Vertical Distributions of Soil Nutrients and Their Stoichiometric Ratios as Affected by Long Term Grazing and Enclosing in a Semi-Arid Grassland of Inner Mongolia

Juan Hu,Qicun Wang,Qiang Li,Daowei Zhou

doi:10.3390/agriculture10090382

Abstract

Grazing and enclosing are two of the most important grassland managements. In order to evaluate the effects of different managements on the ecosystem balance of grassland, the vertical distributions of soil nutrients and their stoichiometric ratios were determined in the plots of grazing and enclosing over 38 years in a semi-arid grassland of Inner Mongolia. The results showed that total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), calcium (Ca), magnesium (Mg) and sulfur (S) contents in 0–100 cm soil in the long term enclosing plot were lower than the long term grazing plot and these changes were much greater in the surface soil than in deep soil. However, the soil organic carbon (SOC) and available phosphorus (AP) contents in the long term enclosing plot in the surface soil were higher (p < 0.01) compared with the long term grazing plot. In addition, long term enclosing increased the C/N ratio in each soil layer and improved C/K and C/P ratios in the surface soil compared with long term grazing. However, significant decreases of N/P and N/K ratios in the long term enclosing plot in each soil layer were observed. In conclusion, enclosing for 38 years decreased most of nutrients and reduced the nutrients’ mineralization in the surface soil especially and thus might restrict nutrients cycling in a semi-arid grassland of Inner Mongolia.

Highlights

Grazing and enclosing are two of the most important grassland managements, which can directly or indirectly affect the balance of the ecosystem [1,2]
The soil organic carbon (SOC) and TK contents in the long term enclosing plot were lower than the long term grazing plot, while total nitrogen (TN) and total phosphorus (TP) contents were higher (Figure 1)
This study found that the SOC content of long term grazing in 0–10 cm soil was 23.5% lower (p < 0.01) relative to long term enclosing and there was little change below the surface soil, which indicated that long term grazing significantly decreased the SOC content in the surface soil

Summary

Introduction

Grazing and enclosing are two of the most important grassland managements, which can directly or indirectly affect the balance of the ecosystem [1,2]. Many studies have focused on the effects of grazing and enclosing on grassland ecosystems; the results of these researches are very different [3,4,5]. Enclosing is widely believed to be an economic, effective and simple method to recover the degenerated grassland ecosystem [3,8], which can improve vegetation cover, richness and biomass of species, as well as litter accumulation [9]. Some scholars have found that enclosing might destroy the over compensation growth mechanism of herbage and decline the turnover rate of grassland productivity [10]

Methods

Results

Discussion

Conclusion