The limited contribution of large trees to biomass dynamics in an old-growth tropical forest (original) (raw)
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Ecological applications : a publication of the Ecological Society of America, 2018
Although the importance of large trees regarding biodiversity and carbon stock in old-growth forests is undeniable, their annual contribution to biomass production and carbon uptake remains poorly studied at the stand level. To clarify the role of large trees in biomass production, we used data of tree growth, mortality, and recruitment monitored during 20 yr in 10 4-ha plots in a species-rich tropical forest (Central African Republic). Using a random block design, three different silvicultural treatments, control, logged, and logged + thinned, were applied in the 10 plots. Annual biomass gains and losses were analyzed in relation to the relative biomass abundance of large trees and by tree size classes using a spatial bootstrap procedure. Although large trees had high individual growth rates and constituted a substantial amount of biomass, stand-level biomass production decreased with the abundance of large trees in all treatments and plots. The contribution of large trees to annua...
Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology predicts that tree abundances will scale as the )2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic predictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of predictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the predictions of metabolic ecology. In most forests, size distributions are much closer to the predictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality.
Contrasting above-ground biomass balance in a Neotropical rain forest
Journal of Vegetation Science, 2010
Question: What are the relative roles of tree growth, mortality and recruitment in variations of aboveground biomass in tropical forests? Location: Paracou, French Guiana. Methods: We quantified the contribution of growth, recruitment and mortality to total biomass of stands (trees DBH ! 10 cm) in six 6.25-ha permanent plots over 16 yr. Live biomass stocks and fluxes were computed for four separate size classes. Results: All plots showed increasing biomass stocks over the study period, with an average value of 10.9 Mg ha À 1 yr À 1. Plots aggrading biomass were characterized by either minor biomass losses due to mortality or substantial increases in the biomass of large trees (DBH ! 60 cm). Conclusions: Within the study period, the rarity of mortality events could not counterbalance the slow permanent increase in biomass, resulting in an apparent increase in biomass. Accounting for such rare events results in no net change in biomass balance.
Above���ground forest biomass is not consistently related to wood density in tropical forests
2009
Aim It is increasingly accepted that the mean wood density of trees within a forest is tightly coupled to above-ground forest biomass. It is unknown, however, if a positive relationship between forest biomass and mean community wood density is a general phenomenon across forests. Understanding spatial variation in biomass as a function of wood density both within and among forests is important for predicting changes in stored carbon in response to global change, and here we evaluated the generality of a positive biomass-wood density relationship within and among six tropical forests.
Abiotic and biotic drivers of biomass change in a Neotropical forest
Journal of Ecology, 2017
This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
Carbon Balance and Management
Background Long-term studies of community and population dynamics indicate that abrupt disturbances often catalyse changes in vegetation and carbon stocks. These disturbances include the opening of clearings, rainfall seasonality, and drought, as well as fire and direct human disturbance. Such events may be super-imposed on longer-term trends in disturbance, such as those associated with climate change (heating, drying), as well as resources. Intact neotropical forests have recently experienced increased drought frequency and fire occurrence, on top of pervasive increases in atmospheric CO2 concentrations, but we lack long-term records of responses to such changes especially in the critical transitional areas at the interface of forest and savanna biomes. Here, we present results from 20 years monitoring a valley forest (moist tropical forest outlier) in central Brazil. The forest has experienced multiple drought events and includes plots which have and which have not experienced fi...
