, and plant growth parameters were approximately half as la rge as for plants supplied with 70 mgL-1 nitrogen. This suggests that this species grows equally well in shade as in unre stricted sunlight and that overapplication of nitrogen may inhibit plant growth. There were no apparent signi ficant differences in growth parameters between the two irradiance treatments. C. americana appears to grow well in full sun or shade as long as adequate nitrogen is supplied. Rates of photosynthesis were generally higher under 100% irradiance at a given nitrogen application rate, but growth was not inhibited at 50% irradiance. This species was shown in a field study to be capable of gr owth and survival under drought conditions in both full irradiance and 50% irradiance, and in plots th at were trenched (to remove root competition) and untrenched (Chapter 1). Morella pumila A two-way interaction of time and irradiance was found for M. pumila PAR increased until 6 August, and then gradually declined until 7 September. Mean photosynthesis was higher for M. pumila earlier in the study, possibly because of decreasing day length as the study progressed. Nitrogen treated plants had higher values for mean photosynthesis (70 mgL-1: 3.0 mol m-2 s-1; 210 mgL-1: 3.2 mol m-2s-1) as compared to plants receiving 0 mgL-1 nitrogen (2.5 mol m-2s-1), but means for nitrogen treated plants were not statistically different from each other. Main effect of irradiance on stomatal conductance was significant (p=0.0053), with higher means for plants in the lo w irradiance treatment (0.09 mol H20 m-2s-1) compared to means 45
for the high irradiance treatment (0.08 mol H20 m-2s-1) at all nitrogen application rates (LSD( 0.05)=0.008). This finding is in contrast to the results of an experiment where Solanum dulcamara grown at differing levels of irradiance and with varying nitrogen application ra where stomatal conductance decreased at low i rradiance and at low nitr ogen application rates (Osmond tes, 1983). Mean plant height was affected by an inte raction of nitrogen a nd irradiance (p<0.0001), with higher means for plants re ceiving 100% irradiance for all ni trogen treatments (Figure 3-6). The greatest difference in mean plant height be tween irradiance treatments was found for plants receiving 70 mgL-1 nitrogen. Plants receiving the same amount of nitrogen grew taller under 100% irradiance. This finding is in contrast with earlier studies that found that understory species did not respond to nitrogen application under high irradiance with an increase in growth (Riddoch et al. 1991; Grubb et al. 19 96; Fetcher et al. 1996). The differences in height between irradiance treatments was statistically si gnificant (p<0.0001) but were not necessarily biologically significant. A main effect of nitrogen was found on means for selected growth parameters and concentration of nitrogen and phosphorus in both r oot and shoot tissues (Table 3-3). Means for leaf area, leaf dry weight, a nd shoot dry weight were higher for plants receiving 70 mgL-1 and 210 mgL-1 nitrogen as compared to plants receivi ng no nitrogen, but the means for nitrogen treated plants were not statistically different fr om each other. Means for root area and root:shoot ratio were similar among the three nitrogen treat ments and between irradiance treatments. Mean concentration of nitrogen for bot h root and shoot tissues was higher for plants receiving 210 mgL-1 nitrogen, while mean concen tration of phosphorus did not show statistical differences between nitrogen treatm ents (Table 3-3). 46
47 Conclusions Plants in this study responded more to vari ations in nitrogen than to differences in irradiance. This finding suppor ts the findings of earlier st udies that found that changing irradiance levels change the amount of nitrogen the plants require for optimum growth (Coutinho and Zingmark 1993). Additionally, the inhibition of plant growth at the highest nitrogen application rate observed for C. americana has been noted in other plant species such as Cryptomeria japonica and Pinus densiflora, and Artemesia californica all of which are found in nitrogen deficient habi tats (Najaki et al. 2001, Padjett and Allen 1998). The lack of any definable trend in root:s hoot ratio across the nitrogen gradient for M. pumila contrasts with the decrease in root:shoot ra tio at increasing nitrogen rates observed in C. americana in this study, and for many other species in earlier studies (Hawkins and Gordon 2004; Padgett and Allen 1998). Additionally, pl ant growth was not inhibited at 210 mgL-1 nitrogen. Photosynthetic effi ciency did not increase for M. pumila at the highest nitrogen application rate. Plant growth was similar for both nitrogen application rates, indicating that while plant growth was not inhibited at 210 mgL-1 nitrogen, the higher nitrogen application rate was not necessary. Plant growth was not influe nced by low irradiance, indicating that this species grows equally well under shade and under unrestricted sunlight. Th is result was obtained under controlled conditions within a greenhouse, a nd may not apply to field or forest conditions where below ground interactions between water, and nutrients are more complex and where irradiance is not as uniform (Grubb et al. 1996; Putz and Canham 1992). More study of the nitrogen response of this species is needed before recommenda tions for growers can be made.
