Title: Climate warming, rather than nitrogen deposition, reduces plant diversity and increases community homogenization in a desert steppe

Authors: Yi Zhu，Guodong Han，Loïc Pellissier，Mai-He Li，Lin Jiang， Jinglei Tang，Cuiping Gao， Haiyan Ren*

Journal: Agricultural and Forest Meteorology

Impact factor: IF2025=5.7（中科院一区TOP）

Abstract: It is still unclear how increasing nitrogen (N) deposition, climate warming, and their interaction affect biotic impoverishment (decreases in α-diversity) and homogenization (decreases in β-diversity) of plant communities at taxonomic, functional, and phylogenetic levels. To address this, we conducted a long-term (17-year) field experiment in Inner Mongolia's temperate desert steppe to investigate the effects of warming and nitrogen deposition on plant taxonomic, functional, and phylogenetic α- and β-diversity. Over this period (2006–2022), warming (mean annual temperature + 1.4 °C) significantly decreased species richness and functional α-diversity throughout the experiment, whereas its effects on phylogenetic α-diversity and community phylogenetic structure were significant only before 2015 and disappeared thereafter, likely due to an extreme drought that reset the community composition. In contrast, β-diversity steadily declined over the entire period. These dynamics led to a shift in the community phylogenetic structure from overdispersion towards randomness during the first 10 years. Nitrogen addition (10 g m2 yr-1) had no significant impact on diversity at the functional and phylogenetic levels but increased β-diversity at the taxonomic level. Our findings reveal that relatively rare species were more likely to go extinct, while species with higher leaf nitrogen concentrations were more prone to colonization, and these patterns were observed across all treatments. These findings suggest that warming can contribute to biotic impoverishment and homogenization by causing the extinction of species distantly related to the resident community.

Linkage: https://doi.org/10.1016/j.agrformet.2025.110937