黄土丘陵区草地土壤微生物C、N及呼吸熵对植被恢复的响应

以野外样地调查和室内分析法研究了黄土丘陵区不同植被恢复年限下草地土壤微生物C、N及土壤呼吸熵的变化.结果表明,土壤微生物量碳明显地随着植被恢复年限的增加而增加.在恢复前23a, 土壤微生物量碳在0～20 cm土层年增加率为24.1%;20～40 cm为104.4%.植被恢复23a后,0～20 cm土层增长率为0.83%,20～40 cm为0.19%.土壤微生物量N表现为在植被恢复的初期略有下降,3a后,开始出现明显增加.0～20 cm土层年增长率为20.14%,20～40 cm为15.11%.在植被恢复23a后,0～20 cm土层的年增长率为0.14%,20～40 cm变化不大.土壤微生物呼吸强度随着恢复年限的增加逐渐加强;土壤呼吸熵随植被封育时间的增加而呈对数降低趋势.土壤呼吸熵(qCO2)在反映土壤的生物质量变化时,显得更加稳定,受植物生长状况影响较小.相关分析表明,土壤微生物量和土壤微生物活性与土壤有机质、碱解氮和粘粒含量显著正相关;与土壤粉粒含量明显负相关;表层土壤pH值对其也有明显影响.草地植被自然恢复过程可增加土壤微生物活性,有利于土壤质量的提高.

Responses of soil microbial biomass C and N and respiratory quotient (qCO2) to revegetation on the Loess Hilly-Gully region

Vegetation recovery in the Loess Plateau of China has been identified as the most effective and useful way to alleviate soil erosion and degradation. This study was to examine the responses of soil microbial indicators to natural vegetation rehabilitation on the Loess Plateau. Soil samples at the depths of 0-20 cm and 20-40 cm were collected from the Yunwu mountain grassland area with an recovered chronosequence of 0, 3, 9, 15, 23, 58, 73, and 78 years. The results showed that microbial biomass C (MBC) was increased significantly along with vegetation rehabilitation time increasing. In the early 23 years revegetation sites, the increasing MBC rate was 24.1% and 104.4% every year at 0-20 cm and 20-40 cm, respectively. However, after 23 years of revegetation, the increasing rate of MBC was only 0.83% and 0.19% at 0-20 cm and 20-40 cm every year, respectively. Soil MBN also increased faster during the first 23 years with increasing rates of 20.14% and 15.11% at the 0-20 cm and 20-40 cm every year, respectively. Soil basal respiration (SBR) increased gradually during the vegetation natural succession. The qCO2 decreased with a logarithm functional trend with the enclosed time increaseed. Compared to soil respiration intensity, the qCO2 reflected the change of microbial activity more clearly and consistently. The MBC, MBN and SBR had a positive relationship with soil organic carbon, available nitrogen and clay contents, but they had a negative relationship with soil silt content. In addition, soil pH at the surface layer also affected the soil microbial properties. These research results reinforced the notion that natural succession of grassland has altered positively soil microbial communities and activities in the surface layer, provided indications that vegetation restoration can have positive impacts on soil microbial quality on the Loess Plateau.