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Lanzhou University (2008)

Effects of Grazing on Soil Physical Chemistry Characteristics and Microbes at Loess Plateau, China

张成霞;

Titre : Effects of Grazing on Soil Physical Chemistry Characteristics and Microbes at Loess Plateau, China

Auteur : 张成霞;

Grade : Doctoral Dissertation 2008

Université : Lanzhou University

Résumé partiel
Grazing is one of the main uses of grassland. Livestock interacts with grassland by its activities of feeding, trampling and excreting. Effects of grazing on soil physical and chemical properties, and soil microbes in semi-arid grassland were studied during the period of 2004 to 2006 at Huanxian County, eastern Gansu Province, which belongs to the Loess Plateau. The stocking rates of sheep used in the experiments were 0 sheep unit/ha, 2.7 sheep unit/ha, 5.3 sheep/ha and 8.7 sheep unit/ha. Soil samples were taken for seven times at various growing stages of grassland plants at the depth of 0-30cm from paddocks with different stocking rates. The soil samples were studied for the contents of soil particles at various size, nutrient components, and soil microbial components. The main results are summarized as the follows:1、The contents of clay, silt, fine sand and coarse sand were significantly different among the soils taken from paddocks with various stocking rates. The contents of clay and silt at paddocks with 0 sheep unit/ha were significantly higher than the paddocks with other stocking rates. Whereas the contents of coarse sand were the highest at paddock grazed at 8.7 sheep unit/ha , and were the lowest at the paddocks grazed at both 0 sheep unit/ha and 2.7 sheep unit/ha. The highest contents of clay, silt and coarse sand were all obtained on September during the year. In the 0-30 cm soil layers, content of coarse sand was the highest at the 0-10cm depth, while the contents of clay, silt and fine sand were increasing with soil depth.2、The contents of soil organic matter and total N were no significant at different treatments. However, the contents of total P and NH4+-N at the paddocks with 0 sheep unit/ha were significantly higher than those at the paddocks with 2.7 sheep unit /ha. NO3— N content at paddocks with 8.7 sheep unit /ha was significantly higher than that obtained at the paddocks grazed at 0 sheep unit/ha. Contents of available P at paddocks with at 0 sheep unit /ha and 2.7 sheep unit /ha were significantly higher than that at paddocks with 8.7 sheep unit/ha. Contents of soil organic matter, total N, NOV - N and pH were highest on September during the year regardless the stocking rates and soil depth, while contents of total P and available P were highest on November. NH4+- N was highest on May or June. In terms of spatial distribution contents of soil organic matter, total N, total P and NO3— N were all increasing with soil depth. However, contents of NH4+- N, available P and pH were decreasing with soil depth. 3、Among the soil organisms isolated from various paddocks the number of soil fungi was the lowest, which was followed by the number of actinomycete, and the number of bacteria was the highest

Mots clés : grassland degradation; grazing intensity; stocking rate; soil particle size; soil nutrients; fungi; bacteria; actinomycete; microbial biomass C; microbial biomass N; microbial biomass P; seasonal dynamics;

Présentation (CNKI)

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