The literature on tropical secondary forests, defined as those resulting from human disturbance (e.g. logged forests and forest fallows), is reviewed to address questions related to their extent, rates of formation, ecological characteristics, values and uses to humans, and potential for management. Secondary forests are extensive in the tropics, accounting for about 40% of the total forest area and their rates of formation are about 9 million ha yr−1. Geographical differences in the extent, rates of formation and types of forest being converted exist.

Secondary forests appear to accumulate woody plant species at a relatively rapid rate but the mechanisms involved are complex and no clear pattern emerged. Compared to mature forests, the structure of secondary forest vegetation is simple, although age, climate and soil type are modifying factors. Biomass accumulates rapidly in secondary forests, up to 100 t ha−1 during the first 15 yr or so, but history of disturbance may modify this trend. Like biomass, high rates of litter production are established relatively quickly, up to 12–13 t ha−1 yr−1 by age 12–15 yr. And, in younger secondary forests (< 20 yr), litter production is a higher fraction of the net primary productivity than stemwood biomass production. More organic matter is pro duced and transferred to the soil in younger secondary forests than is stored in above-ground vegetation. The impact of this on soil organic matter is significant and explains why the recovery of organic matter in the soil under secondary forests is relatively fast (50 yr or so). Nutrients are accumulated rapidly in secondary vegetation, and are returned quickly by litterfall and decomposition for uptake by roots.

We propose a model of the gains and losses, yields and costs, and benefits and tradeoffs to people from the current land-use changes occurring in the tropics. When the conversion of forest lands to secondary forests and agriculture is too fast or land-use stages are skipped, society loses goods and services. To avoid such a loss, we advocate management of tropical forest lands within a landscape perspective, a possibility in the tropics because land tenures and development projects are often large.

Patterns of edge-related environmental changes and plant water relations were investigated in the isolated forest reserves of the INPA-WWF Minimum Critical Size of Eco-systems project near Manaus, Brazil early in the wet season.

Air temperature was elevated and humidity reduced in the understorey within 40 m of the reserve margins, and air temperature and vapour pressure deficit (VPD) were higher in the interiors of 1 ha reserves than in 100 ha reserves. There was increased photosynthetically active radiation penetration to understorey level up to 40 m into a 100 ha reserve.

Soil moisture was depleted in the outer 20 m of both small and large reserves, and surface soil water potentials fell below – 1.5 MPa at the margin of a 1 ha reserve.

Studies of leaf relative water contents (RWCs) in understorey shrubs revealed no appreciable saturation deficits, though RWCs were sometimes lower at the reserve margins. Studies of leaf conductances revealed no evidence of restriction of water loss in these plants, and conductances of plants near the edges were significantly higher and higher for longer.

The implications of these results for reserve design and for local and regional water budgets, as well as the possible role of water stress in increased tree mortality in isolated reserves are discussed.

Padrōes de mudanças ambientais e hídricos de plantas relacionados a bordas de matas isoladas foram investigadas no início da estação seca nas reservas de floresta do Projeto Dinâmica Biológica de Fragmentos Florestais do INPA-WWF, proximo de Manaus, Brasil.

No sub-bosque, até 40 m da borda da mata, a temperatura ambiental estava elevada e a umidade reduzida, e a temperatura do ar e o DPV estavam maiores nas reservas de 1 ha do que nas reservas de 100 ha. A penetração de radiaçao fotosintéticamente ativa no sub-bosque estava aumentada até 40 m da borda em reservas de 100 ha.

A umidade do solo baixou consideravelmente nos 20 m periféricos de reservas grandes a pequenas, e o potencial hídrico na superficie do solo baixou para menos de −1.5 MPa na margem de uma reserva de 1 ha.

Estudos do teor relativo de água (TRA) em folhas de arbustos de sub-bosque nӑo revelaram deficits de saturação apreciaveis apesar de que TRAs foram menores nas bordas das reservas. Estudos da conductancia foliar não revelaram evidência de restrições de perdas hídricas nessas plantas, e as conductancias de plantas próximas a bordas foram significativamente maiores durante um período mais longo.

As impliçõtes desses resultados para o planejamento de reservas e para o balanço hídrico local e regional, assim como as possiveis funçoes de ‘stress’ hídrico na alta mortalidade de árvores em reservas isoladas são discutidas.

