Browsing by Autor "Nataly Ascarrunz"

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Abiotic and biotic drivers of biomass change in a Neotropical forest
(Wiley, 2017) Masha T. van der Sande; Marielos Peña‐Claros; Nataly Ascarrunz; E.J.M.M. Arets; Juan Carlos Licona; Marisol Toledo; Lourens Poorter
Summary Tropical forests play an important role in the global carbon cycle, but the drivers of net forest biomass change (i.e. net carbon sequestration) are poorly understood. Here, we evaluate how abiotic factors (soil conditions and disturbance) and biotic factors (forest structure, diversity and community trait composition) shape three important demographic processes (biomass recruitment, growth and mortality) and how these underlie net biomass change. To test this, we evaluated 9 years of biomass dynamics using 48 1‐ha plots in a Bolivian tropical moist forest, and measured for the most abundant species eight functional traits that are important for plant carbon gain and loss. Demographic processes were related to the abiotic and biotic factors using structural equation models. Variation in net biomass change across plots was mostly due to stand‐level mortality, but mortality itself could not be predicted at this scale. Contrary to expectations, we found that species richness and trait composition – which is an indicator for the mass‐ratio theory – had little effect on the demographic processes. Biomass recruitment (i.e. the biomass growth by recruiting trees) increased with higher resource availability (i.e. water and light) and with high species richness, probably because of increased resource use efficiency. Biomass growth of larger, established trees increased with higher sand content, which may facilitate root growth of larger trees to deeper soil layers. In sum, diversity and mass‐ratio are of limited importance for the productivity of this forest. Instead, in this moist tropical forest with a marked dry season, demographic processes are most strongly determined by soil texture, soil water availability and forest structure. Only by simultaneously evaluating multiple abiotic and biotic drivers of demographic processes, better insights can be gained into mechanisms playing a role in the carbon sequestration potential of tropical forests and natural systems in general.
Author response: Carbon recovery dynamics following disturbance by selective logging in Amazonian forests
(2016) Camille Piponiot; Plínio Sist; Lucas Mazzei; Marielos Peña‐Claros; Francis E. Putz; Ervan Rutishauser; Alexander Shenkin; Nataly Ascarrunz; C. P. de Azevedo; Christopher Baraloto
Full text Figures and data Side by side Abstract eLife digest Introduction Results Discussion Materials and methods Appendix Data availability References Decision letter Author response Article and author information Metrics Abstract When 2 Mha of Amazonian forests are disturbed by selective logging each year, more than 90 Tg of carbon (C) is emitted to the atmosphere. Emissions are then counterbalanced by forest regrowth. With an original modelling approach, calibrated on a network of 133 permanent forest plots (175 ha total) across Amazonia, we link regional differences in climate, soil and initial biomass with survivors’ and recruits’ C fluxes to provide Amazon-wide predictions of post-logging C recovery. We show that net aboveground C recovery over 10 years is higher in the Guiana Shield and in the west (21 ±3 Mg C ha-1) than in the south (12 ±3 Mg C ha-1) where environmental stress is high (low rainfall, high seasonality). We highlight the key role of survivors in the forest regrowth and elaborate a comprehensive map of post-disturbance C recovery potential in Amazonia. https://doi.org/10.7554/eLife.21394.001 eLife digest The Amazon rainforest in South America is the largest tropical forest in the world. Along with being home to a huge variety of plants and wildlife, rainforests also play an important role in storing an element called carbon, which is a core component of all life on Earth. Certain forms of carbon, such as the gas carbon dioxide, contribute to climate change so researchers want to understand what factors affect how much carbon is stored in rainforests. Trees and other plants absorb carbon dioxide from the atmosphere and then incorporate the carbon into carbohydrates and other biological molecules. The Amazon rainforest alone holds around 30% of the total carbon stored in land-based ecosystems. Humans selectively harvest certain species of tree that produce wood with commercial value from the Amazon rainforest. This “selective logging” results in the loss of stored carbon from the rainforest, but the loss can be compensated for in the medium to long term if the forest is left to regrow. New trees and trees that survived the logging grow to fill the gaps left by the felled trees. However, it is not clear how differences in the forest (for example, forest maturity), environmental factors (such as climate or soil) and the degree of the disturbance caused by the logging affect the ability of the forest ecosystem to recover the lost carbon. Piponiot et al. used computer modeling to analyze data from over a hundred different forest plots across the Amazon rainforest. The models show that the forest’s ability to recover carbon after selective logging greatly differs between regions. For example, the overall amount of carbon recovered in the first ten years is predicted to be higher in a region in the north known as the Guiana Shield than in the south of the Amazonian basin where the climate is less favorable. The findings of Piponiot et al. highlight the key role the trees that survive selective logging play in carbon recovery. The next step would be to couple this model to historical maps of logging to estimate how the areas of the rainforest that are managed by selective logging shape the overall carbon balance of the Amazon rainforest. https://doi.org/10.7554/eLife.21394.002 Introduction With on-going climate change, attention is increasingly drawn to the impacts of human activities on carbon (C) cycles (Griggs and Noguer, 2002), and in particular to the 2.1 ± 1.1 Pg C yr-1 of C loss caused by various forms and intensities of anthropogenic disturbances in tropical forests (Grace et al., 2014). Among those disturbances, selective logging, i.e. the selective harvest of a few merchantable tree species, is particularly widespread: in the Brazilian Amazon alone, about 2 Mha yr−1 were logged in 1999–2002 (Asner et al., 2005). The extent of selective logging in the Brasilian Amazon was equivalent to annual deforestation in the same period, and resulted in C emissions of 90 Tg C yr-1 (Huang and Asner, 2010) which increased anthropogenic C emissions by almost 25% over deforestation alone (Asner et al., 2005). In contrast to deforested areas that are used for agriculture and grazing, most selectively logged forests remain as forested areas (Asner et al., 2006) and may recover C stocks (West et al., 2014). Previously logged Amazonian forests may thus accumulate large amounts of C (Pan et al., 2011), but this C uptake is difficult to accurately estimate, because while detecting selective logging from space is increasingly feasible (Frolking et al., 2009) (even if very few of the IPCC models effectively account for logging), directly quantifying forest recovery remains challenging (Asner et al., 2009; Houghton et al., 2012; Goetz et al., 2015). Studies based on field measurements (e.g. Sist and Ferreira, 2007; Blanc et al., 2009; West et al., 2014; Vidal et al., 2016), sometimes coupled with modeling approaches (e.g. Gourlet-Fleury et al., 2005; Valle et al., 2007) or