长江源区沼泽草甸多年冻土活动层土壤水分对模拟增温的响应

气候变化对高寒生态系统地气间水能循环过程产生强烈的影响, 因此, 气候变暖条件下的高寒生态系统水热过程和寒区流域水循环过程具有重要研究意义. 采用开顶式温室(OTC)对长江源沼泽草甸进行模拟增温试验, 分析了模拟增温对多年冻土活动层土壤水分的影响. 结果表明: 短期增温使得沼泽草甸生物量显著增加, 使得多年冻土活动层土壤冻结起始时间推迟、融化起始时间提前, 从而使融化期延长. 室外对比样地在65 cm深度存在明显的干层, 而OTC土壤水分随着深度加深不断降低. 增温使得多年冻土浅层土壤具有更高的含水量, 但并未导致表层土壤干化, 这与沼泽草甸土壤浅层密集的根系层和具有较强的持水和保水能力的有机质层有关.

The response of soil moisture in swamp meadow in the source regions of the Yangtze River to artificially warming

Climate change is now remarkable in the source regions of the Yangtze River, and impacts the plateau ecosystem, particularly, on the heat-water processes of the active layer due to the change in water and heat balance between the permafrost surface and the atmosphere. For this reason, a simulated experiment of artificial warming on the heat-water processes of plateau ecosystem was carried out in experimental chambers without cover to simulate the mean annual air temperature increasing about 6.7℃ and 3.5℃. The experimental results were analyzed and compared with observation in an outdoor comparison sample plot in an alpine swamp meadow ecosystem from 2007 to 2008. It is found that short-term warming will promote plant growth and development, increase significantly the aboveground biomass, postpone the freezing beginning date, make the thawing beginning date in advance, and then shorten the duration of entirely frozen period. There was an obvious dry layer at 65-cm depth of the outdoor comparison sample plot, but the soil moisture decreases with depth in the warming chamber. However, there was an obviously middle dry layer in the warming chamber, which is familiar in the source regions of the Yangtze River. Moreover, experimental warming lead to an increase in topsoil water content due to poorly drained swamp meadow with higher organic matter content and thicker root horizons. Experimental warming makes the soil moisture fluctuating layer migrating down to 40-cm depth. The results of this study will have some contributions to study alpine cold ecosystem water-heat process and water cycle under climate change.