Data from: Plant biomass, not plant economics traits, determines responses of soil CO2 efflux to precipitation in the C4 grass Panicum virgatum

1. Plant responses to major environmental drivers like precipitation can
influence important aspects of carbon (C) cycling like soil CO2 efflux
(JCO2). These responses may be predicted by two independent classes of
drivers: plant size—larger plants respire more and produce a larger
quantity of labile C, and plant economics—plants possessing more
acquisitive plant economics strategies (i.e., high metabolic rate and
tissue nutrient content) produce higher-quality tissue that respires
rapidly and decomposes quickly. 2. At two sites in central Texas, USA with
similar climates and differing soil characteristics, we examined the
response of eight Panicum virgatum genotypes to three annual precipitation
levels defined by the driest, average, and wettest years from each site’s
precipitation history. We evaluated the individual and joint influence of
plant genotypes and precipitation on JCO2 and traits related to plant
economics and plant size. We then used confirmatory path analysis to
evaluate whether effects of precipitation on JCO2 were in part related to
effects of precipitation on plant economics traits or size (‘mediated’
effects). 3. These genotypes exhibited variation in plant economics traits
and aboveground net primary productivity (ANPP), an aboveground measure of
plant size. Increasing precipitation increased JCO2 and ANPP more than
plant economics traits. At both sites, ANPP was the single best predictor
of JCO2. Moreover, the sites differed in the ways that plant size and
plant economics traits combined with precipitation to influence JCO2. At
the Austin site, the positive effect of precipitation on JCO2 was mediated
primarily by ANPP, offset by a smaller effect of leaf nitrogen content; no
direct precipitation effect was detected. At the Temple site, increasing
precipitation had positive direct and ANPP-mediated effects on JCO2. This
suggests that greater water limitation at Austin may strengthen the links
between plant size and JCO2. 4. Synthesis Estimates of C cycling can be
improved by accounting for mediation of precipitation effects on JCO2 by
plant economics traits and plant size in resource-limited environments.