Fates of Trees and Forests in Boliva Subjected to Selective Logging, Fire, and Climate Change

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A priori A posteriori

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Introduction

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Methods Site Description

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Framework

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Field Surveys

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Data Analyses

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Biomass Balance Analyses

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Results Hypothesis 1 Liana-infestion intensity of trees is positively correlated with gap size Border trees New recruits and remnant trees

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Hypothesis 2 Biomass Contributions of New Recruits as a Function of Gap Size Hypothesis 3 Post-logging Biomass Recovery is Lower in Clustered than I so lated Gaps Due to Increased Liana Infestations in the Former

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Border tree growth Discussion

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Swetenia macrophylla)

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33 Figure 1 5. Coefficients for the model pr edicting liana infestati on class based on DBH, gap border status, and species group. T he residuals of this model are used in the model assessing the impact of border status on tree growth rates. Horizontal lines extend +/2 SE (or a total width of 4 SE). -1.0-0.50.00.5DBH Border Func Grp Long-Lived Pioneers Func Grp Slow-Grow Shade-Tol Canopy Func Grp Dry-Forest Func Grp Light-Demanding Canopy Func Grp Intermed-Lived Pioneers Func Grp Colonizing Pioneers Func Grp Fast-Grow Shade-Tol Canopy Func Grp Palms time_since_logging

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37 Figure 1 9. Gap size as a function of DBH of the felled tree. Blue line indicates the OLS regression ofgap area = 84.4 + 0.547 DBH2, adjusted r2 = 0.65, P < 0.001, N=60. Grey envelope is the standard error, and each point indicates a sampled gap.

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Introduction

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Drought per se

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Logging Fire

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Drought + Logging

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Logging + Fire Drought + Fire

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Drought + Fire + Logging Methods

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Statistical Models

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Small Tree Analyses Effects of Drought on Small Trees a priori

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Trema micrantha Spondias mombin Cedrela fissilis, Swietenia macrophylla, Pseudolmedia laevis, Batocarpus amazonicus, Cariniana estrellensis, Cariniana ianeirensis, Gallesia integrifolia, Hymenaea courbaril Aspidosperma cylindrocarpon per se Effects of Drought on Large Trees

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a priori a posteriori a priori Is Crown Exposure or DBH More Closely Linked to Death During Droughts?

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Fire Combined Effects of Drought, Fire, and Logging on Large Trees

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Results Effects of Drought on Small Trees

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Interactive Effects of Drought and Logging on Small Trees

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Logging Effects on Large Trees Drought Effects on Large Trees A priori drought-tolerant species classification algorithm model

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A posteriori separate-environmental-axis association model

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a priori

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Are large trees in logged plots more susceptible to droughts than those in unlogged plots? Is crown exposure or DBH more associated with mortality during droughts?

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Fire

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Interactive Effects of Fire and Logging Drought + Fire + Logging Large Trees

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Discussion Drought Effect on Large Tree Survival

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Drought Effect on Survival of Small trees

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Logging Effects on Residual Mortality of Large Trees Logging Effects on Mortality Across Crown Exposure and DBH Classes

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Crown Exposure is More Associated with Mortality during Droughts than DBH

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Logging does not Change how Crown Exposure Affects Drought Response of Large Trees

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Logging-Drought Interaction Effect on Small Tree Survival

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Fire Effects on Large Trees Fi re Logging Interaction Effects on Large Trees Logging-Drought-Fire Interaction Effect on Adult Tree Survival

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. . .

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.

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114 Figure 2 30. Coefficients for the full model of adult survival during the interval in which the fire occurred (November 2004 Januar y 2005) with predictor variables x = modeled_bark_thickness * DBH * in_burned_area

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Introduction

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Methods

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Results

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Discussion

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131 Figure 3 2. Coefficient values of fixed effects for a mixed model of mortality 8 years after logging of the cohort of trees present pre-loggi ng. Individual trees and treatments crossed with blocks compris ed the random effect s (not shown). Damage classes were coded as numeric predictors, scaled to a standard deviation of 1, and centered around 0. A positive estimate indicates that higher values of that predictor co rrespond to higher mortality rates. -0.4-0.20.00.20.40.6dbh damage depth damage size root damage crown damage tree leaning

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132 Figure 3 3. Coefficients of model predicting total mortalit y in the 8 year post-logging interval as a function of damage severity. Data and methods as in Figure 3 2. 0.00.20.40.60.81.0dbh minor damage major damage (no snaps) snap and resprout

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133 Figure 3 4. Orthogonal polyn omial coefficients for model of stem diameter growth rates as a function of different ty pes of damage, crown position, and dbh. -0.4-0.3-0.2-0.10.00.10.2dbh canopy position tree leaning (linear) tree leaning^2 damage size (linear) damage size^2 root damage (linear) root damage^2 crown damage (linear) crown damage^2 crown damage^3 crown damage^4 crown damage^5

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134 Figure 3 5. Measured (violin/forest plot) and predicted (lines) annual growth rates of trees per DBH class. Widths of violin shapes relate to the number of trees observed with that growth rate for that combination of crown damage and DBH class. All individual shapes hav e the same total areas. Predictions based on the following model: , including individuals, and treat ment crossed with block as random effects. Plot tr uncated at -0.5 and 2 cm/year. There were no trees >50 cm DBH with crown damage classes 4 or 5. Measurements are not balanced with respect to canopy position of trees, and predictions are balanced means of canopy positions cross ed with diameters, with the random

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135 effect of individual set to I ndividual #1 and averaged across block and treatment random effects. Figure 3 6. As in Figure 3 5 but for root damage classes

