凋落物呼吸温度敏感性的变化特征及其影响因素

Variation in the Temperature Sensitivity of Surface Litter Respiration and Its Influencing Factors

地表凋落物呼吸是土壤呼吸的一个重要组成部分,研究凋落物呼吸温度敏感性的变化特征及其影响因素对准确理解地区的土壤碳循环具有重要意义.本研究在黄土高原南部的一个典型人工刺槐林内(Robinia pseudoacacia L.),通过地表凋落物控制试验(对照处理,去除凋落物处理、倍增凋落物处理),研究凋落物呼吸温度敏感性的年际(2009~2013年)变化特征及其驱动因素.凋落物呼吸温度敏感性的年际差异显著(P<0.05):在对照处理下,其最小值为4.15,最大值为6.67,均值为5.10,变异系数为19%;在倍增凋落物处理下,其变化于1.17~6.52之间,均值为3.36,变异系数高达56%.凋落物呼吸温度敏感性的年际变异与年平均土壤水分、地表凋落物量以及二者的交互作用密切相关(P<0.01),同时对凋落物呼吸温度敏感性的贡献呈现出土壤水分大于地表凋落物量的趋势(对照处理:2.68和2.04;倍增凋落物处理:1.37和0.69).此外,地表凋落物倍增后,凋落物呼吸温度敏感性却减少了34%(3.36和5.10).同时,在对照处理下,大约有超过50%的地表凋落物碳滞留在该刺槐林生态系统中[215 g·(m^2·a)^(-1)和113 g·(m^2·a)^(-1)],但在倍增处理下,仅有24%的地表凋落物碳滞留在该林地生态系统中[430 g·(m^2·a)^(-1)和326 g·(m^2·a)^(-1)],即在该人工刺槐林生态系统中地表凋落物的增加未必意味着土壤有机碳储量的增加.因此,探究地表凋落物控制措施、土壤水分、地表凋落物量和凋落物呼吸温度敏感性之间的关系对准确理解地区的土壤碳循环具有重要意义.

Surface litter respiration is a major component of soil respiration in the carbon cycle of terrestrial ecosystems, and studying the variation in the temperature sensitivity of surface litter respiration and its influencing factors is important for the accurate understanding of the regional soil carbon cycle. In a typical locust plantation （Robinia pseudoacacia L.） ecosystem in a small watershed in Wang Donggou of Loess Plateau, China, three surface litter control treatments were established： ① control treatment, ② litter removal treatment, and ③ doubled litter treatment, for studying the interannual variation （2009-2013） in the temperature sensitivity of surface litter respiration and its influencing factors. The interannual variability in the temperature sensitivity of surface litter respiration was statistically significant （P〈0.05）. It ranged from 4.15 in 2012 to 6.67 in 2010, with mean value of 5.10 and a coefficient of variation of 19% in the control treatment, and from 1.77 to 6.52, with mean value of 3.36 and a coefficient of variation of 56% in the doubled litter treatment. It was closely related with annual surface litter biomass, annual mean soil moisture content, and the interplay between annual surface litter biomass and annual mean soil moisture content （P〈0.01）. Moreover, the contribution to temperature sensitivity of surface litter respiration from soil moisture was greater than that from surface litter biomass （control treatment： 2.68 vs. 2.04, respectively; doubled litter treatment： 1.37 vs. 0.69, respectively）. Additionally, under the doubled litter treatment, temperature sensitivity of surface litter respiration decreased by 34%. In the artificial locust plantation ecosystem, over 50% of surface litter carbon was kept under the control treatment [215 g·（m2·a）-1 vs. 113 g·（m2·a）-1], but only 24% of surface litter carbon was kept under the doubled litter treatment [430 g·（m2·a）-1 vs. 326 g·（m2·a）-1], which implied that the soil carbon reserves in the plantation ecosystem will not increase with an increase of surface litter biomass in the Loess Plateau, China. Therefore, investigating the relationships among soil moisture, surface litter biomass, and surface litter biomass control measures are useful for the accurate understanding of the regional soil carbon cycle.