Contrasting responses in leaf nutrient-use strategies of two dominant grass species along a 30-yr temperate steppe grazing exclusion chronosequence

Abstract

Aims Grazing exclusion practices can be promising restoration techniques where ecosystem degradation follows from rapidly increasing grazing pressure, as widely observed in northern Chinese grasslands. However, the mechanisms of plant-soil interactions responsible for nutrient cycling restoration remain unclear. Methods We examined the functional response of the two most dominant grass species with contrasting nutrient economies to a grazing exclusion chronosequence varying greatly in soil moisture and extractable N and P. Results The relative biomass of the nutrient acquisitive species Leymus chinensis increased while that of the nutrient conservative Stipa grandis decreased across the chronosequence. Leymus chinensis displayed increasing leaf nutrient concentration and decreasing nutrient resorption with time since grazing exclusion for both N and P. In contrast, S. grandis showed decreasing leaf N and P concentrations and largely stable nutrient resorption. Conclusions These differences in plasticity, with respect to nutrient stoichiometry and resorption, suggest contrasting abilities of these two dominant species to compete for soil resources and/or differences in their affinity to the changing forms of soil available N and P likely occurring along the restoration gradient. Ecosystem trajectory of change after grazing exclusion appears therefore largely dependent on the nutrient use strategies of co-occurring dominant grassland species.

Heavy grazing effects on stem elongation and internode allometry: Insights from a natural pasture grass

“…What is the mechanism underlying these changes in stem elongation? Previous studies that observed physiological and biochemical changes in plant stems induced by grazing provide some possible answers (Lü et al, 2014;Shen, Wang, & Tang, 2013). The physiological and molecular mechanisms underlying the grazing-induced limitation in stem elongation warrant more detailed studies.…”

“…The field site was subject to pseudo-replication, which is often reported for many chronosequence ecological studies (Blois, Williams, Fitzpatrick, Jackson, & Ferrier, 2013;Lü et al, 2014;Walker, Wardle, Bardgett, & Clarkson, 2010). Under this situation, a paired sampling method is recommended for field sampling.…”

Plant sizes mediate mowing‐induced changes in nutrient stoichiometry and allocation of a perennial grass in semi‐arid grassland

“…Therefore, mowing will promote more biomass to allocate to the leaf obtaining the most light resource (Chapin, Schulze, & Mooney, ). Thirdly, the competition of grassland plants for soil nutrients significantly weakened in mowed habitats, while in nonmowed habitats, increased nutrient concentrations were promoted (Lü et al., ; Veen, de Vries, Bakker, van der Putten, & Olff, ). These results are in agreement with a number of empirical studies on changes in soil nutrient availability and nutrient competition patterns with increased mowing disturbance (Helsen, Ceulemans, Stevens, & Honnay, ; Tilman & Wedin, ).…”

Response of Grazing Land Soil Health to Management Strategies: A Summary Review

“…Nitrogen use efficiency is the ability of plants to use available nitrogen (N), which determines the yield per unit of N input and can be affected by grazing land management such as plant species (e.g., [18]), fertilizer management (e.g., [19]), and grazing activities (e.g., [20]). Improper management such as overuse of synthetic fertilizers can increase the cost of production as well as N loss from the ecosystem, which leads to water contamination and greenhouse gas emissions.…”