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FOREST-USE HISTORY AND THE SOILS AND VEGETATION OF A LOWLAND
FOREST IN BOLIVIA
CLEA LUCRECIA PAZ RIVERA
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
Clea Lucrecia Paz Rivera
To the memory of my grandfather Carlos Alfredo Rivera, whose love and inspiration
have accompanied me through the years.
Numerous individuals and institutions deserve acknowledgment for their
contributions to this thesis. First, I am indebted to my advisor Francis E. "Jack" Putz, for
his mentorship, persistence, enthusiasm, and interest in Bolivia. Also at the University of
Florida, I would like to thank my other committee members Kaoru Kitajima and Nigel
Smith for their advice. I also wish to thank Nick Comerford for his guidance on soil
analysis, Mary Mcleod, Jennie del Marco for helping me in the laboratory.
The Latin American Scholarship Program of American Universities
(LASPAU/Fulbright), Proyecto de Manejo Forestal Sostenible (BOLFOR), the School of
Natural Resources and Environment, the Department of Botany, and the Tropical
Conservation and Development Program at the University of Florida, all provided
generous financial and logistical support for my graduate studies. My excellent field
guide, Jose Chuvifia, deserves praise for his boundless energy and rich knowledge of the
forest. I also thank Marielos Pefia-Claros, Joaquin Justiniano, and Todd Fredericksen at
BOLFOR; Narel Paniagua at the Herbario Nacional de Bolivia; and Sergio Calla (for his
archaeological work). The BOLFOR project staff gave me technical and logistic support
in Santa Cruz. I thank my labmates at the University of Florida (Bonifacio Mostacedo
Geoffrey Blate, and William Grauel) who were always available for grammatical
consultations, statistical guidance, editing, and comic relief. Amy Miller helped me in
many ways, from editing, to sharing the challenges of thesis writing, to being a dear
friend. Catherine Cardelus and Eddie Watkins provided both friendship and draft
I especially thank my parents and siblings for their inspiration and support; and for
taking care of my son while I was in the field. My son Santiago shared with me his
beauty and companionship, and I thank him for his forgiveness when I could not give him
the time and attention he deserved. Last but not least, I could not have completed this
work without the constant love, care, support, and warm meals from my husband
TABLE OF CONTENTS
A C K N O W L E D G M E N T S ................................................................................................. iv
LIST OF TABLES .................................................... ........ .. .............. viii
LIST OF FIGURES ......... ......................... ...... ........ ............ ix
ABSTRACT .............. ................. .......... .............. xi
1 ANTHROPOGENIC SOILS OF A FORESTRY CONCESSION IN LOWLAND
B O L IV IA ................................................................ .. ........ ...............1
History of Study Area ............... ................. ....................... ...... ... 4
Sp aniard s ................................................................... 5
M issionary A activity ........................................... .. ........ ................ .6
Population D ensity ...................................... .......................... .7
L and and R source U se ........................................................... ............... 8
M e th o d s ................................................................ ......................................1 1
Study Site...................................... ............ 11
Soil Sam pling and A nalysis........................................... .......................... 12
Results ................. ............... .................. .. ............................... 13
Area, Shape, and Location of Anthropogenic Soil Patches.............................. 13
Soil Chemistry .................................... .......................... .... ........ .15
D discussion ................................................................ ......... ........... 16
Area, Shape, and Location of Anthropogenic Soil Patches.............................. 16
Soil Chemistry ................ ................................. ......... .....................18
Implications of Anthropogenic Influences on La Chonta Forest ......................20
2 DISTRIBUTION OF USEFUL TREE SPECIES IN RELATION TO HISTORICAL
HUMAN INFLUENCES ON THE FOREST OF A TIMBER CONCESSION IN
L O W L A N D B O L IV IA .................................................................... .....................28
Introduction..................................... .................................. .......... 28
M e th o d s ................................................................... 3 1
Study Site.............................................. 31
Species Selection ................................. ........................... ... .......32
Species Sampling.................. .. ............................. 33
D ata A n a ly sis .................................................................................................. 3 4
R e su lts ...........................................................................................3 4
D isc u ssio n .............................................................................................................. 3 6
R E F E R E N C E S ................................................................47
B IO G R A PH IC A L SK E T C H ........................................................................................ 56
LIST OF TABLES
1-1. Distribution of tierra negra (TN) sites in a 216 ha sample area ............................22
1-2. Mean values (+ one SE) of tierra negra, tierra morena, and non-tierrra negra soil
properties at two depths (0-10 and 40-50 cm) with sites as replicates...................22
1-3. Statistical contrast of the three soil types at two depths................. .... ........... 23
2-1. Characteristics of tree species that are used by humans and selected for study in La
C h o n ta ........................................................... ................ 4 1
2-2. Maximum diameters, mean growth rates for trees > 10 cm DBH and mean annual
diameter increment (MAI, based on 3 years of data) of the selected tree species in
L a C h o n ta ........... ......... ...... ......... ...... .......... .....................................4 3
LIST OF FIGURES
1-1. Location of the study site in lowland Bolivia ........ ...........................................24
1-2. Location and size of the TN sites in La Chonta. ....................................... .......... 25
1-3. Spatial distribution of tierra negra (TN) in relation to tierra morena (MO) and
non-tierra negra (N TN ). ............................................... ............................... 26
1-4. Mean values (+ 1 SE) for tierra negra (TN, N = 10), tierra morena (MO, N = 3,),
and non-tierra negra (NTN, N = 6) at two different depths for a) pH, b) organic
matter content, c) extractable phosphorous, d) extractable calcium, and e)
extractable potassium ....................... .. ...... .................. .. .. ....... ........... 27
2-1. Relative abundances ( 1 SE) of the selected useful tree species among the three
different soil types ............. ................... ... ......... ........ .. .. .. ........ .... 46
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
FOREST-USE HISTORY AND THE SOILS AND VEGETATION OF A LOWLAND
FOREST IN BOLIVIA
Clea Lucrecia Paz Rivera
Chair: Francis E. Putz
Major Department: Natural Resources and Environment
Land-use practices can dramatically affect soils and vegetation, even centuries after
they cease. In Amazonia, soils enriched by nutrient and charcoal additions are indicators
of ancient village sites and old agricultural plots. To ascertain whether past land-use
practices also result in local enrichment with useful plants, I studied the anthropogenic
soils and associated vegetation of a forestry concession in the Department of Santa Cruz,
Bolivia. I compared the chemical properties of anthropogenic soils with surrounding soils
and then compared the concentration of useful tree species on and off of anthropogenic
Two types of anthropogenic soils were identified in the research area: tierra negra
(TN) darkened with charcoal fragments and with abundant buried pottery shards; and
tierra morena (MO), somewhat darkened but with little or no pottery. In an area of
216ha, nine TN soil patches (0.3 to 10 ha) and three MO soil patches were identified and
compared with six nearby non-anthropogenic soils (inceptisols), which are referred to as
non-tierra negra (NTN). The abundance of seventeen useful tree species was measured
in plots on the three soil types (TN, MO, and NTN).
Results of this study demonstrate that La Chonta's soils retain strong effects of past
human activities that ceased 300 to 400 years ago, when the area was abandoned. The TN
soils cover approximately 20% of La Chonta and are chemically different from the MO
and NTN soils but all were circum neutral in pH, high in Ca content, and similar in total
P. The TN soils had significantly higher contents of organic matter, extractable P, and
extractable Ca than did NTN soils; and higher pH and extractable P than did MO soils.
The MO soils had organic matter and Ca content similar to that of NTN soils and
significantly less extractable K. Overall, TN soils had higher nutrient content than
surrounding soils, both at the surface (0-10 cm) and deeper in the soil (40-50 cm).
Of the seventeen useful tree species studied, none were concentrated in TN areas.
This unexpected result may be due to interactions between local dispersal agents and
natural disturbances that masked historical patterns. Alternatively, past inhabitants of La
Chonta may have managed or cultivated their useful tree species beyond anthropogenic
soil areas. In any case, the influence of past land-use practices on plant species
composition is not apparent in La Chonta.
ANTHROPOGENIC SOILS OF A FORESTRY CONCESSION IN LOWLAND
Land-use history has played important roles in shaping modern landscapes and
ecosystems. This study examines the history of the currently uninhabited timber
concession of La Chonta, in the Guarayos Province of lowland Bolivia, and the effects of
past land-use practices on its soil properties.
