Effect of biomass on assemblages of large mammals in a seasonally dry forest in the Brazilian Amazonia

Aiming to understand the relationship between body mass and abundance, a community of middle-sized and larger mammals was studied in a seasonally dry forest in the far north of the Brazilian Amazonia. Diurnal and nocturnal surveys were carried out by the line-transect method along a 10-km transect. Data were collected on density, biomass, use of forest types, forest strata, diet and feeding strategies by the mammals. Biomass explained animal abundance better than did body mass across the two forest types: Terra Firme forest and mixed forest. There was a statistically significant positive relationship between the biomass of all the 33 mammals studied and group density, as well as between biomass and group size, in both forests. When terrestrial and arboreal mammals, and also different feeding guilds were considered separately, they exhibited very similar results, where biomass alone was positively associated with group density and group size. The slope of the relationships between body mass and group density, body mass and group size, biomass and group density, and biomass and group size varied considerably, with significant scatter around the regression line. Food and food competition shaped the relationship between animal mass and abundance, and this relationship can even vary widely between assemblages. As a result of competition for the available resources, group density increased with increasing biomass.     

Primate Diet and Biomass in Relation to Vegetation Composition and Fruiting Phenology in a Rain Forest in Gabon

To test the hypothesis that primate populations are limited by food resources, we studied the feeding ecology of three cercopithecines and one colobine in a rain forest in central Gabon. Simultaneously, we monitored the fruiting phenology of trees and estimated the biomass of the monkey community. The Makandé Forest is dominated by Caesalpiniaceae and characterized by a lack of secondary vegetation and of trees species producing fleshy fruits. Fruit production was irregular intra- and interannually. Fruiting peaks of dry fruits (mainly Caesalpiniaceae) and of fleshy fruits occurred at the same period. However, interseasonal and interannual variability was greater in Caesalpiniaceae than in other families. As a result, the Makandé forest is subject to bottlenecks when food is scarce. On an annual basis, seeds (primarily Caesalpiniaceae) dominated the diet of all monkeys. On a seasonal basis, cercopithecines preferentially consumed fleshy fruits as long as they were available, whereas colobines increased consumption of young leaves when seed availability declined. The consumption of mature leaves was low. The monkey community biomass (ca. 204 kg/km²) is one of the lowest in Central Africa. We suggest that both cercopithecine and colobine populations are limited as a result of the combined effect of the dominance of Caesalpiniaceae, which provide dry fruits according to a mast-fruiting pattern and mature leaves of low quality, and the lack of seral successional stages, which provide fleshy fruit on a more regular pattern and leaves of better quality. During the period of food scarcity, cercopithecines should suffer from the low availability of fleshy fruit, which are their favorite food. At the same period, colobines should be limited by the low availability of edible leaves. Similar low primate biomasses are found in forests dominated by Caesalpiniaceae or Lecythidaceae in South America and in Dipterocarpaceae forests in South Asia, which suggests that their biological characteristics, in particular dry fruits and mast fruiting, are unfavorable to monkey populations. Our results confirm that habitat mosaics may support larger populations of primary consumers than homogeneous primary forests can.     

Density and population size of mammals introduced on a land-bridge island in southeastern Brazil

The introduction of alien species is one of the main threats to the conservation of native species, especially in island ecosystems. Here, we report on the population growth of 15 species of mammals introduced in 1983 on the island of Anchieta, an 828 ha land-bridge island in southeastern Brazil. We estimated the density of mammals through 296 km of line transect census. Five species introduced became extinct (coypu, brocket deer, six-banded armadillo, nine-banded armadillo, maned three-toed sloth); six became over-abundant (marmoset, coati, agouti, seven-banded armadillo, and capybara); one has a stable population (capuchin monkey). Anchieta Island has the highest density of mammals in the entire Atlantic forest (486.77 ind/km²), especially nest predators (232.83 ind/km²) and herbivores (253.58 ind/km²). Agoutis (Dasyprocta spp.) and marmosets (Callithrix penicillata) were, by far, the species with the highest population growth. The high density of mammals in this island may have strong consequences for plant recruitment and bird diversity.     