Inventory data on tree weights of 104 individual trees representing 10 mangrove species were collected from mangrove forests in South-East Asia to establish common allometric equations for the trunk, leaf, above-ground and root weight. We used the measurable tree dimensions, such as dbh (trunk diameter at breast height), DR0.3 (trunk diameter at 30 cm above the highest prop root of Rhizophora species), DB (trunk diameter at lowest living branch), and H (tree height) for the independent variable of equations. Among the mangrove species studied, the trunk shape was statistically identical regardless of site and species. However, ρ (wood density of tree trunk) differed significantly among the species. A common allometric equation for trunk weight was derived, when dbh2H or DR0.32H was selected as the independent variable and wood density was taken into account. The common allometric equations for the leaf and the above-ground weight were also derived according to Shinozaki's pipe model and its extended theory. The common allometric relationships for these weights were attained with given ρ of each species, when DB2 or dbh2 or DR0.32 was selected as the independent variable. For the root weight, the common equation was derived from the allometric relationship between root weight and above-ground weight, since these two partial weights significantly correlated with each other. Based on these physical and biological parameters, we have proposed four common allometric equations for estimating the mangrove tree weight of trunk, leaf, above-ground part and root.

Amazonian forests are being rapidly cleared, and the remaining forest fragments appear unusually vulnerable to fire. This occurs because forest remnants have dry, fire-prone edges, are juxtaposed with frequently burned pastures, and are often degraded by selective logging, which increases forest desiccation and fuel loading. Here we demonstrate that in eastern Amazonia, fires are operating as a large-scale edge effect in the sense that most fires originate outside fragments and penetrate considerable distances into forest interiors. Multi-temporal analyses of satellite imagery from two frontier areas reveal that fire frequency over 12-14-y periods was substantially elevated within at least 2400 m of forest margins. Application of these data with a mathematical core-area model suggests that even large forest remnants (up to several hundred thousand ha in area) could be vulnerable to edge-related fires. The synergistic interactions of forest fragmentation, logging and human-ignited fires pose critical threats to Amazonian forests, particularly in more seasonal areas of the basin.

We investigated the influence of a four-year-old forest edge near Manaus, Brazil, on soil moisture and vertical profiles of air vapour pressure deficit (VPD) within the forest. Soil moisture was measured (with a neutron probe) 0, 5, 10, 20, 40, 60, 80, 100, 150 and 200 m into the forest from the edge, in undisturbed control areas, and in the pasture. Control soil moisture was better explained by rainfall in the previous 2 or 10 days than by longer-term totals. Soil water potentials ≤ – 1.5 MPa occurred at some forest locations during the driest period. The variation in soil moisture with distance from the forest edge was complex, with higher values just inside the edge and depleted zones at the edge and 40–80 m inside it. At a given height, VPD (standardized relative to measurements in the open) was not related to distance from the edge, but VPD increased more with height near the edge than in control areas. The complexity of the edge's influence and the contrast with earlier data from the same edge can be explained by the changing vegetation structure near the edge. Regrowth ‘seals’ the edge with more leaves that transpire and deplete soil moisture, while protecting the understorey just inside the edge from desiccating conditions. A mosaic of gaps of differing ages develops behind the edge, increasing the variation in microclimatic conditions near the ground and consequently in evapotranspiration and soil moisture.

The abundance of all tree and shrub species has been monitored for eight years in a 50 ha census plot in tropical moist forest in central Panama. Here we examine population trends of the 219 most numerous species in the plot, assessing the impact of a long-term drying trend. Population change was calculated as the mean rate of increase (or decrease) over eight years, considering either all stems ≥10 mm diameter at breast height (dbh) or just stems ≥100 mm dbh. For stems ≥10 mm, 40% of the species had mean growth rates <1% per year (either increasing or decreasing) and 12% had changes ≥5% per year. For stems ≥100 mm, the figures were 38% and 8%.

Species that specialize on the slopes of the plot, a moist microhabitat relative to the plateau, suffered significantly more declines in abundance than species that did not prefer slopes (stems ≥10 mm dbh). This pattern was due entirely to species of small stature: 91% of treelets and shrubs that were slope-specialists declined in abundance, but just 19% of non-slope treelets and shrubs declined. Among larger trees, slope and non-slope species fared equally. For stems ≥100 mm dbh, the slope effect vanished because there were few shrubs and treelets with stems ≥100 mm dbh. Another edaphic guild of species, those occurring preferentially in a small swamp in the centre of the plot, were no more likely to decline in abundance than non-swamp species, regardless of growth form. Species that preferentially colonize canopy gaps in the plot were slightly more likely to decrease in abundance than non-colonizing species (only for stems ≥10 mm dbh, not ≥100 mm). Despite this overall trend, however, several colonizing species had the most rapidly increasing populations in the plot.