Table 3-1. Main effect of nitr ogen was observed on means for selected growth para meters and concentration of selected nutrient s in Callicarpa americana. Means for growth parameters were highest for the 70 mg L-1 treatment. Mean concentration of nitrogen in roots and shoots was highest for the 210 mg L-1treatment, while means for all other nutrients were highest for the 0 mg L-1 treatment (n=12). 48 N treatment ( mg L-1) Leaf area (cm2) Leaf dry wt (g) Stem dry wt (g) Root dry wt (g) Shoot dry wt (g) Root area (cm2 ) Root N (%) Shoot N (%) Root P (%) Shoot P (%) ShootFe (ppm) 0 296 bz 0.52 c 0.25 c 72 c 0.90 c 0.77 c 1.17 c 0.86 b 0.39 a 0.32 a 447 a 70 2585 a 9.90 a 6.51 a 341 a 8.48 a 16 a 2.05b 0.88 b 0.09 b 0.07 b 75 b 210 1831 a 5.51 b 3.97 b 189 b 5.88 b 9 b 3.64 a 1.64 a 0.10 b 0.09 b 52 b zMeans with the same letter within a column are similar as determined by Fishers LSD ( =0.05).
Table 3-2. Interactive eff ect of time and irradiance on mean photosynthesis (mol m-2 s-1) for Callicarpa americana (n=36). Mean photosynthesis was highest on earlier dates for both irradiance treatments. Date Photosynthesis (mol m-2 s-1) (100% Irradiance) Photosynthesis (mol m-2 s-1) (50% Irradiance) 9 April 6.63 az 6.81 a 23 April 14.80 b 13.80 b 7 May 3.17 c 3.87 c 21 May 3.86 c 2.95 de 7 June 3.70 c 2.90 d 21 June 4.90 d 3.70 cd 3 July 3.33 c 2.51 de 17 July 2.13 e 2.25 e zMeans followed by the same letter do not differ (LSD( -0.05)=0.87). 49
Table 3-3. Main effect of n itrogen was observed on means for selected growth parameters and concentration of nitrogen and phosphorus in Morella pumila (n=12). Mean leaf area and stem dry weight were highest for pl ants receiving 70 mg L-1 nitrogen, while means for leaf dry weight, root area, and concentration of nitrogen in both root and shoot tissues were highest for plant s receiving 210 mg L-1 nitrogen. 50 N treatment (mg L-1) Leaf area (cm2) Leaf dry wt (g) Stem dry wt (g) Root area (cm2) Shoot dry wt (g) Root N (%) Shoot N (%) Root P (%) Shoot P (%) 0 302 bz zMeans with the same letter within a column are similar as determined by Fishers LSD ( =0.05). 6.73 b 7.23 b 153 a 14 b 0.79 c 1.14 a 0.17 a 0.16 a 70 464 a 9.37 a 9.42 a 158 a 19 a 0.99 b 1.23 b 0.18 a 0.15 a 210 440 a 10.3 a 8.85 ab 171 a 19 a 2.00 a 1.61 b 0.18 a 0.15 a
0 2 4 6 8 10 12 14 16 9 April 23 April 7 May 21 May7 June21 June3 July17 July 0 50 100 150 200 250 300 350 400 450 0 mgL-1Ps 70mgL-1 Ps 210 mgL-1 Ps 0 mgL-1 PAR 70 mgL-1 PAR 210 mgL-1 PAR LSD( -0.05)=1.95(Ps) Mean Photos y nthesis ( mol m-2s-1 ) PAR (mol m-2s-1) 51Figure 3-1. Mean photosynthesis (Ps) (mol m-2 s-1) for Callicarpa americana was affected by an intera ction of amount of nitrogen and time (n=24). Mean Ps was higher on ea rlier dates and for pl ants receiving 70 mg L-1 and 210 mg L-1 nitrogen. Date
52 0 2 4 6 8 10 12 14 16 1 0 50 100 150 200 250 300 350 400 450 Mean Photos y nthesis ( mol m-2s-1 ) 50%Irradiance(Ps) FullIrradiance(Ps) 50%Irradiance(PAR ) Full Irradiance (PAR) 2 3 4 5 6 7 8 Date 23 April 21 May Date 7 June 17 July 3 July 21 June 7 May 9 April Figure 3-2. Mean photosynthesis (Ps) (mol m-2 s-1) was higher for plants under 100% irradi ance on all dates aside from 7 May and 17 July. A two-way interaction of time and irradiance were found on Ps for Callicarpa americana (n=36).
-0.2 -0.1 0 0.1 0.2 0.3 0.4 1 234 567 8Date 0 mg/L 70 mg/L 210 mg/L Mean Stomatal Conductance ( mol H 2 0 m-2s-1 ) LSD( -0 .05)=.0253 17 Jul y 3 Jul y 21 June 7 June 21 Ma y 7 Ma y 23 A p ril 9 A p ril Date Figure 3-3. Mean stomatal conductance (molH20 m-2s-1) for C. americana was affected by an interaction of time and nitrogen concentration (n=24). Mean stomatal conductance was higher for nitrogen treated plants on every date aside from April 9, July 3, and July 17.