airborne light detection and ranging (LiDAR) measurements (e.g. Andersen et al., 2014) have assessed post-logging dynamics at particular sites. Nonetheless, to our knowledge no spatially-explicit investigation of post-logging C dynamics at the Amazon biome scale is available. C losses from selective logging are determined by harvest intensity (i.e. number of trees felled or volume of wood extracted) plus the care with which harvest operations are conducted, which affects the amount of collateral damage. After logging, C losses continue for several years due to elevated mortality rates of trees injured during harvesting operations (Shenkin et al., 2015). Logged forests may recover their aboveground carbon stocks (ACS) via enhanced growth of survivors and recruited trees (Blanc et al., 2009). Full recovery of pre-disturbance ACS in logged stands reportedly requires up to 125 years, depending primarily on disturbance intensity (Rutishauser et al., 2015). The underlying recovery processes (i.e. tree mortality, growth and recruitment) are likely to vary with the clear geographical patterns in forest structure and dynamics across the Amazon Basin and Guiana Shield. In particular, northeast-southwest gradients have been reported for ACS (Malhi and Wright, 2004), net primary productivity (Aragão et al., 2009), wood density (Baker et al., 2004), and floristic composition (ter Steege et al., 2006). Such gradients coincide with climate and edaphic conditions that range from nearly a seasonal nutrient-limited in the northeast to seasonally dry and nutrient-rich in the southwest (Quesada et al., 2012). These regional differences in biotic and abiotic conditions largely constrain demographic processes that ultimately shape forest C balances. Here we partition the contributions to post-disturbance ACS gain (from growth and recruitment of trees ≥20 cm DBH) and ACS loss (from mortality) of survivors and recruited trees to detect the main drivers and patterns of ACS recovery in forests disturbed by selective logging across Amazonia sensu lato (that includes the Amazon Basin and the Guiana Shield). Based on long-term (8–30 year) inventory data from 13 experimentally-disturbed sites (Sist et al., 2015) across Amazonia (Figure 1—figure supplement 1), 133 permanent forest plots (175 ha in total) that cover a large gradient of disturbance intensities (ACS losses ranging from 1% to 71%) were used to model the trajectory of those post-disturbance ACS changes (Figure 1) in a comprehensive Bayesian framework. We quantify the effect of pre-disturbance ecosystem characteristics [the site’s average pre-logging ACS (a⁢c⁢s⁢0) and the relative difference between each plot and a⁢c⁢s⁢0 as a proxy of forest maturity (d⁢a⁢c⁢s)], disturbance intensity [percentage of pre-logging ACS lost (l⁢o⁢s⁢s)], and interactions with the environment [annual precipitation (p⁢r⁢e⁢c), seasonality of precipitation (s⁢e⁢a⁢s), and soil bulk density (b⁢d)] (Figure 2) on the rates at which post-disturbance ACS changes converge to a theoretical steady state (as in Figure 1, see Materials and methods for more details). With global maps of ACS (Avitabile et al., 2016), climatic conditions (Hijmans et al., 2005) and soil bulk density (Nachtergaele et al., 2008), we up-scale our results to Amazonia (sensu lato) and elaborate predictive maps of potential ACS changes over 10 years under the hypothesis of a 40% ACS loss, which is a common disturbance intensity after conventional logging in Amazonia (Blanc et al., 2009; Martin et al., 2015; West et al., 2014). Summing these ACS changes over time gives the net post-disturbance rate of ACS accumulation. Disentangling ACS recovery into demographic processes and cohorts is essential to reveal mechanisms underlying ACS responses to disturbance and to make more robust predictions of ACS recovery compared to an all-in-one approach (see Appendix). Figure 1 with 1 supplement see all Download asset Open asset Post-disturbance annual ACS changes of survivors and recruits in 133 Amazonian selectively logged plots. Data is available between the year of minimum ACS (t=0) and t=30 years. ACS changes are: recruits’ ACS growth (orange), recruits’ ACS loss (gold), new recruits’ ACS (red), survivors’ ACS growth (light green) and survivors’ ACS loss (dark green). Thick solid lines are the maximum-likelihood predictions (for an average plot, when all covariates are null), and dashed lines are the model theoretical behaviour. New recruits’ ACS, recruits’ ACS growth, and recruits’ ACS loss converge over time to constant values. A dynamic equilibrium is then reached: ACS gain from recruitment and recruits’ growth compensate ACS loss from recruits’ mortality. Survivors’ ACS growth and loss. decline over time and tend to zero when all initial survivors have died. https://doi.org/10.7554/eLife.21394.003 Figure 2 with 1 supplement see all Download asset Open asset Effect of covariates on the rate at which post-disturbance ACS changes converge to a theoretical steady state (in yr-1). Covariates are : disturbance intensity (l⁢o⁢s⁢s) , i.e. the proportion of initial ACS loss; mean site’s ACS (a⁢c⁢s⁢0), and relative forest maturity, i.e. pre-logging plot ACS as a % of a⁢c⁢s⁢0 (d⁢a⁢c⁢s); annual precipitation (p⁢r⁢e⁢c); seasonality of precipitation (s⁢e⁢a⁢s), soil bulk density (b⁢d). Covariates are centred and standardized. Red and black levels are 80% and 95% credible intervals, respectively. The median rate is the prediction of the convergence rate for an average plot (when all covariates are set to zero). Negative covariate values indicate slowing and positive values indicate accelerating rates. (a) Survivors’ ACS growth. (b) New recruits’ ACS. (c) Recruits’ ACS growth. (d) Survivors’ ACS loss. (e) Recruits’ ACS loss. https://doi.org/10.7554/eLife.21394.005 Figure 2—source data 1 Parameters posterior distribution. Columns are the 2.5%, 10%, 50%, 90% and 97.5% quantiles of the posterior distribution of the model parameters (rows). https://doi.org/10.7554/eLife.21394.006 Download elife-21394-fig2-data1-v2.xlsx Results Local variations of ACS changes At a given site, variations of post-logging ACS changes are explained with the disturbance intensity (l⁢o⁢s⁢s) and the relative forest maturity (d⁢a⁢c⁢s). At high disturbance intensity (positive l⁢o⁢s⁢s) as well as in relatively immature forests (negative d⁢a⁢c⁢s), ACS gain from recruits is high: recruitment decreases slowly (Figure 2b and Figure 3b) and recruits’ growth increases rapidly (Figure 2c and Figure 3c). In the same conditions of high disturbance intensity, survivors’ ACS growth is lower in the first years following logging than for low disturbance intensities, but declines slowly (Figure 2a and Figure 3a). Disturbance intensity and relative forest maturity have a weak effect on ACS loss from both survivors and recruits (Figures 2d,e and 3d,e). Overall, net ACS change stays high longer at high disturbance intensity (Figure 3f). Figure 3 Download asset Open asset Predicted effect of disturbance intensity on ACS changes along time in an Amazonian-average plot. (a) Survivors’ ACS growth. (b) New recruits’ ACS. (c) Recruits’ ACS growth. (d) Survivors’ ACS loss. (e) Recruits’ ACS loss. (f) Net ACS change. The net ACS change is the sum of all five ACS changes. ACS changes were calculated with all parameters set to their maximum-likelihood value and covariates (except standardized disturbance intensity l⁢o⁢s⁢s) set to 0. Time since minimum ACS varies from 0 to 30 year (i.e. the calibration interval) and disturbance intensity ranges between 5% and 60% of initial ACS loss. https://doi.org/10.7554/eLife.21394.008 Regional variations of ACS