封育对羊草草地土壤碳矿化激发效应和温度敏感性的影响

土壤碳矿化(或土壤异养呼吸)的温度敏感性和激发效应是深入揭示土壤呼吸控制机理及其对未来气候变化响应与适应的重要研究方向.该文以自由放牧(FG0)、封育11年(FG11)、封育31年(FG31)的羊草(Leymus chinensis)草地为研究对象,通过0、5、10、15、20、25℃培养,探讨了封育对羊草草地土壤碳矿化激发效应和温度敏感性的影响.结果表明:封育年限、添加葡萄糖、培养温度和培养时间对土壤碳矿化速率均具有显著的影响,不同因素间存在显著的交互效应(p＜ 0.000 1).FG0的羊草草地土壤碳矿化累积量显著高于FG11和FG31的,在添加葡萄糖处理下也呈现相同的趋势.长期封育降低了羊草草地土壤碳矿化的激发效应.在添加葡萄糖后,培养前7天的土壤碳矿化的激发效应随温度增加而增加,增加2.28-9.01倍;在整个56天培养期间,激发效应介于2.21-5.10倍,最高值出现在10或15℃.土壤碳矿化速率可用经典的指数方程来表示,FG0草地的土壤碳矿化的温度敏感性指数(Q10)大于长期封育草地(FG11和FG31);与未添加处理相比,添加葡萄糖显著增加了土壤碳矿化速率的温度敏感性,即在添加葡萄糖后土壤微生物呼吸受温度的影响更大.长期封育会降低羊草草地土壤的碳矿化速率、温度敏感性和激发效应,从而降低土壤碳周转速率和释放速率,使内蒙古地区长期封育草地仍然具有碳固持能力.

Effect of grazing enclosure on the priming effect and temperature sensitivity of soil C mineralization in Leymus chinensis grasslands, Inner Mongolia, China

Aims The temperature sensitivity and priming effect of soil respiration, or soil carbon (C) mineralization, have been important topics for global change ecology in recent decades. They can provide new evidence on the controlling mechanisms of soil respiration in future climate change. Our objective was to investigate the effect of grazing enclosure on the priming effect and temperature sensitivity of soil C mineralization in grasslands.
Methods We selected three Leymus chinensis grasslands subjected to different grazing-exclusion durations in Inner Mongolia, i.e., grazing-free grassland (FG0), 11-year fenced grassland (FG11), and 31-year fenced grassland (FG31). We incubated the soils at 0, 5, 10, 15, 20, 25 °C, respectively.
Important findings Enclosure duration, glucose addition, incubation temperatures and incubation time all had significant impact on soil C mineralization rate, and there were significant interaction effects among these factors (p < 0.000 1). The cumulative emission of soil C mineralization was significantly higher in FG0 than in FG11 and FG31, and showed the same trend after glucose addition. Long-term enclosure decreased the priming effect of soil C mineralization in L. chinensis grasslands. After glucose addition, the priming effect of soil C mineralization was about 2.28–9.01 times and increased with increasing temperature in 7-day incubation. In 56-day incubation, the priming effect was in the range of 2.21–5.10, with the highest value at 10 or 15 °C. The temperature sensitivity of soil C mineralization can be well depicted by classical exponential equations, and the temperature sensitivity index (Q₁₀) of soil C mineralization was higher in FG0 than in FG11 and FG31. Glucose addition significantly increased Q₁₀, which indicated that soil microbial respiration under glucose addition was more affected by temperature. In conclusion, long-term enclosure reduced soil C mineralization rates, temperature sensitivity and priming effect in Inner Mongolian grasslands, which indicated that these long-term fenced grasslands have the capacity to further sequester CO₂ from the atmosphere.