季节性冻融格局变化对高山森林土壤DOC淋洗的影响

Effect of Changes in Seasonal Freeze-thaw Pattern on DOC Loss from Leaching in the Alpine Forest Soil

采用土柱培养实验,利用海拔形成的温度差异模拟气候变暖过程,将高山森林(海拔3 600m)土壤分别培养在海拔3 600m(A1),3 300m(A2)和3 000m(A3)的森林地表,研究生长季节与非生长季节内5个关键时期的土壤可溶性有机碳(DOC)淋溶特征。结果表明:川西高山输入土壤和土壤输出的DOC集中于生长季节末期至深冻期,DOC淋溶量表现为非生长季节>生长季节,非生长季节最高淋溶输入量可达7.30kg/hm2,最高淋溶输出量达8.69kg/hm2。冻融循环促进了土壤DOC的淋溶,且初冻期(OF)的冻融循环使得DOC大量淋溶。整个土层DOC淋溶量在生长季节为A1(5.91kg/hm2)>A2(2.99kg/hm2)>A3(1.79kg/hm2),非生长季节为A1(3.77kg/hm2)<A2(5.11kg/hm2)<A3(7.24kg/hm2)。这些结果意味着气候变暖将加速高山森林土壤DOC的淋溶,导致高山森林土壤碳库减小,水体和溪流DOC增加。

Soil columns sampled from an alpine forest at 3 600-m altitude were incubated in the forest floor at the sites of 3 600-m （A1）, 3 300-m （A2） and 3 000-m （A3） altitudes, which was used to simulate climate warming scenarios. In turn, the leaching characteristics of soil dissolved organic carbon （DOC） in these soil columns were studied in five critical periods of the non-growing season and growing season from May 2010 to April 2012. The results indicated that the large amounts of soil DOC input and output were observed from the end of growing season to deeply frozen period, and the leached DOC in non-growing season ~growing season. The highest leached DOC input was 7.30 kg/hm2 and output was 8.69 kg/hm2 in the non-growing season. Freeze-thaw cycles promoted soil DOC leaching, and the freeze-thaw cycles in onset of freezing peri- od （OF） led to higher DOC leaching. The ranked order of leached DOC in the whole soil layer in the growing season was A1 （5.91 kg/hm2） 〉A2 （2.99 kg/hm2） 〉A3 （1.79 kg/hm2）, and that in the non-growing sea- son was （3.77 kg/hm2） 〈A2 （5.11 kg/hm2） 〈A3 （7.24 kg/hme）. The results implied that climate war- ming would accelerate alpine forest soil DOC leaching, and lead to the loss of soil organic carbon pool in the alpine forest, and the increase of water DOC in the forest stream.