Humans are now recognized as having dramatically influenced Amazon Basin
forests (Roosevelt et al. 1991, Denevan 1992b, Balee 1994, Smith 1999). Forests once
considered pristine or virgin are increasingly viewed as resulting from regeneration after
the cessation of human activities (Lentz 2000b). Human influences are to be expected,
given that archeological studies reveal that humans were present in Amazonia at least
12,000 years ago (Roosevelt et al. 1991). Although hotly debated, estimates of pre-
Columbian population density in Amazonia are all high. For example, Dobyns (1966)
estimated 6 million for all of tropical South America, whereas Denevan (1992a)
estimated a population of 8.6 million in lowland South America alone, a number that
declined by 90% within 100 years after European contact. pre-Columbian societies in the
Amazon have affected the region at all scales up to the landscape level, through
constructing raised fields, earthen causeways, and hydraulic earthworks (Denevan 1966,
2001, Lippi 1988, Erickson 2000, Roosevelt 2000) as well as through use of more subtle
forest-management practices (Posey 1985, Balee 1994, Denevan 1998, Peters 2000).
Past human disturbances may have influenced several attributes of present-day
Neotropical landscapes (Balee 1994, Lentz 2000a). For example, Peters (2000) and
Erickson (2000) working in Central American forests and Amazonian savannas
respectively, showed that modem vegetation in their study sites was greatly altered by
direct and indirect enrichment by pre-Columbian societies. Direct enrichment of useful
plant species occurred through manipulations such as planting or thinning, while indirect
enrichment was the creation or alteration of habitats such as those conducive to
colonization by early successional species.
Despite the extent of landscape alterations by pre-Columbian societies, land-use
history in dynamic tropical ecosystems can be difficult to unravel because ecological
processes such as bioturbation, heavy rainfall, and rapid plant growth can obscure
evidence of earlier human activities (Stahl 1995). Nevertheless, soils generally reflect
human-induced alterations for long periods of time and therefore can serve as useful
indicators of past land-use practices (Glaser 2002).
In Amazonia, dark anthropogenic soils (referred to as tierra negra in Bolivia, and
terra preta and terra preta do Indio in Brazil) occur in patches from 0.5 to 300 ha,
typically embedded in a matrix of infertile soils (mainly oxisols and ultisols). Terrapreta
are defined by a distinctive anthropogenic epipedon with intermixed potsherds and celts
(Sombroek 1966, Smith 1980, Woods et al. 2000, Glaser et al. 2001). High organic
matter and elevated nutrient contents (especially phosphorous, calcium, potassium, and
sodium) distinguish the Amazonian anthropogenic soils from those in their surroundings
(Smith 1980, Woods et al. 2000, Glaser et al. 2001, McCann et al. 2001).
Although the origin, distribution, and use of Amazonian anthropogenic soils are
still unclear, it seems that fire was the most important factor in their formation (Woods et
al. 2000). Apparently incorporation of charcoal (black carbon) and wood ash increases
nutrient retention capacity, cation exchange capacity (CEC), and soil pH (Woods et al.
2000); ant it stabilizes soil organic matter (SOM) while reduces nutrient leaching from
soils (Glaser et al. 2000 and 2001). Charcoal is also extremely resistant to weathering and
can persist in soil for millennia (Rainho Texeira et al. 2002), thereby contributing to the
maintenance of anthropogenic soil properties through time. The second factor related to
the formation of these soils was the incorporation of household waste, such us food
remains, shells, bones, feces, blood, and urine, all of which increased soil nutrient content
(Smith 1980, McCann et al. 2001).
Initially, anthropogenic soils were reported on floodplains, especially on river
bluffs along the main Amazon river (Sombroek 1966, Smith 1980). More recently, large
areas of terrapreta have been reported in terrafirme, or upland forests (Heckenberger et
al. 1999), and in floodplains along tributaries of the Amazon river (McCann et al. 2001).
In any case, most of the reported occurrences of anthropogenic soils in South America to
date are near permanent sources of water.
Two kinds of anthropogenic soils, terrapreta and terra mulata, have been
described as being clearly distinguishable in Brazil (Sombroek et al. 2002). Terrapreta
appears in former human settlements and, besides being enriched in nutrients and
charcoal, is always associated with pottery and cultural debris (Smith 1980,
Heckenberger et al. 1999). Terra mulata is thought to have developed in permanent
agricultural fields, enriched by long-term soil-management practices such as mulching
and infield burning (Denevan 1996, Woods et al. 2000, McCann et al. 2001). Despite
some recent advances in our understanding, the nature and characteristics of pre
Columbian agriculture that originated terra mulata still remain little known.
High nutrient levels of anthropogenic soils and the different ways vegetation was
managed in and surrounding these areas are expected to influence the vegetation that
either persists or colonizes the sites after their abandonment. In any event, it is obvious
that the original vegetation in these areas was substantially modified by humans, and that
certain species were either favored or introduced from other areas, perhaps permanently
altering local species composition.
This study has two objectives. The first is to reconstruct the history of the
Guarayos area through review of bibliographic sources. The second is to describe the
anthropogenic soils of La Chonta and compare soil properties between anthropogenic and
History of Study Area
Unraveling the history of human activities can help us understand the soils,
vegetation, landscape, and successional patterns in modern ecosystems (Glenn 1999).
Given that there are few published historical accounts of Guarayos, colonial archives and
historical reports from nearby regions were used to reconstruct its probable land-use
patterns and settlement history (Orbigny 1835, Cardus 1886).
Guarayos is a biological and cultural transitional region with influences from the
humid forests of Amazonia to the north, the drier forests of Chiquitos (Chiquitania) and
Chaco to the southeast, and the savannas ofMojos (Moxos) to the west (Figure 1-1).
Both Mojos and Chiquitos were explored and settled by Europeans earlier than Guarayos
and as a result there is relatively more historical information about them, but the histories
of the three regions are intertwined.
Although the Swedish anthropologist Erland Nordenskiold excavated in Guarayos
in the early twentieth century (Nordenskiold 1930), the secondary urn burials (urns
containing fleshless bones) he unearthed have apparently not been dated. I am aware of
no other pre-contact archeological data. Early reports from European explorers and
missionaries provide the only descriptions of cultural and ecological conditions following
The Guarayos region is believed to have been inhabited by the Guarayo Indians,
who likely migrated from Paraguay and inhabited the Guarayos region since at least 1400
(Orbigny 1835, Cardus 1886). The Guarayo language is of the Tupi-Guarani family and
is closely related to Guarani (Cardus 1886), spoken by the Guarani Indians who
historically inhabited the Chaco region of southeastern Bolivia and northern Argentina
and Paraguay. Despite their common language, the Guarayo and Guarani have marked
cultural and physical differences, suggesting that if the two groups were once more
closely related, their separation took place long before European contact (Finot 1939).
The region now referred to as Guarayos and inhabited primarily by the Guarayo
was probably first encountered by Europeans during a Spanish expedition that set out
from Asuncion, Paraguay in the 1540s. The objective of this and numerous similar
explorations was to find the tierra ricas of indigenous legends that described the
treasures and gold of El Dorado, El Gran Paititi, or El Gran Mojos, this last believed at
one time to be located north of Chiquitos (Finot 1939).
Apparently the first expedition to pass through the Guarayos region was led by the
Spanish captain Nuflo de Chavez, who left Asunci6n in 1558 with 150 Spanish soldiers
and 1500 Guarani Indians. His mission was to establish a new town in the Xarayes
marshes (located in Mato Grosso, Brazil, and southeastern Bolivia) but upon arrival, he
found the area unsuitable for settlement and decided to continue the expedition, traveling
west and northwest in search of ElDorado. Although maps that reconstruct Nuflo de
Chavez's expeditions show the route passing through Guarayos region, there is no direct
mention of Guarayo people in the chronicles of the trip, contrasting with the extensive
description of surrounding indigenous groups such as Chiquito, Chiriguano, Mojo, and
others (Levillier 1976).
According to the interpretation of Levillier (1976), Chavez encountered the
Guarayo indians north of latitude 160 South when he was attacked by an unidentified
indigenous group living at a heavily fortified settlement. Chavez, uncertain of victory,
turned away from the settlement and returned to Chiquitos.
In the late 17th century the Spaniards approach to conquest shifted from one of
broad exploration to a more systematic effort at populating areas where they had been
able to establish a presence. Because of its distance from Santa Cruz de al Sierra, the
Guarayos region was not colonized and there is little mention of the area until the 18th
Religious missionaries entered South America with objectives quite different from
those of the explorers-in place of gold they sought the souls of indigenous infieles.
Unlike the explorers, who in most cases passed quickly over through the landscape,
missionaries had sustained contact with local people. Jesuit missionaries arrived on the
continent in the late 1500s and in the Bolivian lowlands the first reducciones (Jesuit and
Franciscan missions) were established roughly a century later. In Mojos, the first mission
(Loreto) was established in 1682; San Francisco Javier in Chiquitos was established in
Between 1700 and 1845, there were five attempts, first by Jesuits and later by
Franciscans, to establish reducciones among the Guarayo. The first four failed at
retaining significant numbers of people. It was only later (1845) that thousands of
Guarayo were concentrated in several towns in the region, including the present-day
capital, Ascenci6n, founded by Franciscans in 1826.
