本研究比较了青藏高原高寒草甸土壤呼吸速率(Rs)、自养呼吸速率(Ra)和异养呼吸速率(Rh)随施氮梯度的变化,揭示土壤呼吸及其组分变化的主要影响因素,为评价未来氮沉降背景下高寒草甸土壤碳释放提供科学依据.于2014年在四川红原青藏高原高寒草甸建立长期氮素添加平台,采取完全随机区组试验设计,设置 0(N0,对照)、2(N2)、4(N4)、8(N8)、16(N16)和 32 g N·m-2·a-1(N32)6 个水平氮素添加控制实验.于2020年生长季对Rs、Ra和Rh进行监测.结果表明:施氮显著降低了土壤呼吸及其组分(P＜0.05),且Ra的下降幅度大于Rh,导致Rh/Rs随施氮水平逐渐上升;不同施氮处理下Ra和Rh与土壤温度均呈显著的指数正相关(P＜0.05);施氮降低了 Ra的温度敏感性(Q10),但提高了 Rh的Q10值;土壤呼吸各组分与土壤湿度的关系均不显著,但土壤温度和土壤湿度双因子模型对Ra和Rh的解释度高于单因素模型.本研究揭示了高寒草甸土壤呼吸及其组分对氮添加的响应特征及机制,可为评估高寒草甸生态系统对大气氮沉降的响应以及生态系统管理提供科学依据.
Abstract
This study aimed to compare the changes of soil respiration rate(Rs),autotrophic respiration rate(Ra),and heterotrophic respiration rate(Rh)across a nitrogen application gradient in an alpine meadow on the Qinghai-Tibet Plateau,reveal the main influencing factors of soil respiration and its components,and provide a sci-entific basis for evaluating soil carbon release from alpine meadows under future nitrogen deposition.In 2014,a nitrogen addition platform was established in the alpine meadow of the Qinghai-Tibet Plateau in Hongyuan,Sichuan,following a completely randomized block experimental design with six levels of nitrogen addition,inclu-ding 0(N0,control),2(N2),4(N4),8(N8),16(N16)and 32(N32)g N·m-2·a-1.Nitrogen applica-tion significantly decreased soil respiration and its components(P＜0.05),and Ra decreased more than Rh,resul-ting in a gradual increase of Rh/Rs with the nitrogen addition gradient.There were significant exponential positive correlations between Ra and Rh and soil temperature under different nitrogen addition treatments(P＜0.05).Nitro-gen addition decreased the temperature sensitivity(Q10)of Ra,but increased that of Rh.The relationship between the components of soil respiration and soil moisture was not significant,but the two-factor model of soil temperature and soil moisture explained Ra and Rh better than the single-factor model.Our results enhance mechanistic under-standing of soil respiration and its components in response to nitrogen addition in an alpine meadow,and provide a theoretical basis for evaluating the response of alpine meadow ecosystems to atmospheric nitrogen deposition and guiding ecosystem management.
维普
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