Estimating brocket deer (<Emphasis Type="Italic">Mazama gouazoubira</Emphasis> and <Emphasis Type="Italic">M. americana</Emphasis>) abundance by dung pellet counts and other indices in seasonal Chiquitano forest habitats of Santa Cruz,Bolivia

We assessed dung and track counts for indexing brocket deer abundance in seasonal habitats on a ranch where hunting is not practiced in the Bolivian lowlands. Surveys were replicated along four 10-km trails (totaling 180 km in the wet season and 90 km in the dry season) through four semideciduous forest habitats. Dung pellets and tracks were identified as belonging to Mazama gouazoubira or M. americana by size and shape. Pellet groups lasted more than 1 month during the dry season, but decayed within 1–2 weeks in the wet season. Mean density estimates based on dung counts varied widely between seasons for gray brockets (from 6.77±4.0 to 30.57±23.5 ind/km²; mean±SD) but not for reds (from 3.52±4.6 to 6.98±7.2 ind/km²). These values were probably too high due to underestimation of daily deposition rate, and were reduced during the wet season because of dung decay. We found consistently more dung in the dry season and more tracks in the wet season. Sightings of red brockets were too few for line-transect analysis (n=6), but those of gray brockets (n=42) produced an overall estimate of 5.6 ind/km² (95% CI=3.5–9.0 ind/km²). Different estimates indicated that gray brockets were more abundant than reds in all situations, except perhaps in the riverine forest. Environmental factors affected these indices of abundance differently, and while we recommend the use of dung counts in dry-season scenarios, we think that index reliability should be assessed locally before conducting population comparisons.     

Nutrient dynamics within amazonian forests

Summary Relationships between fine root growth, rates of litter decomposition and nutrient release were analysed in a mixed forest on Tierra Firme, a Tall Amazon Caatinga and a Low Bana on podsolized sands near San Carlos de Rio Negro. Fine root growth in the upper soil layers (root mat+10 cm upper soil) was considerably higher in the Tierra Firme forest (1117 g m^-2 yr^-1) than in tall Cattinga (120) and Bana (235). Fine root growth on top of the root mat was stimulated significantly by added N in Tall Caatinga and Low Bana forests, by P in Tierra Firme and Bana forests, and by Ca only in the Tierra Firme forest. Rate of fine root growth in Tierra Firme forest on fresh litter is strongly correlated with the Mg and Ca content of litter. Rate of litter decomposition was inversely related to % lignin and the lignin/N ratio of litter. Litter contact with the dense root mat of the Tierra Firme increased rates of disappearance for biomass, Ca and Mg as compared with litter permanently separated or lifted weekly from the root mat to avoid root attachment. Nitrogen concentration of decomposing litter increased in all forests, net N released being observed only in Caryocar glabrum and Aspidosperma megalocarpum of the Tierra Firme forest after one year of exposure. Results emphasize the differences in limiting nutrients in amazonian forest ecosystems on contrasting soil types: Tierra Firme forests are particularly limited by Ca and Mg, while Caatinga and Bana forests are limited mainly by N availability.     

Census,habitat preference,and polyspecific associations of six monkeys in the Lomako Forest,Zaire

This paper reports preliminary data on a number of poorly known cercopithecids inhabiting the Lomako Forest, Zaire. Data include those on density, biomass, group size, the relationship between group type (mono vs. polyspecific) and forest type (mixed primary, secondary, monodominant primary, and swamp), and vertical stratification. Species examined are Colobus angolensis, Cercocebus aterrimus, Cercopithecus wolfi, Cercopithecus ascanius, Cercopithecus neglectus, and Allenopithecus nigroviridis. The density and biomass for the Lomako Forest anthropoids (excluding Cercopithecus neglectus and A. nigroviridis) are 165 ind/km² and 1,034 kg/km², respectively. Cercopithecus wolfi and Colobus angolensis are found in group sizes similar to those reported from other sites while Cercopithecus ascanius, Cercocebus aterrimus, and A. nigroviridis display group sizes unique to the Lomako. While Colobus angolensis, Cercocebus aterrimus, Cercopithecus ascanius and Cercopithecus wolfi were found, to varying extents, in all four forest types, Cercopithecus neglectus and A. nigroviridis inhabited only swamp forest. The different species sort out along vertical continua both within and between the four forest types. © 1994 Wiley-Liss, Inc.     

