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1. Litter dynamics recover faster than arthropod biodiversity during tropical forest succession

   https://doi.org/10.1111/btp.12740  

   Cole, Rebecca J. ; Selmants, Paul ; Khan, Shafkat ; Chazdon, Robin ( December 2019 , Biotropica)

   Litterfall and litter decomposition are key elements of nutrient cycling in tropical forests, a process in which decomposer communities such as macro‐arthropods play a critical role. Understanding the rate and extent to which ecosystem function and biodiversity recover during succession is useful to managing the growing area of tropical successional forest globally. Using a replicated chronosequence of forest succession (5–15, 15–30, 30–45 years, and primary forest) on abandoned pastures in lowland tropical wet forest, we examined litterfall, litter chemistry, and effects of macro‐arthropod exclusion on decomposition of two litter types (primary and 5‐ to 15‐years‐old secondary forest). Further, we assessed macro‐arthropod diversity and community composition across the chronosequence. Overstory cover, litterfall, and litter nutrients reached levels similar to primary forest within 15–30 years. Young secondary forest litter (5–15 years) had lower initial N and P content, higher C:N, and decayed 60 percent faster than primary forest litter. The presence of macro‐arthropods strongly mediated decomposition and nutrient release rates, increasing litter mass loss by 35–44 percent, N released by 53 percent, and P release by 84 percent. Forest age had no effect on soil nutrients, rates of litter decomposition, nutrient release, or macro‐arthropod influence. In contrast, abundance and community composition of macro‐arthropods remained significantly lower and distinct in all ages of secondary compared with primary forest. Order richness was lower in 5–15 years of secondary compared with primary forest. Our results suggest that in highly productive tropical wet forest, functional recovery of litter dynamics precedes recovery of decomposer community structure and biodiversity.

   Abstract in Spanish is available with online material.

    

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2. Leaf litter arthropod responses to tropical forest restoration

   https://doi.org/10.1002/ece3.2220  

   Cole, Rebecca J. ; Holl, Karen D. ; Zahawi, Rakan A. ; Wickey, Philipp ; Townsend, Alan R. ( June 2016 , Ecology and Evolution)

   Soil and litter arthropods represent a large proportion of tropical biodiversity and perform important ecosystem functions, but little is known about the efficacy of different tropical forest restoration strategies in facilitating their recovery in degraded habitats. We sampled arthropods in four 7‐ to 8‐year‐old restoration treatments and in nearby reference forests. Sampling was conducted during the wet and dry seasons using extractions from litter and pitfall samples. Restoration treatments were replicated in 50 × 50‐m plots in four former pasture sites in southern Costa Rica:plantation– trees planted throughout the plot;applied nucleation/islands– trees planted in patches of different sizes; andnatural regeneration– no tree planting. Arthropod abundance, measures of richness and diversity, and a number of functional groups were greater in the island treatment than in natural regeneration or plantation treatments and, in many cases, were similar to reference forest. Litter and pitfall morphospecies and functional group composition in all three restoration treatments were significantly different than reference sites, but island and plantation treatments showed more recovery than natural regeneration. Abundance and functional group diversity showed a much greater degree of recovery than community composition.Synthesis and applications: The less resource‐intensive restoration strategy of planting tree islands was more effective than tree plantations in restoring arthropod abundance, richness, and functional diversity. None of the restoration strategies, however, resulted in similar community composition as reference forest after 8 years of recovery, highlighting the slow rate of recovery of arthropod communities after disturbance, and underscoring the importance of conservation of remnant forests in fragmented landscapes.

    

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3. Do lianas shape ant communities in an early successional tropical forest?

   https://doi.org/10.1111/btp.12709  

   Adams, Benjamin J. ; Gora, Evan M. ; van Breugel, Michiel ; Estrada‐Villegas, Sergio ; Schnitzer, Stefan A. ; Hall, Jefferson S. ; Yanoviak, Stephen P. ( October 2019 , Biotropica)

