更频繁和更严重的干扰越来越多地打开森林冠层并开始树木再生。同时,极端天气增加,比如干旱和炎热,是适应凉爽潮湿气候的威胁物种。森林冠层缓解炎热和干燥天气条件的微气候缓冲能力的大小及其干扰引起的减少仍未量化。此外,干扰遗产的影响(例如,枯木)对森林小气候的影响尚未解决。在一项独特的操作实验中,我们研究了(i)在不同气候条件下年份林冠的微气候缓冲能力;(ii)空间干扰模式对表面光和微气候的影响;(iii)枯木的存在和类型对微气候的影响。治疗包括两种干扰模式(即,聚合和分布式),四种枯木类型(即,站立,坠落,站立和倒下,已移除),和一个未经处理的对照(即,总共九种治疗),在德国东南部以欧洲山毛榉(FagussylvaticaL.)为主的五个地点复制。我们测量了森林地面光照条件,并得出了连续四个夏季(2016年至2019年)的昼夜极值和温度(T)和蒸气压赤字(VPD)的变化。在温暖和干燥的年份,完整的林冠的缓冲能力更高。与类似严重程度的分布式干扰相比,空间聚集的干扰间隙中的表面光明显更高。相对于封闭天篷,表面光增加10%,Tmax和VPDmax升高0.42°C和0.04kPa,分别。枯木的存在和类型对森林小气候没有显着影响。林冠下的微气候缓冲可以抑制气候变化的影响。然而,增加冠层干扰导致更多的光穿透冠层,降低森林的微气候缓冲能力。我们得出的结论是,森林管理应促进森林中的微气候缓冲,这是应对气候变化的多管齐下战略的一个要素。
More frequent and severe disturbances increasingly open the forest canopy and initiate tree regeneration. Simultaneously, increasing weather extremes, such as drought and heat, are threatening species adapted to cool and moist climate. The magnitude of the microclimatic buffering capacity of forest canopies to mitigate hot and dry weather conditions and its disturbance-induced reduction remains poorly quantified. Also, the influence of disturbance legacies (e.g., deadwood) on forest microclimate is unresolved. In a unique manipulation experiment we investigated (i) the microclimatic buffering capacity of forest canopies in years with different climatic conditions; (ii) the impacts of spatial disturbance patterns on surface light and microclimate; and (iii) the effect of deadwood presence and type on microclimate. Treatments included two disturbance patterns (i.e., aggregated and distributed), four deadwood types (i.e., standing, downed, standing and downed, removed), and one untreated control (i.e., nine treatments in total), replicated at five sites dominated by European beech (Fagus sylvatica L.) in southeastern Germany. We measured forest floor light conditions and derived diurnal extremes and variation in temperature (T) and vapor pressure deficit (VPD) during four consecutive summer seasons (2016 - 2019). The buffering capacity of intact forest canopies was higher in warm and dry years. Surface light was significantly higher in spatially aggregated disturbance gaps compared to distributed disturbances of similar severity. An increase in surface light by 10 % relative to closed canopies elevated Tmax and VPDmax by 0.42°C and 0.04 kPa, respectively. Deadwood presence and type did not affect the forest microclimate significantly. Microclimatic buffering under forest canopies can dampen the effects of climate change. However, increasing canopy disturbances result in more light penetrating the canopy, reducing the microclimatic buffering capacity of forests. We conclude that forest management should foster microclimatic buffering in forests as one element of a multi-pronged strategy to counter climate change.