DataSheet_1_Climate and fragment area jointly affect the annual dynamics of seedlings in different functional groups in the Thousand Island Lake.docx

Habitat fragmentation and climate change are the two main threats to global biodiversity. Understanding their combined impact on plant community regeneration is vital for predicting future forest structure and conserving biodiversity. This study monitored the seed production, seedling recruitment and mortality of woody plants in the Thousand Island Lake, a highly fragmented anthropogenic archipelago, for 5 years. We analyzed the seed-seedling transition, seedling recruitment and mortality of different functional groups in the fragmented forests and conducted correlation analyses involving climatic factors, island area, and plant community abundance. Our results showed that: 1) shade-tolerant and evergreen species had higher seed-seedling transition, seedling recruitment and survival rate than shade-intolerant and deciduous species in time and space, and these advantages increased with the island area. 2) Seedlings in different functional groups responded differently to island area, temperature and precipitation. 3) Increasing active accumulated temperature (the sum of the mean daily temperature above 0 °C) significantly increased seedling recruitment and survival, and warming climate favored the regeneration of evergreen species. 4) The seedling mortality rate of all plant functional groups increased with the increase of island area, but the increasing strength weakened significantly with the increase of the annual maximum temperature. These results suggested that the dynamics of woody plant seedlings varied among functional groups, and can be regulated separately and jointly by fragmentation and climate.

生境破碎化（habitat fragmentation）与气候变化是全球生物多样性面临的两大主要威胁。厘清二者对植物群落更新的联合影响，对预测未来森林结构及保护生物多样性至关重要。
本研究针对千岛湖（Thousand Island Lake）——这一高度破碎化的人工群岛——内的木本植物（woody plants），开展了为期5年的监测，记录其种子产量、幼苗招募与死亡动态。本研究分析了破碎化森林中不同功能群植物的种子-幼苗转化效率、幼苗招募率与死亡率，并针对气候因子、岛屿面积及植物群落多度开展了相关性分析。
研究结果显示：1）耐荫常绿物种在时空维度上的种子-幼苗转化效率、幼苗招募率与存活率均高于非耐荫落叶物种，且该优势随岛屿面积增大而愈发显著；2）不同功能群的幼苗对岛屿面积、温度与降水的响应模式存在显著差异；3）活动积温（Active Accumulated Temperature，即日均温高于0℃的逐日累积总和）的升高可显著提升幼苗招募率与存活率，气候变暖亦有利于常绿物种的更新；4）所有植物功能群的幼苗死亡率均随岛屿面积增大而升高，但这一上升幅度随年最高温的升高而显著减弱。
上述结果表明，木本植物幼苗动态存在功能群间差异，且可分别或联合受到破碎化与气候因子的调控。