changes Variations of post-logging ACS changes between sites are explained with the mean ACS of each site (a⁢c⁢s⁢0), climatic conditions [annual precipitation (p⁢r⁢e⁢c), seasonality of precipitation (s⁢e⁢a⁢s)] and the soil bulk density (b⁢d). Contribution of survivors’ growth to ACS recovery declined slowly in sites with low a⁢c⁢s⁢0 and high water stress (low precipitation, high seasonality and high bulk density) (Figure 2a). Survivors’ ACS loss showed the opposite pattern (Figure 2d) except in apparent response to high seasonality of precipitation (s⁢e⁢a⁢s) that slowed the post-disturbance rates of decline of both ACS growth and loss. Despite slower recruits’ ACS growth in sites with high pre-logging ACS (a⁢c⁢s⁢0), no other regional covariate had significant effects on recruits’ ACS changes (Figure 2b,c and e). Prediction maps While no significant environmental effects were detected for recruits’ ACS changes (Figures 2 and 4), the survivors showed a highly structured regional gradient: (i) ACS gain from survivors’ ACS growth is high in the west and in the Guiana Shield, but low in the south (Figure 4a), whereas (ii) survivors’ ACS loss is low in the south and in the Guiana Shield but high in the west (Figure 4d). To illustrate how these regional differences will be critical for future ACS across Amazonia, we developed a map of net ACS recovery over the first 10 years after a 40% ACS loss by integrating the sum of ACS change predictions through time (Figure 5). Across the region, net ACS recovery over the first ten years after a 40% ACS loss is predicted to be 17 ± 7 Mg C ha-1, with higher values in the west and in the Guiana Shield (Figure 5a). The uncertainty in predictions was low to medium (coefficient of variation under 40%) in 82% of the mapped area, and high (coefficient of variation above 50%) in 5% of the mapped area (Figure 5b). Figure 4 Download asset Open asset Predicted cumulative ACS changes (Mg C ha−1) over the first 10 year after losing 40% of ACS. Extrapolation was based on global rasters: topsoil bulk density from the Harmonized global soil database (Nachtergaele et al., 2008), Worldclim precipitation data (Hijmans et al., 2005) and biomass stocks from Avitabile et al. map (Avitabile et al., 2016). Cumulative ACS changes are obtained by integrating annual ACS changes through time. We here show the median of each pixel. Top graphs are ACS gain and bottom graphs are ACS loss. (a) ACS gain from survivors’ growth. (b) ACS gain from new recruits. (c) ACS gain from recruits’ growth. (d) ACS loss from survivors’ mortality. (e) ACS loss from recruits’ mortality. Black dots are the location of our experimental sites. Survivors’ ACS changes (a and d) show strong regional variations unlike to recruits’ ACS changes (b,c and e). https://doi.org/10.7554/eLife.21394.009 Figure 5 Download asset Open asset Predicted net ACS recovery over the first 10 year after losing 40% of pre-logging ACS. (a) median predictions. (b) coefficient of variation (per pixel). Four areas were arbitrarily chosen to illustrate four different geographical behaviours: (1) the Guiana Shield and (2) northwestern Amazonia are two areas with high ACS recovery; the Guiana Shield has higher initial ACS and slower ACS dynamics whereas northwestern Amazonia has lower initial ACS and faster ACS dynamics. (3) central Amazonia has intermediate ACS recovery. (4) southern Amazonia has low ACS recovery. https://doi.org/10.7554/eLife.21394.010 Four areas (Figure 5a) were selected to represent four contrasted cases of net ACS recovery in time (Figure 6): two areas, northwestern Amazonia and the Guiana Shield, with high ACS accumulation (21 ± 3 Mg C ha-1 over 10 year), one intermediate area, central Amazonia (15 ± 1 Mg C ha-1 over 10 year) and one area with low ACS accumulation, southern Amazonia (12 ± 3 Mg C ha-1 over 10 year). Survivors’ contribution to the sum of ACS gains (recruitment and growth) over the first 10 years after disturbance was 71 ± 4% in the Guiana Shield, 71 ± 2% in the west; 63 ± 4% in central Amazonia and 55 ± 6% in the south. Predicted net ACS recovery (Figure 5) and survivors’ ACS growth (Figure 4a) are highly correlated: ρ=0.90 (Pearson’s correlation coefficient). Figure 6 Download asset Open asset Predicted contribution of annual ACS changes in ACS recovery in four regions of Amazonia (Figure 5). The white line is the net annual ACS recovery, i.e. the sum of all annual ACS changes. Survivors’ (green) and recruits’ (orange) contribution are positive for ACS gains (survivors’ ACS growth, new recruits’ ACS and recruits’ ACS growth) and negative for survivors’ and recruits’ ACS loss. Areas with higher levels of transparency and dotted lines are out of the calibration period (0–30 year). In the Guiana Shield and in nothwestern Amazonia, high levels of net ACS recovery are explained by large ACS gain from survivors’ growth. Extrapolation was based on global rasters: topsoil bulk density from the Harmonized global soil database (Nachtergaele et al., 2008), precipitation data from Worldclim (Hijmans et al., 2005) and biomass stocks from Avitabile et al. (Avitabile et al., 2016) map. https://doi.org/10.7554/eLife.21394.011 Discussion Contrasting post-disturbance ACS dynamics were detected among the western Amazon, Guiana Shield, and southern Amazon (Figure 4). (i) In the western Amazon, environmental stress is reduced due to fertile soils and abundant, mostly non-seasonal precipitation, but forests are prone to frequent and sometimes large-scale wind-induced disturbances (Espírito-Santo et al., 2014). Such conditions of low stress and high disturbance tend to favor fast-growing species with rapid life cycles (He et al., 2013), which results in fast ACS gain and loss from survivors even after the logging disturbance (Figures 4a,d and 6). (ii) Forests of the Guiana Shield are generally dense and grow on nutrient-poor soils (Quesada et al., 2012), where wood productivity is highly constrained by competition for key nutrients, especially phosphorus and nitrogen (Santiago, 2015; Mercado et al., 2011). The short duration pulse of nutrients released from readily decomposed stems, twigs and leaves of trees damaged and killed by logging may thus explain the substantial but limited-duration increase in growth of survivors on these nutrient-poor soils (Figure 6). Yet post-disturbance ACS loss from survivors’ mortality decreases slowly in the Guiana Shield (Figure 6). This is consistent with the low mortality rates and the high tree longevity reported in old-growth forests of this region (Phillips et al., 2004). (iii) In the southern Amazon, high seasonal water stress is the main constraint on ACS recovery (Wagner et al., 2016). Stress-tolerant trees are generally poor competitors (He et al., 2013) and this may explain the slow ACS changes of survivors in this region (Figures 4a,d and 6). Finally, Central Amazonia is a transition zone for the main environmental and biotic gradients found in Amazonia: (1) a competition gradient between dense and nutrient-poor northeastern forests and nutrient-rich western forests; (2) an environmental gradient between northern wet forests and southern drier forests (Quesada et al., 2012). Across Amazonia, survivors contribute most to post-disturbance ACS recovery. In regions where survivors’ ACS gain is high (west and northeast), net ACS recovery is also high: annual ACS recovery is between 1 and 3 Mg C ha-1 yr-1 in the first 10 year after logging (Figure 6), lower than in Amazonian secondary forests (3–5 Mg C ha-1 yr−1 in the first year after of et al., for their have very low geographical variations in post-logging ACS 10 years after