极端干旱对若尔盖高原泥炭地生态系统CO2通量的影响

采用野外控制试验和静态箱法，研究极端干旱事件对若尔盖高原泥炭地净生态系统二氧化碳交换（net ecosystem CO₂ exchange, NEE）、生态系统呼吸（ecosystem respiration, R_e）和总初级生产力（gross primary productivity, GPP）的影响及其响应机制。研究结果表明：极端干旱显著降低若尔盖高原泥炭地生态系统的NEE、R_e和GPP（P<0.05），导致生态系统固碳能力减弱，而温度（空气温度和土壤温度）和土壤含水量（SWC）是若尔盖高原泥炭地碳收支变化的主要驱动因子。在对照处理（CK）和极端干旱处理（D）中，NEE、R_e和GPP与空气温度呈显著正相关关系（P<0.05），极端干旱减弱NEE、R_e和GPP对空气温度变化的敏感性。表层土壤温度与NEE、R_e和GPP的相关性高于深层土壤温度与NEE、R_e和GPP的相关性。分析5 cm土壤温度与NEE和R_e的相关关系。极端干旱减弱NEE对5 cm土壤温度的敏感性，增强R_e对5 cm土壤温度的敏感性。若尔盖高原泥炭地生态系统NEE、R_e和GPP与土壤含水量显著正相关（P<0.05），而极端干旱对土壤全碳、全氮和有机碳的含量无显著影响（P > 0.05）。

Effects of extreme drought on CO2 fluxes of Zoige alpine peatland

To study the effects of extreme drought on net ecosystem CO₂ exchange (NEE), ecosystem respiration (R_e), and gross primary productivity (GPP) of Zoige alpine peatland, the carbon fluxes in both extreme drought treatment (D) and control treatment (CK) were monitored by using static enclosed chamber technique in a control platform of extreme climate event. The results showed that extreme drought significantly decreased NEE, R_e, and GPP (P<0.05) of Zoige alpine peatland and hence reduced the carbon fixation capacity of targeted ecosystem. We also found that temperatures (air temperature (T_a) and soil temperature (T_s)) and soil water content (SWC) were the main driving factors of carbon budget dynamics in Zoige alpine peatland. NEE, R_e, and GPP were significantly positively correlated with air temperature (P < 0.05), and their sensitivity to the T_a change was weakened by extreme drought. The correlations of NEE, R_e, and GPP with topsoil temperature were much stronger than those with subsoil temperature. Besides, we found that extreme drought reduced the sensitivity of NEE to soil temperature at depth of 5 cm, but strengthened the sensitivity of R_e. Furthermore, NEE, R_e, and GPP were significantly positively correlated with soil water content (P<0.05). However, extreme drought had no significant effect on soil total carbon, nitrogen, and soil organic carbon contents (P>0.05).