Asymmetric effects of litter accumulation on soil temperature and dominant plant species in fenced grasslands

Abstract

Excess litter accumulates on the soil surface of fenced grasslands and alters the abiotic environment and plant population dynamics. However, little is known about the effect of litter accumulation on the interaction between environmental factors and plant population characteristics in fenced grasslands, especially over different time scales. We applied a three-year litter removal experiment to two kinds of fenced grasslands in Inner Mongolia, China. We measured soil temperature in situ and plant phenology and population characteristics of three dominant species (Stipa grandis, S. krylovii, and Leymus chinensis). During the growing season, litter accumulation (i.e., the control) significantly decreased soil temperature, with a larger effect in the daytime than at night. The diurnal negative effect gradually weakened across the growing season, whereas the negative effect in the nighttime shifted to a positive effect on soil temperature in the late growing season. The decreased soil temperature delayed plant phenology, with longer delays in S. grandis and S. krylovii than L. chinensis. Litter accumulation also significantly increased the height, cover, root biomass, and relative dominance of L. chinensis but decreased cover, density, root biomass, and relative dominance of both Stipa, driving replacement of S. grandis or S. krylovii by L. chinensis in two grasslands. Our findings emphasize the critical function of litter in grassland management and provide a new insight to elucidating the mechanism of how litter accumulation regulates the abiotic environment, community composition and structure, and successional change in fenced grasslands.