Effects of grazing on leaf traits and ecosystem functioning in Inner Mongolia grasslands: scaling from species to community

Abstract

Abstract. More attention has focused on using some easily measured plant functional traits to predict grazing influence on plant growth and ecosystem functioning. However, there has been much controversy on leaf traits response to grazing, thus more research should be conducted at the species level. Here we investigated the leaf area, leaf mass and specific leaf area (SLA) of 263 species in eight grassland communities along a soil moisture gradient in the Xilin River Basin, a semiarid grassland of northern China, to explore the grazing effects on ecosystem functioning. Results demonstrated that grazing decreased the leaf area and leaf mass in more than 56% of species in the Xilin River Basin, however, responses of SLA to grazing varied widely between species. Grazing increased SLA in 38.4% of species, decreased SLA in 31.3% of species and had no effect on 30.3% of species. Annuals and biennials generally developed high SLA as grazing tolerance traits, while perennial graminoids developed low SLA as grazing avoidance traits. Considering the water ecotypes, the SLA-increased and SLA-unchanged species were dominated by hygrophytes and mesophytes, while the SLA-decreased species were dominated by xerophytes. At the community level, grazing decreased the mean leaf area index (LAI) of six communities by 16.9%, leaf biomass by 35.2% and standing aboveground biomass (SAB) by 35.0% in the Xilin River Basin, indicating that overgrazing greatly decreased the ecosystem functioning in the semi-arid grassland of northern China. Soil properties, especially fielding holding capacity and soil organic carbon and total nitrogen could mediate the negative grazing impacts. The results suggest SLA is a better leaf trait to reveal plant adaptability to grazing. Our findings have practical implications for range management and productivity maintenance in the semiarid grassland, and it is feasible to take some measures such as ameliorating soil water and nutrient availabilities to prevent grassland degradation.

Environmental controls override grazing effects on plant functional traits in Tibetan rangelands

“…As two of the most important numerical traits that relate to plant relative growth rate and stress tolerance (Westoby, 1998), SLA and plant N content did not show significant responses to grazing. This is in line with an earlier study across Tibetan pastures (Heberling, 2015), but in contrast with positive grazing responses of SLA reported from eastern alpine meadows (Niu et al, 2015) and negative responses in Inner Mongolia (Zheng, Ren, Lan, Li, & Bai, 2010).…”

Influence of herbivory pressure on the growth rate and needle morphology of Taxus baccata L. juveniles

“…This might characterise an escape mechanism from grazing, in particular due to the small leaf size and the high leaf dry matter content, however, in our study, the SLA of juvenile yew needles increased under herbivore pressure and was higher in grazed than in non-grazed saplings. This finding is in agreement which the observation of other authors who confirmed that grazing tolerance can be expressed as high specific leaf area (SLA) and low leaf toughness, which increase shoot regrowth ability and selectivity by herbivores (Zheng et al, 2010).…”

“…This finding is surprising because these calculated leaf traits are common predictors of light intensity (Fabjanowski et al, 1974;Zheng et al, 2010), our results therefore indicate that these methods are not suitable to evaluate light conditions of T. baccata stands in small a range of light intensity (between 3 and 16% of full sunlight). Another reason for the lack of correlation could be the distribution of sample points within this range and also the sampling method and sample size.…”