Fine Root Decomposition Dynamics during Freeze-Thaw Season in the Subalpine/Alpine Forests | 季节性冻融期亚高山/高山森林细根分解动态

chinois. 为了解季节性冻融期不同阶段土壤冻融作用对细根分解的影响,采用凋落物分解袋法测定粗枝云杉、红桦和岷江冷杉细根在川西亚高山/高山森林区不同海拔地段（3 023,3 298,3 582 m）5个冻融阶段（初冻期、深冻期、融化前期、融化中期和完全融化期）的分解动态.结果表明：经过一个季节性冻融期细根残留率为88％ ～92％,不同海拔和不同树种之间差异显著.季节性冻融期各阶段均对3个树种细根分解具有明显贡献,但贡献率随着分解的延读表现出降低的趋势,且较低海拔的这种趋势更加明显.细根分解速率常数在0.177 6 ～0.242 4之间,各阶段细根相对失质量率与土壤温度密切相关,但细根分解速率与细根初始质量多项指标的相关性均不显著.建立包含季节性冻融期土壤平均温度、土壤温度波动、细根钙含量和细根木质素与氮比值的回归模型,可解释95％的细根分解速率差异形成原因.这些结果表明温度导致的土壤冻融过程是影响季节性冻融期细根分解速率的重要原因,而细根质量的影响相对较弱.

anglais. The ongoing winter warming inevitably alters the process of fine root decomposition in high-altitude area by changing the pattern of seasonal soil freezing and thawing.As yet,the dynamics of fine root decomposition at different stages in the freeze-thaw season remain uncertainty.In order to characterize the dynamics of fine root decomposition at different stages of a freeze-thaw season in cold biomes under climate change scenarios,litterbags with 10 g fine roots of Picea asperata,Betula albo-sinensis and Abies faxoniana were buried in the forest soil at the 3 582,3 298 and 3 023 m altitudes in western Sichuan,China.These litterbags were recovered at onset of freezing （OF）,deep frozen stage （DF）,early thawing stage （ETS）,middle thawing stage （MTS）,and later thawing stage （LTS） from December 10,2009 to April 28,2010.The residual rate of fine roots was 88％-92％ after a freeze-thaw season,and varied significantly with altitudes and tree species.The fine root decomposition occurred at all stages of the freeze-thaw season,among which OF had the highest rate of fine root decomposition.However,the rate of the fine root decomposition declined as decomposing,especially in the lower altitude.The decay rate constant of fine roots varied from 0.177 6 to 0.242 4,and the relative mass loss was correlated closely with soil temperature at the different stages,but the rate of the fine root decomposition was not significantly correlated with the indices of the measured initial qualities of fine roots.The regression model based on average soil temperature,fluctuated soil temperature,calcium concentration of fine roots and the ratio of lignin to nitrogen in fine roots during the freeze-thaw season,interpreted 95％ of the reason of differences in the fine root decay rate.It is concluded that the soil freeze-thaw process caused by temperature fluctuations was an important factor in influencing the rate of the fine root decomposition during the freeze-thaw season in the high-frigid forest ecosystem,and the fine root quality also had minor impact on the fine root decomposition. 关 键 词：细根分解 亚高山 高山森林 季节性冻融 相对失质量率