-0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 Mean Stomatal Conductance ( mol H 2 0 m-2s-1 ) LSD( -0 .05)=.01 100% Irradiance 50% Irradiance541 2 3 7 e 4 Dat 5 6 8Figure 3-4. Mean stomatal conductance (molH20 m-2s-1) for C. americana was affected by an interaction of time and irradiance (n=36). Mean stomatal conductance was higher for plants under 50% irradiance on all dates aside from April 23. 21 May 17 Jul y 3 Jul y 21 June 7 June Date 7 Ma y 23 A p ril 9 A p ril
0 5 10 15 20 25 30 35 40 45 50 9 April 23 April 7 May 21 May 7 June 21 June 3 July 17 July Date 0 mgL-1 L 1 70 mgL-1 210 mgL-1 LSD ( -0.05)=3.8 Mean Plant Hei g ht ( cm ) 55Figure 3-5. An interaction of e was observed on mean plant height (cm) for Callicarpa americana (n=24). Increase in mean plant height was much greater in plants receiving nitrogen. Means for plants receiving 70 mgL nitrogen and tim Date-1 and 210 mgL-1 nitrogen were similar.
0 5 10 15 20 25 30 35 40 123 Nitrogen 50% irradiance 100% irradiance 56Figure 3-6. Mean pl ant height (cm) for Morella pumila was affected by an interaction of amount of nitrogen and irradiance (n=72). Means were higher for plants under 100% irra diance for all nitrogen treatments. The largest difference between irradiance trea tment means was in plants receiving 70 mgL-1 nitrogen. LSD( -0.05)=1.81 210 70 Nitrogen (mgL-1) 0 Mean Plant Hei g ht ( cm )
57 CHAPTER 4 CONCLUSION The results of both of these experime nts indicate support the conclusions of previous studies, which found that below ground competition for resources such as nitrogen and water have a greater influence on plant growth th an irradiance (Clough et al. 1983; Montieth et al. 1991; Osmund 1983; Zamora et al. 2008). The onl y exception to this w ould be the survival rates of S. matsudana, which performed poorly under partial sh ade irrespective of the presence of root competition. This result is unsurprising considering that this species grows best in full sun conditions in its native range (He and Dong 2002). The performance of C. americana in both studies demonstrates that this species is highly versatile and ca n grow well under a wide range of conditions. It is reasonable to expect that a species that is tolerant of a wide range of environmental conditions in its native habitat woul d be a good choice for gr owers to include in a low maintenance agroforestry system or landsca pe design. In contrast, the closely related C. americana var. lactea proved to be less tolerant of variati ons in irradiance and root competition than C. americana, which may explain why this species is far less common in the wild. Also, the high rates of survival in all treatments of C. marshallii demonstrate that this species is also highly versatile in th e range of conditions it can tolerate. Differences in the way that various species r espond to variations in irradiance and supply of nutrients and water are important to understa nd when considering potential plant choices for inclusion in agroforestry systems or in landscape designs. Based on the results of th is study, it is clear that interactions between tree crops and hor ticultural crops are comp lex and are challenging to study under field conditions. For example, Ilex myrtifolia is known to be resi stant to periodic drought conditions in its native habitat, and it has been used in landscapes with some success (Nelson 2003). Nevertheless this species performed very poorly in this trial.
58 An understanding of how various factors interact to influence plant growth is essential when designing an ecologicall y sound approach to producing a horticultural crop in a low maintenance agroforestry setting. An agroforest ry approach can provide a viable alternative to full sun production of woody cuts stems if grow ers can make informed decisions about what species are most suitable for in clusion in alley cropping arrangements. These studies provide a basis for further research by quan tifying the interactions of the three primary limiting factors to plant growth and survival: light, water, and nutri ents on a range of species with potential use as woody cuts. While it is critical to include plants that are capa ble of survival and growth under field conditions and to further quantify the intera ction of the important factors in plant growth under more controlled settings, it is necessary to determine the conditions under which any plant choice will produce commercially valuable stems be fore final recommendations can be made.
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64 BIOGRAPHICAL SKETCH Edward H. Fletcher III was born in 1971 in Ta llahassee, Florida, USA. After graduating from Robert F. Munroe Day School in 1989, he attended Santa Fe Community College in Gainesville, Florida and transferred to Tallahasse e Community College in Tallahassee, Florida, where he completed an Associate of Arts degree in 1992. He en tered Florida State University that same year and completed a Bachelor of Science Degree in anthropology in 1996, and returned in 2002 to complete a bachelors degree in geology. He then worked as a grower for Fletcher Nurseries, Inc. in Greensboro, Flor ida until 2004, when he was accepted into the Department of Natural Resources and the Environment at the Univ ersity of Florida to seek a Master of Science degree in interdisciplin ary ecology, which was completed in 2009.