Plant biomass, not plant economics traits, determines responses of soil CO2 efflux to precipitation in the C4 grass Panicum virgatum. (3rd April 2020)

• Record Type: Journal Article
• Authors: Heckman, Robert W.; Khasanova, Albina R.; Johnson, Nicholas S.; Weber, Sören; Bonnette, Jason E.; Aspinwall, Michael J.; Reichmann, Lara G.; Juenger, Thomas E.; Fay, Philip A.; Hawkes, Christine V.
• Editors: Schwinning, Susan
• Is Part Of: Journal of ecology. Volume 108:Number 5(2020:Sep.)
• Page Start: 2095
• Page End: 2106
• Publication Date: 2020-04-03
• Subjects: above‐ground–below‐ground linkages -- ecosystem functioning -- genotype‐by‐environment interactions -- plant economics spectrum -- precipitation variability -- switchgrass -- trait‐based ecology; Plant ecology -- Periodicals; 577.05
• DOI: 10.1111/1365-2745.13382
• Languages: English
• ISSNs: 0022-0477

Abstract

Abstract: Plant responses to major environmental drivers like precipitation can influence important aspects of carbon (C) cycling like soil CO2 efflux ( J CO 2 ). 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. 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 J CO 2 and traits related to plant economics and plant size. We then used confirmatory path analysis to evaluate whether effects of precipitation on J CO 2 were in part related to effects of precipitation on plant economics traits or size ('mediated' effects). These genotypes exhibited variation in plant economics traits and above‐ground net primary productivity (ANPP), an above‐ground measure of plant size. Increasing precipitation increased J CO 2 and ANPP more than plant economics traits. At both sites, ANPP was the best predictor of J CO 2 . Moreover, the sites differed in the ways that plant size and plant economics traits combined with precipitation to influence J CO 2 . At the Austin site, the positive effect of precipitation on J CO 2 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 J CO 2 . This suggests that greater water limitation at Austin may strengthen the links between plant size and J CO 2 . Synthesis . Estimates of C cycling can be improved by accounting for mediation of precipitation effects on J CO 2 by plant economics traits and plant size in resource‐limited environments. Abstract : Plant responses to precipitation can influence important aspects of carbon cycling like soil CO2 efflux. In this study, one class of responses –plant size – increased soil CO2 efflux in response to increasing precipitation, while another class – plant economics traits – influenced soil CO2 efflux independent of precipitation. Accounting for different effects of plant size and plant economics traits on soil CO2 efflux can improve estimates of carbon cycling.