模拟增温对青藏高原东部高寒灌丛土壤氮转化的影响

本文研究了青藏高原东部窄叶鲜卑花高寒灌丛生长季前期、生长季后期和非生长季3个生育期的土壤氮转化速率对模拟增温的响应,分析全球气候变暖对高寒灌丛土壤氮循环过程的影响。结果表明: 模拟增温使高寒灌丛土壤温度显著升高1.2 ℃,土壤水分显著降低2.5%。高寒灌丛生长季土壤净氮矿化(氨化和硝化)速率显著高于非生长季,但土壤净氮固持速率显著低于非生长季。土壤氮矿化在生长季前期以硝化作用为主,在生长季后期和非生长季以氨化作用为主。模拟增温对高寒灌丛土壤氮转化过程的影响在不同时期存在显著差异。模拟增温显著增加了生长季前期土壤净氨化、净硝化、净氮矿化、净氮固持速率和非生长季土壤净硝化、净氮矿化速率,并显著降低了生长季后期土壤净硝化、净氮矿化、净氮固持速率和非生长季土壤净氨化速率。但模拟增温对高寒灌丛非生长季净氮固持速率和生长季后期净硝化速率的影响不显著。未来气候变暖将显著改变青藏高原东部高寒灌丛土壤氮转化,进而加速高寒灌丛土壤氮循环过程。

Effects of experimental warming on soil nitrogen transformation in alpine scrubland of eastern Qinghai-Tibet Plateau,China

We investigated the effects of warming on soil nitrogen cycling process in alpine scrub ecosystem, with an in-situ simulated warming experiment at Sibiraea angustata alpine scrubland on the eastern Qinghai-Tibet Plateau, China. We examined the responses of soil nitrogen transformation rate to warming in three critical periods (the early, late, and non-growing seasons). The results showed that warming increased soil temperature by 1.2 ℃, but decreased soil moisture by 2.5%. The soil net nitrogen mineralization rates (i.e., ammonification and nitrification) in the growing season were significantly higher than those in the non-growing season. The rates of soil net nitrogen fixation in the non-growing season were significantly higher than that in the growing season. Soil nitrification was the major process of soil nitrogen transformation in the early growing season, while soil ammonification was the major one in the late growing season and non-growing season. The effects of experimental warming on soil nitrogen transformation differed among those three periods. Experimental warming significantly increased soil net ammonification, nitrification, nitrogen mine-ralization and fixation in the early growing season, and enhanced soil net nitrification and nitrogen mineralization in the non-growing season. However, warming significantly decreased soil net nitrification, nitrogen mineralization and fixation in the late growing season and soil net ammonification in the non-growing season. Moreover, warming did not affect soil net nitrogen fixation rates in the non-growing season and soil net nitrification rates in the late growing season. Future climate warming would significantly change soil nitrogen transformation by accelerating soil nitrogen cycling in the alpine scrub ecosystem on the eastern Qinghai-Tibet Plateau.