Land-use changes and forest management decisions can profoundly alter soil organic carbon (SOC) stocks. Therefore, the objective of this study was to investigate whether existing SOC stocks in the forests of Singapore can be related to successional stages of forest vegetation following disturbances. A forest classification system was developed using information about land use history and vegetation data from 21 inventory plots collected within the framework of Singapore’s IPCC-compatible greenhouse gas reporting system. The forest successional classes obtained were related to SOC stocks (0–50 cm) determined on the same plots. The inventory plots were assigned to four classes. Primary forests (Class 1) were dominated by late succession native species. Secondary forests representing natural forest succession (Class 2) contained younger native trees and a few large trees. Secondary forests after tree plantation/fruit orchard (Class 3) and after agricultural crop cultivation (Class 4) were characterised by large proportions of exotic tree species. Maximum stocks of SOC declined from Class 1 (127.7 Mg ha−1) to Class 4 (35.2 Mg ha−1). The results of a principal component analysis confirmed our forest classification. Plant-related parameters can be successfully used to classify the forests in Singapore, which also show clear differences in SOC.

In 2000, we established a 24-ha plot in Peninsular Thailand to investigate how forest composition, structure and dynamics vary with spatial heterogeneity in resource availability. Detailed soil and topographic surveys were used to describe four edaphic habitats in the plot. Disturbance history was inferred from historical records and floristic analysis. The plot included >119 000 trees ≥1 cm dbh in 578 species, and was recensused in 2010. Species distributions, floristic turnover, stand structure, demographic rates and biomass dynamics were strongly influenced by heterogeneity in soils, topography and disturbance history. Over 75% of species were aggregated on specific edaphic habitats leading to strong compositional turnover across the plot. Soil chemistry more strongly affected species turnover than topography. Forest with high biomass and slow dynamics occurred on well-drained, low fertility ridges. The distribution and size structure of pioneer species reflected habitat-specific differences in disturbance history. Overall, above-ground biomass (AGB) increased by 0.64 Mg ha−1 y−1, from 385 to 392 Mg ha−1, an increase that was entirely attributable to recovery after natural disturbance. Forest composition and stand structure, by reflecting local disturbance history, provide insights into the likely drivers of AGB change in forests. Predicting future changes in tropical forests requires improved understanding of how soils and disturbance regulate forest dynamics.

Drivers of forest structure in central African rain forests are largely unknown. Using forest inventory data (3024 0.4-ha plots) in a forest concession of 154 456 ha in north-eastern Gabon covering an altitudinal gradient (from 485 to 1009 m asl), relationships between above-ground plot biomass and environmental variables (soil type, altitude, slope, aspect) and floristic composition (score given by an ordination method) were tested. After controlling for confounding variables, biomass was significantly related to altitude (with a modal response peaking at 346 Mg ha–1 on western slopes at an altitude of 707 m asl) and to aspect (additional 18.3 Mg ha–1 on eastern slopes) but not to floristic composition. Biomass and basal area responded differentially to the environment. Mean wood density was significantly related to soil, altitude and floristic composition, with a predicted minimum of 0.60 g cm–3 at an altitude of 1009 m asl in stands characterized by Scorodophloeus zenkeri and a maximum of 0.69 g cm–3 at an altitude of 458 m asl in monodominant Gilbertiodendron dewevrei stands. Variation in forest structure in the concession was primarily driven by altitude while floristic composition played a role in differentiating the variation in biomass and basal area.

Plant communities and ecosystem processes in seres at multiple altitudes in the tropical montane forest zone of northern Borneo were studied to understand the patterns and mechanisms of the secondary succession after shifting cultivation. A total of 25 stands (and additional three stands) were sampled with stand ages ranging from 2 to 55 y after slash and burn at altitudes between 900 and 1400 m asl. Plant species composition, above-ground biomass (AGB), chemical properties of soils, litter and foliar samples were investigated in each stand. A TWINSPAN analysis classified five plant communities primarily as a sere but with two altitudinal communities in the later successional phase. AGB accumulated steadily at the rate of 2.42 Mg ha−1 y−1 during the succession for the first 55 y due to the ontogenetic development of plants as well as plant community shifts. At the onset of secondary succession, pool of soil NO3-N and soil total P was high probably because burning caused flushes of minerals originating from the burnt plant materials. Pool of soil NO3-N and soil total P decreased with increasing stand age during the succession. Leaf-litter N:P ratios of dominant species significantly increased with increasing stand age suggesting disproportionately greater P deficiency than N deficiency in the later successional phase. It is suggested that tree species shifted to those of greater P-use efficiency during succession in response to decreasing soil P availability. We conclude that the interaction of altitude with the reduction of soil N and P availability was related to the altitudinal split of plant communities in the later phase, while pioneer communities were wide-ranging across altitudes reflecting richer soil nutrients.

