岷江上游华山松林冬季土壤呼吸对模拟增温的短期响应

Short-term response of winter soil respiration to simulated warming in a Pinus armandii plantation in the upper reaches of the Minjiang River,China

冬季的土壤呼吸是生态系统呼吸的重要组成部分,对气候变化的响应可能更为敏感。该文采用红外辐射加热器模拟土壤增温,研究了岷江上游华山松(Pinus armandii)人工林冬季的土壤呼吸、微生物生物量及无机氮库对模拟增温的响应。结果表明:在冬季(2009年11月–翌年3月),模拟增温往往能显著提高土壤呼吸速率,平均增幅达31.4%;同样模拟增温使土壤微生物生物量碳、氮分别增加23.2%和22.7%,而对微生物生物量碳氮比没有影响,温度升高显著促进了微生物的生长,但没有改变微生物的群落结构;增温样地土壤的NO3–-N和NH4+-N浓度较对照分别增加了38.5%和12.3%,增温显著提高了土壤的可溶性无机氮含量。综上所述,该区针叶林冬季土壤呼吸、微生物生长和养分矿化对未来气候变暖非常敏感。

Aims Winter soil respiration is reported to be a significant component of the annual carbon budgets. In order to understand how projected global warming affects winter soil respiration and soil microbial properties, we con-ducted a warming experiment in a young Pinus armandii plantation during the winter period to assess short-term response of winter soil CO2 efflux and microbial properties to artificial warming. Methods We used an infrared heater and monitored soil temperature and relative air humidity in November 2009 and analyzed soil respiration, microbial biomass and inorganic nitrogen pools throughout the winter. Important findings The average daily air and soil temperatures were 2.1 and 6.7 ℃ higher in the warmed plots than in the control plots, respectively. Warming declined relative air humidity and soil water content by 15.2% and 7.2%, respectively. Across all measuring dates, simulated warming increased average soil CO2 efflux by 31.4%. Warming significantly enhanced the soil microbial biomass carbon （SMB-C） and nitrogen （SMB-N） by 23.2% and 22.7%, respectively, but did not affect the ratio of SMB-C to SMB-N, which indicated that elevated temperature tended to accelerate the growth of SMB, but did not change the community structure of SMB. Likewise, warming tended to increase soil inorganic nitrogen pools. Nitrate （NO3–-N） and ammonium （NH4＋-N） in the warmed soil increased 38.5% and 12.3%, respectively, compared with control soil. Results indicate that winter soil respiration, microbial activities and nutrient mineralization in the coniferous forest soils could be sensitive to future global warming.