封育对黄土高原草地深层土壤pH的影响

土壤酸碱度变化, 直接影响植被类型及植物对土壤养分的吸收效率, 同时在土壤有机碳和无机碳相互转化过程中起重要作用, 为明确草地封育过程中土壤酸碱度的变化特征。以黄土高原云雾山自然保护区放牧草地(封育0年)、封育15年草地、封育30年草地为研究对象, 采用空间代替时间方法, 研究封育过程中深层(0-500 cm)土壤酸碱度变化特征。结果表明: (1)3个封育年限草地土壤pH随着土层深度的增加而增加, 放牧草地土壤pH变化范围为8.54-9.26、封育15年草地土壤pH变化范围为8.56-8.97、封育30年草地土壤pH变化范围为8.12-8.74。(2)不同封育年限0-500cm土壤各粒级差异较大, 放牧草地在40-60 cm土层, 3-2 mm土壤团粒结构的土壤pH最低为8.38, 显著低于其它粒级(P?0.05); 封育15年草地土壤pH各粒级差异较小; 封育30年草地土壤pH整体呈上升趋势, 0-20 cm各粒级土壤pH差异显著。(3) 在0-500 cm, 封育30年草地土壤pH显著低于放牧草地和封育15年草地(P?0.05), 其平均值分别为8.50、8.94和8.87。因此, 长期封育显著降低土壤pH值。

Effects of fencing on soil pH in deep Loess Plateau grassland

The pH of soil changes directly affects the vegetation type and the nutrients absorption efficiency of plants.Meanwhile,soil pH plays an important role in the process of soil organic carbon and inorganic carbon mutual transformation.In this study,based on space instead of time method for grassland fencing sequence,the pH of grazing land(0 years after fencing),fencing 15 years grassland and fencing 30 years grassland in the Yunwu Mountain Nature Reserve of the loess plateau were measured to study the variation characteristics of soil pH in deep layer(0-500cm).The results show that:(1)soil pH increased with the increase of soil depth,the soil pH rang of 8.54 to 9.26,8.56 to 8.97 and 8.12-8.74 in grazing grassland,fencing 15 years grassland and fencing 30 years grassland,respectively.(2)The soil pH value(8.38)of the soil aggregates of 3-2mm was significantly lower than that of other soil aggregates in the grazing land in 40-60cm soil layer(P?0.05),and there was no difference of the soil pH value in any soil aggregates in the fencing 15 years grassland.(3)In the 0-500 cm soil layers,soil pH of fencing 30 years grassland was significantly lower than fencing 15 years and grazing grassland(P<0.05),and the average pH was 8.50,8.94 and 8.87,respectively.Therefore,long-term fencing significantly decreased soil pH value.