Browsing by Subject "selective logging"

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    Constituents and drivers of composition, diversity and structure of a Congolese forest
    (2016-04-29) Gopalakrishna, Trisha
    Tropical forest systems occupy 2% of the earth’s land surface but host nearly 50% of the world’s forests and support unique flora and fauna and ecological processes. They also provide a multitude of ecosystem services ranging from the provision of food and water to supporting livelihoods and climate change mitigation. However, tropical forests are under immense anthropogenic pressures, including conversion of forestland for agricultural purposes, logging and extraction of timber, and exploitation via hunting and poaching. These pressures fragment forests and alter ecological processes that are linked to the many ecosystem services they provide. The Congolese forest of Central Africa is an important tropical forest belt of the world with a unique history of anthropogenic pressures, particularly logging and hunting activities. In this study, I examine the forests of the northern Republic of the Congo to understand the role of logging and hunting on forest diversity, composition, and structure. Specifically, I identify forest tree communities and determine the extent to which environmental drivers versus anthropogenic disturbance dictate forest composition, diversity and structure. To do so, I use a range of statistical techniques, including non-metric multidimensional scaling, classification and multi-level pattern analysis and multiple regression approaches. The results of my study reveal that variation in species composition is explained by disturbance type (combination of logging and hunting, logging only, and no disturbance), distance to Kabo village (proxy for disturbance), and logging. I determined five tree species groups across the study area that largely represents a gradient of disturbance. Areas having combined pressures of hunting and selective logging included the highest number of species groups, while pristine areas included the lowest number of species groups. In addition, the indicator tree species characterizing the species groups also reflected the level of disturbance, with highly disturbed plots containing more characteristic secondary tree species and pristine areas containing primary tree species. For drivers of tree species diversity, I concluded that edaphic factors including pH and phosphorous explain variation in diversity. Lastly, I determined there to be no significant driver of basal area across the plots, but variation in wood density was driven by total nitrogen and soil texture. My study highlights the effects of disturbance on species composition across this forested landscape; whereas soil characteristics seemed to have a stronger role in controlling forest diversity and structure, although additional research is needed to fully elucidate the observed results. More studies are needed to decouple the effects of anthropogenic pressures and environmental factors on forest composition, diversity and structure, thereby providing more insight about these forests.
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    Low-intensity logging and hunting have long-term effects on seed dispersal but not fecundity in Afrotropical forests.
    (AoB PLANTS, 2019-02) Nuñez, Chase L; Clark, James S; Clark, Connie J; Poulsen, John R
    Hunting and logging, ubiquitous human disturbances in tropical forests, have the potential to alter the ecological processes that govern population recruitment and community composition. Hunting-induced declines in populations of seed-dispersing animals are expected to reduce dispersal of the tree species that rely on them, resulting in potentially greater distance- and density-dependent mortality. At the same time, selective logging may alter competitive interactions among tree species, releasing remaining trees from light, nutrient or space limitations. Taken together, these disturbances may alter the community composition of tropical forests, with implications for carbon storage, biodiversity conservation and ecosystem function. To evaluate the effects of hunting and logging on tree fecundity and seed dispersal, we use 3 years of seed rain data from a large-scale observational experiment in previously logged, hunted and protected forests in northern Republic of Congo (Brazzaville). We find that low-intensity logging had a meaningful long-term effect on species-specific seed dispersal distances, though the direction and magnitude varied and was not congruent within dispersal vector. Tree fecundity increased with tree diameter, but did not differ appreciably across disturbance regimes. The species-specific dispersal responses to logging in this study point towards the long-lasting toll of disturbance on ecological function and highlight the necessity of conserving intact forest.