A comparative analysis of biomass production in five tropical tree species
Forest Ecology and Management, 1990
Lugo, A.E., Wang, D. and Bormann, F.H., 1990. Comparative analysis of biomass production in five tropical tree species. For. Ecol. Manage., Trees of Casuarina equisetifolia, Albizia procera, Eucalyptus robusta, and two varieties of Leucaena leucocephala (an exotic and a native) were grown for maximum biomass production under the same climatic (1102 mm mean annual rainfall and 25°C mean annual air temperature) and edaphic conditions in the Lajas Valley of Puerto Rico (lat. 18 ° N., long. 67 ° W.). Management was intensive during early growth and establishment phases. Rates of large-branch/stem production ( diameter >/2.5 cm ) at age 5.5 years were 27.8, 20.4, 10.1, 7.7, and 5.5 t ha-1 year -1 for Casuarina, Albizia, Eucalyptus, exotic Leucaena, and native Leucaena, respectively. Stemwood biomass production of 40 tropical tree plantations established elsewhere for biomass production averaged 7.9 t ha-1 year-1. Species ranking in terms of total above-ground biomass and litter accumulation followed the same order. At age 5.5 years, the litter accumulation in plantations was (in the same order): 16.2, 10.2, 11.8, 7.0, and 6.5 t ha -1. Thirty-five natural tropical forest stands averaged 6 t ha-1. Intensive management on fertile soils increases biomass yield of energy plantations, but not all species respond equally well to such treatments. Rodrlgues Pereira et al.,
Biomass Dynamics in a Fragment of Brazilian Tropical Forest (Caatinga) over Consecutive Dry Years
Applied Sciences, 2020
Increases in water scarcity due to climate change, especially in dry regions, can affect the dynamics of successional species. In view of the longest sequence of dry years (2010–2019) to have occurred in the Brazilian semi-arid region, with a consequent reduction in water availability, the influence of rainfall distribution on the production of above-ground plant biomass was investigated in a Dry Tropical Forest (DTF). This natural change monitoring experiment was conducted over 11 years (2009–2019) in a fragment of DTF under regeneration for 40 years, in the district of Iguatu, Ceará, Brazil. All living individuals of the woody component with a Diameter at Ground Level (DGL) ≥3 cm and a height (h) ≥100 cm were measured during 2009–2010, 2015–2016, 2018–2019. Biomass production was calculated using an allometric equation defined for DTF species. A mean mortality rate of 134 ind. ha−1 yr−1 was registered, with a recruitment of 39 ind. ha−1 yr−1, generating a mean deficit of 95 ind. h...
2006
Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology predicts that tree abundances will scale as the )2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic predictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of predictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the predictions of metabolic ecology. In most forests, size distributions are much closer to the predictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality.
Conservative species drive biomass productivity in tropical dry forests
Forests account for a substantial part of the terrestrial biomass storage and productivity. To better understand forest productivity, we need to disentangle the processes underlying net biomass change. 2. We tested how above-ground net biomass change and its underlying biomass dynamics (biomass recruitment, growth and mortality) can be explained by four alternative and contested hypotheses; the soil fertility, biomass ratio, niche complementarity and vegetation quantity hypotheses. 3. Above-ground biomass dynamics were evaluated over a 5-year period in 200 permanent sample plots in 8 tropical dry forests in Brazil, and related to soil fertility, community-weighted mean (CWM) traits that are important for carbon storage and sequestration (wood density, specific leaf area, maximum stem diameter and deciduousness), species richness, functional diversity and initial stand biomass. 4. Initial stand biomass was the best predictor of all three processes of biomass dynamics, providing strong support for the vegetation quantity hypothesis. In these dry forests, the dominance of conservative species, rather than of acquisitive species, is associated with high biomass growth and storage, probably because their low specific leaf area and high wood density allow them to keep on functioning during drought stress. 5. Paradoxically, high soil fertility (Ca) led to low biomass productivity, probably because of nutrient imbalance. 6. In contrast to what is shown for controlled experiments, we found no support for niche complementarity (in terms of functional diversity or species richness) for forest productivity. Biomass storage was favoured by low-rather than high trait diversity, as most of the biomass is concentrated in species with large stem diameter and high wood density. 7. Synthesis. Biomass dynamics are mainly shaped by vegetation quantity, and then by vegetation quality, in line with the mass ratio hypothesis. Dry forests show different trait-productivity relationships than wet forests, as stands with 'slow' trait values are 'fast' in terms of productivity. Diversity matters, but in a different way than expected; high trait diversity does not enhance productivity, but instead, does low trait diversity enhance carbon storage.