the disturbance are predicted to amounts of ACS almost in Amazonia. trees with cm have not been for in our and may play an important role in post-logging ACS changes. The cm as much as of total ACS and may be highly dynamic in Amazonian forests et al., 2004). of the slow tree growth rates in Amazonia et al., 2005; et al., trees will not the cm 10 years after the effects of the cm on post-logging ACS changes are likely to be in sites with less than 10 years of measurements (e.g. and be with the in the At the high disturbance intensities survivors’ survivors’ ACS growth is lower (Figure in lower net ACS change during the first 10 years of the recovery period (Figure 3f). disturbance intensities as well as relatively low forest maturity and this is ACS contributions from recruits remain high for longer (Figure in such enhanced growth conditions et al., In the first years after logging, net ACS recovery on disturbance intensity (Figure but recovery is predicted to longer in logged In immature et al., may explain fast ACS losses from survivors’ mortality (Figure In the logging et al., are to collateral to stands and results reveal that lower disturbance intensities, as a of the of increase survivors’ ACS growth and slow their ACS loss. that minimum cycles are year in the Brazilian Amazon et al., 2011), and that commercial species are and et al., 2005; et al., available stocks for the next will be mostly of be to high harvest intensities substantial due to poor harvesting that stocks of even if trees that are fast-growing that are by disturbance but are to water stress et al., 2016) and competition and 2008), and because their is lower than in forests (Rutishauser et al., 2016), have reduced carbon With climate change and increased and intensities of in Amazonia (Malhi et al., 2008), on recruits to C in forests disturbed by selective logging thus be a In this we on one of selective of value and for forest selective logging is a human disturbance in tropical and the data by the network are in of duration and We that our gives on the regional differences in Amazonian forests response to large ACS losses by other disturbances (e.g. that are to increase in with global changes et al., 2016). Materials and methods a includes data from long-term (8–30 year) experimental forest sites in the Amazon Basin and the Guiana Shield (Figure 1—figure supplement the following (i) in tropical forests with mean annual precipitation above (ii) a total area above 1 (iii) at one pre-logging and at two post-logging For each site, we annual precipitation and seasonality of precipitation data from (Hijmans et al., topsoil bulk density data from the Harmonized database (Nachtergaele et al., 2008), and the climatic from et al. et al., in all cases the data available For one of our sites see Figure 1—figure supplement 1), field measurements of precipitation from data in this particular we used the value and the climatic in the et al., 2014) data is available at et al., 2016). ACS a In all at of trees cm were and trees were to the to the species when or to the of trees were not To the wood we the following standardized to all (i) trees to the species were the wood value from the et al., (ii) trees to the were a wood (iii) trees with no or that were not in the were the wood The aboveground biomass was with the from et al. et al., 2014). was to be carbon et al., The ACS of tree was then as (1) where and are the wood density and at of the tree and is the climatic et al., 2014). The ACS changes data that was is available at et al., 2016). The recovery period a After logging, plot ACS decreases rapidly it minimum value a few years This transition the of the recovery was as the minimum ACS in the 4 years following logging our is on post-logging ACS recovery, we not in our plots where the minimum ACS value was not the 4 years after logging, because the logging not affect the plot or because were other of disturbance long after logging ACS changes a For each plot and with the time since the of the recovery period we 5 ACS changes : new recruits’ ACS is the ACS of all trees cm at and ≥20 cm at recruits’ ACS growth is the ACS of recruits between and recruits’ ACS loss is the C in recruits that between and survivors’ ACS growth is the ACS of survivors between and survivors’ ACS loss is the ACS of survivors that between and ACS gains are positive and ACS losses are ACS changes are to variation over because we are less in variations than in long-term ACS we cumulative ACS changes of annual ACS changes. Cumulative ACS changes (Mg C ha-1) were as (2) where is the plot, the time since and is the annual ACS change (Mg C ha-1 recruits’ ACS recruits’ ACS growth recruits’ ACS loss survivors’ ACS growth or survivors’ ACS loss Covariates a To model ACS we covariates : (1) disturbance intensity, i.e. of initial ACS loss; (2) a⁢c⁢s⁢0 mean ACS of the (3) relative ACS of the plot, as a % of (4) annual precipitation topsoil bulk To equivalent to all we centred and standardized in to have a mean of zero and a of one over all The uncertainty with ACS covariates is less than et al., 2014). covariates precipitation and precipitation seasonality were
Biodiversity and climate determine the functioning of Neotropical forests
(Wiley, 2017) Lourens Poorter; Masha T. van der Sande; E.J.M.M. Arets; Nataly Ascarrunz; Brian J. Enquist; Bryan Finegan; Juan Carlos Licona; Miguel Martínez‐Ramos; Lucas Mazzei; Jorge A. Meave
Abstract Aim Tropical forests account for a quarter of the global carbon storage and a third of the terrestrial productivity. Few studies have teased apart the relative importance of environmental factors and forest attributes for ecosystem functioning, especially for the tropics. This study aims to relate aboveground biomass (AGB) and biomass dynamics (i.e., net biomass productivity and its underlying demographic drivers: biomass recruitment, growth and mortality) to forest attributes (tree diversity, community‐mean traits and stand basal area) and environmental conditions (water availability, soil fertility and disturbance). Location Neotropics. Methods We used data from 26 sites, 201 1‐ha plots and >92,000 trees distributed across the Neotropics. We quantified for each site water availability and soil total exchangeable bases and for each plot three key community‐weighted mean functional traits that are important for biomass stocks and productivity. We used structural equation models to test the hypothesis that all drivers have independent, positive effects on biomass stocks and dynamics. Results Of the relationships analysed, vegetation attributes were more frequently associated significantly with biomass stocks and dynamics than environmental conditions (in 67 vs. 33% of the relationships). High climatic water availability increased biomass growth and stocks, light disturbance increased biomass growth, and soil bases had no effect. Rarefied tree species richness had consistent positive relationships with biomass stocks and dynamics, probably because of niche complementarity, but was not related to net biomass productivity. Community‐mean traits were good predictors of biomass stocks and dynamics. Main conclusions Water availability has a strong positive effect on biomass stocks and growth, and a future predicted increase in (atmospheric) drought might, therefore, potentially reduce carbon storage. Forest attributes, including species diversity and community‐weighted mean traits, have independent and important relationships with AGB stocks, dynamics and ecosystem functioning, not only in relatively simple temperate systems, but also in structurally complex hyper‐diverse tropical forests.
