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.