Relationship between a high density of sika deer and productivity of the short-grass (<Emphasis Type="Italic">Zoysia japonica</Emphasis>) community: a case study on Kinkazan Island,northern Japan

An extremely high-density (ca. 800 deer km^–2) wild sika deer population uses a short-grass community dominated by Zoysia japonica on Kinkazan Island in northeastern Japan. To explain why the density of wild deer is quite high on the Zoysia community, (1) we quantified the seasonal productivity of the Zoysia community, (2) we compared food availabilities among the plant communities, and (3) we described the habitat selection by the deer in different seasons. Food availability was greater on the Zoysia community than in the forest understory from spring to fall. The productivity of the Zoysia community was high enough to support the actual high density of the deer (814 deer km^–2) in summer. However, the productivity markedly decreased in winter, when the deer density decreased to less than half (358 deer km^–2) of the summer value. In contrast, the deer density of the adjacent forests was highest in winter (154 deer km^–2) and lowest in spring (19 deer km^–2). These results suggest that the deer using the Zoysia community in summer left and were absorbed into the adjacent forest in winter. If such an adjacent community were absent, many deer would not survive, and consequently the deer density on the Zoysia community in summer would not be so high. This intercommunity movement is particularly important for the deer using a plant community like the Zoysia community, which is highly productive but has a small standing biomass.     

Does the tropical agricultural matrix bear potential for primate conservation? A baseline study from Western Uganda

As for most large mammals, conservation research on primates usually focuses on protected areas, and yet not much is known about primate communities in land-use systems in the absence of hunting. Using line transects, we estimated population densities for four primate species in a mixed agroforest landscape up to a distance of 4000 m from a forest reserve, in a region where no primate hunting takes place. We then modelled encounter rates and cluster size in relation to landscape parameters by means of bivariate analysis and Generalised Linear Models (GLMs). Black-and-white colobus (Colobus guereza) were most common, with confidence intervals for density estimates of 31.1–62.8 individuals/km². Red-tailed monkeys (Cercopithecus ascanius) and blue monkeys (Cercopithecus mitis) occurred at 15.2–37.9 ind/km² and 13.9–36.7 ind/km² respectively, and chimpanzees (Pan troglodytes) at 1.0–2.8 ind/km². Chimpanzee nest numbers and distribution appeared to be significantly constrained by transect forest coverage, forest coverage within 500 m and distance from the main forest, whereas monkey sightings were generally less restricted by landscape variables. The considerable population density of monkeys suggests that, in the absence of hunting, mixed agroforest systems may play a relevant role in primate conservation and highlight that it is useful to consider primate ecology in land sharing approaches to conservation.     

Hyper‐abundance of Native Wild Pigs (Sus scrofa) in a Lowland Dipterocarp Rain Forest of Peninsular Malaysia1

This study reports extraordinarily high density estimates for the wild pig (Sus scrofa) from an aseasonal tropical forest site within the species'native range. At Pasoh Forest Reserve, a 2500 ha area of lowland dipterocarp rain forest in Peninsular Malaysia, line transects were used to estimate pig density from May to October in 1996 and 1998. In 1996, 44 sightings of S. scrofa consisting of 166 individuals were recorded along 81 km of transects. In 1998, 39 sightings documented 129 individuals along 79.9 km of transects. Estimated population density was 47.0 pigs/km² in 1996 and 27.0 pigs/km²‐ in 1998. Sus scrofa biomass in this forest was estimated at 1837 kg/km² and 1346 kg/ km² in 1996 and 1998, respectively. Differences between years were attributed to changes in the density of young pigs, coincident with a mast‐seeding year of dipterocarp trees in 1996. Pig densities at Pasoh Forest Reserve were much higher than at other forest locations within the species' native range in Europe and Asia. Because Pasoh Forest Reserve is a forest fragment, two factors likely account for the extremely high pig densities: (1) local extinction of natural predators (mainly tigers and leopards) and (2) an abundant year‐round food supply of African oil palm fruits from extensive plantations bordering the reserve.     

The distribution and abundance of scyphomedusae (Scyphozoa) of the family Ulmaridae in the pelagic zone of the Sea of Okhotsk and the Sea of Japan

The distribution and abundance of jellyfish of the family Ulmaridae was studied based on the data of trawl surveys conducted in the Sea of Okhotsk (1998–2006) and the Sea of Japan (2003) in the fall. The jellyfish Aurelia aurita mainly inhabits the waters of the Sea of Japan, while in the Sea of Okhotsk small quantities of this species were recorded in southern areas, and solitary individuals, off North Sakhalin. Aurelia limbata tends to shelf waters of the Sea of Okhotsk, being less abundant in the southern deepwater area and in the Sea of Japan. Phacellophora camtschatica, in contrast, aggregates mostly over deep basins, whereas in shallow areas a significant quantity of this species was found only off West Kamchatka. In the northern Sea of Okhotsk, the species A. limbata dominated in biomass and abundance among Ulmaridae. During the studied period, its biomass varied from 27 to 803 kg/km² and its abundance varied from 69 to 1706 ind/km². In the southern Sea of Okhotsk, as a rule, P. camtschatica prevailed (1–16 kg/km² and 6–46 ind/km²). In the Sea of Japan, the most abundant species was A. aurita (29 kg/km² and 104 ind/km²). The jellyfish size structure in catches is presented.     

