青藏高原东缘高寒灌丛根系分泌物碳氮输入对增温的响应

根系分泌物是植物根系向土壤输入有机碳和养分的重要途径之一,深刻影响着根际土壤碳和养分循环过程。环境温度变化可通过改变植物初级生产力和根系性状等直接或间接地影响根系分泌过程,但其具体机制仍缺乏必要关注。为了揭示气候变暖对高寒灌丛根系碳、氮分泌过程的影响,以青藏高原东缘典型的高寒灌丛类型-窄叶鲜卑花(Sibiraea angustata)灌丛为研究对象,设置OTC(Open top chamber)增温试验,采用根系分泌物原位连续动态收集技术,分析了窄叶鲜卑花根系分泌物碳、氮输入速率与通量对土壤增温(+1.3℃)的响应。结果表明:窄叶鲜卑花灌丛根系分泌物碳、氮输入速率具有明显的季节差异,生长季中期根系分泌物碳、氮输入速率显著高于生长季初期和末期。整个生长季,对照处理根系分泌物碳、氮输入速率分别为0.55-0.74mg·g-^1·d-^1和0.05-0.08mg·g-^1·d-^1,增温分别使根系分泌物碳、氮输入速率显著增加了14.0%-69.1%和15.3%-70.2%。对照组根系分泌物碳、氮输入通量分别为26.94 g·m^–2和3.03 g·m^–2,增温分别使根系分泌物碳、氮输入通量显著增加了57.2%和46.9%。进一步分析表明,增温使根系分泌物碳、氮输入通量的增加主要归因于根系分泌物碳、氮输入速率和细根生物量显著提高。这些结果表明,气候变暖将促进青藏高原东缘高寒灌丛根系碳、氮分泌过程,提高根系分泌物碳、氮输入通量,进而加速该区域根际土壤碳和养分循环过程。

Responses of Root Exudative Carbon and Nitrogen Inputs to Warming in An Alpine Scrub Ecosystem on the Eastern Qinghai-Tibet Plateau

Plant root exudates,as one of the important pathways of plant root-derived soil organic carbon and nutrient inputs,can deeply affect the carbon and nutrient cycling in the rhizosphere soils.The changes of environmental temperature can directly and indirectly affect plant root exudative processes by altering plant primary productivity and root traits.However,the underlying mechanism still remain uncertainty.To explore the effects of climate warming on root exudative carbon and nitrogen inputs in the alpine scrub ecosystem,a field OTC(Open top chamber)warming experiment was conducted in an typical scrubland,which were dominated with Sibiraea angustata on the eastern Qinghai-Tibet Plateau,China.The objective of this study was to investigated the responses of root exudative carbon and nitrogen inputs to soil warming(+1.3℃).The method was used by a modified culture-based cuvette system.The results showed that there were siginficant seasonal differences in root exudative carbon and nitrogen input rates of S.angustata.The root exudative carbon and nitrogen input rates in the middle growing season were significantly higher than those in the early and late growing seasons.Throughout the whole growing season,the root exudative carbon and nitrogen input rates in the control plots ranged from 0.55 to 0.74 mg·g^–1·d^–1 and from 0.05 to 0.08 mg·g^–1·d^–1,respectively,and those in the warmed plots significantly increased by 14.0%–69.1%and 15.3%–70.2%,respectively.Moreover,the root exudative carbon and nitrogen fluxes in the control plots were 26.94 g·m^–2 and 3.03 g·m^–2,respectively,and those in the warmed plots were significantly increased by 57.2%and 46.9%,respectively.Further analysis showed that warming-induced increases in root exudative carbon and nitrogen fluxes mainly resulted from the increased fine root biomass and root exudate rates.These results indicated that climate warming will stimulate plant root exudative processes by enhancing root exudative carbon and nitrogen fluxes,and accelerate soil carbon and nutrient cycling in the rhizosphere soils in these alpine scrub ecosystems on the eastern Qinghai-Tibet Plateau.