The impact of a 25-year drying trend and an associated increase in the severity of the 4-month dry season is having an obvious impact on the BCI forest. At least 16 species of shrubs and treelets with affinities for moist microhabitats are headed for extinction in the plot. Presumably, these species invaded the forest during a wetter period prior to 1966. A severe drought of 1983 that caused unusually high tree mortality contributed to this trend, and may also have been responsible for sharp increases in abundance of a few gap-colonizers because it temporarily opened the forest canopy. The BCI forest is remarkably sensitive to a subtle climatic shift, yet we do not know whether this is typical for tropical forests because no other large-scale censuses exist for comparison.

The abundance and diversity of lianas were examined along a tropical forest chronosequence at the Barro Colorado Nature Monument, Panama. Lianas ≥0.5 cm diameter were sampled along transects in two replicated stands in secondary (20, 40, 70 and 100 y after abandonment) and old-growth (>500 y) forests. Ordination of stands based on relative abundance, but not presence-absence, showed a significant separation of stands by age. Lianas were significantly more abundant and diverse (Fisher's α) in younger forests (20 and 40 y) than in older forests (70 and 100 y, and old-growth). The decline in liana abundance with stand age was offset by increased mean basal area per individual, resulting in a relatively constant total basal area and estimated biomass across stand age. The proportions of tendril climbers decreased and stem twiners increased over stand age. Decline in liana abundance and changes in liana composition may be related to changes in support and light availability. Although lianas are recognized as playing an important role in the early secondary sucession of many tropical forests, these results have shown that their important contribution to total basal area and biomass can continue as the forest matures, even as the numbers of established lianas declines.

Many organisms create or alter resource flows that affect the composition and spatial arrangement of current and future organismal diversity. The phenomenon called ecosystem engineering is considered with a case study of the mound building termite Macrotermes michaelseni. It is argued that this species acts as an ecosystem engineer across a range of spatial scales, from alteration of local infiltration rates to the creation of landscape mosaics, and that its impacts accrue because of the initiation of biophysical processes that often include feedback mechanisms. These changes to resource flows are likely to persist for long periods and constrain the biological structure of the habitat. The value of ecosystem engineering is discussed as a holistic way of understanding the complexity of tropical ecology.

To study the impact of the annual long-term flooding (flood-pulse) on seasonal tree development in Amazonian floodplains, the phenology and growth in stem diameter of various tree species with different leaf-change patterns were observed over a period of 2 y. The trees of the functional ecotypes, evergreen, brevi-deciduous, deciduous and stem-succulent showed a periodic behaviour mainly triggered by the flood-pulse. Trees have high increment during the terrestrial phase. Flooding causes a shedding of some or all leaves leading to a cambial dormancy of about 2 mo and the formation of an annual ring. Studies carried out in tropical dry forests verify a strong relationship between the phenological development and the water status of the trees, strongly affected by seasonal drought. The comparison of the phenology and the diameter growth of the corresponding ecotypes in floodplain forest and a semi-deciduous forest in Venezuela shows a displacement of at least 2 mo in the periodicity, except for stem-succulent tree species. For stem-succulent trees it remains unclear which factors influence phenology and stem diameter growth.

A large number of newly published and unpublished hectare plots in Amazonia and the Guiana Shield area allow an analysis of family composition and testing of hypotheses concerning alpha-diversity in the south American rain forest. Using data from 94 plots the family-level floristic patterns in wet tropical South America are described. To test diversity patterns, 268 plots are used in this large area. Contrary to a widely held belief, western Amazonian plots are not necessarily the most diverse. Several central Amazonian plots have equal or even higher tree diversity. Annual rainfall is not a good estimator for tree diversity in the Amazonia area and Guiana shield. Plots in the Guiana Shield area (and eastern Amazonia) usually have lower diversity than those in central or western Amazonia. It is argued that this is not because of low rainfall or low nutrient status of the soil but because of the small area of the relatively isolated rain forest area in eastern Amazonia and the Guiana Shield. The low diversity on nutrient-poor white sand soils in the Amazon basin is not necessarily due to their low nutrient status but is, at least partly, caused by their small extent and fragmented nature.