There are apparently no published estimates of population density in Guarayos
before the missionary period. Nevertheless, as mentioned above, several lines of evidence
indicate that the native population was high in pre-Columbian times. For example, near
Guarayos in the savannas of Mojos, Jesuit missionaries reported 37 related yet distinct
indigenous groups in 1696 (Chavez 1986). Denevan estimated a native population of
350,000 in the same region and calculated that that number decreased to 100,000 by the
1690s as a consequence of epidemic diseases (Denevan 1992a).
Spanish chronicles of expeditions from Paraguay to Santa Cruz and Mojos in the
late 1500s and early 1600s reported encounters with hundreds of indigenous groups.
Reports from this time stated that the Guarani and Guarani-related groups, including
Chiriguano, Sirion6, and Itantines, tended to be the more populous and bellicose (Finot
1939, Pinckert-Justiniano 1991).
After Gregorio Salvatierra, a Franciscan missionary, visited four mission towns in
1794 (Asenci6n, Yaguaru, Yotau and Urubicha), he estimated a population between 3000
and 4000 in the region (Cardus 1886). D'Orbingy, who visited Asenci6n de Guarayos in
1831, estimated 1,000 Guarayo Indians in the area (Orbigny 1835). During the mission
period, the Jesuits concentrated hundreds of families in towns, but they repeatedly
reported the existence of many "wild" Guarayo living in the forest who maintained only
sporadic contact with people living in towns. The Jesuits carried out several recruitment
expeditions into forested areas and reported dispersed families along their route and
returned with groups of varied sizes, the last (1825) returning with 200 Guarayo (Cardus
The population estimates of D'Orbigny and Salvatierra were likely gross
underestimates because they were based only on the established mission settlements, and
did not include people dispersed through the forest. It also seems relevant to note that
these censuses were carried out more than 200 years after the arrival of Europeans to the
region, when populations were probably greatly diminished by introduced diseases such
as smallpox and the flu. The impact diseases brought by Europeans was reported in
Chiquitos by D'Orbigny who noted that half of the Chiquitano residing in San Javier died
from smallpox in 1825. Similarly Cardus mentioned that a "malignous fever" attacked
and killed hundreds of Guarayo in 1845.
Land and Resource Use
Archaeologists and ecologists are currently trying to understand land-use practices
prior to European contact. Descriptions by Jesuits and Franciscans, admittedly biased by
their belief that indigenous peoples were ignorant savages, and reports by D'Orbingy,
provide the earliest reports of the land-use practices and customs. Unfortunately, the
land-use practices they described already reflected European influences, the most
important of these being the introduction of metal tools. Metal tools are several times
more efficient for cutting trees than stone tools (the ratio varies from 10 to 1 to 23 to 1,
Denevan 1992c), allowing faster forest clearing, and the development of long fallow
shifting cultivation. Due to the inefficiency of stone axes, some authors claim that pre-
Columbian agriculture was based in home gardens and permanent crop fields instead of
modern shifting cultivation with short cropping periods followed by long forest fallows,
which would be too labor intensive to be a common agricultural practice (Denevan 1998).
D'Orbigny, who visited Asenci6n de Guarayos in 1823, provides the first
description of anthropogenic soils, reporting "black fields ready to be planted". After his
arrival he described the Guarayo living in mission towns with the Franciscans as having
maintained more of their customs and otherwise were less influenced by Europeans than
the Chiquitano. D'Orbigny asserts that agriculture was their main food producing
activity, and that hunting was more of a past time than an essential activity (this
contradicts the missionaries descriptions, who assert the Guarayo were mainly hunters).
D'Orbigny's claims, however, are corroborated by the great number of religious
ceremonies devoted to Tamoi (grandfather), the most important god of the Guarayo, who
was believed to have taught them agriculture. When D'Orbigny arrived in the region, the
Guarayo had a well-developed shifting cultivation system centered on squash, corn,
yucca, papaya, pineapples, and sugar cane (an old world crop introduced by the Jesuits in
the early 1800s) using metal axes. Agricultural fields were managed by the whole
community while they lived divided in small families in octagonal-shaped cabafias roofed
with palm leaves, similar to those used by the Caribe of Central America. They
reportedly planted near the houses a sacred tree called turienda (apparently Ceiba
pentandra), which they claimed was used by their gods to come down and take them
when they died. They wore clothes made of the bibosi tree bark (Ficus spp.) and painted
their bodies with achiote (Bixa orellana; Orbigny 1835).
Cards, a Franciscan missionary who visited the area between 1883 and 1884,
provides a similar description of the Guarayo agricultural system (Cardus 1886). He
described low, forested, rolling hills intermixed with forested wetlands to the south,
extensive, flat, lowland forests to the north, and to the west, beyond several leguas
(leagues, approximately four to seven kilometers) of forest, began the huge savannas of
Mojos region. He also observed that the Rio Blanco (Figure 1-1), was navigable to
Carmen del Mojos whereas today, the river is navigable only seasonally, and then by
small canoe. Cards described the Guarayo as primarily hunters and fishers, with their
principal crops being corn, yucca, plantain (an old world crop), beans, peanuts, and
squash. Spider monkey was their preferred meat and chicha, a fermented beverage made
of corn or yucca, was their most common beverage.
The different views on human cultures and ecology in the Guarayos region
provided by early explorers, missionaries, and scientists, offer an opportunity to consider
the dramatic changes that took place over the previous centuries. Although Guarayos
was at first a region on the periphery of European activities in Bolivia, it was still
affected, finally to a large degree, by the arrival of explorers and missionaries.
Unfortunately, the accounts of D'Orbigny, Cardus, and others begin at least two centuries
after the arrival of Europeans to the region, sufficient time for forests to regenerate on
abandoned sites following the massive indigenous population declines that occurred
throughout the Americas (Denevan 1992a, Block 1994). This lapse in time prevents us
from understanding pre-colonial landscapes that may have been quite different from
those D'Orbigny, Cardus, and others observed. For instance, if native populations were
large before contact, the landscape was likely much less forested than it was more than a
century after the population crash.
Study of the anthropogenic soils of La Chonta affords an opportunity to piece
together the past at a much different level of detail than that made possible by historical
and religious records. It allows us to estimate the area of long-abandoned settlements or
cultivated plots, and the effects of human induced soil alterations on soil chemistry and
plant species composition.
This study was conducted in La Chonta, a lowland tropical forest in Guarayos
Province, Department of Santa Cruz, Bolivia (15047'S, 62055'W, Figure 1-1). A
100,000 ha private timber concession since 1974, the area was selectively logged for
mahogany (Swietenia macrophylla) and tropical cedar (Cedrela odorata) for the first
decade after its establishment. When mahogany was depleted, the focus shifted to other
species and today loggers extract up to a dozen species. La Chonta was certified by the
Forest Stewardship Council as well managed in 1998. A long-term silvicultural research
project was started in La Chonta in 2000 as part of the BOLFOR Sustainable Forest
Management Project (Putz et al. in press).
The vegetation of La Chonta is classified as subtropical humid forest (Holdridge
1971), with mean annual temperature of 24.50C and mean annual rainfall of ca. 1500
mm. The canopy is semideciduous and fairly open, with heights of mature forests of 20
to 25 m. Common canopy tree species are characteristic of humid forests and include
Hura crepitans and Pseudolmedia laevis (Navarro and Maldonado 2002). Lianas are
abundant and dominate disturbed areas (Alvira et al. 2003). The area has a long history of
both human-induced and 'natural' fires, but there were no signs of recent fires in my
study area. The region has numerous ephemeral streams, and the rivers Blanco and Negro
border the peripheries of the concession (Figure 1-1).
Soil Sampling and Analysis
An area of 216 ha was surveyed for anthropogenic soils by sampling at 200 m
intervals along walking trails separated by 150 m. The trails delimit research plots in La
Chonta and are kept clear of vegetation; changes in soil color and type were easily
recognized. Surface soil was cursorily examined and soil color was recorded using a
Munsell Soil Color Chart. When soil color darkened markedly, sampling intervals were
reduced to 100 m and examined more thoroughly for charcoal and pottery.
Soils were classified as tierra negra (TN) when extremely dark in color (7.5 YR
3/1 and 2.5/1; dark brown and very dark brown) and both charcoal and pottery sherds
were present. Soils that were somewhat darkened (7.5 YR 4/3 3/2, brown to dark
brown) but with little or no pottery were classified as tierra morena (MO). Soils with no
apparent indicators of anthropogenic influences were classified as non-tierra negra
(NTN), and are tentatively classified as inceptisols (Navarro 2002). When TN soils were
encountered, their area was estimated by sampling in the four cardinal directions every
20 m with a soil auger until the patch limits were identified. Patch locations were
recorded with a handheld Garmin GPS.
