Effect of grassland degradation on soil quality and soil biotic community in a semi-arid temperate steppe

Abstract

Grasslands provide a number of ecosystem services for human society. Degradation of grasslands results in the loss of biodiversity and leads to the deterioration of ecosystem functions. In order to accurately assess the influence of grassland degradation on belowground ecosystems, we conducted experiments on a temperate steppe with different levels of degradation and investigated the influence of degradation on soil quality and soil biotic communities. Our results showed that grassland degradation significantly decreased soil quality, with lower values of soil quality index (SQI) observed in the degraded grassland than the meadow steppe and the grassland from the forest-steppe ecotone. Changes in the SQI along the grassland degradation gradient were positively correlated with soil carbon stock and the aboveground biomass, and negatively correlated with the root shoot ratio. Nematode trophic diversity and the ratio of fungal to bacterial PLFA were lower in the degraded grassland than the grassland from the forest-steppe ecotone. The dissimilarities in soil microbial and nematode community composition increased with the changes in soil quality index. Our results indicate that soil quality index based on the minimum data sets could effectively assess the influence of grassland degradation on soil biodiversity and ecosystem function. In order to effectively restore degraded grasslands, the key contributors to the soil quality, such as soil carbon, should be taken on priority basis for revitalizing the soil biodiversity and ecosystem function.

Grazing and Mowing Affect the Carbon-to-Nitrogen Ratio of Plants by Changing the Soil Available Nitrogen Content and Soil Moisture on the Meadow Steppe, China

“…However, excessively intensive grassland use (e.g., overgrazing) has led to ecosystem degradation of semi-arid grasslands in Northern China over the last several decades [ 7 , 8 , 9 ]. The process of grassland degradation is largely mediated by the grazing effects on carbon (C) and nitrogen (N) cycling [ 10 , 11 , 12 , 13 ]. As a critical element for plants and microorganisms, C and N are linked to biological processes such as N fixation, organic matter decomposition, and plant photosynthesis [ 4 , 14 ].…”

“…The change in the plant and soil C/N ratio caused by grazing has attracted much attention because of its influence on the availability of grassland essential nutrients [ 11 , 12 , 13 , 15 ]. The C/N ratio affects biogeochemical cycles through effects on ecosystem production and decomposition processes [ 16 ].…”

Selection of r-K strategies by soil bacterial communities in response to grassland degradation

“…Grassland host biodiversity, and participate in climate regulation, carbon (C) sequestration, water purification, and erosion control, among other functions, which are critical ecosystem services and are essential for ecological stability (Habel et al, 2013;Bengtsson et al, 2019;Lyu et al, 2020). However, due to climate change and human activity, almost a half of the grassland ecosystems are undergoing degradation (Gang et al, 2014), with subsequent biodiversity loss and ecosystem function impairment (Han et al, 2020).…”

“…Soil microbial communities regulate soil biogeochemistry and ecological function (Morin & McGrady-Steed, 2004; Yang et al, 2013). Researchers have previously attempted to elucidate the responses of microbial communities to grassland degradation, which could facilitate the restoration of degraded grassland ecosystems (Yao et al, 2018;Han et al, 2020;Raiesi & Salek-Gilani, 2020).…”

“…The diverse micro habitats and available nutrient resources in grasslands potentially influence soil microbial community structure (Maharning et al, 2009). In addition, shifts in vegetation composition and soil characteristics in the course of grassland degradation can influence soil microbial community structure and activity (Bardgett et al, 2001;Yao et al, 2018;Han et al, 2020). Plant growth and development are highly correlated with soil factors, so that plant activities can indirectly influence soil microbial community structure through their influence on soil factors (Ke et al, 2015;Chen et al, 2016;Yao et al, 2018;Widdig et al, 2020).…”