Can timber provision from Amazonian production forests be sustainable?
(IOP Publishing, 2019) Camille Piponiot; Edna Rödig; Francis E. Putz; Ervan Rutishauser; Plínio Sist; Nataly Ascarrunz; Lilian Blanc; Géraldine Derroire; Laurent Descroix; Marcelino Carneiro Guedes
Abstract Around 30 Mm 3 of sawlogs are extracted annually by selective logging of natural production forests in Amazonia, Earth’s most extensive tropical forest. Decisions concerning the management of these production forests will be of major importance for Amazonian forests’ fate. To date, no regional assessment of selective logging sustainability supports decision-making. Based on data from 3500 ha of forest inventory plots, our modelling results show that the average periodic harvests of 20 m 3 ha −1 will not recover by the end of a standard 30 year cutting cycle. Timber recovery within a cutting cycle is enhanced by commercial acceptance of more species and with the adoption of longer cutting cycles and lower logging intensities. Recovery rates are faster in Western Amazonia than on the Guiana Shield. Our simulations suggest that regardless of cutting cycle duration and logging intensities, selectively logged forests are unlikely to meet timber demands over the long term as timber stocks are predicted to steadily decline. There is thus an urgent need to develop an integrated forest resource management policy that combines active management of production forests with the restoration of degraded and secondary forests for timber production. Without better management, reduced timber harvests and continued timber production declines are unavoidable.
Carbon recovery dynamics following disturbance by selective logging in Amazonian forests
(eLife Sciences Publications Ltd, 2016) Camille Piponiot; Plínio Sist; Lucas Mazzei; Marielos Peña‐Claros; Francis E. Putz; Ervan Rutishauser; Alexander Shenkin; Nataly Ascarrunz; C. P. de Azevedo; Christopher Baraloto
When 2 Mha of Amazonian forests are disturbed by selective logging each year, more than 90 Tg of carbon (C) is emitted to the atmosphere. Emissions are then counterbalanced by forest regrowth. With an original modelling approach, calibrated on a network of 133 permanent forest plots (175 ha total) across Amazonia, we link regional differences in climate, soil and initial biomass with survivors' and recruits' C fluxes to provide Amazon-wide predictions of post-logging C recovery. We show that net aboveground C recovery over 10 years is higher in the Guiana Shield and in the west (21 ±3 Mg C ha-1) than in the south (12 ±3 Mg C ha-1) where environmental stress is high (low rainfall, high seasonality). We highlight the key role of survivors in the forest regrowth and elaborate a comprehensive map of post-disturbance C recovery potential in Amazonia.
Commercial Logging of Timber Species Enhances Amazon (Brazil) Nut Populations: Insights from Bolivian Managed Forests
(Multidisciplinary Digital Publishing Institute, 2021) Marlene Soriano; Pieter A. Zuidema; Cristina Barber; G.M.J. Mohren; Nataly Ascarrunz; Juan Carlos Licona; Marielos Peña‐Claros
A typical case of multiple-use forest management (MFM) in Southwestern Amazon is the commercial harvesting of Amazon or Brazil nut (Bertholletia excelsa) seeds and of timber of other tree species. Although the Amazon nut is the most important non-timber forest product (NTFP) in the Amazon basin, the species is under serious threat due to deforestation and may also be affected by overharvesting. However, selective logging of other tree species coexisting with Bertholletia may positively affect Bertholletia populations, thus enabling a special case for MFM. For this research, we investigated the impact of the intensity of Amazon nut harvesting and timber logging on Bertholletia populations in the Bolivian Amazon. We used demographic data from 72 two-hectare transects located within 24 community-based household forests varying in the intensity of nut collection (0–100%) and timber logging (0–15% of logging-disturbed forest area). Simulated Bertholletia population size increased with logging intensity but decreased with Amazon nut harvesting intensity. Bertholletia populations were projected to grow at the average MFM harvesting scenario tested: 57.4% of nut harvesting, 5.3% of logging-disturbed area (λ100 = 1.011). Our simulations also revealed that up to 89% of Amazon nut seeds can be harvested while sustaining Bertholletia populations, under 15% of logging-disturbed area, and applying liana cutting. Modest levels of timber logging and application of liana cutting may compensate for the negative effect of Amazon nut collection on Bertholletia populations for the next century. Our study demonstrates that Amazon nut and timber production could be combined in a sustainable MFM scheme, thus increasing the economic value of managed tropical forests and its promotion to reduce the increasing pressure by deforestation.
