Direct and indirect effects of land-use intensity on plant communities across elevation in semi-natural grasslands

Abstract

Grassland biodiversity is vulnerable to land use change. How to best manage semi-natural grasslands for maintaining biodiversity is still unclear in many cases because land-use processes may depend on environmental conditions and the indirect effects of land-use on biodiversity mediated by altered abiotic and biotic factors are rarely considered. Here we evaluate the relative importance of the direct and indirect effects of grazing intensity on plant communities along an elevational gradient on a large topographic scale in the Eastern Carpathians in Ukraine. We sampled for two years 31 semi-natural grasslands exposed to cattle grazing. Within each grassland site we measured plant community properties such as the number of species, functional groups, and the proportion of species undesirable for grazing. In addition, we recorded cattle density (as a proxy for grazing intensity), soil properties (bare soil exposure, soil organic carbon, and soil pH) and densities of soil decomposers (earthworms and soil microorganisms). We used structural equation modelling to explore the direct and indirect effects of grazing intensity on plant communities along the elevation gradient. We found that cattle density decreased plant species and functional diversity but increased the proportion of undesirable species. Some of these effects were directly linked to grazing intensity (i.e., species richness), while others (i.e., functional diversity and proportion of undesirable species) were mediated via bare soil exposure. Although grazing intensity decreased with elevation, the effects of grazing on the plant community did not change along the elevation gradient. Generally, elevation had a strong positive direct effect on plant species richness as well as a negative indirect effect, mediated via altered soil acidity and decreased decomposer density. Our results indicate that plant diversity and composition are controlled by the complex interplay among grazing intensity and changing environmental conditions along an elevation gradient. Furthermore, we found lower soil pH, organic carbon and decomposer density with elevation, indicating that the effects of grazing on soil and related ecosystem functions and services in semi-natural grasslands may be more pronounced with elevation. This demonstrates that we need to account for environmental gradients when attempting to generalize effects of land-use intensity on biodiversity.

The Natural and Socioeconomic Influences on Land-Use Intensity: Evidence from China

“…Our overall assessment found that elevations negatively impact LUI with an SRC value of −0.033, implying that cities with higher elevations restrict efficient land use and thus the product from land-we use the indicator STGRPP (second and tertiary gross regional product per km 2 , unit: CNY 10,000 per km 2 ) as the proxy for the output from land to reflect the degree of LUI. Our findings of the impact of elevations agree with previous findings [30,62,63].…”

Landscape Pattern Vulnerability of the Eastern Hengduan Mountains, China and Response to Elevation and Artificial Disturbance

“…Ultimately, vertical zone boundaries such as forest and snow lines will be higher in the center of the mountain system than at the periphery. In addition, Buzhdygan et al [85] suggested that human grazing practices on grassland ecosystems could become more obvious with increasing elevation, which may lead to the severe spatial fragmentation of the landscape [86]. Reclamation and deforestation in high mountains in order to meet food and timber needs will result in highly vulnerable regional landscapes [87][88][89].…”

Grassland type and seasonal effects have a bigger influence on plant diversity than prairie dog disturbances in semi-arid grasslands

“…This can be explained by the tendency of mountain grasslands to have leptosol soils, highly variable slopes as well as higher elevation and lower atmospheric pressure, leading to higher precipitation and lower temperatures (Gommes, 2002;Anjos et al 2015). These conditions are known to often cause an increase in plant species richness and cover (Speed et al 2013;Buzhdygan et al 2020). In addition, Pando- Moreno et al (2013) found that many of the sites in mountain grasslands within GPCA El Tokio had a lower level of electrical conductivity and absence of gypsum, while sites that fall within calcareous, arid and agricultural grassland types had at least some percentage of gypsum in them.…”