From town to national park: Understanding the long-term effects of hunting and logging on tree communities in Central Africa
Description
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 a density increase 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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In 2005, we established 30 1-ha plots, with ten plots randomly distributed among three disturbance categories: 1. unhunted and unlogged forest; 2. unhunted and logged forest in the KLC; and, 3. hunted and logged forest. In each plot, all trees ≥ 10 cm diameter at breast height (DBH) were measured, tagged, mapped, and identified to species. To control for the effects of logging and hunting on forest dynamics, the plots were re-censused in 2009 and 2013. All trees were remeasured, mortality was recorded, and newly recruited trees ≥10 cm DBH were tagged, mapped, and identified to species following the same protocol.