Soil samples were taken from each of the TN and MO patches, and the surrounding
NTN soils. From the approximate center of each patch, soil samples were taken at two
depths (0-10 and 40-50 cm) at the corners of a 10x10 m square. Samples from each of the
depths were mixed together and 200 g of each was air dried in the field and stored for
As a preliminary archaeological assessment of the area, one test pit (lxlm3) was
excavated in the central area of each TN site to quantify the abundance of pottery sherds
and to determine the depth of the TN soils. During the early phase of this study, two large
charcoal fragments that were found intermixed with abundant pottery sherds at 10 and 20
cm depths in an anthropogenic soil patch (tierra negra 3 Table 1-1) were submitted to
Beta Analytic Laboratory for accelerator mass spectrometry (AMS) radio-carbon dating.
In the laboratory, soil organic matter was estimated using the weight loss on
ignition method (Nelson 1996). Total phosphorous (P) was measured colorimetrically
after sulfuric acid digestion (Olsen and Sommers 1982). Extractable phosphorous was
measured colorimetrically after a Mehlich double-acid solution (Olsen and Sommers
1982). Finally, extractable calcium (Ca), magnesium (Mg), and potassium (K) were
assayed using atomic absorption (AA) following extraction in a Mehlic double-acid
solution (Thomas 1982). To compare soil types, the chemical data were analyzed with a
two-way ANOVA model using soil type (TN, MO and NTN) and depth as factors and
sites as replicates.
Area, Shape, and Location of Anthropogenic Soil Patches
In an area of 216 ha, nine patches of tierra negra (TN, Table 1-1, Figure 1-2), three
patches of tierra morena (MO), and six nearby (within 1 km) areas of non-tierra negra
(NTN) soil were identified. The TN patches were commonly located on flat terraces
within 200 m of streams that at least flow during the rainy season (Figure 1-3). TN patch
sizes varied in La Chonta and were grouped in two categories: small circular patches
(0.3-2.5 ha), and larger, irregular patches (5-10 ha). Mapping of the larger areas was not
completed because they extended past the perimeters of the research plots. Within TN
sites, I found areas with higher concentration of charcoal and pottery sherds, probably
corresponding to kitchen middens (S. Palma, unpublished data). The cumulative area of
the most prominently affected anthropogenic soils (TN) accounts for approximately 20%
of the study area (Table 1-1, Figure 1-2). The patches of MO were 0.3-1.0 ha and tended
to surround the TN sites (Figure 1-3). I did not quantitatively measure areas of MO but
estimate them to cover an additional 5% of the area.
The preliminary archaeological investigations carried out in TN soil pits revealed
distinguishable layers, defined by abundant pottery sherds and charcoal, which differed
between the small and large patches. In both patches sizes the surface 10 cm were dark in
color but usually contained no pottery and charcoal, with the exception of areas disturbed
by animals or roads. The small patches (0.3-1 ha) in general had one continuous stratum
of dark soil from 10 to 30-45 cm depth with intermixed charcoal and pottery whereas the
larger patches generally had two separated layers with anthropogenic traces, one at 10-40
cm depth and other at 45-75 cm depth. The 5 cm separation between the two
anthropogenic layers in the large patches consisted of a layer of sandy-loam soil with
large quartz crystals.
The density of buried pottery sherds in the intensively inventoried soil pits varied
from 19 to 187 pieces per m3. I also found solid pieces of macroscopic black carbon
(between 1 and 5 cm size) from 10 to 75 cm soil depth in both the small and large
patches. The two charcoal fragments found mixed with pottery in tierra negra site 3 at 10
and 20 cm below the surface were AMS dated from 330 + 80 to 420 60 years BP
The pH of soils in La Chonta were all high, averaging 7.2 in the TN soils, 6.4 in the
MO soils and 7.2 in the NTN (Table 1-2); pH was significantly higher in TN and NTN
soils than in the MO soils (P < 0.006, Figure 1-4a). Organic matter content at 10 and 50
cm depth averaged 5.7% and 2.6% in TN soils, 4.8% and 2.1% in MO soils, and 4.7%
and 2.1% in NTN soils, being significantly higher in the TN soils than the NTN soils (P <
0.039, Figure 1-4b).
Total phosphorous was relatively high in all three soil types while extractable
phosphorous was relatively low. Total P was not significantly different among the three
soil types and averaged 15522-358+8 (Table 1-2) Extractable P content averaged 49.65
and 35.92 mg/kg (at 10 and 50 cm respectively) in TN soils, being significantly higher
than MO soils at both depths and significantly higher than NTN at 50 cm (P < 0.015,
Extractable Ca was extremely high in all La Chonta soils, averaging (at 10 and 50
cm depths, respectively) 3179 and 1428 mg/kg in TN soils, 1975 and 587 mg/kg in MO
soils and 2435 and 805 in NTN soils, being significantly higher in TN soils than NTN
and MO soils (P < 0.002 Figure 1-4d). Extractable K was significantly higher in NTN
soils and TN soils when compared to MO soils (P < 0.015, Figure 1-4e), averaging 94.36
and 62.54 mg/kg in TN soils, 57 and 28.39 mg/kg in MO soils, and 91.82 and 55.24
mg/kg in NTN soils (at 10 and 50 cm, respectively).
All of the soil properties tested, with the exception of pH and total P, were
significantly higher at 10 cm than at 50 cm depth (Table 1-3). Organic matter content,
extractable P and extractable Ca were significantly higher in TN than MO and NTN at 50
cm depth (P < 0.015, P < 0.001, and P < 0.0001 respectively, Figure 1-4b, c, and d).
Overall, the transitional MO soils had lower nutrient concentrations than NTN soils.
Area, Shape, and Location of Anthropogenic Soil Patches
In contrast with the majority of anthropogenic soil areas in the Amazon Basin
(Sombroek 1966, Smith 1980, Heckenberger et al. 1999, Woods et al. 2000, McCann et
al. 2001), the anthropogenic soils of La Chonta are located in an area lacking big rivers or
wetlands. In fact, researchers and logging crews currently working in the area are faced
with the hardship of bringing barrels of water long distances to their camps. The closest
rivers, Rio Negro and Rio Blanco, are 14-30 km from the TN areas I mapped (Figure 1-1)
and the water flow in La Chonta streams has ceased completely during the latter portions
of the dry seasons (between May and October). Ancient village sites in the Brazilian
Amazon described to date are mostly associated with large rivers (Roosevelt 1989, Smith
1980, McCann et al. 2001). However, a large terrapreta site (200 ha) relatively far away
from rivers (15 kilometers from the Amazon River floodplain) was reported in
Comunidade Terra Preta, at km 55 of the Juriti-Tabatinga road in Para, Brazil (Smith
1999, p. 25). Further detailed analyses of the archaeology, pollen, and phytoliths in La
Chonta are needed to determine if the water regime was the same when the area was last
inhabited, and how the former inhabitants managed to provide themselves enough water
to survive, given that I found no evidence of prehistoric wells or dams.
The processes of settlement, abandonment, and reoccupation of the large patches of
TN may help explain the great differences in patch size. Apparently the larger patches (5-
10 ha) were occupied more than once (S. Palma, unpublished data), which makes the size
of the patches an inaccurate indicator of village size, as suggested by Meggers (1995) for
TN areas in the Brazilian Amazon. Alternatively, the larger patches could represent old
agricultural plots in which forms of indigenous agriculture not currently used may have
been practiced. Denevan (1992c), for example, suggests that management of house
gardens and permanent plots of mixed annuals and perennials were common indigenous
pre-Columbian agricultural practices. Nevertheless, more archaeological research is
needed to determine precisely the land-use practices carried in the large areas of TN and
The two C-14 dates for charcoal that was mixed with pottery at 10 and 20 cm depth
suggest tierra negra site 3 was inhabited between 300 and 400 years B.P, but do not
indicate the prior duration of settlement. However, charcoal and pottery were present at
deeper in the soil (to 75 cm) in other TN sites, consequently, a series of soil charcoal C-
14 dates along several soil excavation units replicated in different archaeological sites in
the area will be necessary to establish more precisely the sequence of human occupation
of La Chonta.
In this study, charcoal was found at greater depths than those Glaser et al. (2000)
reported in Brazil (30-40 cm depth). However, charcoal, presumably from wild fires, is
commonly reported to one meter depth in neotropical forests soils (Saldarriaga et al.
1988, Horn 1992). The presence of charcoal and pottery sherds buried deep in the soil
could also result from bioturbation, a process that is particularly strong in the tropics. In
addition, repeated periods of afforestation and deforestation result in the burial of
charcoal and pottery (Glaser et al. 2000).
