Demographic variation and habitat specialization of tree species in a diverse tropical forest of Cameroon

作     者：David Kenfack George B Chuyong Richard Condit Sabrina E Russo Duncan W Thomas 

作者机构：Center for Tropical Forest Science - Forest GEO Botany Department Smithsonian Tropical Research Institute Department of Botany and Plant Physiology University of Buea Center for Tropical Forest Science Smithsonian Tropical Research Institute School of Biological SciencesUniversity of Nebraska Department of Biological Sciences Washington State University 

出 版 物：《Forest Ecosystems》 (森林生态系统（英文版）)

年 卷 期：2014年第1卷第4期

页      面：201-213页

学科分类：07[理学] 0713[理学-生态学] 

基　　金：the National Institutes of Health award U01 TW03004 under the NIH-NSF-USDA funded International Cooperative Biodiversity Groups program financial support from the U.S. Agency for International Development’s Central Africa Regional Program for the Environment and the Smithsonian Tropical Research Institute Financial support for the 2008 recensus was provided by the Frank Levinson Family Foundation supported by U.S. National Science Foundation award DEB-9806828 provided by the Bioresources Development and Conservation Programme-Cameroon the WWF Korup Project 

主　　题：tree Demographic variation and habitat specialization of tree species in a diverse tropical forest of Cameroon Figure 

摘      要：Background： Many tree species in tropical forests have distributions tracking local ridge-slope-valley topography. Previous work in a 50-ha plot in Korup National Park, Cameroon, demonstrated that 272 species, or 63% of those tested, were significantly associated with topography. Methods： We used two censuses of 329,000 trees ≥1 cm dbh to examine demographic variation at this site that would account for those observed habitat preferences. We tested two predictions. First, within a given topographic habitat, species specializing on that habitat （＇residents＇） should outperform species that are specialists of other habitats （＇foreigners＇）. Second, across different topographic habitats, species should perform best in the habitat on which they specialize （＇home＇） compared to other habitats （＇away＇）. Species＇ performance was estimated using growth and mortality rates. Results： In hierarchical models with species identity as a random effect, we found no evidence of a demographic advantage to resident species. Indeed, growth rates were most often higher for foreign species. Similarly, comparisons of species on their home vs. away habitats revealed no sign of a performance advantage on the home habitat. Conclusions＂ We reject the hypothesis that species distributions along a ridge-valley catena at Korup are caused by species differences in trees _〉1 cm dbh. Since there must be a demographic cause for habitat specialization, we offer three alternatives. First, the demographic advantage specialists have at home occurs at the reproductive or seedling stage, in sizes smaller than we census in the forest plot. Second, species may have higher performance on their preferred habitat when density is low, but when population builds up, there are negative density-dependent feedbacks that reduce performance. Third, demographic filtering may be produced by extreme environmental conditions that we did not observe during the census interval.