放牧及围封对科尔沁沙质草地土壤呼吸的影响

放牧及围封是引起沙质草地生态系统变化的重要因素。对科尔沁地区放牧和围封不同年限的沙质草地进行土壤呼吸动态测定与分析,结果表明:(1)植物生长初期土壤呼吸速率日平均值,围封样地的显著大于放牧样地的(p<0.05);植物生长末期土壤呼吸速率日平均值,放牧样地的显著大于围封样地的(p<0.05)。围封17年和围封22年样地的土壤呼吸速率日平均值相比较,7月上旬之前,围封17年样地的较围封22年样地的大,而7月中旬以后,围封22年样地的较围封17年样地的大,且差异均显著(p<0.05)。(2)土壤呼吸速率的季节动态对放牧和围封的响应过程相似,但围封引起的变异相对较小;土壤呼吸速率季节平均值,围封22年样地的显著大于围封17年的(p<0.05)和放牧的(p<0.01),围封17年样地的大于放牧的(p>0.05),故围封可以增强土壤CO₂的排放,且在一定的时间内,土壤CO₂的排放速率与围封时间正相关。(3)土壤温度和土壤体积含水率可解释土壤呼吸速率的变异从大到小依次为放牧(58%)>围封22年(39%)>围封17年(28%)。

Effects of Grazing and Enclosure on Soil Respiration Rate in the Horqin Sandy Grassland

Grazing and enclosure recovery measurement are important factors to the change of sandy grassland ecosystem. Daily and seasonal variations of soil respiration rates were measured in 2013 to understand effects of continuous grazing and differently aged enclosures on soil respiration rate in the Horqin Sandy Grassland, and results showed that:(1) In the growing season, dynamic response of soil respiration for grazing and enclosure is not the same, at the early stage of plant growth, soil respiration rate of enclosed area is significantly greater than that of grazing area(p<0.05); In the late period of plant growth, soil respiration rate of grazing area is significantly greater than that in the enclosed area(p<0.05). In the early monitoring period, soil respiration rate of 17-year enclosed area is bigger than that of the 22-year enclosed area, but that is adverse in the late monitoring period, and the differences were both significant(p<0.05).(2) Seasonal dynamic responses of soil respiration rate to grazing and enclosure are similar, but soil respiration variation caused by enclosing is relatively small.(3) Soil respiration rate of seasonal dynamics for 22-year enclosed area is significantly greater than that in 17-year enclosed(p<0.05) and grazed area(p<0.01) respectively, and that of 17-year enclosed is greater than grazed area(p>0.05). Consequently, Enclosure can boost the emission of soil CO₂, and long-term enclosure(22 years) has a bigger influence on soil CO₂ emission rate than the relatively short-term enclosure(17 years).(4) Soil temperature and soil moisture can explain the variation of soil respiration rate in the order of grazing(58%)>enclosure 22(39%)>enclosure 17(28%).