Animal biomass in a New Zealand forest compared with other parts of the world

Summary Data on mammalian, avian and invertebrate biomass in mixed broadleaf-podocarp forest of the Orongorongo Valley are summarised and compared with the biomass in other forests. Animal biomass totalled at least 504 kg/ha — more than twice that in several tropical forests but less than that reported from temperate deciduous forests of Europe. Earthworms (333 kg/ha) provided most animal biomass: arthropods at least 145 kg/ha, mammals (all introduced) 25 kg/ha, and birds 0.6 kg/ha. By world standards the biomass of mammals, and litter-dwelling and underground arthropods, is high and that of birds moderate. Introduced mammals have greatly altered the distribution of biomass in this forest, herbivores and predatory mammals gaining biomass at the expense of some native aboveground invertebrates and birds, several of which have been lost to this community.     

The density and biomass of large mammals in Lake Nakuru National Park

Over the past 70 years, human activity has severely limited the diversity and movements of large mammals in the region of Lake Nakuru National Park, Kenya. Game counts were begun in April 1970 to assess the status of those species remaining. The density of large mammals per km² was found to be 64.20±8.86 (mean ±S.D.) and the biomass density of the six major species in kg/km² was 6298±801. The biomass was most heavily concentrated in the grassland-woodland area south of the lake. Defassa water-buck was the dominant species accounting for 76% of the biomass density. The probable reasons for their dominance are: (1) favourable habitat; (2) decreased competition; (3) reduced predation; (4) control of poaching; and (5) non-migratory habits. Future management may ultimately depend on the relationship of waterbuck to the food resources available.     

Model estimation of energy flow in North American grassland bird communities

Summary The energy demands and general food consumption rates of bird populations breeding in North American grasslands are estimated using a simulation model which employs information on population natural history and individual metabolism gathered from several study locations. The total breeding season energy demand of the grassland/shrub-steppe avifaunas ranged from 0.89 kcal m^-2 season^-1 in arid shrub-steppe to 2.92 kcal m^-2 season^-1 in a mesic tallgrass prairie. There was substantial variation between years and between census plots, however, and in general the average avian community energy demands did not differ significantly over the range of locations. Production accounted for 0.9 to 1.5% of the total seasonal energy demand. Roughly 11 to 18% of the seasonal energy flow was required in the production of eggs and maintenance and growth of nestlings and fledglings.On the average, between 209 and 386 kg dry wt km^-2 of prey were consumed by the bird communities breeding in the grassland locations. Seeds contributed more to the total biomass consumed at the drier plots, but in general, animal prey types comprised roughly 80% of the total biomass eaten. Phytophagous insects were the major component of the animal prey.These low magnitudes of energy flow and biomass consumption attest to the relatively minor role of birds in the processing of energy and biomass in grassland ecosystems. If these populations do play an importnat role in the functioning of grassland ecosystems, it must be quite subtle and indirect.     

Habitat use,abundance, and persistence of Neotropical migrant birds in a habitat matrix in northeast Belize

ABSTRACT To ensure adequate protection of nonbreeding habitats used by Neotropical migratory landbirds, we must first address questions about habitat use and quality. On the Yucatan peninsula, migrants use many habitats, several of which remain unstudied, and methodological differences preclude interhabitat comparisons based on studies to date. We used distance sampling along line transects in six habitats in northeast Belize to examine use of previously unstudied habitats (e.g., salt marsh) by Neotropical migrants and to permit comparison across habitats. We calculated unadjusted and adjusted (for detectability) density estimates for individual migrant species and for all species combined to generate hypotheses about habitat quality based on the assumption that density and quality are positively correlated. Adjusted density estimates for all migrants were highest in black mangrove habitat (1799 ± 110 ind/km²), intermediate in three forest types and milpa (range 598–802 ind/km²), and lowest in salt marsh (207 ± 32.3 ind/km²). By combining density estimates with habitat availability in our study region, we estimated that evergreen forest and black mangrove supported 70% and 9% of the region's migrant population, respectively. At the species level, five of the 10 most common species had habitat preferences (>50% detections in one habitat). Given the diversity of habitat preferences among species and apparent seasonal movements, our results indicate that Neotropical migrants in northeast Belize are dependent on a matrix of interconnected habitats.     