Diversity enhances carbon storage in tropical forests
(Wiley, 2015) Lourens Poorter; Masha T. van der Sande; Jill Thompson; E.J.M.M. Arets; Alejandro Alarcón; Javier Álvarez-Sánchez; Nataly Ascarrunz; Patricia Balvanera; Guadalupe Barajas-Guzmán; Alice Boit
Abstract Aim Tropical forests store 25% of global carbon and harbour 96% of the world's tree species, but it is not clear whether this high biodiversity matters for carbon storage. Few studies have teased apart the relative importance of forest attributes and environmental drivers for ecosystem functioning, and no such study exists for the tropics. Location Neotropics. Methods We relate aboveground biomass ( AGB ) to forest attributes (diversity and structure) and environmental drivers (annual rainfall and soil fertility) using data from 144,000 trees, 2050 forest plots and 59 forest sites. The sites span the complete latitudinal and climatic gradients in the lowland Neotropics, with rainfall ranging from 750 to 4350 mm year −1 . Relationships were analysed within forest sites at scales of 0.1 and 1 ha and across forest sites along large‐scale environmental gradients. We used a structural equation model to test the hypothesis that species richness, forest structural attributes and environmental drivers have independent, positive effects on AGB . Results Across sites, AGB was most strongly driven by rainfall, followed by average tree stem diameter and rarefied species richness, which all had positive effects on AGB . Our indicator of soil fertility (cation exchange capacity) had a negligible effect on AGB , perhaps because we used a global soil database. Taxonomic forest attributes (i.e. species richness, rarefied richness and Shannon diversity) had the strongest relationships with AGB at small spatial scales, where an additional species can still make a difference in terms of niche complementarity, while structural forest attributes (i.e. tree density and tree size) had strong relationships with AGB at all spatial scales. Main conclusions Biodiversity has an independent, positive effect on AGB and ecosystem functioning, not only in relatively simple temperate systems but also in structurally complex hyperdiverse tropical forests. Biodiversity conservation should therefore be a key component of the UN Reducing Emissions from Deforestation and Degradation strateg y.
Does functional trait diversity predict above‐ground biomass and productivity of tropical forests? Testing three alternative hypotheses
(Wiley, 2014) Bryan Finegan; Marielos Peña‐Claros; Alexandre A. Oliveira; Nataly Ascarrunz; M. Syndonia Bret‐Harte; Geovana Carreño‐Rocabado; Fernando Casanoves; Sandra Dı́az; Paúl Eguiguren; Fernando Fernández‐Méndez
Summary Tropical forests are globally important, but it is not clear whether biodiversity enhances carbon storage and sequestration in them. We tested this relationship focusing on components of functional trait biodiversity as predictors. Data are presented for three rain forests in Bolivia, Brazil and Costa Rica. Initial above‐ground biomass and biomass increments of survivors, recruits and survivors + recruits (total) were estimated for trees ≥10 cm d.b.h. in 62 and 21 1.0‐ha plots, respectively. We determined relationships of biomass increments to initial standing biomass ( AGB i ), biomass‐weighted community mean values ( CWM ) of eight functional traits and four functional trait variety indices (functional richness, functional evenness, functional diversity and functional dispersion). The forest continuum sampled ranged from ‘slow’ stands dominated by trees with tough tissues and high AGB i , to ‘fast’ stands dominated by trees with soft, nutrient‐rich leaves, lighter woods and lower AGB i . We tested whether AGB i and biomass increments were related to the CWM trait values of the dominant species in the system (the biomass ratio hypothesis), to the variety of functional trait values (the niche complementarity hypothesis), or in the case of biomass increments, simply to initial standing biomass (the green soup hypothesis). CWM s were reasonable bivariate predictors of AGB i and biomass increments, with CWM specific leaf area SLA , CWM leaf nitrogen content, CWM force to tear the leaf, CWM maximum adult height H max and CWM wood specific gravity the most important. AGB i was also a reasonable predictor of the three measures of biomass increment. In best‐fit multiple regression models, CWM H max was the most important predictor of initial standing biomass AGB i . Only leaf traits were selected in the best models for biomass increment; CWM SLA was the most important predictor, with the expected positive relationship. There were no relationships of functional variety indices to biomass increments, and AGB i was the only predictor for biomass increments from recruits. Synthesis . We found no support for the niche complementarity hypothesis and support for the green soup hypothesis only for biomass increments of recruits. We have strong support for the biomass ratio hypothesis. CWM H max is a strong driver of ecosystem biomass and carbon storage and CWM SLA , and other CWM leaf traits are especially important for biomass increments and carbon sequestration.
Formalizing community forest tenure rights: A theory of change and conditions for success
(Elsevier BV, 2022) Koen Kusters; Maartje de Graaf; Nataly Ascarrunz; Charlotte Benneker; René Boot; Rudi van Kanten; John Livingstone; Alphonse Maindo; Heidi Mendoza; Edi Purwanto
Grassy biomes: An inconvenient reality for large‐scale forest restoration? A comment on the essay by Chazdon and Laestadius
(Wiley, 2017) Joseph W. Veldman; Fernando A. O. Silveira; Forrest Fleischman; Nataly Ascarrunz; Giselda Durigan
In their essay, Forest and landscape restoration: Toward a shared vision and vocabulary, Chazdon and Laestadius (2016) made an impassioned case for the restoration of deforested land at the global scale. Unfortunately, they did not address the risks posed to the world's ancient grassy biomes (i.e., grasslands, savannas, and open-canopy woodlands) by forest-biased conservation agendas that promote tree planting and fire exclusion, and indirectly incentivize agricultural conversion of ecosystems with naturally low tree cover (Parr et al., 2014; Overbeck et al., 2015; Searchinger et al., 2015; Veldman et al., 2015a, b). The risk of misapplying forest restoration, resulting in the establishment of forests where they did not historically occur (i.e., afforestation and forest expansion; Fig. 1), is particularly high in the tropics where, for at least a century, European and North American ecologists have confused old-growth savannas (shaped over millions of years by fire and megafaunal herbivores; Veldman et al., 2015a; Bond, 2016) with deforested land, recently cleared by humans (Fairhead and Leach, 1996; Veldman, 2016). We agree with Chazdon and Laestadius that forest restoration can provide benefits when implemented on deforested and degraded forest land, but misapplication of tree-promoting land management strategies in historically grassy biomes has many clear, long-lasting, negative consequences for people and nature. Such negative consequences include the loss of pastoral livelihoods, perpetuation of poverty, reduced groundwater recharge, and declines in plant and animal diversity (Cao et al., 2011; Fleischman, 2014; Parr et al., 2014; Overbeck et al., 2015). Ancient grassy biomes (left, an old-growth savanna in Bolivia) are important to human livelihoods (e.g., livestock production) and support a tremendous diversity of long-lived herbaceous plants and endemic animals (Parr et al., 2014; Veldman et al., 2015a). Misapplication of forest restoration to grassy biomes results in afforestation (center, a Eucalyptus plantation in Brazil), forest expansion (right, due to fire exclusion in Brazil), and declines in biodiversity and ecosystem services (Veldman et al., 2015b). It is not our intent to fully reiterate these previously published concerns, but rather to address their relevance