Response of a facultative CAM plant and its competitive relationship with a grass to changes in rainfall regime

Abstract

Background and aims We investigated the response of a model facultative CAM plant (Mesembryanthemum crystallinum) and its competition with a C 3 grass (Bromus mollis) to changes in rainfall regime. Methods Seedlings of M. crystallinum and B. mollis in both monoculture and mixtures growing in shallow and deep pots were subjected to three levels of intra-seasonal rainfall variability and rainfall seasonality in both high water and low water conditions. Response of plants were evaluated by nocturnal carboxylation and biomass. Results A high rate of water drainage beneath root zones in coarse soil led to a negative response of M. crystallinum and B. mollis in monoculture under increased intra-seasonal rainfall variability. Seasonal rainfall shifts to later dates during the growing season generally favored the growth of M. crystallinum and B. mollis in monoculture, with the exception of high water stress conditions whereby drought-intolerant species B. mollis was disfavored. Rainfall seasonality but not intra-seasonal rainfall variability affected nocturnal carboxylation by M. crystallinum in monoculture. Conclusions We suggest that soil texture, root depth, and rainfall gradient are important mediators of plant growth under increased intra-seasonal rainfall variability. Drought severity and the ability of a plant to tolerate drought and can greatly affect its response to the seasonal timing of rainfall. Nocturnal carboxylation by M. crystallinum in response to rainfall variability depends on the timescale.

Plant Hydraulic Stress Strategy Improves Model Predictions of the Response of Gross Primary Productivity to Drought Across China

“…Although few observations of HR in China are available, our studies suggest that upward HR is ubiquitous during dry events in China and has a significant influence on carbon fluxes. Furthermore, HR has even been reported to affect species interaction or coexistence of terrestrial ecosystem (Moreno‐Gutierrez et al, 2012; Yu, Carr, et al, 2018).…”