Abstract
Tropical forests are notable for their high species diversity, even on small spatial scales, and right-skewed species and size abundance distributions. The role of individual species as drivers of the spatial organization of diversity in these forests has been explained by several hypotheses and processes, for example, stochastic dilution, negative density dependence, or gap dynamics. These processes leave a signature in spatial distribution of small trees, particularly in the vicinity of large trees, likely having stronger effects on their neighbors. We are exploring species diversity patterns within the framework of various diversity-generating hypotheses using individual species–area relationships. We used the data from three tropical forest plots (Wanang—Papua New Guinea, Barro Colorado Island—Panama, and Sinharaja—Sri Lanka) and included also the saplings (DBH ≥ 1 cm). Resulting cross-size patterns of species richness and evenness reflect the dynamics of saplings affected by the distribution of large trees. When all individuals with DBH ≥1 cm are included, ~50% of all tree species from the 25- or 50-ha plot can be found within 35 m radius of an individual tree. For all trees, 72%–78% of species were identified as species richness accumulators, having more species present in their surroundings than expected by null models. This pattern was driven by small trees as the analysis of DBH >10 cm trees showed much lower proportion of accumulators, 14%–65% of species identified as richness repellers and had low richness of surrounding small trees. Only 11%–26% of species had lower species evenness than was expected by null models. High proportions of species richness accumulators were probably due to gap dynamics and support Janzen–Connell hypothesis driven by competition or top-down control by pathogens and herbivores. Observed species diversity patterns show the importance of including small tree size classes in analyses of the spatial organization of diversity.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 8085-8095 |
| Number of pages | 11 |
| Journal | Ecology and Evolution |
| Volume | 11 |
| Issue number | 12 |
| DOIs | |
| State | Published - Jun 2021 |
Bibliographical note
Funding Information:We thank the staff of the New Guinea Research Binatang Center and landowners of Wanang village for their assistance. The research on all three plots was supported by the Smithsonian ForestGEO. We thank the Uva Wellassa University, the University of Peradeniya, and the Forest Department of Sri Lanka for administrative support and the field staff who contributed to the censuses on the Sinharaja plot. The study was supported by the Czech Science Foundation Grant No. 20-17282S and the European Research Council Grant No. 669609. Computational resources were supplied by the project “e-Infrastruktura CZ” (e-INFRA LM2018140) provided within the program Projects of Large Research, Development and Innovations Infrastructures. The BCI forest dynamics research project was made possible by National Science Foundation Grants to Stephen P. Hubbell: DEB-0640386, DEB-0425651, DEB-0346488, DEB-0129874, DEB-00753102, DEB-9909347, DEB-9615226, DEB-9405933, DEB-9221033, DEB-9100058, DEB-8906869, DEB-8605042, DEB-8206992, and DEB-7922197, support from the Center for Tropical Forest Science-Forest Global Earth Observatory, the Smithsonian Tropical Research Institute, the John D. and Catherine T. MacArthur Foundation, the Mellon Foundation, the Small World Institute Fund, and numerous private individuals, and through the hard work of over 100 people from 10 countries over the past three decades.
Funding Information:
We thank the staff of the New Guinea Research Binatang Center and landowners of Wanang village for their assistance. The research on all three plots was supported by the Smithsonian ForestGEO. We thank the Uva Wellassa University, the University of Peradeniya, and the Forest Department of Sri Lanka for administrative support and the field staff who contributed to the censuses on the Sinharaja plot. The study was supported by the Czech Science Foundation Grant No. 20‐17282S and the European Research Council Grant No. 669609. Computational resources were supplied by the project “e‐Infrastruktura CZ” (e‐INFRA LM2018140) provided within the program Projects of Large Research, Development and Innovations Infrastructures. The BCI forest dynamics research project was made possible by National Science Foundation Grants to Stephen P. Hubbell: DEB‐0640386, DEB‐0425651, DEB‐0346488, DEB‐0129874, DEB‐00753102, DEB‐9909347, DEB‐9615226, DEB‐9405933, DEB‐9221033, DEB‐9100058, DEB‐8906869, DEB‐8605042, DEB‐8206992, and DEB‐7922197, support from the Center for Tropical Forest Science‐Forest Global Earth Observatory, the Smithsonian Tropical Research Institute, the John D. and Catherine T. MacArthur Foundation, the Mellon Foundation, the Small World Institute Fund, and numerous private individuals, and through the hard work of over 100 people from 10 countries over the past three decades.
Publisher Copyright:
© 2021 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
Keywords
- individual species–area relationship
- null model
- spatial pattern
- species diversity
- species evenness
- tropical forest
