Abstract:

To understand the soil nitrogen transformation and plant nitrogen nutrient processes of the alpine shrubland ecosystems, this study examined the responses of the content of soil nitrogen in different forms to warming and plant removal in a Sibiraea angustata shrubland of eastern Qinghai-Tibetan Plateau. The results showed that in the removal-plant plots, warming significantly decreased soil total nitrogen and organic nitrogen contents during the mid- and late- growing seasons. At the same time, warming significantly decreased soil inorganic nitrogen by 16.1% during the late-growing season, but significantly increased soil microbial biomass nitrogen by 37.7% during the early growing season. In the unremoval-plant plots, warming significantly increased the content of soil inorganic nitrogen and microbial biomass nitrogen by 17.5% and 122.1%, respectively, during the mid-growing season, and decreased soil inorganic nitrogen content by 21.8% during the late-growing season. In the control plots (controlled temperature), unremoval-plant treatment significantly decreased soil inorganic nitrogen and microbial biomass nitrogen content by 29.3% and 68.9%, respectively, during the mid-growing season, and decreased soil total nitrogen and organic nitrogen by 11.6% and 12.1%, respectively, during the late-growing season, but significantly increased soil inorganic nitrogen content during the late-growing season and microbial biomass nitrogen content during the early-growing season by 18.7% and 26.0%, respectively. However, in the warming plots, unremoval-plant treatment significantly increased soil microbial biomass nitrogen content by 49.2% during the mid-growing season and inorganic nitrogen content by 12.7% during the late-growing season. These findings indicate that climate warming and plants will change soil nitrogen contents, and further affect soil nitrogen transformation and plant nitrogen nutrient processes during the growing season in these alpine shrub ecosystems in the eastern Qinghai-Tibetan Plateau.

Key words: alpine shrub, warming, plant removal, different forms of nitrogen, soil nitrogen transformation

摘要：

研究青藏高原东部窄叶鲜卑花（Sibiraea angustata）高寒灌丛土壤不同形态氮含量对增温和植物去除的响应,以理解高寒灌丛土壤氮转化和植物氮素营养过程。结果表明,增温仅在生长季中期和末期使去除植物样方的土壤全氮和有机氮含量显著降低。同时,增温在去除植物样方使生长季末期土壤无机氮含量显著降低16.1%,使生长季初期土壤微生物生物量氮含量显著升高37.7%;在不去除植物样方,增温分别使生长季中期土壤无机氮和微生物生物量氮含量显著升高17.5%和122.1%,使生长季末期土壤无机氮含量显著降低21.8%。与去除植物相比,不去除植物处理在对照样方（不增温）分别使生长季中期土壤无机氮和微生物生物量氮含量以及生长季末期土壤全氮和有机氮含量显著降低29.3%、68.9%、11.6%和12.1%,分别使生长季末期土壤无机氮含量和生长季初期土壤微生物生物量氮含量显著升高18.7%和26.0%。而在增温样方,不去除植物处理分别使生长季中期土壤微生物生物量氮含量和生长季末期土壤无机氮含量显著升高49.2%和12.7%。以上结果表明,气候变暖和植物将显著改变青藏高原东部高寒灌丛生长季土壤不同形态氮含量,进而影响土壤氮转化和植物氮素营养过程。

关键词: 高寒灌丛, 增温, 去除植物, 不同形态氮, 土壤氮转化