The effects of local-scale resource heterogeneity on tropical tree communities

tropical forest;community assembly;niche partitioning;habitat heterogeneity;soil resources

Baldeck, Claire

关键词: tropical forest;    community assembly;    niche partitioning;    habitat heterogeneity;    soil resources;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/31999/Baldeck_Claire.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

The role of niche assembly processes in shaping ecological communities is a subject of great interest to ecologists, especially in species rich communities such as tropical forests, as niche processes may play an important part in biodiversity maintenance. An important part of the environmental niche for tropical tree species is their specialization for particular soil resource conditions. My dissertation research examines the soil resource and topographic niches of tropical forest tree species and how they affect local (< 1 km) tree community structure. This research draws upon data from eight large (24-50 ha) tropical forest plots located around the globe, for which all trees > 1 cm in diameter have been mapped. Additionally, topographic variation has been mapped within these plots and I use data from a recent, extensive soil sampling effort that mapped the small-scale heterogeneity in many soil variables (including P, Ca, Mg, K, Mn, Al, and pH) within these plots. Previous research using these data has demonstrated that many tree species are non-randomly distributed with respect to soil resource and topographic variation, indicating that local-scale soil resource specialization is common and widespread for tropical trees. I use a variety of multivariate techniques to investigate whether the soil resource and topographic niches of individual tree species have important emergent effects at the community level. I demonstrate that environmental variation is often a strong driver of variation in community composition within these forest plots. I also relate the soil resource and topographic niches of species to their evolutionary relationships and show that closely related species often have more similar habitat niches than distant relatives. The combined effects of habitat heterogeneity on community structure and phylogenetic signal in habitat niches create communities where soil resource and topographic variation affects the overall phylogenetic structure of the community. Furthermore, I examine a possible mechanism for the controls of soil resources on spatial variation in leaf chemistry, an important component of ecosystem biogeochemical cycling. I find that leaf nutrient profiles are highly conserved within a species and thus I predict that soil resources are likely to influence community-level variation in leaf chemistry through their effects on species composition, rather than by intraspecific responses to soil nutrients. Overall, my dissertation has helped to reveal and explain local-scale environmental controls on community structure and to clarify likely controls of soil resources on spatial variation in ecosystem biogeochemistry.