Effects of Grazing Exclusion on Soil Properties and on Ecosystem Carbon and Nitrogen Storage in a Sandy Rangeland of Inner Mongolia, Northern China

Abstract

The Horqin sandy rangeland of northern China is a seriously desertified region with a fragile ecology. The sandy alluvial and aeolian sediments have a coarse texture and loose structure and are therefore vulnerable to damage caused by grazing animals and wind erosion. We investigated whether grazing exclusion could enhance ecosystem carbon (C) and nitrogen (N) storage and thereby improve overall soil quality. We compared soil properties, C and N storage in biomass (aboveground and below-ground), and the total and light fraction soil organic matter between adjacent areas with continuous grazing and a 12-year grazing exclosure. The soil silt + clay content, organic C, total Kjeldahl N, available N and K, and cation-exchange capacity were significantly (P < 0.05) greater in the exclosure. We found that to a depth of 100 cm, the exclosure plots had greater light fraction C storage (by 267.2 g m(-2) = 73.3 %), light fraction N storage (by 16.6 g m(-2) = 105.7 %), total soil C storage (by 1174.4 g m(-2) = 43.9 %), and total N storage (by 91.1 g m(-2) = 31.3 %). Biomass C and N storage were also 205.0 and 8.0 g m(-2) greater (154.8 and 181.8 %, respectively). The increase was greatest in the light fraction organic matter and biomass and decreased with increasing depth in the soil. The results suggest that light fraction C and N respond more rapidly than total soil C and N to grazing exclusion and that vegetation recovers faster than soil. Our results confirmed that the degraded sandy rangeland is recovering and sequestering C after the removal of grazing pressure.

Effects of grazing exclusion on soil carbon and nitrogen storage in semi-arid grassland in Inner Mongolia, China

“…Our study showed that the 6-year grazing exclusion had resulted in a significant recovery in vegetation with higher aboveground biomass, but a lower soil bulk density and pH value, which are consistent with earlier researches (Wu et al, 2009;Chen et al, 2012). The reduced perturbation had a direct effect on the aboveground biomass, demonstrating that grazing exclusion is an effective practice to improve vegetation productivity in degraded grassland (Tanentzap et al, 2009;Zhou et al, 2011).…”

“…These differences may partly due to whether grazing pressure exceeds carrying capacity of a site and whether it is sufficiently far beyond that capacity to reach the ecological threshold (Sasaki et al, 2011). Additionally, the discrepancies in duration of exclosure, climatic conditions, original and post-grazing vegetation, soil properties from different studies were also found to be the causes for the inconsistent results (Reeder et al, 2004;Chen et al, 2012;Medina-Roldan et al, 2012).…”

Short-term grazing exclusion has no impact on soil properties and nutrients of degraded alpine grassland in Tibet, China

“…This result was not consistent with the results from the Imam Kandi Rangelands, Iran (Mofidi et al, 2013), and in the sandy rangeland of Inner Mongolia, northern China (Li et al, 2011;Chen et al, 2012), in which grazing exclusion led to greater fine soil particle content and lower coarse sand content due to an increased ability of vegetation to prevent soil erosion and trap windblown fine particles H. Wen et al, 2013).…”

“…F value P value F value P value F value P value F value P value F value P value BD Grazing exclusion substantially improved soil N availability in the temperate steppe in northern China, which suggests that there are positive effects of ecological restoration on soil N availability (Wang et al, 2010;Chen et al, 2012). However, this improvement was not found in alpine grasslands with ecological restoration by grazing exclusion (Fig.…”

Effect of Grazing Exclusion on Vegetation Characteristics and Soil Organic Carbon of Leymus chinensis Grassland in Northern China

“…Meanwhile, the maintenance of heterogeneous vegetation and associated topsoil structures is essential for the accumulation of SOC in semi-arid grassland ecosystems [34]. Increases in SOC resulted in decreased soil erosion by wind in this region due to increased vegetation cover, which enable nutrients to easily fix to the soil surface after livestock exclusion [35]. Another reason was that grazing cessation enhanced the soil aggregation as the physical protection of SOC [36].…”