Researchers led by Prof. WANG Xugao from the Institute of Applied Ecology of the Chinese Academy of Sciences, in collaboration with international colleagues, have proposed a new biological hypothesis that combines tree dispersal modes and mycorrhizal types to explain the latitudinal variation in forest biodiversity.
The study, published in Nature, offers new insights into how forest ecosystems maintain biodiversity across different biomes.
Forest ecosystems are essential for biodiversity conservation, with tropical biomes hosting the highest levels of forest biodiversity, while subtropical and temperate forests support relatively lower levels. Understanding the mechanisms that sustain biodiversity from temperate to subtropical forests is critical for informing future conservation efforts. However, this remains a complex challenge due to the significant latitudinal gradient in biodiversity.
To explore these mechanisms, the researchers analyzed data from 720 tree species across 21 large forest dynamics plots, ranging from 16 to 50 hectares, spanning tropical, subtropical, and temperate biomes.
By applying advanced spatial analysis techniques to this extensive dataset, they discovered that abundant species tend to be less spatially aggregated than rare species, revealing a negative aggregation-abundance relationship. Notably, this relationship was stronger in temperate forests than in tropical ones.
The researchers then used spatially explicit simulation models alongside functional trait data to further investigate the underlying dynamics. Their findings suggest that the combination of animal seed dispersal and mycorrhizal associations underpins the negative aggregation-abundance relationship and supports biodiversity maintenance across forest biomes.
In tropical forests, where the aggregation-abundance relationship is weak (abundant species often have more conspecific neighbors than rare species), simulations revealed that the spatial distribution of recruits, particularly those dispersed by animals, stabilizes species coexistence. In contrast, in temperate forests, where the relationship is stronger (abundant species have a similar number of conspecific neighbors as rare species), species rely more heavily on ectomycorrhizal associations.
These fungi play a crucial role in protecting host plants from pathogens and promoting the clustering of recruits near conspecific adults, thereby maintaining community diversity.
"These findings offer a novel perspective on forest biodiversity maintenance by linking dispersal mechanisms with mycorrhizal interactions and highlight the distinct roles that animals and fungi play in temperate and tropical forests," said Prof. WANG, corresponding author of the study.
This research provides a comprehensive framework of analytical models to help ecologists integrate spatial information into future biodiversity studies.
