| After the implement of grassland contracting system on the Qinghai-Tibetan Plateau,two grassland management patterns ? single-household management pattern(SMP,neighboring households are separated by fences)and multi-household management pattern(MMP,two or more households share grassland with each other)? coexisted due to various reasons.Studying the effects of two grassland managements on soil nutrients and their ecological stoichiometric ratios is of great importance for optimizing grassland management and accurately assessing soil quality.In comparing the soil quality under these two different management patterns,30 single households and 30 multi-households were selected to study the difference of soil organic carbon,soil total nitrogen,soil total phosphorus and their stoichiometric ratios in Maqu County,eastern Qinghai-Tibetan Plateau.The nutrient limiting elements of soil and the relationship between soil carbon,nitrogen and phosphorus contents and stoichiometric characteristics were also studied.The results of the study are as follows:(1)The content of soil C,N,P under MMP was higher than that under SMP.The values of the former and the later were 47.27 g·kg-1,4.60 g·kg-1,0.80 g·kg-1and41.53 g·kg-1,4.28 g·kg-1,0.73 g·kg-1,respectively.However,soil p H under MMP(6.86)was lower than that under SMP(7.11).In profile,soil p H of both MMP and SMP increased with soil depth,while soil C,N,and P decreased with soil depth,and soil C,N,and P were mainly distributed in the surface(0~15 cm)soil.(2)The soil C/N under SMP(10.14)was significantly lower than that under MMP(10.72).However,the difference in C/P and N/P between this two patterns of grassland management were not significant.In the vertical direction,as the soil depth increased,soil C/N increased both in SMP and MMP,while C/P and N/P were in the opposite trend.Besides,the mean N/P of Maqu grassland was 6.52,indicating that soil N was the main limiting factor of soil nutrient in this area.(3)The results of Pearson correlation analysis and regression analysis showed that there was a significant negative correlation between soil p H and soil C,P;and there was a very significant positive correlation among C,N and P.There was a very significant negative correlation between C/N and N(r =-0.299,P < 0.001),P wasnegatively correlated with C/P(r =-0.448,P < 0.001)and N/P(r =-0.452,P < 0.001).The correlation coefficients between soil C and soil N,C/P and N/P were higher,which were 0.84 and 0.93,respectively.(4)The soil nutrient and stoichiometric ratios of Maqu grassland showed moderate variability.And there was no significant difference in the coefficient of variation of soil stoichiometric ratio between single-and multi-household grazing management pattern in horizontal and vertical directions.There was also no difference in the average coefficient of variation of soil p H,C,N and P between single-and multi-household,and there was no difference in the coefficient of variation of soil nutrients among different soil layers except for soil N in the surface(0~15 cm)soil.In the vertical direction,the coefficient of variation of soil C under SMP and MMP and soil N under MMP increased with the increase of soil depth,but the difference was not significant.Besides,there was no significant difference in the coefficient of variation of soil p H,P under MMP and SMP,soil N under MMP between different soil layer.The results showed that the soil nutrients under SMP on Maqu were lower than those under MMP and the soil degradation was more likely caused in single household management grassland.Therefore,the government should protect existing multi-households and/or encourage more single-households to be reintegrated into new ones.In addition,effective measures should be taken to prohibit overgrazing,particularly anthropogenic activities which seriously damage the surface soil.Besides,the results also indicated that the soil quality of Maqu grassland can be effectively assessed by soil stoichiometric ratios. |
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