10-years water and nutrient addition in a field experiment
Results from the field manipulation experiment showed that the CWM of genome size increased significantly after resource addition (F = 20.72,P < 0.001; Fig. 5; Table S3). This effect was generally consistent across different years, with the interactive effect of resources addition and experimental year being marginally non-significant (F = 2.02, P = 0.052). These results were in line with our model prediction from HMSC, i.e., enhanced resources generally have positive effects on CWM genome size by favoring large-GS species and suggest that large-GS plants are stronger competitors than small-GS plants when resource availability increases. Results from the 10-yr resources manipulation study can represent responses to natural resource fluctuations over the relatively short term, while results from our transect study can represent the consequences for selection over long-term ecological and evolutionary scales. Taken together, these results confirm that increased resource availability favors large-GS plants and provide direction for a new dimension of ecological studies in the face of global change.
Water is the most limiting resource in temperate grasslands (Baiet al. 2004), here we showed that increased precipitation boosted the abundance of the large-GS plants within the community. Genome size is positively correlated with cell size while negatively correlated with tissue elasticity (Castro‐Jimenez et al. 1989). Increased elastic tissue and smaller cell size are important for turgor maintenance in plants under drought stress, suggesting that natural selection should favor plants with smaller genomes in xeric environments (Castro‐Jimenezet al. 1989). Similarly, a positive correlation was found between 2C DNA content of Californian angiosperms and annual precipitation (Knight & Ackerly 2002). In addition to water availability, soil nutrient availability can also constrain the performance of large-GS species. Previous studies found that the large-GS species became more dominant after nutrient addition (Šmarda et al. 2013; Guignardet al. 2016), in line with our results from the transect study and the 10-yr resource manipulation experiment. Our work combines spatial investigation and temporal monitoring to show that the enhancement of resource availability can shift plant dominance in grassland communities by favoring large-GS species.