Ranging Patterns of Chimpanzees in a Montane Forest of Kahuzi,Democratic Republic of Congo

I studied ranging patterns of a semihabituated unit-group of chimpanzees for 60 mo at Kahuzi. They had a total home range of 12.81 km² and a mean annual home range of 7.55 km². Considering the low density of chimpanzees in the area vis-à-vis chimpanzees in arid areas, their home range is very small. Kahuzi chimpanzees used the home range in a clumped pattern, frequently visiting the core area and only rarely entering peripheral areas. The monthly range changes with fruit availability, increasing during periods of fruit scarcity. There was no consistent seasonal difference in the size of the home range. However, use of different habitat types may vary seasonally. While there was no seasonal effect in the use of primary forest, the chimpanzees showed a statistically consistent seasonal difference in their use of secondary forest, visiting it mainly during the dry season when fig trees were in fruit. Since the primary forest provides them with more food fruits, chimpanzees tended to use more frequently the small patches of primary forest in their home range. Thus, the size and distribution of small fragmented primary forests may be an important factor influencing the ranging pattern of chimpanzees at Kahuzi.     

Drivers of truffle biomass,community composition,and richness among forest types in the northeastern US

Truffle-producing fungi (hypogeous sporocarps) are important mycorrhizal symbionts and provide a key food source for many animals, including small mammals. To better understand truffle diversity and associations in the northeastern US, we surveyed for truffles and analyzed spores in eastern chipmunk (Tamias striatus) scat across hardwood (angiosperm-dominated), softwood (gymnosperm-dominated), and mixed forest at Bartlett Experimental Forest, New Hampshire. Truffle biomass ranged from 3.8 kg/ha in hardwood forest to 31.4 kg/ha in softwood forest and was up to 35 times greater than mushroom (epigeous sporocarp) production in softwood forest. Elaphomyces species were the most common truffle taxa in both field surveys and chipmunk scat. Scat analysis indicated that truffle richness increased over the summer and accurately reflected fruiting time, providing greater resolution of richness than field surveys alone. Basal area of eastern hemlock (Tsuga canadensis) was the primary driver of Elaphomyces biomass and was the best explanatory variable of truffle community composition. We discuss implications of hemlock loss, due to the introduced hemlock woolly adelgid (Adelges tsugae), on forest mycorrhizal communities and food webs.     

Application of Protein-to-Fiber Ratios to Predict Colobine Abundance on Different Spatial Scales

The biomass of arboreal folivorous primates in Africa and Asia is related to an index of mature leaf quality: the ratio of protein-to-fiber concentration. Investigations have considered variation in folivore biomass and forest composition among sites separated by hundreds or thousands of km. However, large variation in folivore abundance has been documented over much smaller spatial scales. We quantify the degree to which the average protein-to-fiber ratio of mature leaves of the 20 most abundant tree species predicts the biomass of western red colobus (Piliocolobus trephosceles) and black-and-white colobus (Colobus guereza) over very small spatial scales. Four sites within Kibale National Park, Uganda, varied markedly in forest structure. Colobine biomass varied among sites from 191 to 2675 kg/km² and was related to the average protein-to-fiber ratio of mature leaves of the 20 most abundant tree species at each site. We examined the generality of the relationship between protein-to-fiber ratios and colobine abundance by adding our biomass and leaf chemistry values to previously published values to produce 9 comparable sites. At these locations, colobine biomass varied from 84 to 2675 kg/km² (mean biomass among sites = 910 kg/km²), and mean protein/fiber ratios varied from 0.167 to 0.577. Colobine biomass was related to the protein-to-fiber ratios of mature leaves (R ² = 0.616, P = 0.012).     