Finally, terra mulata in Brazil have been described as large areas in which terra
preta were embedded (Sombroek et al. 2002), but in La Chonta, MO areas appear to be
smaller and only as a ring surrounding the TN areas. Further detailed mapping of MO
areas in La Chonta are necessary to compare them with terra mulata, which is apparently
the same sort of soil in Brazil.
Perhaps the main difference between the tierra negra of La Chonta and terrapreta
soils reported in other parts of the Amazon Basin is the type of soils from which the soils
are derived. All La Chonta soils have neutral pH contrasting with the typically acidic
Amazonian soils (oxisols and ultisols). Therefore, even though reported pH values in
Brazilian anthrosols (averaging 4.8-5.5; Smith 1980, Glaser et al. 2000, Sombroek et al.
2002) are higher than their surrounding oxisols, ultisols or inceptisols (< 4.8), they are
much more acidic than the TN of La Chonta. The pH of TN of La Chonta was not
significantly different from the NTN, which was also reported by Eden et al. (1984) for
much more acidic terrapreta and their surrounding inceptisols in Caqueta, Colombia (pH
4.3-4.8 for terrapreta and 4.0-4.5 for inceptisols).
In La Chonta, soil organic matter (SOM) was significantly higher in TN soils than
NTN soils, corresponding with the results of several other researchers working in the
Brazilian Amazon (Smith 1980, Glaser et al. 2000, Sombroek et al. 2002). However, in
La Chonta SOM did not differ between MO and NTN, contrasting with Brazilian terra
mulata, which has higher SOM content, sometimes even higher that terrapreta (Woods
and McCann 1999, McCann et al. 2001, Sombroek et al. 2002).
Although total P is considered a good indicators of former human occupations (Eidt
1977), total P did not differ between TN, MO, and NTN in La Chonta. However,
McGrath et al. (2001) had similar results, reporting no differences among Amazonian
soils under different land-use practices (primary forest, secondary forest, and pasture;
with values of total P ranging between 180 41 to 231 + 26 mg/kg).
In contrast with the results for total P, extractable P differed among the three soil
types, being higher in TN than NTN and MO of La Chonta. The amounts of extractable P
in TN (49.6 and 35.92 mg/kg at 10 cm and 50 cm respectively) were not as high as
reported for terrapreta in Brazil (358.1 and 619.2 mg/kg at 30 cm, Heckenberger et al.
1999; 175 mg/kg at 20 cm, Smith 1980; and 600 mg/kg, Woods and McCann 1999).
While P is limiting in most tropical soils, occurring typically at less than 6 mg/kg
(Kellman and Tackaberry 1997, McGrath et al. 2001, Fardeau and Zapata 2002), its
presence at higher concentrations in TN, particularly deeper in the soil, positively
influences soil fertility in TN. Not surprisingly, in present-day Brazil terrapreta soils are
valued as agricultural sites for both indigenous people and mestizos, and are sold in urban
areas for spreading on yards to promote plant growth (Smith 1980).
Terra mulata has been reported as having slightly higher extractable P content than
the surrounding non-anthropogenic soils in Brazil (McCann et al. 2001, Sombroek et al.
2002 ), but in La Chonta, MO soils had the same (at 50 cm) and less (at 10 cm)
extractable P than NTN soils. One possible explanation for the relative lack of nutrients
(particularly P and Ca) in MO soils may be that former inhabitants of La Chonta removed
plant material and therefore nutrients from MO areas. Plant material may have been
removed from the MO areas and incorporated into TN soils as green manure or through
infield burning of vegetation. Certainly, the removal of plant material can locally
diminish nutrients. However more studies in MO soils in La Chonta are necessary to test
The high levels of Ca in the TN soils of La Chonta, coincide with those found by
Heckenberger et al. (1999) (from 2626 to 3212 ppm at 20-50 cm depth) near the Negro
and Xingu rivers in the Brazilian Amazon, and can be explained by additions of bones,
shells, and the influence of ash deposition (Smith 1980, McCann et al. 2001). However,
although significantly lower than in TN, extractable Ca was still very high for MO and
NTN in La Chonta. These results can be explained by the nature of the parent material, in
addition to the anthropogenic influences that might have affected MO and NTN areas,
and require further study.
Implications of Anthropogenic Influences on La Chonta Forest
The large extent of anthropogenic soils in La Chonta should be taken into account
by forest managers and researchers. The presence and extent of anthropogenic soils
demonstrates that, in the past, the landscape of the region was dramatically different from
what is found today and that the present forest developed in the wake of earlier human
activities. This study, while not conclusive, shows that human settlements in La Chonta
were quite large and of considerable duration. These settlements altered soil chemistry
and their effects persist today.
Higher nutrient content deep in the anthropogenic soils of La Chonta are expected
to strongly influence plant communities. The higher levels of extractable P in TN sites
when compared with surrounding soils at 50 cm might be particularly influential. This
difference is likely to be influencing present day plant species composition and growth.
In the future, careful studies of the larger TN areas, including comprehensive
identification of concentrations of archaeological material, will be necessary to
understand the ecological history of La Chonta at the landscape level. The present study
concentrated on history and soil chemistry, which, integrated with additional
archaeological studies, could contribute to a historical reconstruction of the area and a
better understanding of current human-influenced landscapes.
In La Chonta, loggers should avoid disturbing archaeological sites until additional
investigations are carried out. In addition, researchers should replicate experiments in
areas with TN and NTN soils to understand the interactions between land-use history and
the variables under examination. Interactions between TN soils and plant communities
are still poorly understood and, considering the length of time needed for the formation of
anthropogenic soils (1 cm/10 years, Smith 1980), silvicultural and research treatments
that disturb TN soils should be minimized.
Table 1-1. Distribution of tierra negra (TN) sites in a 216 ha sample area
Site Area Geographic coordinates (UTM,
Tierra negra 1 2.4 ha N 8266140 E 526015
Tierra negra 2 0.3 ha N 8265393 E 525920
Tierra negra 3 1 ha N 8265166 E 525950
Tierra negra 4 0.5 ha N 8264084 E 521534
Tierra negra 5 10 ha Not registered
Tierra negra 6 10 ha N 8267455 E 521670
Tierra negra 7 5 ha N 8270277 E 520462
Tierra negra 8 1 ha N 8269390 E 520130
Tierra negra 9 Undetermined N 8263147 E524504
Table 1-2. Mean values ( one SE) of tierra negra, tierra morena, and non-tierrra negra soil properties at two depths (0-10 and 40-
50 cm) with sites as replicates. Total P was measured colorimetrically after sulfuric acid digestion. Extractable P was
measured colorimetrically, and Ca, Mg and K were measured and using atomic absorption (AA) after a Mehlich double-
Soil property Tierra negra
pH (in water)
% Organic matter
Total P (pg/g)
Extractable P (mg/kg)
Extractable K (mg/kg)
Extractable Ca (mg/kg)
Extractable Mg (mg/kg)
7.3 + 0.10
5.7 + 0.40
10.77 + 0.55
203.17 + 33.78
49.65 + 16.36
94.36 + 8.17
3179.75 + 288.50
2.6 + 0.20
12.00 + 0.64
322.15 + 41.33
35.92 + 17.69
62.54 + 7.92
1428.95 + 115.24
35.53 + 3.75
(n = 3)
4.8 + 0.80
170.62 + 29.68
6.66 + 1.44
57.00 + 9.64
1975.96 + 328.71
6.3 + 0.30
2.1 + 0.30
11.85 + 0.07
165.63 + 53.74
2.84 + 0.82
28.39 + 6.42
40.77 + 7.17
Non- tierra negra
(n = 6)
7.3 + 0.30
155.31 + 22.31
26.04 + 9.82
2434.71 + 333.62
60.12 + 3.69
7.0 + 0.20
2.1 + 0.20
12.07 + 0.32
357.84 + 88.12
4.34 + 1.07
55.24 + 8.86
31.62 + 5.77
Table 1-3. Statistical contrast of the three soil types at two depths
pH (in water)
% Organic matter
Total P (ug/g)
Extractable P (mg/kg)
Extractable K (mg/kg)
Extractable Ca (mg/kg)
Extractable Mg (mg/kg)
Soils (tierra negra, tierra morena,
and non-tierra negra)
df F P-value
2 6.03 0.006
2 3.60 0.039
2 0.21 0.812
2 1.55 0.230
2 5.81 0.007
2 4.83 0.015
2 7.71 0.002
Depth (0-10 cm and 40-50 cm)
Soils x Depth
N La Chonta
Scale 1: 7.000,000
Figure 1-1. Location of the study site in lowland Bolivia
S1 2 ha
i 3-5 ha
La Chonta sawmill
| Research blocks
WGS 84 Zone 20S
Figure 1-2. Location and size of the TN sites in La Chonta
Figure 1-3. Spatial distribution of tierra negra (TN) in relation to tierra morena (MO)
and non-tierra negra (NTN)
I 40- 50 cm
soil type P < 0 006
A Soil type
NTN MO TN
C Soil type
soil type P < 00022
depth P < 0 0001
B Soil type
soil type P < 0 002
depth P <0 001
Figure 1-4. Mean values (+ 1 SE) for tierra negra (TN, N = 10), tierra morena (MO, N -
3,), and non-tierra negra (NTN, N = 6) at two different depths. A) pH. B)
Organic matter content. C) Extractable phosphorous. D) Extractable calcium.
