高寒灌丛对气候变暖的生态响应及适应性研究进展

The ecological respsonses and adaptability of alpine shrubs to global warming

灌丛通常指高度在5 m以下的以灌木为优势的植被类型。高寒灌丛因地处高海拔或高纬度的寒冷生境,对气候变暖响应尤为敏感。然而,随着近几十年的气候变暖,大量研究数据表明环北极地区树木生长对夏季温度的敏感性逐渐下降,但目前并不清楚高寒灌丛如何响应和适应气候变暖,是否也存在敏感性下降问题。本文主要基于长时间序列数据、样带调查及模拟试验等研究方法综述不同时空尺度下高寒灌丛对气候变暖的生态响应相关研究成果,并指出当前的研究趋势和存在问题。长时间序列数据基于长期定位监测和(或)树轮数据及遥感、航拍和重复拍照手段揭示灌木的扩展、生长变化趋势及其可能的影响因子;样带调查主要表现为相关生态指标沿海拔梯度的变化规律;模拟试验主要体现在植物物候、叶性状变化等。综合来看,变暖促进了高寒灌丛的生长,体现在植被盖度、生物量等指标的增加。就灌木叶功能性状而言,一些性状(如比叶面积等)在胁迫生境中体现出趋同适应特征。不同研究方法受研究尺度的限制存在明显的局限性,未来应开展全方位、多尺度的全球性联网综合观测体系;加强对不同功能型灌木的对比研究,探索高寒区趋同适应的普遍性和环境阈值;加强沿水分梯度的样带调查,开展人工模拟增(减)雪试验;重点关注冻融、微生物活动等地下生态过程对气候变化的响应。

Shrubland is defined as a vegetation type dominated by shrubs with heights of less than 5 m.Given the adaptation of alpine shrubs to the cold habitats characterizing high altitudes or latitudes,these plants are particularly sensitive to climate warming.In recent decades,many studies have identified a declining trend in tree growth sensitivity to summer temperatures in circumarctic regions.However,it remains unclear as to how alpine shrubs respond and adapt to climate warming,and whether there would be a reduction in the temperature sensitivity of shrub growth.In this study,we mainly review findings on the responses of alpine shrubs to climate warming at different spatiotemporal scales based on different research methods,and describe the associated research trends and current problems.Long-term sequence data,based on long-term positional observations,tree-ring data,remote sensing,and aerial and recurrent photography,have revealed the changing trends and possible factors influencing shrub expansion and growth.Transect surveys mainly show variations along altitudinal gradients,and studies have focused on changes in associated ecological indices,whereas manipulation experiments have identified changes in plant phenology and leaf traits.In general,warming has been found to promote the growth of alpine shrubs,which is reflected in increases in vegetation coverage,biomass,and related indices.With respect to leaf functional traits,those such as specific leaf area have been observed to undergo convergent adaptation in stressed habitats.However,given the limitations of scale,research methodology is constrained by boundedness.In the future,we should develop more comprehensive multi-scale global network observation systems.In terms of scientific issues,comparative studies between different functional types should be further conducted to examine the universality of convergence adaptation and the environmental thresholds of alpine shrubs.Moreover,we need to focus to greater extent on transect studies along water gradients,simulation studies examining changes in snow cover,and the responses of belowground ecological processes,such as freeze-thaw cycles and microbial activities,to climate change.