沙坡头人工植被演替过程的土壤呼吸特征

为探讨人工植被演替过程对土壤呼吸速率的影响,本文利用碱液吸收法同步测定了腾格里沙漠东南缘1956、1964、1981、1987、1989、2007年始植的人工植被区和2007年新铺设的草方格固沙区及流沙区的土壤呼吸速率变化,同时分析了土壤水分和温度对上述不同样地土壤呼吸的影响。结果表明:1) 总体而言,土壤呼吸速率随着人工植被演替时间的延长而逐渐增大。当土壤含水量较高时,不同始植年代人工植被区的土壤呼吸速率具有显著的差异(P<0.05);当土壤含水量较低时,不同始植年代植被区的土壤呼吸速率没有显著的差异(P>0.05)。2)土壤呼吸速率与土壤含水量呈正相关关系,且相关系数随着人工植被演替时间的延长而逐渐增大。3)利用土壤呼吸速率-土壤温度指数函数关系计算得到不同人工植被演替阶段土壤呼吸速率的Q₁₀值均较低(平均值仅为1.02)。土壤温度对1987、1989年人工植被区内的土壤呼吸速率产生了显著影响(P<0.05),而对其他样地的土壤呼吸速率影响不显著 (P>0.05)。综合说明,人工植被的演替过程改变了土壤呼吸速率大小及其对土壤水分和温度的响应。

Soil respiration patterns during restoration of vegetation in the Shapotou area, Northern China

As one of the important constituents of the carbon cycle, soil respiration is the primary mechanism by which soil carbon is released and an important source of atmospheric CO₂, which plays a critical role in regulating atmospheric CO₂ concentration and world climate dynamics. Even a small change in soil respiration could profoundly affect the concentration of atmospheric CO₂. Numerous studies have been conducted into the relationship between soil respiration, environmental factors (eg. temperature, soil moisture) and anthropogenic disturbance (eg. land use change). However, most of these studies have focused on forest and steppe ecosystems, rather than on desert ecosystems. There is little available information on the effect of vegetation succession on soil respiration in a desert ecosystem. The establishment of artificial sand-binding vegetation in the Shapotou region has changed the landscape from moving dunes to stabilized dunes covered by shrubs, which has, in turn, modified soil respiration patterns. This study has characterized soil respiration patterns and the effects of soil moisture and temperature on soil respiration during vegetation restoration of a desert ecosystem. The study was conducted in the Shapotou revegetated area, located on the southeast fringe of the Tengger Desert (37°32'N, 105°02'E). Soil respiration rates were measured, using the alkali absorption method, in revegetated enclosures, which were constructed in 1956, 1964, 1981, 1987, 1989 and the area was revegetated with Caragana korshinskii in 2007. Soil respiration was also investigated in a sandy area stabilized with straw checkerboard in 2007 and in an area of shifting sand dunes. Based on the traditional space-for-time succession approach, these study plots represented vegetations of different successional stages. The results showed that: 1) In general, soil respiration rates gradually increased with the increasing age of the revegetation. This trend was significant when the soil volume moisture were higher than the mean value (0.0487 cm³ /cm³) for the whole of the experimental period (P<0.05). Soil respiration in the revegetated areas established in 1956, 1964, 1981 was significantly higher than in the areas revegetated in 2007, the area stabilized in 2007 with straw checkerboard and in the shifting sand dunes (P<0.05). No significantly increase was detected when soil volume moisture was lower than the mean value (P>0.05); 2) Soil moisture is an important environmental factor influencing soil respiration. Positive correlations were found between soil volume moisture and the soil respiration rates in every study plot and the correlation coefficients progressively increased with increasing age of the revegetation (P<0.05) and 3) An exponential model has been used to describe the relationship between soil respiration rates and soil temperature. Soil temperature only had a significant effect on soil respiration in the revegetated areas established in 1987 and 1989, but not in the other revegetated enclosures. In every study plot, the Q₁₀ values were uniformly lower than the mean values for temperate regions (1.57). These results suggest that the vegetation restoration process can alter the magnitude of soil respiration rate as well as its response to soil moisture and temperature variations.