六种温带森林类型凋落物量长期动态及其环境驱动

阐明凋落物动态及其环境控制机制，可以为森林生态系统生产力及碳汇功能的维持提供重要的数据支持和理论依据。以长白山系余脉张广才岭西坡林龄相近但立地条件不同的4种天然次生林（即硬阔叶林、杨桦林、杂木林和蒙古栎林）和2种人工林（落叶松人工林和红松人工林）为研究对象，对其地上凋落物产量及其组分以及相关环境因子进行了14年（2008-2021年）的连续测定，旨在揭示森林凋落物量及其组分的时空变化（林型间和年际变异）及其环境驱动机制。结果表明：6种森林类型的凋落总量（TL）无显著差异，波动范围为500.5-556.1 g m^-2 a^-1；但其叶凋落量（LL）、繁殖组织凋落量（RT）和其他组织凋落量（OT）均存在显著差异，波动范围依次分别为333.9-391.8 g m^-2 a^-1、8.43-69.93 g m^-2 a^-1和93.4-185.9 g m^-2 a^-1。6种森林类型的TL均存在显著的年际变化；其中LL和OT年际变化的显著性因森林类型而不同，而RT的年际变化不显著。除落叶松人工林外，其余5种森林类型的LL与生长季平均气温、日最低气温均值、土壤10 cm深度处的平均温度、最低温度（Ts_min）和土壤5 cm含水量（Ms）均呈显著正相关。杂木林、硬阔叶林和红松人工林的RT与Ms呈显著负相关；杂木林、杨桦林和硬阔叶林的OT与Ts_min呈显著负相关。样地水平的LL与土壤10 cm处含水量存在显著的正相关关系，而RT和OT则与其呈现显著负相关关系。这些结果表明林龄相似的温带森林地上凋落物总量有趋同趋势，但其通过改变组分分配格局来适应立地条件的变化；土壤湿度和温度变化会引起凋落物量的年际变化，但不同森林类型的凋落物量对环境波动的敏感性不同。

Long-term dynamics in litter production and their environmental drivers in six temperate forest types

Exploring dynamics in litter production and their environmental driving mechanisms are important for maintaining the productivity and carbon sequestration of forest ecosystem. In this study, we selected four natural secondary forest stands (i.e., hardwood stand, aspen-birch stand, mixed deciduous stand, and Mongolian oak stand) and two plantations stands (Dahurian larch plantation and Korean pine plantation) in the Zhangguangcai Range of Changbai Mountain, which had similar stand age but various site conditions and stand compositions; and we continuously measured the litterfall and its components and related environmental factors for 14 years (from 2008 to 2021) with an aim of understanding the spatio-temporal variations in above-ground litter production and their environmental drivers. The results showed that there was no significant difference in the total litterfall (TL) among the six forest types, varying from 500.5 to 556.1 g m^-2 a^-1. However, there were significant differences in the litter production of leaves (LL), reproductive tissues (RT), and other tissues (OT) among the forest types, varying from 333.9 to 391.8 g m^-2 a^-1, 8.43 to 69.93 g m^-2 a^-1, and 93.4 to 185.9 g m^-2 a^-1, respectively. There were significant inter-annual variations in TL of the six forest types, of which the significance degree for LL and OT varied with forest types; but there was no significant inter-annual difference in RT of all the forest types. LL was positively correlated with mean daily temperature, mean daily minimum temperature, mean daily soil temperature at the 10 cm depth, mean daily minimum soil temperature at 10 cm depth (Ts_min) and soil moisture content at the 5 cm depth (Ms) during the growing season in all the forest types except for Dahurian larch plantation. RT was negatively correlated with Ms in the mixed deciduous stand, hardwood stand and Korean pine plantation, while OT was negatively correlated with Ts_min in the mixed deciduous stand, aspen-birch stand and hardwood stand. The plot-level LL was positively correlated with soil moisture content at 10 cm depth, whereas the plot-level RT and OT were negatively correlated. These findings indicated that the temperate forests with similar forest age tended to converge their above-ground litter production, and adapted to various site conditions by changing the distribution pattern of litter components. The fluctuation of soil moisture and temperature resulted in inter-annual variations in litter production, and their sensitivity to environmental changes depended on forest types.