Seed bank dynamics and tree‐fall gaps in a northwestern Mexican Quercus‐Pinus forest

Questions: How does the seed bank respond to different types of tree‐fall gaps and seasonal variations? How does the soil seed bank influence recovery of the standing vegetation in the mature forest and tree‐fall gaps? Location: 1800 — 2020 m a.s.l., Quercus‐Pinus forest, Baja California Sur, Mexico. Methods: Seed size, species composition and germination were estimated under different environmental conditions during dry and rainy seasons: a mature forest plot and gaps created by dead standing trees, snapped‐of f trees and uprooted trees. The soil seed bank was investigated using direct propagule emergence under laboratory conditions, from soil cores obtained during both seasons. Results: 21 species, 20 genera and 14 families constitute the seed bank of this forest community. Fabaceae, Asteraceae, Euphorbiaceae and Lamiaceae were the most frequently represented families in the seed bank. Floristic composition and species richness varied according to the different modes of tree death. Species composition of seed banks and standing vegetation had very low similarity coefficients and were statistically different. Seed bank sizes varied between 164 and 362 ind.m^‐2 in the mature forest plot for the dry and rainy seasons, respectively, while soil seed bank sizes for gaps ranged between 23–208 ind.m^‐2 forthe dry season and between 81–282 ind.m^‐2 for the rainy season. Conclusions: Seed bank sizes and germination response were always higher in the rainy season under all the environmental conditions analysed. Results suggest that timing responses to gap formation of the soil seed bank could be more delayed in this temperate forest than expected.     

Spring distribution and ecological role of seabirds and marine mammals in the Weddell Sea,Antarctica

Summary The early spring distribution of seabirds, pinnipeds and cetaceans was quantitatively determined in the northern Weddell Sea during the EPOS 1 cruise of the icebreaking RV Polarstern. Two hundred and ninety-one half hour counts were made in the Antarctic region between October 18 and November 16, 1988 (+94 counts in sub-antarctic and sub-tropical water). The bird populations were dominated by the Adélie Penguin Pygoscelis adeliae, which represented 90% of the birds counted in the closed pack ice (CPI), with a mean density of 31 penguins per km². Crabeater seal Lobodon carcinophagus, the most common pinniped, had a mean density of 1.2/km² in the CPI with local concentrations reaching 14/km². Expressed as biomass, mean values of about 90 kg/km² were found in the whole Antarctic zone for seabirds, 50 for seals, and 35 for baleen cetaceans. Densities were higher in the CPI: 140, 180 and 115 kg/km² respectively, were found for birds, pinnipeds and baleen whales, and lowest in open water (8 kg/km² for the birds, 0.2 for the pinnipeds and no whales). A minimum value of food intake by seabirds and marine mammals was estimated to be 2.7 mg C/m²/day for the Antarctic zone (4.1 in the CPI). Taking into account that pinnipeds density and cetacean food uptake are underestimated, and that Antarctic seabirds consume much more fish than generally suspected, a minimum krill production of 16 mg C/m²/day is proposed for the Antarctic zone: 22.5 in the CPI, 3 in open water, and intermediate values in the marginal ice zones.Data presented here were collected during the European Polarstern Study (EPOS) sponsored by the European Science Foundation     

The regional variation of aboveground live biomass in old-growth Amazonian forests

The biomass of tropical forests plays an important role in the global carbon cycle, both as a dynamic reservoir of carbon, and as a source of carbon dioxide to the atmosphere in areas undergoing deforestation. However, the absolute magnitude and environmental determinants of tropical forest biomass are still poorly understood. Here, we present a new synthesis and interpolation of the basal area and aboveground live biomass of old‐growth lowland tropical forests across South America, based on data from 227 forest plots, many previously unpublished. Forest biomass was analyzed in terms of two uncorrelated factors: basal area and mean wood density. Basal area is strongly affected by local landscape factors, but is relatively invariant at regional scale in moist tropical forests, and declines significantly at the dry periphery of the forest zone. Mean wood density is inversely correlated with forest dynamics, being lower in the dynamic forests of western Amazonia and high in the slow‐growing forests of eastern Amazonia. The combination of these two factors results in biomass being highest in the moderately seasonal, slow growing forests of central Amazonia and the Guyanas (up to 350 Mg dry weight ha^?1) and declining to 200–250 Mg dry weight ha^?1 at the western, southern and eastern margins. Overall, we estimate the total aboveground live biomass of intact Amazonian rainforests (area 5.76 × 10⁶ km² in 2000) to be 93±23 Pg C, taking into account lianas and small trees. Including dead biomass and belowground biomass would increase this value by approximately 10% and 21%, respectively, but the spatial variation of these additional terms still needs to be quantified.