title: Individual species-area relationship of woody plant communities in a heterogeneous subtropical monsoon rainforest.
abstract: The spatial structure of species richness is often characterized by the species-area relationship (SAR). However, the SAR approach rarely considers the spatial variability of individual plants that arises from species interactions and species' habitat associations. Here, we explored how the interactions of individual plants of target species influence SAR patterns at a range of neighborhood distances. We analyzed the data of 113,988 woody plants of 110 species from the Fushan Forest Dynamics Plot (25 ha), northern Taiwan, which is a subtropical rainforest heavily influenced by typhoons. We classified 34 dominant species into 3 species types (i.e., accumulator, repeller, or no effect) by testing how the individual species-area relationship (i.e., statistics describing how neighborhood species richness changes around individuals) of target species departs (i.e., positively, negatively, or with no obvious trend) from a null model that accounts for habitat association. Deviation from the null model suggests that the net effect of species' interactions increases (accumulate) or decreases (repel) neighborhood species richness. We found that (i) accumulators were dominant at small interaction distances (<10-30 m); (ii) the detection of accumulator species was lower at large interaction distances (>30 m); (iii) repellers were rarely detected; and (iv) large-sized and abundant species tended to be accumulators. The findings suggest that positive species interactions have the potential to accumulate neighborhood species richness, particularly through size- and density-dependent mechanisms. We hypothesized that the frequently disturbed environment of this subtropical rainforest (e.g., typhoon-driven natural disturbances such as landslides, soil erosion, flooding, and windthrow) might create the spatial heterogeneity of species richness and promote positive species interactions.
authors.affiliation: School of Forestry and Resource Conservation, National Taiwan University, Taipei, Taiwan; Institute of Oceanography, National Taiwan University, Taipei, Taiwan.
authors.forename: Cheng-Han
authors.initials: CH
authors.lastname: Tsai
authors.affiliation: Department of Life Science, Tunghai University, Taichung, Taiwan.
authors.forename: Yi-Ching
authors.initials: YC
authors.lastname: Lin
authors.affiliation: Department of Ecological Modelling, UFZ Helmholtz Centre for Environmental Research, Leipzig, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Wiegand
authors.affiliation: Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Nakazawa
authors.affiliation: Taiwan Forestry Research Institute, Taipei, Taiwan.
authors.forename: Sheng-Hsin
authors.initials: SH
authors.lastname: Su
authors.affiliation: Institute of Oceanography, National Taiwan University, Taipei, Taiwan; Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan.
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Hsieh
authors.affiliation: School of Forestry and Resource Conservation, National Taiwan University, Taipei, Taiwan.
authors.forename: Tzung-Su
authors.initials: TS
authors.lastname: Ding
mesh_terms: D065928:Forests; D008962:Models, Theoretical; D016012:Poisson Distribution; D011891:Rain; D014329:Tropical Climate