E) extractable potassium. Different letters indicate overall significant
differences among means of the three soil types.
DISTRIBUTION OF USEFUL TREE SPECIES IN RELATION TO HISTORICAL
HUMAN INFLUENCES ON THE FOREST OF A TIMBER CONCESSION IN
Enrichment of native plant communities with species used by humans (hereafter
useful species) near settlements likely occurred prior to as well as after the advent of
agriculture, when hunters and gatherers selected and favored certain plant species both
purposefully by planting or inadvertently by consuming fruits and disposing of seeds in
or near their settlements (Smith 1995, Peters 2000). Tropical fruits were harvested by
humans and their seeds transported at least as long ago as 10,500 years B.P. (Roosevelt et
al. 1996). These activities may have altered the distribution and enlarged the populations
of selected plant species (Lentz 2000a) and are part of the process that transforms plants
from wild to domesticated (Clement 1999). The alteration of forests and landscapes was
even more dramatic after development of intensive agricultural systems, such as maize
cultivation, which developed in the tropical lowlands of the Americas 6,000 7,000 years
B.P. (Bush et al. 1989, Pearsall 1992, Piperno and Pearsall 1998).
Historical and archaeological records of pre-contact agriculture are scarce because
of the severe depopulation and rapid reforestation that took place soon after European
colonization of the Americas (Denevan 1992b, Block 1994). Using colonial documents
and ethnographies of modern indigenous people to extrapolate pre-historic land-use
practices can be inaccurate due to the effects of acculturation coupled with rapid
environmental and demographic changes (Denevan 1992a, Lentz 2000b). During the last
several decades, archaeological, ecological, paleobotanical, and geographical research
carried out in the lowland tropics have revealed pre-Columbian agriculture of scales and
intensities previously not considered (Denevan 1966, 1998, Roosevelt 2000). This study
examines the influence of past land-use by native human populations on forest
composition in the La Chonta timber concession in lowland Bolivia.
In modern times, as in the past, people increase the concentration of semi-
domesticated and domesticated plants near their settlements by transplanting, planting,
tending, and, in general, managing landscapes in favor of useful species (Posey 1985,
Balee 1994, Dalle et al. 2002, Smith 2002). Moreover, a positive relationship between
biodiversity and management of useful plants has been reported in certain tropical areas
(Salick et al. 1999).
Accompanying the management of useful species, soils of ancient indigenous
villages and their agricultural lands in tropical lowlands were dramatically changed
through the addition of plant and animal refuse, charcoal and ash, and mulching, which
resulted in darkened anthropogenic soils (referred as to terrapreta in Brazil and tierra
negra in Bolivia, black soil, and dark earth, Chapter 1). Anthropogenic soils persist for
centuries after abandonment, acting as indicators of former villages (Smith 1980, Eden et
al.1984, Denevan 1998, Heckenberger et al. 1999). Anthropogenic dark soils usually
have higher organic matter and nutrient content than the surrounding soils even several
centuries after abandonment (see Chapter 1).
The influence of historical land-uses on modern vegetation has been studied in
several temperate forests (e.g., Peterken and Game 1984, Foster 1988, 1992, Zbigniew
and Loster 1997, Motzkin et al. 1999) but there are few such studies in tropical forests
(e.g., Foster et al. 1998, Dalle et al. 2002). Detecting changes in the distribution of
species managed by humans in the past is particularly challenging in tropical regions
because the vegetation and species are not well known, there is high diversity, dating tree
age is difficult (but see Chambers et al. 1998, Martinez-Ramos and Alvarez-Buylla
1998), and many plant distributions are substantially influenced by stochastic forces
(Hubbell and Foster 1986). Furthermore, animals other than humans disperse the seeds of
the plants humans find useful (Andresen 1999, Galetti et al. 2001, Quiroga-Castro and
Roldan 2001, Zuidema and Boot 2002). Nevertheless, soils and land-use history have
been shown to play important roles in the distribution of tropical forests trees (Moran
1993, Clark et al. 1995, Clark et al. 1999, Lentz 2000b).
As in other Bolivian forests, many of the most important timber tree species are
poorly represented among the smaller trees and regenerate poorly in the forest after
logging in La Chonta (Mostacedo and Fredericksen 1999). In contrast, these same
species seem to regenerate well in heavily disturbed areas such as along logging roads
and in large logging gaps, especially where surface soils have been disturbed by
harvesting equipment (Fredericksen and Mostacedo 2000, Fredericksen and Pariona
2002) or following large-scale natural disturbances (Gould et al. 2002). Past land-use
practices by indigenous people in La Chonta including large-scale clearing and frequent
burning (Chapter 1) may also have provided suitable habitats for colonization and
recruitment by these poorly regenerating species. Several of these species may also have
been cultivated in the past by indigenous people in the Amazon region such as Bactris
gasipaes (Clement 1986, Mora-Urpi et al. 1997) and Spondias mombin (Smith et al.
1992, Smith 1995). Did individuals of these useful species or their parents regenerate in
abandoned clearings and/or are they relicts of former indigenous cultivation? By
investigating the relationship between these species and anthropogenic soils we can start
to answer these questions.
In this study I compared the concentration of useful tree species in areas with
anthropogenic and non-anthropogenic soils. I predicted that domesticated and semi-
domesticated plant species are more abundant in areas with tierra negra than in the
surrounding forest. I studied an array of purportedly domesticated and useful wild species
including long-lived canopy tree species with dense wood (e.g., Pouteria spp.), pioneer
species (e.g., Pourouma cecropiaefolia), and palms (e.g., Attaleaphalerata).
The study was carried out in La Chonta, a lowland tropical forest located in the
Guarayos Province, Department of Santa Cruz, Bolivia (15047'S, 62055'W). The annual
mean precipitation is ca. 1,500 mm with a severe dry season between May to October and
the mean annual temperature of 24.3 C.
The vegetation of La Chonta is classified as subtropical humid forest (Holdridge
1971); common tree species include Pseudolmedia laevis, Ocotea guianensis, Clarisia
racemosa, Terminalia oblonga, and Hura crepitans (Pizarro-Romero 2001, Fredericksen
and Pariona 2002). Lianas are remarkably abundant in the forest (Alvira et al. 2003). The
area has a history of human-induced disturbances indicated by the presence of extensive
areas of anthropogenic soils (Chapter 1) but the sites examined have apparently not been
inhabited for at least 300 years. Uncontrolled selective logging for mahogany (Swietenia
macrophylla) and tropical cedar (Cedrela odorata) was carried out until 1996 when
management plans were written and followed and current extraction of 18 species has
occurred in the area since the 1970s.
La Chonta was formerly inhabited by Guarayo Indians (see Chapter 1), and is
characterized by three different soils that they helped create: Tierra negra (TN) dark
anthropogenic soils present in patches of 0.3->10 ha, surrounded by tierra morena (MO)
a transitional anthropogenic soil that occurs adjacent to TN; and a matrix of non-
anthropogenic soils (NTN), tentatively classified as inceptisols. The TN areas are likely
former village sites or agricultural fields but the MO area's past land-use is unclear. The
chemical properties differ between these soils; TN soils have higher organic matter
content, extractable phosphorous (P), and extractable calcium (Ca), than NTN soils and
higher pH and extractable P than MO soils. MO and NTN soils had similar organic
matter and Ca content, and MO had significantly less extractable K than TN and NTN
soils (see Chapter 1).
Based on a preliminary floristic inventory of the area coupled with literature search,
seventeen tree species reportedly used by humans were selected for study (Table 2-1).
These species are described as semi-domesticated or domesticated (mostly for their fruits
or seeds) by tropical South American indigenous groups (Clement 1986, Smith et al.
