DOI: 10.5061/dryad.wstqjq2h7
title: Data from: Plant biomass, not plant economics traits, determines responses of soil CO2 efflux to precipitation in the C4 grass Panicum virgatum

description: 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.
description: Data file supporting the manuscript, "Plant biomass, not
 plant economics traits, determines responses of soil
 CO<sub>2</sub> efflux to precipitation in the
 C<sub>4</sub> grass <i>Panicum
 virgatum". </i>plot_global is a unique identifier for each
 plant; site is the location of the experiment (Austin or Temple); block is
 a spatial block; sub_block is a plot, the level at which precipitation
 treatments were applied; treatment is a precipitation treatment with three
 levels (low, mean, high); genotype is one of eight genotypes used in this
 study (see Table S2 for more information); precip_cm is the annual
 precipitation applied to individual plots (cm); precip_dm_centered is the
 mean-centered annual precipitation applied to a plot (dm); efflux_avg is
 the soil CO<sub>2 </sub>efflux, calculated as an area under
 the curve of seasonal measurements; soiltemp_summer is the soil
 temperature measured during the July (Austin) or August (Temple) soil
 efflux measurement (max soil temperature); soilmois_avg is the average
 soil moisture (%) from monthly measurements; annp is aboveground net
 primary productivity (kg plant <sup>-1</sup>); leaf_n is %
 leaf N; ldmc is leaf dry matter content (mg g<sup>-1</sup>);
 bnpp is belowground net primary productivity (g) measured from root
 ingrowth cores; root_cn is root C:N.