Edge Effects on Foliar Stable Isotope Values in a Madagascan Tropical Dry Forest

PLoS One

Shawn M. Lehman¹  Keriann C. McGoogan¹  Brooke E. Crowley² 

[1] Department of Anthropology, University of Toronto, Toronto, Ontario, Canada;Departments of Geology and Anthropology, University of Cincinnati Cincinnati, Ohio, United States of America

关键词: Forests;    Leaves;    Forest ecology;    Trees;    Isotopes;    Soil ecology;    Ecosystems;    Humidity;   

DOI  :  10.1371/journal.pone.0044538

学科分类：医学（综合）

来源: Public Library of Science

【 摘 要 】

Edge effects represent an inevitable and important consequence of habitat loss and fragmentation. These effects include changes in microclimate, solar radiation, or temperature. Such abiotic effects can, in turn, impact biotic factors. They can have a substantial impact on species, communities, and ecosystems. Here we examine clinal variations in stable carbon and nitrogen isotope values for trees along an edge-interior gradient in the dry deciduous forest at Ankarafantsika National Park. We predicted that soil respiration and differences in solar irradiance would result in stratified δ13C values where leaves collected close to the forest floor would have lower δ13C values than those growing higher up in the canopy. We also anticipated that plants growing at the savannah-forest boundary would have higher δ13C and δ15N values than plants growing in the forest interior. As expected, we detected a small but significant canopy effect. Leaves growing below 2 m from the forest floor exhibit δ13C values that are, on average, 1.1‰ lower than those growing above this threshold. We did not, however, find any relationship between foliar δ13C and distance from the edge. Unpredictably, we detected a striking positive relationship between foliar δ15N values and increasing distance into the forest interior. Variability in physiology among species, anthropogenic influence, organic input, and rooting depth cannot adequately explain this trend. Instead, this unexpected relationship most likely reflects decreasing nutrient or water availability, or a shift in N-sources with increasing distance from the savannah. Unlike most forest communities, the trees at Ampijoroa are growing in nutrient-limited sands. In addition to being nutrient poor, these well-drained soils likely decrease the amount of soil water available to forest vegetation. Continued research on plant responses to edge effects will improve our understanding of the conservation biology of forest ecosystems in Madagascar.

【 授权许可】

CC BY