Published work on the dynamics of forest tree recruitment, growth and mortality in natural tropical forest is reviewed. In most forests studied, annual mortality is between 1% and 2% and is independent of size class in trees >10 cm dbh; mortality is negatively correlated with growth rate and crown illumination; growth rate is highly variable between individual trees, but shows strong autocorrelation between successive measurements on the same tree.

Differences in the rate of dynamic processes can be detected between some species at a site, but data are presently insufficient to determine whether these differences are preserved at other sites where the species occur. None of the studies discussed are of sufficient duration to permit us to draw any conclusions about the equilibrium or non-equilibrium of floristic composition.

Within the last decade the study of phenology has taken on new importance because of its contribution to climate-change research. However, phenology data sets spanning many years are rare in the tropics, making it difficult to evaluate possible responses of tropical communities to climate change. Here we use two data sets (1970–1983 and 1990–2002) to describe the fruiting patterns of the tropical tree community in Kibale National Park, Uganda. To address variation in spatial patterns, we describe fruiting over 2–3 y among four sites each separated by 12–15 km. Presently, the Kibale region is receiving c. 300 mm more rain than it did at the start of the century, droughts are less frequent, the onset of the rainy season is earlier, and the average maximum monthly temperature is 3.5 °C hotter than it was 25 y ago. The 1990–2002 phenology data illustrated high temporal variability in the proportion of the populations fruiting. Interannual variation in community-wide fruit availability was also high; however, the proportion of trees that fruited has increased over the past 12+y. At the species level a variety of patterns were exhibited; however, a number of the most common species currently rarely fruit, and when they do, typically <4% of the individuals take part in fruiting events. Combining the data set from 1990 to 2002 with that from 1970 to 1983 for specific species again reveals an increase in the proportion of trees fruiting between 1990 and 2002; however, the proportion of the populations fruiting decreased during the earlier period. When one examines particular species over this whole period a variety of patterns are evident. For example, Pouteria altissima exhibited a relatively regular pattern of fruiting during the 1970s; however, it rarely fruited in the 1990s. Contrasting phenological patterns at four sites revealed that at the community level the fruiting patterns of only one of the six pair-wise site combinations were correlated. Relationships between rainfall and fruiting were variable among sites. Contrasting changes in fruiting patterns over the 30 y with differences among the four sites varying in rainfall, suggests that the changes observed in fruiting may be due to climate change. Responses to this climate change are likely complex and will vary among species. However, for some species, current conditions appear unsuitable for fruiting.

Conversion to permanent agriculture is rapidly occurring over vast areas of the 1.8 million km2; Brazilian Cerrado; a region that is naturally a mosaic of grasslands, savannas and evergreen tropical woodlands. Yet, few studies have quantified total biomass of plant communities in this ecosystem, particularly the belowground component; a C pool of potential global significance. Total biomass (aboveground and belowground), and the quantity of biomass consumed by fires were measured in four plant communities comprising a vegetation gradient from pure grassland (campo limpo) to a woodland with a closed canopy of tall shrubs and scattered trees (cerrado denso) near Brasilia, DF, Brazil. Total aboveground biomass (TAGB) increased along this gradient from 5.5 Mg ha-1 in campo limpo to 29.4 Mg ha-1 in cerrado denso. Vegetation structure varied among communities; trees were nonexistent in campo limpo, but were at a density of 1000 ha-1 and a biomass of 12.9 Mg ha-1 in cerrado denso. Fires consumed 92 and 84% of the TAGB in campo limpo (pure grassland) and campo sujo (savanna), respectively. In cerrado aberto and cerrado denso, trees and tall shrubs were little affected by fire. Combustion factors of the TAGB in these communities was 54 and 33%, respectively. The total biomass consumed by fire ranged from 5.0 Mg ha-1 in campo limpo to 13.5 Mg ha-1 in cerrado aberto. Compared to other widespread Brazilian ecosystems (tropical dry forest and evergreen forest), the Cerrado has a lower aboveground biomass. The TAGB of cerrado denso is > 9% of that of Amazonian tropical evergreen forest. The total quantity of biomass consumed by fire, and hence emissions to the atmosphere is lower in intact Cerrado communities compared to fires in slashed tropical forest.