1992, Balee 1994, Henderson 1995, Clement 1999) or are presently used by indigenous
peoples in lowland Bolivia (Centuri6n and Krajlevic 1996, Vasquez and Coimbra 1996,
DeWalt et al. 1999, Mostacedo and Uslar 1999, Paz et al. 2001). Information about uses
and regeneration status was gathered for each species based on field observations,
interviews with local foresters, and available literature (Table 2-1). Geographical
distributions are based on the Missouri and New York Botanical Garden databases
(Solomon 2002, New York Botanical Garden 2003). Maximum stem diameters and
growth rates are derived from unpublished BOLFOR databases (Table 2-2). Maximum
age was calculated by dividing maximum DBH by the mean annual growth increment
(MAI). The criteria for classifying species as domesticated or semi-domesticated were
from Clement (1999) who defines them as follows:
Domesticated species are those whose ecological adaptability has been reduced to a
point that they can only survive in human-created environments, and if human
interventions ceases, the population dies out in short order. Semi-domesticated
species are those significantly modified by human selection and intervention, but
that retain enough ecological adaptability to survive in the wild without human
Because edible plants are often dispersed to and planted in or near dwellings, ten of
the seventeen useful plant species belong to this category. Camps, trails, and settlements
were enriched with fruit and nut trees; a process that still takes place in Amazonian
backyards and homegardens (Balee 1994, Smith 1995, Lamont et al. 1999). Five species
are palms that are used in many ways and found in many present-day indigenous villages
and abandoned village sites (Brticher 1989, Clark et al. 1995, Henderson 1995, Moraes-
Ramirez 1996, Morcote-Rios and Bemal 2001). Most of the studied palm species
regenerate at least sparsely in the forest, with the exception ofBactris gasipaes, which
has not been observed as seedlings in La Chonta (T.S. Fredericksen 2002, pers. comm.)
and is cultivated through tropical Latin America (Killeen et al. 1993, Postma and Verheij
1994, Clement 1999, Morcote-Rios and Bemal 2001).
The total abundance of each selected species was recorded in 50 x 20 m plots in
each soil type (TN, MO, and NTN) studied in Chapter 1. Plots were established in 14
NTN sites, 10 MO sites, and 14 TN sites. The area of each of the soil type site varies
between 0.3 ha and >10 ha for TN sites, surrounded by MO sites of approximately 0.5 -
1 ha, all embedded in a matrix of NTN soils (Chapter 1). The number of plots per site
(TN, MO, or NTN site) varied from one to five according the size of the site and the
condition of vegetation (whether or not the area had been logged). One to three plots
were established in 0.1-0.5 ha sites and five plots were established in sites >0.5 ha.
The mean abundance of useful species in each site was calculated by averaging
sample plot abundance data scaled up to 1 ha. To test whether species densities differed
among soil types, Kruskal-Wallis tests were performed, using a probability of
significance of 0.05 with a sequential Bonferroni correction for the error probability
The tree species I studied all occurred at low densities, but total abundance among
the species also varied considerably. Bactris gasipaes (chonta de castilla, peach palm),
Astrocaryum aculeatum (chonta de anillo), Ceibapentandra (hoja de yuca), Pourouma
cecropiaefolia (uvilla) and Eugenia sp. (arrayan) were all very scarce, with overall mean
abundances between 0.02 to 0.09 individuals/ha. Talisia sculenta (pit6n), Spondias
mombin (ocorocillo, yellow mombim), Batocarpus amazonicus (murure), Syagrus
sancona (sumuque), Attaleaphalerata (motacu), Inga spp. (pacay), Myrcia sp. (sawinto),
Sapindus saponaria (isotouvo), and Astrocaryum murumuru (chonta) were more common
with overall mean abundances between 0.2 to 0.9 individuals/ha. Pouteria nemorosa
(coquino), Pouteria macrophylla (lucma) and Ampelocera ruizii blanquilloo) were the
most abundant species, with 1.1-3.5 individuals/ha (Table 2-2).
The species vary in geographical distributions and growth characteristics.
Pourouma cecropiaefolia is a geographically widespread, fast-growing tree, typical of
pioneer species. Spondias mombin, Inga spp., Ceiba pentandra, and Ampelocera ruizii
are widespread canopy trees with intermediate growth rates. Their sizes vary between 73
to 200 cm DBH and their maximum ages are estimated between 180 to 227 years.
Finally, Eugenia sp., Talisia sculenta, Batocarpus amazonicus, Myrcia sp., Sapindus
saponaria, Pouteria nemorosa, and Pouteria macrophylla are relatively slow-growing
trees with widespread geographical distribution, except Pouteria nemorosa which is
found only in Bolivia and Ecuador. Their sizes range between 51 and 150 cm DBH and
their estimated maximum ages (249-468) are negatively correlated with their growth rates
(Table 2-2). The distribution of the palms ranges from extremely widespread (Bactris
gasipaes) to widespread (Astrocaryum murumuru, Astrocaryum aculeatum, found
throughout the Amazon) to restricted (Syagrus sancona, Attaleaphalerata, found in
southwestern Amazon) (Table 2-2).
Contrary to my expectations, the densities of the seventeen species studied did not
differ significantly among the three soil types (Figure 2-1) but they were trends that
might indicate soil preferences or historical effects. Six species (Inga spp., Spondias
mombin, Astrocaryum aculeatum, Bactris gasipaes, Ceiba pentandra, and Pouteria
nemorosa) appear to be most abundant in MO areas, and Pouteria macrophylla, appears
to be more abundant in NTN soils when compared to MO and TN soils, but the
differences were not statistically significant due to high variances
When analyzing the differences between anthropogenic (TN and MO pooled
together) and non-anthropogenic soils (NTN), the only species showing significant
differences was Pouteria macrophylla, which was more abundant in NTN soils than in
anthropogenic soils (MO and TN soils together, Mann-Whitney U = 254, P = 0.009,
df= 1, Figure 2-1 O). Although not statistically significant probably due to small sample
sizes, two species, Astrocaryum aculeatum and Ceibapentandra, were only recorded in
TN and MO soils and were not present in NTN soils (Figure 2-1 B and 2-1 G).
Contrary to my expectations, the results showed few differences in the abundances
of the 17 useful tree species studied between anthropogenic (TN and MO) and non-
anthropogenic soils (NTN) in La Chonta, contradicting the original hypothesis (a
concentration of useful species in anthropogenic soils). This unexpected result may be
due to a misunderstanding of past land-use practices, but contemporary disturbances
cannot be disregarded. It seems most likely that past inhabitants of La Chonta altered the
forest beyond the TN areas, influencing both MO and NTN areas. This would be the case
if TN areas were villages and surrounding areas (MO and NTN areas) were managed
forest or agricultural plots. Alternatively, a former concentration of useful tree species in
TN and MO areas may have been masked by modern disturbances, natural dispersal and
The overall low densities and high variability in the distributions of the species
studied are consistent with other studies that report canopy species in tropical forests as
rare, with densities of tress > 10 cm DBH of < 1 individual/ha of (Hubbell 1979, Hubbell
and Foster 1986, Clark and Clark 1992). Nevertheless, the six species that appear to be
more abundant on MO soils than TN and NTN soils may have been concentrated there if
the TN areas were indeed village sites that were mostly devoid of vegetation, and the MO
sites were the surrounding agricultural plots.
Four of the six species that appear to be more abundant in MO areas (Spondias
mombin, Astrocaryum aculeatum, Bactris gasipaes, and Ceiba pentandra) are present at
overall low densities (0.21, 0.04, 0.02, and 0.05 trees/ha respectively), are widely
distributed long-lived species, and regenerate poorly in La Chonta (Table 2-1, Table 2-2).
In addition, they are all known to be cultivated near human settlements elsewhere in the
tropics (particularly Bactris gasipaes, Brucher 1989, Smith et al. 1992, and Clement
1999). It is possible, therefore, were planted by the people who lived in La Chonta 300-
400 years ago, but further studies at a bigger scale will be necessary to test this
While palms are influenced by several disturbance regimes (Anderson et al. 1991,
McPherson and Williams 1998) they are commonly associated with human settlements
(Clement 1999, Morcote-Rios and Bernal 2001). There are several reasons to expect that
the B. gasipaes population of La Chonta is a relict of ancient cultivation. Despite
maximum age estimations of 50-100 years for each mature stem (Brucher 1989, Smith et
al. 1992, Mora-Urpi et al. 1997), the clone from which new stems emerge could be
centuries old, perhaps planted by former inhabitants. In addition, it is the only species I
studied that is considered fully domesticated (Clement 1999) and does not regenerate
naturally in La Chonta. However, several authors (Clement 1986, 1999, Mora-Urpi et al.
1997) recognize that there are different varieties of Bactris gasipaes, comprising a
continuum between domesticated and semi-domesticated varieties. In La Chonta, further
studies of seed/fruit ratios will determine where Bactris falls in this continuum. Similar to
Bactris, the small population of the semi-domesticated palm, Astrocaryum aculeatum
(Clements 1999), may also be a relict from earlier plantings given that it is generally
associated with human settlements (Wessels Boer 1965) and regenerates poorly in La
Chonta (Table 2-1). The fact that Bactris gasipaes and Astrocaryum aculeatum are not
significantly concentrated in the anthropogenic soils suggests in the past their
management was not restricted to TN and MO sites.