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136 Figure 3 7. As in Figure 3 5 but for bark damage size classes

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137 Figure 3 8. As in Figure 3 5 but for tree lean damage classes

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138 Figure 3 9. Growth rates (DBH increm ents) modeled as a function of damage groups, canopy position, and dbh. -0.4-0.3-0.2-0.10.00.10.2dbh canopy position minor damage major damage (no snaps) snap and resprout

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139 Figure 3 10. Coefficients of mortality model 8 years after logging as in Figure 3 2, with interactions betwe en DBH and damage types Table 3 3. Likelihood ratio tests for interactive terms in the mortality model of Figure 3 10. AIC LRT Pr(> Chisq) dbh : dam_size 0 1.981160.1593 dbh : dam_roots 0 1.913880.1665 dbh : dam_crown 2 0.061660.8039 dbh : dam_leaning 1 1.076930.2994 -0.6-0.4-0.20.00.20.40.6dbh dam_size dam_roots dam_crown dam_leaning dbh:dam_size dbh:dam_roots dbh:dam_crown dbh:dam_leaning

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140 Figure 3 11. Mortality model as in Fi gure 3 2, with interactions between DBH and damage groups and DBH. -0.20.00.20.40.60.81.0dbh minor damage major damage snapped and resprouted dbh : minor dbh : major dbh : resprouted

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141 Figure 3 12. Mortality model including wood density as a predictor. Data and methods as in Figure 3 2. -0.10.00.10.20.3dbh wood density damaged (yes/no) wood density : damaged

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142 Table 3 4. Likelihood ratio test for the model fit in Figure 3 12 with the direct effect of wood density (WD, model 2) and its in teraction with the damaged category (dam, model 3) removed. Df AIC logLik deviance Chi sq Chi Df Pr(> Chisq) Signif dbh.0 + dam 5 22597.9 -11294.0 22587.9 dbh.0 + dam + dam:WD 7 22600.2 -11293.1 22586.2 1.7 2 0.421 dbh.0 + WD * dam 7 22600. 2 -11293.1 22586.2 0.0 0 0 ***

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143 Figure 3 13. Repeated-measures survival m odel including all terms and corrected for variable census lengths. A positive es timate indicates t hat the term is associated with higher survival rates. Th is survival model fits survival (coded as 1) and mortality (coded as 0) event s of individual trees as repeated measures over each census interval . Random effects include a term for individual trees and a term for tr eatment crossed with block. -0.2-0.10.00.10.20.3dbh canopy position MCWD damaged time since logging canopy position : MCWD damaged : MCWD damaged : time since logging

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190 34 328 38 12 19 6 4 15

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132 16 62 284 37 31 187

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114 481 86 in 447 29 37 12 32 271 47 7

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166 46 3 in 319 97 in 259

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262 38 142 363 88 398 79 256 255

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323 13 16 40 65 38 182 24 1

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82 165 162 108 100 71 93

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dc:title Fates of Trees and Forests in Boliva Subjected to Selective Logging, Fire, and Climate Change
dc:date 2014
dc:creator Shenkin, Alexander F
dc:publisher University of Florida
dc:subject biomass; damage; drought; forest; logging; tropical
dc:description Tropical forests are under siege, but more attention is paid to their total removal (i.e., deforestation) than to their degradation(i.e., loss of values without loss of forest). Here the focus in on forests degraded by logging and fires, coupled with the less obvious impacts of climate change. I evaluated the impacts of these factors and their interactions on tree mortality, growth, and species composition in a transitional tropical forest in Eastern Bolivia.  To understand how this forest responds to the direct impacts of controlled selective logging,  evaluated the patterns and rates of stand recovery in logging gaps and the fates of trees damaged by timber harvests. To understand the effects of logging on carbon dynamics, I surveyed 60 logging gaps 8-9 years after reduced-impact logging.  I found that newly-recruited trees in large gaps are less likely to be liana-infested than those in small gaps, and that trees on gap borders grew 0.15 cm/year more rapidly in diameter and harbored fewer lianas than trees away from gaps. Also, new recruits contributed more biomass to the recovery of large than small gaps. Finally, tree biomass in gaps was not detectably related to the proximity of other gaps. Logging, drought, and fire as well as their interactions all influenced tree species assembly and forest structure over a 7-yearobservation period.  Models of tree mortality and growth in response to these forces revealed that logging shifts tree species composition into assemblages that should be more tolerant of future droughts. This shift was evident in the increased survival rates of seedlings of drought-tolerant tree species but might be counter-balanced by the observed higher mortality rates of trees >10 cm DBH of species characteristic of relatively dry forests. While species composition shifted towards drought tolerance, forest structure did not: large trees in this forest suffered disproportionally from droughts.  Increased vulnerability to droughts was more closely related to crown exposure than to DBH. Finally, to clarify one longer-term impact of selective logging, I tracked the fates of trees damaged during the harvest for up to 8years afterwards.  While damaged trees initially suffered elevated mortality rates, those that survived 8 years after being damaged then exhibited similar mortality rates to undamaged trees. Over that same period, trees with damaged roots suffered particularly high mortality rates and trees with damaged crowns grew very slowly. Taken together, these studies illustrate that the while responses of tropical forests to disturbance and stress are complex, some factors standout as particularly important.  Large trees suffer disproportionally from drought and while logging may favor seedlings of drought-tolerant species, larger trees characteristic of dry forests may not endure droughts better than those from wetter forests.  While mitigating climate change, improved forest management interventions such as liana cutting may enable forests to recoup carbon emissions from logging quickly.
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palmm:graduationDate 2014-05-03
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