Quantifying uncertainty about forest recovery 32-years after selective logging in Suriname
Tropical forests managed principally for timber production, if logging is well done, provides important carbon storage and sequestration services. Forestry practices that reduce damage to the forest during and after logging, can help maintain and promote timber stock recovery as well as carbon storage and carbon sequestration services.
In this study we evaluated the performance of the CELOS timber harvest system as it relates to the time needed to recover timber and carbon stocks. The CELOS timber harvest system is one of the oldest improved logging methods implemented in tropical forests. We monitored tree growth and mortality over a 32-year period beginning in 1978 in forests logged with the CELOS harvest system located in Suriname. We used this data to predict the time needed to recover carbon and timber stocks similar to unlogged forests using a probabilistic framework.
We found there is a 90% probability that forests logged at 25 m3 ha-1, the maximum cutting limit in Suriname, recover carbon and timber stocks after 70 and 40 years, respectively. The less time needed to recover timber for the 2nd harvest potentially offers an opportunity to use carbon payments to capture additional carbon by extending the time between timber harvests. Such a carbon payment scheme could also promote timber sustainability beyond the second harvest as their is more time for commercial tree species to grow to log grade sizes.
Tropical forests managed principally for timber production, if logging is well done, provides important carbon storage and sequestration services. Forestry practices that reduce damage to the forest during and after logging, can help maintain and promote timber stock recovery as well as carbon storage and carbon sequestration services.
In this study we evaluated the performance of the CELOS timber harvest system as it relates to the time needed to recover timber and carbon stocks. The CELOS timber harvest system is one of the oldest improved logging methods implemented in tropical forests. We monitored tree growth and mortality over a 32-year period beginning in 1978 in forests logged with the CELOS harvest system located in Suriname. We used this data to predict the time needed to recover carbon and timber stocks similar to unlogged forests using a probabilistic framework.
We found there is a 90% probability that forests logged at 25 m3 ha-1, the maximum cutting limit in Suriname, recover carbon and timber stocks after 70 and 40 years, respectively. The less time needed to recover timber for the 2nd harvest potentially offers an opportunity to use carbon payments to capture additional carbon by extending the time between timber harvests. Such a carbon payment scheme could also promote timber sustainability beyond the second harvest as their is more time for commercial tree species to grow to log grade sizes.
Logging and indigenous hunting impacts on large Neotropical animals
Areas allocated for industrial logging and community-owned forests account for over 50% of all remaining tropical forests. Landscape-scale conservation strategies that include these forests are expected to have substantial benefits for biodiversity, especially for large mammals and birds that require extensive habitat but that are susceptible to extirpation due to synergies between logging and hunting. Additionally, the response of large vertebrates to logging alone are poorly understood due to their cryptic behaviour and low densities.
In this study, we assessed the effects of logging and hunting on detection and occupancy rates of large vertebrates in a multiple-use forest on the Guiana Shield. Our study site was certified as being responsibly managed for timber production and indigenous communities are legally guaranteed use-rights to the forest. We coupled camera trap data for wildlife detection with a spatially-explicit dataset on indigenous hunting.
Our multi-species occupancy model found a weak positive effect of logging on occupancy and detection rates, whilst hunting had a weak negative effect. Model predictions of species richness were also higher in logged forest sites compared to unlogged forest sites. Density estimates for jaguars and ocelots in our multiple-use forest were also similar to estimates reported for fully protected areas. Involvement of local communities in forest management, control of forest access, and nesting production forests in a landscape that includes strict protected areas seemed important for these positive biodiversity outcomes. The maintenance of vertebrate species bodes well for both biodiversity and the humans that depend on multiple-use forests.
Areas allocated for industrial logging and community-owned forests account for over 50% of all remaining tropical forests. Landscape-scale conservation strategies that include these forests are expected to have substantial benefits for biodiversity, especially for large mammals and birds that require extensive habitat but that are susceptible to extirpation due to synergies between logging and hunting. Additionally, the response of large vertebrates to logging alone are poorly understood due to their cryptic behaviour and low densities.
In this study, we assessed the effects of logging and hunting on detection and occupancy rates of large vertebrates in a multiple-use forest on the Guiana Shield. Our study site was certified as being responsibly managed for timber production and indigenous communities are legally guaranteed use-rights to the forest. We coupled camera trap data for wildlife detection with a spatially-explicit dataset on indigenous hunting.
Our multi-species occupancy model found a weak positive effect of logging on occupancy and detection rates, whilst hunting had a weak negative effect. Model predictions of species richness were also higher in logged forest sites compared to unlogged forest sites. Density estimates for jaguars and ocelots in our multiple-use forest were also similar to estimates reported for fully protected areas. Involvement of local communities in forest management, control of forest access, and nesting production forests in a landscape that includes strict protected areas seemed important for these positive biodiversity outcomes. The maintenance of vertebrate species bodes well for both biodiversity and the humans that depend on multiple-use forests.
Effects of reduced-impact selective logging on palm regeneration in Belize
Palms are geographically widespread, ecologically diverse and often critical for the maintenance of ecosystem functions, wildlife populations, and local livelihoods. We however know little about the impacts of selective logging on palms and their ability to persist in these logged forests. Palms are especially prone to logging related damage as they are generally not avoided during road and skid trail construction because of their lack of both tap roots and large buttresses that make them easy to topple.
To assess the impacts of a low-intensity selective timber harvest on a palm community in Belize, we sampled palms across a gradient of increasing logging impact severity from areas not directly affected by logging (NADA), in felling gaps, on secondary and primary skid trails, and on log landings. We used generalised linear mixed-effect models fitted in a Bayesian framework and applied a non-metric multi-dimensional scaling to evaluate differences in palm seedling regeneration density and species composition, respectively.
The harvest of an average of 2.5 trees ha−1 caused 0.4% of the forest to be converted to log landings, 0.7% and 3.6% to roads and skid trails, and 2.3% to felling gaps, which left 93.0% of the 350 ha harvest block with no direct impacts of logging (NADA). The difference in abundance and species composition of palm regeneration in unlogged areas compared to felling gaps and skid trails was small, but log landings had markedly lower densities.
Our results highlight that the impacts of selective logging are minor at least where harvest intensities are low and reduced-impact logging practices are employed. If further reductions in canopy opening and soil disturbance are desired, we recommend that logs be cable-yarded (i.e., winched) the final 20 m to skid trails instead of driving to the tree stumps. We estimate that implementation of this practice would reduce total skid trail coverage from 3.6% to 2.9% and overall forest disturbance from 7.0% to 6.3%. However, further reductions in disturbance might be inimical to the maintenance of palms and will certainly not favour regeneration of light-demanding commercial timber species like Mahogany (Swietenia macrophylla).
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Neotropical forests are shifting in species and trait composition
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 (CO2, 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. |
Licania heteromorpha
Miconia sp.
Mora excelsa
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