土壤湿度对东北3种主要树种凋落物分解的影响

结合丰林国家自然保护区原始阔叶红松林1998-2017年表层(0～10 cm)土壤湿度监测数据,评估了全球变化背景下土壤湿度变化对东北主要森林树种红松、臭冷杉和白桦凋落物分解的影响.结果表明: 在同一土壤湿度水平下,凋落物分解速率随着凋落物质量的增加而增大,即表现为白桦>臭冷杉>红松.凋落物的分解速率随着土壤湿度的降低而减小.白桦、臭冷杉和红松3种凋落物的土壤湿度敏感性指数(M₁₀)分别为0.782、0.789和0.827,土壤湿度水平每降低10%,初始分解速率分别减小21.8%、21.1%和17.3%.高质量凋落物(高氮含量、低碳氮比、低木质素含量)的分解速率对土壤湿度变化的响应更敏感.凋落物分解速率在不同凋落物类型间的差异随着土壤湿度的降低而缩小.近20年间,原始阔叶红松林土壤湿度呈显著减少趋势,对凋落物分解表现为抑制作用.在全球变化背景下,随着气温的升高,土壤湿度将继续降低,对凋落物的抑制作用会进一步增强,并将部分抵消因温度升高所带来的凋落物分解速率增大的压力.

Effects of soil moisture on litter decomposition of three main tree species in Northeast China.

The effects of soil moisture variation on the litter decomposition of main tree species Betula platyphylla, Abies nephrolepis and Pinus koraiensis were evaluated in a primary forest of Korean pine (P. koraiensis) in Fenglin National Nature Reserve of the Northeast China, based on the measurements of surface (0-10 cm) soil moisture from 1998 to 2017. The results showed that litter decomposition rates increased with the increase of litter quality. The order of litter decomposition rate was B. platyphylla > A. nephrolepis > P. koraiensis at the same soil moisture. The litter decomposition rates decreased with the decrease of soil moisture. The sensitivity index of litter decomposition rates on soil moisture (M₁₀) were 0.782, 0.789 and 0.827, respectively, for B. platyphylla, A. nephrolepis and P. koraiensis. The initial litter decomposition rate decreased by 21.8%, 21.1% and 17.3% for B. platyphylla, A. nephrolepis and P. koraiensis, respectively, when soil moisture decreased by 10%. The decomposition rates of high-quality litter (high nitrogen content, low carbon to nitrogen ratio, and low lignin content) were more sensitive to the variation of soil moisture. The difference in decomposition rate among different litter types was reduced with the decrease of soil moisture. In the recent 20 years, the average soil moisture presented a significantly decreasing trend, which would inhibit litter decomposition in the primary Korean pine forest. Under the scena-rios of global change, soil moisture would further decrease with the increase of air temperature. It would definitely intensify the inhibitory effect on litter decomposition, and partly offset the enhanced effects of increased air temperature.