川西北高寒草甸不同放牧模式对土壤呼吸的影响

采用土壤二氧化碳(CO_2)通量自动测量系统,对不同放牧模式(全年禁牧、夏季放牧、冬季放牧和自由放牧)下川西北高寒草甸的土壤呼吸进行监测,比较了不同放牧模式下土壤呼吸的季节动态和温度敏感性。研究发现:1)放牧模式可以改变高寒草甸土壤呼吸的季节动态变化。禁牧、夏季放牧以及自由放牧样地的土壤呼吸在季节上的变化趋势基本相似,而冬季放牧样地的土壤呼吸最大值与前者相比明显向后推迟;2)放牧模式并不改变高寒草甸年平均土壤呼吸速率,但对不同季节土壤呼吸速率的影响不同;3)不同放牧模式可以改变土壤呼吸对温度的敏感性(Q_(10))。不同放牧模式下土壤呼吸Q_(10)值大小依次为:禁牧1a(8.13)冬季放牧(7.49)禁牧3a(5.46)夏季放牧(5.20)自由放牧(4.53)。该地区土壤呼吸的Q_(10)值均明显高于热带和其它温带草地土壤呼吸的Q_(10)值。结果表明,放牧模式是影响高寒草甸土壤碳排放的一个重要因素。此外,在未来全球气候变暖背景下,在生长季节无放牧干扰的高寒草甸可能比放牧干扰的高寒草甸释放出更多的CO_2到大气中。

Response of soil respiration rate to grazing patterns in an alpine meadow, Northwestern Sichuan, China

In this study, an automated soil CO₂ flux system was used to measure soil respiration rates from 2008 to 2009 in an alpine meadow subjected to different grazing patterns (no grazing, grazing in summer, grazing in winter, and free grazing). We compared the seasonal dynamics and temperature sensitivity of soil respiration under the different grazing patterns, and found that 1) the seasonal dynamics of soil respiration were affected by grazing patterns. Soil respiration peaked later in the year in meadows subjected to winter grazing than in those in the no grazing, grazing in summer, and free grazing treatments; 2) the grazing pattern used affected seasonal variations in the rate of soil respiration, but not that of the mean annual rate of soil respiration; and 3) the sensitivity of soil respiration to soil temperature (Q₁₀) at a depth of 5 cm was affected by variations in grazing pattern. The Q₁₀ value was the highest under the no grazing for one year treatment, followed by, in descending order, the winter grazing, no grazing for three years, grazing in summer, and free grazing treatments. The Q₁₀ value of the alpine meadow was higher than that of the tropical and other temperate grasslands. These results suggest that grazing pattern plays an important role in carbon release from soils in alpine meadows. Additionally, in the future, global warming may cause more carbon to be released from non-grazed meadows than from those under grazing pressure during the growing season.