Existing short-lived species (less than 100 years old) could not have been planted
by former inhabitants of La Chonta because the area was abandoned more than 300 years
ago. For example, the maximum age of Inga spp. in La Chonta is estimated to be 117
years, while in Brazil Laurence (unpublished data) estimated the age of three species of
Inga to be between 50 to 160 years. While several species oflnga are considered semi-
domesticated, in particular Inga edulis, (Clements 1999), they are also dispersed by
monkeys (Andresen 1999) and regenerate well in La Chonta (Table 2-1). Consequently,
the apparent concentration oflnga spp. on MO soils (Figure 2-1 H) may be the product of a
secondary ecological adaptation rather than the result of enrichment by past inhabitants of
The species with abundant regeneration, overall high densities, and no apparent
pattern of concentration according to soil type, such as Ampelocera ruizii and Sapindus
saponaria, may be wild species that are used by people, but past uses apparently have not
altered their present distribution in La Chonta. Ampelocera ruizii is not reported as
domesticated or semi-domesticated in the literature and has a fairly narrow distribution,
growing only in Brazil and the Bolivian lowlands (Table 2-1). In contrast, Sapindus
saponaria is extremely widespread, and is reported to be used by several indigenous
groups (Bruchner 1989). If the range Sapindus saponaria was expanded by humans, its
regeneration status and distribution (Table 2-1) suggest that it has become wild in La
The lack of apparent differences in the abundances of most of the species I studied
on the different soil types may be explained by numerous interacting factors that are
know to determine forest composition (topography, physiography, land use history, etc.)
as well as stochastic forces (Hubbell and Foster 1986). Certainly, edaphic and historic
factors alone are not enough to explain forest composition in La Chonta, but their
interactions with several other factors might do so. Clark et al. (1999) for example,
determined that the distributions of only 30% of the species they studied in a lowland
forest in Costa Rica were correlated with edaphic conditions, and concluded that only
mesoscale vegetation and soil sampling will estimate the true degree of edaphically
influenced distributions. A larger scale study in La Chonta and its surroundings,
integrating other environmental variables to the analysis may allow us to do the same.
One of the main factors influencing the results of this study might be the extended
period post-abandonment forest dynamics in the area. The two C-14 dates of charcoal
buried among pottery sherds in tierra negra site 3 (Chapter 1) suggest that the site was
probably inhabited most recently 380 and 430 years BP. This extended time since
abandonment might be sufficient to mask the effects of humans' enrichment with useful
species in the anthropogenic soil areas. In this time period, two or three generations of the
short-lived trees can have developed and biotic and abiotic seed dispersal processes may
have extended the species' distribution range beyond the TN patches, if they were indeed
initially concentrated there. In addition, disturbances such as fires and tree falls may
have played a role in the distribution of useful species.
It is also possible that TN areas were maintained as permanently cleared areas in
villages as they are and were in Amazonian Brazil (Heckenberger et al. 1999). If village
sites were maintained clear of vegetation with a large central plaza and compacted soils
(Heckenberger et al. 1999, Woods et al. 2000), it is likely that the perimeter of these areas
(MO and NTN areas) represent the agricultural zone that was enriched with useful
species. If this is true in La Chonta, the soils surrounding TN sites are those more
affected by past agricultural practices and are areas where useful species would have
been managed or cultivated. Consequently, NTN areas adjacent to TN areas might not
constitute a good control for testing the influence of past land-use practices on species
composition. A better control area would be a similar forest without a history of human
disturbances, which will be difficult to find.
The results of this study suggest that short-lived species with good regeneration and
no pattern of concentration in anthropogenic soils, while perhaps used by former
inhabitants, are now wild species that do not reflect the influence of past human use. In
contrast, large individuals of long-lived species with poor regeneration may in fact be
remnants of former cultivation. The lack of significant concentrations of useful species
in TN and MO soils suggests that species may have been cultivated or managed in
adjacent NTN areas and that plant communities on all sites were influenced by human
Table 2-1. Characteristics of tree species that are used by humans and selected for study in La Chonta.
Ocorocillo Multiuse (edible fruit,
roots and medicinal
Chonta de Multi-use (edible
anillo fruits and seeds, oil,
Chonta Multi-use (edible
fruits and seeds, oil,
Motaci Multi-use (edible
fruits and seeds,
Chonta de Multi-use (edible
castilla fruit, medicine, bows,
and seeds used to
Hoja de Multi-use (religious,
yuca fiber, oil from seeds);
Pacay Edible fruit; Inga
Mexico to Bolivia.
Subcanopy Amazonia, from
Colombia to Bolivia
Colombia to Bolivia
South and West
Brazil and Bolivia.
Central America to
Amazon and Eastern
Colombia to Bolivia.
Genus is widespread Good
in tropics and
Table 2-1, Continued
Moraceae Batocarpus amazonicus Mururd Multi-use (edible Canopy Panama to Bolivia Poor
fruit, dye, latex)
Moraceae Pourouma cecropiaefolia Uvilla Edible fruit, Canopy, Costa Rica to Bolivia. Good
medicinal; cultivated, pioneer
Myrtaceae Eugenia sp. Arrayan Edible fruit Subcanopy Pantropical Good
Myrtaceae Myrcia sp. Sawinto Edible fruit Canopy Amazonia, Bolivia Poor
Sapindaceae Sapindus saponaria Isotouvo Soap from fruit, Subcanopy Arizona to Bolivia Good
Sapindaceae Talisia sculenta Pit6n Edible fruit; Subcanopy Amazonia, from Poor
cultivated. Colombia to Bolivia.
Sapotaceae Pouteria macrophylla* Lucma Edible fruit Canopy Bolivia, Brazil and Good
Sapotaceae Pouteria nemorosa Coquino Edible fruit Canopy Disjunct, only in Good
Ecuador and Bolivia
Ulmaceae Ampelocera ruizii Blanquillo Edible fruit Canopy Bolivia, Brazil and Good
"Good = seedlings, saplings (<1.50 m), juveniles (>1.50 m) and adults present in the forest; Medium = juveniles and adults present, regeneration
scarce; Poor = only adults present, regeneration scarce. This classification is valid only for La Chonta.
* = Semi-domesticated; ** = Domesticated, according to (Clement 1999).
Table 2-2. Maximum diameters, mean growth rates for trees > 10 cm DBH, and mean annual diameter increment (MAI, based on 3
years of data) of the selected tree species in La Chonta, based on unpublished data from permanent sample plots of
BOLFOR Project. Estimated maximum age was calculated by dividing maximum DBH by MAI.
Overall mean abundance / ha
( one SE)
0.21 (+ 0.04)
0.91 (+ 0.12)
0.04 (+ 0.03)
0.41 (+ 0.07)
0.02 (+ 0.01)
0.37 (+ 0.07)
0.05 (+ 0.02)
0.49 (+ 0.12)
0.33 (+ 0.08)
0.06 (+ 0.03)
0.09 (+ 0.03)
0.60 (+ 0.21)
0.83 (+ 0.13)
0.17 (+ 0.05)
1.49 (+ 0.24
1.12 (+ 0.15)
3.51 (+ 0.38)
NTN MO TN
NTN MO TN
Soil type D
NTN MO TN
Figure 2-1. Comparisons of the relative abundances (+ 1 SE) of the selected useful tree
species among the three different soil types: non-tierra negra (NTN, N = 14),
tierra morena (MO, N = 10), and tierra negra (TN, N = 14).
NTN MO TN
NTN MO TN NTN
Figure 2-1. Continued
NTN MO TN
u --------- ^~ ~ ^
Q Soil type
Figure 2-1. Continued
NTN MO IN
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Clea Lucrecia Paz Rivera was born in La Paz, Bolivia. As a child, she lived in Peru,
Mexico, and Colombia, while her mother, a sociologist, was in political exile. While
living in these countries she developed a love and curiosity for the natural and cultural
diversity of Latin America.
As an undergraduate she studied biological sciences at the Universidad Mayor de
San Andres in La Paz. Her undergraduate thesis focused on the effects of cattle grazing
on floristic diversity in the savannas of Beni, Bolivia. She graduated with her
Licenciatura in 1998. She the worked as an associate researcher at the Herbario Nacional
de Bolivia, conducting floristic inventories in secondary forests in the Chapare region.
She also collaborated in the initial phase of the Catalog of Vascular Plants of Bolivia. In
2000, the Herbarium nominated her for a LASPAU/Fulbright fellowship. The fellowship
was granted and she began her graduate work in the University of Florida's
Interdisciplinary Ecology Program in Spring 2001, hosted by the Department of Botany.
Upon completing her master's degree, Clea will return to her country with her
husband and son. She intends to resume work at the Herbario Nacional de Bolivia and
explore dissertation topics.