   Almost half of lowland tropical forests are at various stages of regeneration following deforestation or fragmentation. Changes in tree communities along successional gradients have predictable bottom‐up effects on consumers. Liana (woody vine) assemblages also change with succession, but their effects on animal succession remain unexplored. Here we used a large‐scale liana removal experiment across a forest successional chronosequence (7–31 years) to determine the importance of lianas to ant community structure. We conducted 1,088 surveys of ants foraging on and living in trees using tree trunk baiting and hand‐collecting techniques at 34 paired forest plots, half of which had all lianas removed. Ant species composition, β‐diversity, and species richness were not affected by liana removal; however, ant species co‐occurrence (the coexistence of two or more species in a single tree) was more frequent in control plots, where lianas were present, versus removal plots. Forest stand age had a larger effect on ant community structure than the presence of lianas. Mean ant species richness in a forest plot increased by ca. 10% with increasing forest age across the 31‐year chronosequence. Ant surveys from forest >20 years old included more canopy specialists and fewer ground‐nesting ant species versus those from forests <20 years old. Consequently, lianas had a minimal effect on arboreal ant communities in this early successional forest, where rapidly changing tree community structure was more important to ant species richness and composition.

    

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4. From town to national park: Understanding the long-term effects of hunting and logging on tree communities in Central Africa

   https://doi.org/https://doi.org/10.1016/j.foreco.2021.119571  

   Maicher, Vincent ; Clark, Connie J. ; Harris, David J. ; Medjibe, Vincent P. ; Poulsen, John R. ( January 2021 , Forest ecology and management)

   null (Ed.)

   Anthropogenic disturbances are changing the structure and composition of tropical forests worldwide. Multiple disturbances often occur simultaneously in forests: for example, hunting and logging are within-forest disturbances that impact vast areas of seemingly intact rainforests. Despite recent work on the individual effects of these disturbances, our understanding of how they interact to influence tree communities is still limited. In northern Republic of Congo, we explored the effects of hunting and logging on tree communities. Over an 8-year period, we monitored 12,552 tree stems (≥ 10 cm diameter-at-breast height) spread over 30 1-ha plots along a gradient of human disturbance to compare the tree diversity between hunted and logged forest, once-logged forest, and protected forest free of both disturbances. Tree density, species richness, and community composition were affected by both hunting and logging. Forest close to human settlements was richer, more heterogenous, and more dynamic in species composition across censuses. In hunted and logged forest, fast-growing secondary species with low shade tolerance replaced old growth species. Comparatively, the once-logged forest had the greatest stem density and intermediate species richness with an increased density of shade-bearing species over time. Both tree species spatial turnover and tree recruitment were greatly affected by proximity to human settlements. A shift towards abiotically dispersed trees and increasing seed predation by rodents near villages can partly explain the differences in tree recruitment across the forest types. The combination of hunting and logging seems to have a greater impact on tree communities than either single disturbance, especially with nearness to villages. 

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5. Trade‐offs between carbon stocks and timber recovery in tropical forests are mediated by logging intensity

   https://doi.org/10.1111/gcb.14155  

   Roopsind, Anand ; Caughlin, T. Trevor ; van der Hout, Peter ; Arets, Eric ; Putz, Francis E. ( May 2018 , Global Change Biology)

   Forest degradation accounts for ~70% of total carbon losses from tropical forests. Substantial emissions are from selective logging, a land‐use activity that decreases forest carbon density. To maintain carbon values in selectively logged forests, climate change mitigation policies and government agencies promote the adoption of reduced‐impact logging (RIL) practices. However, whetherRILwill maintain both carbon and timber values in managed tropical forests over time remains uncertain. In this study, we quantify the recovery of timber stocks and aboveground carbon at an experimental site where forests were subjected to different intensities ofRIL(4, 8, and 16 trees/ha). Our census data span 20 years postlogging and 17 years after the liberation of future crop trees from competition in a tropical forest on the Guiana Shield, a globally important forest carbon reservoir. We model recovery of timber and carbon with a breakpoint regression that allowed us to capture elevated tree mortality immediately after logging. Recovery rates of timber and carbon were governed by the presence of residual trees (i.e., trees that persisted through the first harvest). The liberation treatment stimulated faster recovery of timber albeit at a carbon cost. Model results suggest a threshold logging intensity beyond which forests managed for timber and carbon derive few benefits fromRIL, with recruitment and residual growth not sufficient to offset losses. Inclusion of the breakpoint at which carbon and timber gains outpaced postlogging mortality led to high predictive accuracy, including out‐of‐sampleR²values >90%, and enabled inference on demographic changes postlogging. Our modeling framework is broadly applicable to studies that aim to quantify impacts of logging on forest recovery. Overall, we demonstrate that initial mortality drives variation in recovery rates, that the second harvest depends on old growth wood, and that timber intensification lowers carbon stocks.

    

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