with respect to two assertions advanced by Chazdon and Laestadius (2016). These assertions were (1) to achieve the level of political support necessary for the success of large-scale forest restoration, scientists need to be more pragmatic in their selection of evidence and attention to detail; and (2) such pragmatism is essential to the development of a “shared vision and vocabulary”, understandable to both scientists and policymakers. While we fully agree with Chazdon and Laestadius about the need to bridge science and policymaking in a process that “integrates the best available technical, traditional, and practical knowledge” (p. 1870), these two assertions warrant critical evaluation by scientists. With regard to pragmatism and evidence, we are concerned that Chazdon and Laestadius, along with their colleagues at the World Resources Institute (WRI) and the International Union for Conservation of Nature (IUCN; i.e., Laestadius et al., 2015; DeWitt et al., 2016), continue to overestimate the amount of deforested and degraded forest land that is suitable for reforestation. Chazdon and Laestadius (2016, p. 1869) write “Over 2 billion hectares (7,722,043 square miles) of dysfunctional land (former forest and mixed woodland) provide opportunities for forest landscape restoration (Laestadius et al., 2011).” This estimate—based on remote sensing of tree cover and the overly simplistic assumption that low tree cover is evidence of deforestation (Laestadius et al., 2011)—mistakenly includes nearly 1 billion hectares of the world's grassy biomes (i.e., 40% of the total “opportunities for forest landscape restoration”; Veldman et al., 2015b). Much of these classification errors occurred in tropical regions where tree cover is an unsuitable metric to diagnose ecosystem degradation (Veldman, 2016), let alone prioritize landscapes for restoration efforts (Bond, 2016). This same flawed analysis (i.e., Laestadius et al., 2011) is the basis for the interactive online Atlas of Forest Restoration Opportunities (WRI, 2014). Promoted by WRI (2014) as an information management tool for stakeholders and decision makers, the Atlas allows users to peruse the globe and zoom in on identified “deforested” and “degraded” land, categories that erroneously include many old-growth savannas and grasslands (Veldman et al., 2015b). Given the ecological and human risks posed by misapplied reforestation efforts, a politically pragmatic approach requires that scientists provide policymakers with the best possible information (Pielke, 2007). In this case, the best information should be used to substantially narrow the area deemed suitable for restoration and thereby help governments and funding organizations allocate limited resources to truly degraded land. The reliance of Chazdon and Laestadius (2016) on analyses that overestimate forest degradation and misrepresent grassy biomes as deforested (Veldman et al., 2015b) is also worrisome given their goal to establish a “shared vision and vocabulary” for forest restoration globally. We are particularly concerned about language that seems to equate “grazing land” with “cleared land” (p. 1869), given that herbivores (native and domestic) are important to the maintenance of old-growth grassland biodiversity and are critical to human livelihoods (e.g., Trauernicht et al., 2013). Similarly, we are concerned by calls to “return forest cover to barren lands” while broadly referring to low tree cover ecosystems as “dysfunctional” (p. 1869). We urge scientists and politicians to take great care to avoid vocabulary that is reminiscent of the degradation discourse of western European colonialism, which portrayed indigenous land management practices—such as savanna burning and livestock grazing—as causes of degradation and served as a pretext for the subjugation of native peoples and the appropriation of natural resources (Fairhead and Leach, 1996). Moving forward, thoughtful vocabulary will be important to avoid the pitfalls of other well-intentioned conservation initiatives that inadvertently play a negative role in processes of dispossession and environmental degradation in many parts of the world (Larson and Ribot, 2007; Kashwan, 2017). Indeed, there is a long history of oversights in the communication of ecological knowledge that translated into long-lasting policy prescriptions with negative environmental and social consequences (Fleischman, 2014). Although the best defense against such mistranslations is to clearly communicate both knowledge and uncertainty at the outset, Chazdon and Laestadius omit reference to cautionary literature on the implementation of Forest and Landscape Restoration (FLR) in grassy biomes. Such omission may reflect a general viewpoint among FLR proponents that concerns over threats to grassy biomes are unwarranted (but see Mansourian et al., 2017). For example, in response to Veldman et al. (2015b) and Bond (2016), Laestadius et al. (2015, p. 1210) and DeWitt et al. (2016, p. 1036) wrote: “FLR does not call for increasing tree cover beyond what would be ecologically appropriate for a particular location, and should not cause any loss or conversion of natural forests, grasslands, or other ecosystems.” Unfortunately, such assurances provide no safeguard against the entrenched interests of forestry bureaucrats and timber companies who plant trees, often under the guise of restoration, without regard to ecological histories or cultural values (Fleischman, 2014; Andersson et al., 2016). We thus urge Chazdon and Laestadius to seriously consider the risks of misapplied forest restoration efforts (e.g., water shortages; Cao et al., 2011) and ask that their WRI and IUCN colleagues (Laestadius et al., 2015; DeWitt et al., 2016) either revise, or take off-line, their flawed map of forest restoration opportunities (WRI, 2014). More generally, we encourage scientists and environmental policymakers to better acknowledge the conservation values of tropical savannas (e.g., Searchinger et al., 2015) and to work with us to incorporate grasslands and fire, alongside forests, in conservation and restoration efforts (Overbeck et al., 2015; Veldman, 2016). The authors thank W. J. Bond, R. F. Noss, and two anonymous reviewers for helpful comments on previous versions of this manuscript.
Interactive effects of tree size, crown exposure and logging on drought-induced mortality
(Royal Society, 2018) Alexander Shenkin; Benjamin M. Bolker; Marielos Peña‐Claros; Juan Carlos Licona; Nataly Ascarrunz; Francis E. Putz
Large trees in the tropics are reportedly more vulnerable to droughts than their smaller neighbours. This pattern is of interest due to what it portends for forest structure, timber production, carbon sequestration and multiple other values given that intensified El Niño Southern Oscillation (ENSO) events are expected to increase the frequency and intensity of droughts in the Amazon region. What remains unclear is what characteristics of large trees render them especially vulnerable to drought-induced mortality and how this vulnerability changes with forest degradation. Using a large-scale, long-term silvicultural experiment in a transitional Amazonian forest in Bolivia, we disentangle the effects of stem diameter, tree height, crown exposure and logging-induced degradation on risks of drought-induced mortality during the 2004/2005 ENSO event. Overall, tree mortality increased in response to drought in both logged and unlogged plots. Tree height was a much stronger predictor of mortality than stem diameter. In unlogged plots, tree height but not crown exposure was positively associated with drought-induced mortality, whereas in logged plots, neither tree height nor crown exposure was associated with drought-induced mortality. Our results suggest that, at the scale of a site, hydraulic factors related to tree height, not air humidity, are a cause of elevated drought-induced mortality of large trees in unlogged plots. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.
