亚热带林地恢复过程的植物多样性与水分利用效率变化

Changes in plant diversity and water use efficiency during the restoration process of subtropical forests

受扰动的森林系统可以通过一系列演替过程进行修复,其中植物物种多样性变化是评估演替进程的重要指标,而植物的水分利用效率又是了解土壤水分条件对林带恢复影响的直观指标。因此,解析林带恢复(演替)过程中植物多样性变化与水分利用效率差异,对了解林带恢复过程的控制因素及森林生态系统的保护和可持续发展具有重要的意义。然而,中国相关研究大多集中于温带大陆性山地气候林带,亚热林带水热状况截然不同,但相关研究仍较欠缺。在此基础上,本研究选取受严重人为/自然灾害影响的四川小寨子沟自然保护区,通过传统的样地植被调查和辛普森指数、贝格-派克指数、香农指数等生物多样性指标,归纳不同林型的植被演替过程中物种多样性的变化规律;结合叶片稳定碳同位素方法,对其不同演替阶段三种林型(原始林、次生林和人工林)的植物水分利用效率差异进行分析。结果表明不同林型演替具有阶段性差异,原始林演替阶段最高,但水分胁迫和氮营养竞争较强,植被的生长受到限制;人工林物种单一阶段最低,优势种的氮营养竞争是限制该林型植被生长的主控因子;而次生林由于恢复时间较长,处于较高演替阶段,氮营养和水分充足,植被生长较快。

The disturbed forest system can be restored through a series of succession,where changes in plant species diversity serve as an important indicator for evaluating the successional progress.Meanwhile,the water use efficiency of plants provides a direct measure to understand the impact of soil moisture conditions on forest recovery.Therefore,analyzing the differences in plant diversity and water use efficiency during forest recovery(succession)processes is of significant importance for understanding the controlling factors of forest recovery and the conservation and sustainable development of forest ecosystems.However,most of the relevant studies in China have focused on temperate continental mountainous climatic zones,while the water-thermal conditions in subtropical forest zones are distinctly different,and related research in these areas is still relatively scarce.To address this research gap,we conducted a study in the Xiaozhaizigou Nature Reserve,located in Sichuan,China,an area significantly affected by both human and natural disturbances.We performed traditional vegetation surveys and employed biodiversity indices,including Simpson's index,BergerParker index,and Shannon's index,to assess the patterns of species diversity changes in different forest types during vegetation succession.Additionally,we utilized stable carbon isotope analysis of leaf samples to investigate the variations in water use efficiency among three forest types(primary forest,secondary forest,and plantation) at different stages of succession.Our findings revealed distinct stage-specific differences in forest succession among different forest types.The primary forest exhibited the highest stage during succession;however,its vegetation growth was limited by water stress and nitrogen competition.The plantation displayed the lowest species diversity,primarily attributed to the dominance of certain species and nitrogen competition acting as the primary controlling factor for vegetation growth.In contrast,the secondary forest,characterized by a longer recovery time,reached a higher stage of succession,benefiting from sufficient nitrogen and water supply,which resulted in accelerated vegetation growth.This study underscores the significance of analyzing plant diversity dynamics and water use efficiency during forest succession to gain insights into the controlling factors of forest recovery and facilitate effective conservation and sustainable development of subtropical forest ecosystems.Further research in subtropical regions is warranted to enhance our understanding of restoration mechanisms and optimize restoration strategies in these ecologically important areas.