Abstract
Overgrazing has been the primary cause of grassland degradation in the semi-arid grasslands of the agro-pastoral transition zone in northern China. However, there has been little evidence regarding grazing intensity impacts on vegetation change and soil C and N dynamics in this region. This paper reports the effects of four grazing intensities namely un-grazed (UG), lightly grazed (LG), moderately grazed (MG) and heavily grazed (HG) on vegetation characteristics and soil properties of grasslands in the Guyuan county in the agro-pastoral transition region, Hebei province, northern China. Our study showed that the vegetation height, canopy cover, plant species abundance and aboveground biomass decreased significantly with increased grazing intensity. Similarly, soil organic carbon (SOC) and total nitrogen (STN) in the 0–50 cm were highest under UG (13.3 kg C m−2 and 1.69 kg N m−2) and lowest under HG (9.8 kg C m−2 and 1.22 kg N m−2). Soil available nitrogen (SAN) was significantly lower under HG (644 kg N hm−2) than under other treatments (725–731 kg N hm−2) in the 0–50 cm. Our results indicate that the pasture management of “take half-leave half” has potential benefits for primary production and livestock grazing in this region. However, grazing exclusion was perhaps the most effective choice for restoring degraded grasslands in this region. Therefore, flexible rangeland management should be adopted in this region.
Highlights
Grazing, the most common use of grasslands, can influence plant community structure, soil properties and nutrient cycling within the plant-soil system[1]
Vegetation characteristics Our study demonstrated that the vegetation height, canopy cover, plant species abundance and aboveground biomass of grasslands in the agro-pastoral zone, decreased significantly with increased grazing intensity over 10-years (Table 1)
Our research showed that increased grazing significantly decreased the canopy cover, with no significant difference between the UG and lightly grazed (LG) plots
Summary
The most common use of grasslands, can influence plant community structure, soil properties and nutrient cycling within the plant-soil system[1]. Milchunas and Lauenroth[2] analyzed 236 grazing studies worldwide and found different results with dynamics of species composition, root biomass, soil organic C and soil N of grasslands not closely associated with grazed or non-grazed measurements. These contradictory findings suggested that the effects of grazing on nutrient cycling and ecosystem functioning still needs further study [2]
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