Latin America's Nitrogen Challenge
(American Association for the Advancement of Science, 2013) Amy T. Austin; Mercedes Bustamante; Gabriela Bielefeld Nardoto; S. K. Mitre; Tibisay Pérez; Jean Pierre Ometto; Nataly Ascarrunz; M. C. Forti; K. Longo; Mayra E. Gavito
Human impacts on the N cycle require sustainable ecological solutions to preserve ecosystem and human health.
Modelling carbon stock and carbon sequestration ecosystem services for policy design: a comprehensive approach using a dynamic vegetation model
(Taylor & Francis, 2018) Sandra Quijas; Alice Boit; Kirsten Thonicke; Guillermo N. Murray‐Tortarolo; Tuyeni H. Mwampamba; Margaret Skutsch; Margareth Simões; Nataly Ascarrunz; Marielos Peña‐Claros; Laurence Jones
Ecosystem service (ES) models can only inform policy design adequately if they incorporate ecological processes. We used the Lund-Potsdam-Jena managed Land (LPJmL) model, to address following questions for Mexico, Bolivia and Brazilian Amazon: (i) How different are C stocks and C sequestration quantifications under standard (when soil and litter C and heterotrophic respiration are not considered) and comprehensive (including all C stock and heterotrophic respiration) approach? and (ii) How does the valuation of C stock and C sequestration differ in national payments for ES and global C funds or markets when comparing both approach? We found that up to 65% of C stocks have not been taken into account by neglecting to include C stored in soil and litter, resulting in gross underpayments (up to 500 times lower). Since emissions from heterotrophic respiration of organic material offset a large proportion of C gained through growth of living matter, we found that markets and decision-makers are inadvertently overestimating up to 100 times C sequestrated. New approaches for modelling C services relevant ecological process-based can help accounting for C in soil, litter and heterotrophic respiration and become important for the operationalization of agreements on climate change mitigation following the COP21 in 2015.
Old‐growth Neotropical forests are shifting in species and trait composition
(Wiley, 2016) Masha T. van der Sande; E.J.M.M. Arets; Marielos Peña‐Claros; Angela Luciana de Ávila; Anand Roopsind; Lucas Mazzei; Nataly Ascarrunz; Bryan Finegan; Alfredo Alarcón; Yasmani Cáceres‐Siani
Abstract Tropical forests have long been thought to be in stable state, but recent insights indicate that global change is leading to shifts in forest dynamics and species composition. These shifts may be driven by environmental changes such as increased resource availability, increased drought stress, and/or recovery from past disturbances. The relative importance of these drivers can be inferred from analyzing changes in trait values of tree communities. Here, we evaluate a decade of change in species and trait composition across five old‐growth Neotropical forests in Bolivia, Brazil, Guyana, and Costa Rica that cover large gradients in rainfall and soil fertility. To identify the drivers of compositional change, we used data from 29 permanent sample plots and measurements of 15 leaf, stem, and whole‐plant traits that are important for plant performance and should respond to global change drivers. We found that forests differ strongly in their community‐mean trait values, resulting from differences in soil fertility and annual rainfall seasonality. The abundance of deciduous species with high specific leaf area increases from wet to dry forests. The community‐mean wood density is high in the driest forests to protect xylem vessels against drought cavitation, and is high in nutrient‐poor forests to increase wood longevity and enhance nutrient residence time in the plant. Interestingly, the species composition changed over time in three of the forests, and the community‐mean wood density increased and the specific leaf area decreased in all forests, indicating that these forests are changing toward later successional stages dominated by slow‐growing, shade‐tolerant species. We did not see changes in other traits that could reflect responses to increased drought stress, such as increased drought deciduousness or decreased maximum adult size, or that could reflect increased resource availability ( CO 2 , rainfall, or nitrogen). Changes in species and trait composition in these forests are therefore most likely caused by recovery from past disturbances. These compositional changes may also lead to shifts in ecosystem processes, such as a lower carbon sequestration and “slower” forest dynamics.
Socio-ecological costs of Amazon nut and timber production at community household forests in the Bolivian Amazon
(Public Library of Science, 2017) Marlene Soriano; G.M.J. Mohren; Nataly Ascarrunz; Wolfram Dressler; Marielos Peña‐Claros
The Bolivian Amazon holds a complex configuration of people and forested landscapes in which communities hold secure tenure rights over a rich ecosystem offering a range of livelihood income opportunities. A large share of this income is derived from Amazon nut (Bertholletia excelsa). Many communities also have long-standing experience with community timber management plans. However, livelihood needs and desires for better living conditions may continue to place these resources under considerable stress as income needs and opportunities intensify and diversify. We aim to identify the socioeconomic and biophysical factors determining the income from forests, husbandry, off-farm and two keystone forest products (i.e., Amazon nut and timber) in the Bolivian Amazon region. We used structural equation modelling tools to account for the complex inter-relationships between socioeconomic and biophysical factors in predicting each source of income. The potential exists to increase incomes from existing livelihood activities in ways that reduce dependency upon forest resources. For example, changes in off-farm income sources can act to increase or decrease forest incomes. Market accessibility, social, financial, and natural and physical assets determined the amount of income community households could derive from Amazon nut and timber. Factors related to community households' local ecological knowledge, such as the number of non-timber forest products harvested and the number of management practices applied to enhance Amazon nut production, defined the amount of income these households could derive from Amazon nut and timber, respectively. The (inter) relationships found among socioeconomic and biophysical factors over income shed light on ways to improve forest-dependent livelihoods in the Bolivian Amazon. We believe that our analysis could be applicable to other contexts throughout the tropics as well.
The Latin America Regional Nitrogen Centre: Concepts and Recent Activities
(2020) Jean Pierre Ometto; Nataly Ascarrunz; Amy T. Austin; Mercedes Bustamante; Gisleine Cunha‐Zeri; M. C. Forti; Judith J. Hoelzemann; Vı́ctor J. Jaramillo; Luiz Antônio Martinelli; F. Pacheco