Biomass content and turnover rate were estimated for a lowland wet rain forest in French Guiana. A regression model relating the biomass of a tree to its dbh (diameter at breast height) was deduced from previously published data. A power-law allometric relationship of the form AGTB = aDb was used to estimate the tree biomass, AGTB (Mg ha−1), from its dbh D (cm). Using direct measurements of tree biomass in the literature, the best-fit allometric exponent b = 2.42 (SD = 0.02) was found. The logarithm of the coefficient a was normally distributed with an average of −2.00 (SD = 0.27). This method was applied to two permanent research stations of the lowland tropical rain forest of French Guiana: the Nouragues and Piste de Saint-Elie. At the Nouragues, the biomass was estimated from trees 10 cm in diameter on two plots covering a total surface area of 22 ha and yielded an average biomass of 309 Mg ha−1 (± 32 Mg ha−1, 95% confidence interval). Spatial variability was also addressed at the Nouragues by estimating the biomass of trees ≥ 30 cm dbh over a total surface area of 82 ha. For the wet tropical forest vegetation type, an average of 284 Mg ha−1 was obtained (spatial variability ±55 Mg ha−1). Biomass turnover was evaluated at Piste de Saint-Elie from two transects (0.78 and 1 ha) on which all trees ≥5 cm in diameter were recorded and mapped twice in 10 y. Transect 1 showed a slight increase in biomass, from 245 to 260 Mg ha−1 (338 to 345 Mg ha−1 for transect 2), corresponding to a net increase of 1.9 Mg ha−1 y−1 (0.7 Mg ha−1 y−1), and the biomass ingrowth was 3.2 Mg ha−1 y−1 (2.8 Mg ha−1 y−1). These figures are discussed in the light of the natural recruitment dynamics of tropical forests.

Tropical forest demography and dynamics were examined in three inventory plots across a precipitation gradient in central Panama. The harsh dry season of 1998 that accompanied the 1997–98 El Niño was spanned by censuses at all three sites. The wet and intermediate plots were similar in total species richness, the dry site somewhat lower in diversity; all three sites differed substantially from each other in species composition. Forest-wide growth of large trees was higher at the wet and intermediate sites than at the dry site, but sapling growth was highest at the dry site and lowest at the intermediate site. Forest-wide growth differences were reflected by individual species, for example, saplings of species at the dry site grew faster than saplings of the same species at the intermediate site. Forest-wide mortality was lowest at the dry site and highest at the wet, and this difference was also reflected by individual species. We suggest that low mortality and growth in the drier forest was due to the longer annual dry season and higher deciduousness, and that high sapling growth at the dry site was due to greater light penetration to the forest floor. Growth rates were elevated at all three sites during 1998, possibly due to reduced cloud-cover during the El Niño. Contrary to expectation, mortality during 1998 was not elevated at wet and intermediate sites during the El Niño drought, but was at the dry site. Finally, we found that some species performed poorly at one site and declined in abundance, while having stable or increasing populations at another site, demonstrating that the communities are not at equilibrium.

The impact of the unusually severe drought associated with the 1997–1998 El Niño on tropical forest dynamics in Sarawak, Malaysia was examined. Mortality during the non-drought period (1993–1997) in a core plot (1.38 ha) was 0.89 % y−1, while that during the drought period (1997–1998) in the same plot and a peripheral plot was 6.37 and 4.35 % y−1, respectively. The basal area lost in the drought interval was 3.4 times that of the annual incremental basal area in 1993–1997. Drought mortality was higher for the smaller trees, though it was less size dependent than the non-drought mortality. Dipterocarpaceae, which is the dominant family in the study plot, had a mortality 12–30 times higher in the drought than the non-drought period. There were no significant differences in mortality among the topographic types. From the results of a log-linear model (multi-factored contingency table), the death of trees was correlated with size class, indicating a change in the size-class structure of the forest. Thus, both the species composition and structure are totally affected by such an episodic drought even in a per-humid tropical forest.

The Asian elephant's foraging strategy in its natural habitat and in cultivation was studied in southern India during 1981–83. Though elephants consumed at least 112 plant species in the study area, about 85% of their diet consisted of only 25 species from the order Malvales and the families Leguminosae, Palmae, Cyperaceae and Gramineae. Alteration between a predominantly browse diet during the dry season with a grass diet during the early wet season was related to the seasonally changing protein content of grasses.