Fires can significantly affect the structure, floristic composition and biomass content of tropical forests, which are not adapted to this disturbance. To assess the impact of understorey fires on above-ground biomass, this study was conducted in the northern Brazilian Amazon (Roraima state), where uncontrolled forest fires are recurrent. Fifty plots (0.25 ha each) distributed across five fire disturbance classes were inventoried. Losses in biomass stocks were significant (−57% and −63%) for forests that suffered from recurrent fires and progressively occurred until some point between 3 and 7 y after the last fire, as deduced from previous studies. Twelve years after a fire event, biomass stocks were reconstituted, although differences in the floristic composition were associated with greater fire severity, particularly driven by the dominance of the Cecropia spp. In thrice-burned forests, live biomass reached levels of secondary forests of the same region. For large trees (> 50 cm dbh), the reduction (−54%) in biomass was significant in thrice-burned areas. These findings highlight the threat that fires represent for tropical rain forests and emphasise the need for long-term surveys in order to distinguish between the effects of fire severity, fire frequency and time-since-fire artefact.

The dynamics of tropical forest woody plants was studied at the Nouragues Field Station, central French Guiana. Stem density, basal area, above-ground biomass and above-ground net primary productivity, including the contribution of litterfall, were estimated from two large permanent census plots of 12 and 10 ha, established on contrasting soil types, and censused twice, first in 1992–1994, then again in 2000–2002. Mean stem density was 512 stems ha−1 and basal area, 30 m2 ha−1. Stem mortality rate ranged between 1.51% and 2.06% y−1. In both plots, stem density decreased over the study period. Using a correlation between wood density and wood hardness directly measured by a Pilodyn wood tester, we found that the mean wood density was 0.63 g cm−3, 12% smaller than the mean of wood density estimated from the literature values for the species occurring in our plot. Above-ground biomass ranged from 356 to 398 Mg ha−1 (oven-dry mass), and it increased over the census period. Leaf biomass was 6.47 Mg ha−1. Our total estimate of aboveground net primary productivity was 8.81 MgC ha−1 y−1 (in carbon units), not accounting for loss to herbivory, branchfalls, or biogenic volatile organic compounds, which may altogether account for an additional 1 MgC ha−1 y−1. Coarse wood productivity (stem growth plus recruitment) contributed to 4.16 MgC ha−1 y−1. Litterfall contributed to 4.65 MgC ha−1 y−1 with 3.16 MgC ha−1 y−1 due to leaves, 1.10 MgC ha−1 y−1 to twigs, and 0.39 MgC ha−1 y−1 to fruits and flowers. The increase in above-ground biomass for both trees and lianas is consistent with the hypothesis of a shift in the functioning of Amazonian rain forests driven by environmental changes, although alternative hypotheses such as a recovery from past disturbances cannot be ruled out at our site, as suggested by the observed decrease in stem density.

Flood depth has been frequently used to explain the distribution of plant species in seasonally flooded grasslands, but its relation with vegetation production has remained ambiguous. The relationship between flooding and above-ground biomass at the end of the flooding season and during the dry season was studied to assess the impact of reflooding on the Logone floodplain, Cameroon. Above-ground biomass of a combination of all species and of the individual perennial grasses Oryza longistaminata and Echinochloa pyramidalis showed a positive linear relationship with maximum flood depth up to 1 m. The gradient of these relationships became steeper and their fit better during the 2 y following the installation of the flooding, showing the response lag to floodplain rehabilitation. Flood duration only explained the above-ground biomass of the combination of all species and not of the individual species. Above-ground biomass data from other floodplains in the three main African geographic regions showed a similar relationship with maximum flood depth less than 1 m. Dry-season regrowth, important because of its high nutrient quality during forage scarcity, was not directly related to maximum flood depth, possibly because of its dependency on the period of burning and soil moisture. Presented data indicate that a rise of water level of 1 cm corresponds to an increase in above-ground biomass of c. 150 kg DM ha−1.

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.