Spatial assemblage of grassland communities and interrelationships with productivity

<p><span>Knowledge on the fine-scale spatial structure is very important for understanding plant community dynamics, as interactions among sessile plants mainly occur in the neighborhood. However, the spatial assemblage mechanism and interrelationships with productivity remain poorly understood. Here, species segregation index (Ms_com) was used to quantify the interspecific segregation (or intraspecific aggregation) of the neighborhood in plant communities from three contrasting plateaus. We employed the coordinates for 125,726 individual plants (within 1 m² plots) sampled in natural grassland communities across Loess Plateau (LP), Mongolian Plateau (MP), and Tibetan Plateau (TP) to elucidate the assembly mechanisms of Ms_com and interrelationships with above-ground net primary productivity (ANPP). We found that these grassland communities tended to assemble in intraspecific aggregations; the phenomena were more apparent in desert grassland communities. </span><span>Apart from the controls of self-organization, climatic heterogeneity also plays an important role in determining Ms_com. In grassland communities on LP and MP, Ms_com was predominantly affected by </span><span>reproductive allocation</span><span> (RA); whereas on TP, Ms_com was more responsive and sensitive to climatic heterogeneity (especially precipitation and low temperatures).</span><span> We also found that Ms_com better explained the overall variations in ANPP than species diversity, and mediated the response of ANPP to environmental variations; Ms_com and environmental effects jointly explained 22.7, 19.1, and 49.8% of the variations in ANPP on LP, MP, and TP, respectively. Our findings provide new insights into the underlying mechanisms of spatial assemblage of grassland communities, and emphasize the critical role of spatial structure in predicting the impacts of environmental change.</span></p>