季节性雪被对川西亚高山岷江冷杉林冬季土壤氮矿化和淋溶的影响

Effects of Seasonal Snow Pack on Winter Soil Nitrogen Mineralization and Leachate in Subalpine Abies faxoniana Forest in Western Sichuan Province

采用封顶埋管-原位培养和淋溶水原位收集法对川西亚高山岷江冷杉林不同厚度雪被梯度(浅雪被、中度厚度雪被和厚雪被)下冬季土壤净氮素矿化量和氮淋溶进行估算。结果表明:土壤温度随雪被厚度的降低而降低;冬季土壤净硝化量明显大于净氨化量,且决定着净氮矿化量;土壤净氨化量、净硝化量和净氮矿化量均随雪被厚度的降低而升高;川西亚高山冷杉林冬季土壤铵态氮、硝态氮及可溶性有机氮的淋溶量分别为0.07,0.58,0.42g/m2,分别占冬季土壤氮素淋溶量的6.88%,53.62%和39.50%;中度厚度雪被土壤氮淋溶量最大,但总体上不同厚度雪被间差异不显著。综上所述,未来气候变化所引发季节性雪被减少可能会降低该林区冬季土壤温度,增加土壤冻融循环,进而提高冬季土壤净氮矿化量和早春土壤氮淋溶。

In situ close-top incubation and leachate collection method were used to estimate soil net nitrogen mineralization and leaching flux under three depths of snow pack（deep snow pack,middle snow pack and shallow snow pack）over the winter of 2012-2013 in subalpine Abies faxoniana forest in western Sichuan province.The results showed that soil temperature decreased with decreasing depth of snow pack.Soil net nitrification was significantly higher than soil net ammonification,and soil net nitrogen mineralization was mainly determined by nitrification during the winter.Soil net ammonification,nitrification and mineralization were inversely proportional to the depth of snow pack and significant differences in net nitrogen mineralization were found among snow packs.Soil ammonium,nitrate and dissolved organic nitrogen leaching fluxes was 0.07,0.58,0.42g/m2,accounting for 6.88%,53.62% and 39.50% of soil nitrogen leaching fluxes in winter respectively.Soil nitrogen leaching fluxes in the middle snow pack（MS）were higher than that in the deep snow pack（DS）and shallow snow pack（SS）,but no significant differences were observed among snow packs.In a word,the decrease of snow pack which induced by climate change might reduce soil temperature in this region in future.However,freeze-thaw cycles might increase,which could enhance nitrogen mineralization over the winter and nitrogen leaching during the early spring.