Crop raiding, which was sporadic during the dry season, gradually increased with more area being cultivated with the onset of rains. Raiding frequency reached a peak during October-December, with some villages being raided almost every night, when finger millet (Eleusine coracana) was cultivated by most farmers. The monthly frequency of raiding was related to the seasonal movement of elephant herds and to the size of the enclave. Of their total annual food requirement, adult bull elephants derived an estimated 9.3% and family herds 1.7% in quantity from cultivated land. Cultivated cereal and millet crops provided significantly more protein, calcium and sodium than the wild grasses. Ultimately, crop raiding can be thought of as an extension of the elephant's optimal foraging strategy.

Diameter growth rates and age-size relationships are reported for 45 abundant tree species and one liana in tropical wet forest at La Selva, Costa Rica. Thirteen-year increments in each species were analysed using growth simulation, a stochastic technique which projects growth trajectories.

Median growth rates ranged from 0.35 mm yr-1 (Anaxagorea crassipetala) to 13.41 mm yr-1) (Stryphnodendron excelsum). Maximum ranges ranged from 0.95 mm yr-1 (Quararibea brac-teolosa) to 14.62 mm yr-1 (Hernandia didymanthera). Minimum rates ranged from zero growth (Capparis pittieri, Colubrina spinosa, Doliocarpus spp.) to 7.45 mm yr-1 (Stryphno dendron excelsum).

Projected lifespan (from 100 mm dbh to the maximum dbh for the species) varied from 52 years (Anaxagorea crassipetala, Guatteria inuncta) to 442 years (Carapa guianensis). The mean longevity among the 45 tree species studied is 190 years.

Four main patterns of growth behaviour are recognized, based upon longevity and growth rates: (1) understorey species have slow maximum growth rates and short lifespans; (2) shade-tolerant subcanopy trees live around twice as long as understorey trees and grow at approxi-mately the same maximum rates; (3) canopy and subcanopy trees that are shade-tolerant but respond opportunistically to increased light levels have long lifespans and fast maximum growth rates; (4) shade-intolerant canopy and subcanopy species are short-lived and have fast maximum growth rates. Understorey species intergrade with shade-tolerant subcanopy species in terms of growth behaviour; shade-tolerant subcanopy species with opportunistic, shade-tolerant species; and opportunistic, shade-tolerant with shade-intolerant species.

Intraspecific variation in growth rates is lower in short-lived trees (understorey species with uniformly slow growth and shade-intolerant species with uniformly rapid growth) than in the two long-lived groups. These patterns are discussed in the context of tree ecophysiology and forest light environments.

Vegetation and environment change mutually during secondary succession, yet the idiosyncrasies of the vegetation effect on the understorey environment are poorly understood. To test whether the successional understorey environment changes predictably and is shaped by the structure and seasonality of tropical dry forests, we estimated basal area and vegetation cover, and measured understorey temperature, light and moisture conditions, in 17 plots forming a 60-y chronosequence and a mature forest. Light and air and soil temperature decreased with time (75−15% of open-sky radiation, 31.7−29.3 °C, and +2.5 °C to −0.5 °C relative to ambient, respectively), whereas relative humidity increased (67−74%). Soil water availability increased with early-successional development (−45 to −1 kPa) but decreased afterwards (to −18 kPa). The first axis of a PCA of the rainy-season environment explained 60% of the variation and was strongly related to air temperature and relative humidity. During tropical dry-forest succession, such factors may be more important than light, the reduction in which is not extreme compared with taller and more vertically stratified wet forests. Seasonality significantly affected the successional environmental gradients, which were marked mainly during the wet season. Environmental heterogeneity was higher in the wet than in the dry season, and larger for resources (light and water) than for conditions (temperature and humidity). The wet-season increase in environmental heterogeneity potentially creates differential growing scenarios; the environmental harshness of the dry season would mostly challenge seedling survival.

Stand structure, species richness and population structures of tree species were characterized in 12 stands representing 50 y of succession following slash-and-burn agriculture in a tropical dry forest in lowland Bolivia. Estimates of tree species richness, canopy cover and basal area reached or surpassed 75% of mature forest levels in the 5-, 8-, and 23-y-old stands respectively. Total stem density of the 50-y-old stand was almost twice that of the mature forest stand. This rapid recovery may be due to a high percentage of sprouting tree species, potentially high seed fall into abandoned fields, or the disturbance history of the mature stand. The even-aged size-class structures, dominance of long-lived pioneers, and presence of charcoal and pottery shards in soils of the mature forest stand suggest it formed after a severe disturbance, possibly fire of anthropogenic origin.