Fenner School of Environment and Society, The Australian National University, Canberra, Australian Capital Territory, Australia.
National Environmental Science Programme, Threated Species Recovery Hub, Fenner School of Environment and Society, The Australian National University, Canberra, Australian Capital Territory, Australia.
PLoS One. 2018 Feb 23;13(2):e0193132. doi: 10.1371/journal.pone.0193132. eCollection 2018.
Large old trees are critically important keystone structures in forest ecosystems globally. Populations of these trees are also in rapid decline in many forest ecosystems, making it important to quantify the factors that influence their dynamics at different spatial scales. Large old trees often occur in forest landscapes also subject to fire and logging. However, the effects on the risk of collapse of large old trees of the amount of logging and fire in the surrounding landscape are not well understood. Using an 18-year study in the Mountain Ash (Eucalyptus regnans) forests of the Central Highlands of Victoria, we quantify relationships between the probability of collapse of large old hollow-bearing trees at a site and the amount of logging and the amount of fire in the surrounding landscape. We found the probability of collapse increased with an increasing amount of logged forest in the surrounding landscape. It also increased with a greater amount of burned area in the surrounding landscape, particularly for trees in highly advanced stages of decay. The most likely explanation for elevated tree fall with an increasing amount of logged or burned areas in the surrounding landscape is change in wind movement patterns associated with cutblocks or burned areas. Previous studies show that large old hollow-bearing trees are already at high risk of collapse in our study area. New analyses presented here indicate that additional logging operations in the surrounding landscape will further elevate that risk. Current logging prescriptions require the protection of large old hollow-bearing trees on cutblocks. We suggest that efforts to reduce the probability of collapse of large old hollow-bearing trees on unlogged sites will demand careful landscape planning to limit the amount of timber harvesting in the surrounding landscape.
大型老树木在全球森林生态系统中是至关重要的基石结构。在许多森林生态系统中，这些树木的数量也在迅速减少，因此，量化不同空间尺度上影响它们动态的因素变得尤为重要。大型老树木通常出现在也受到火灾和采伐影响的森林景观中。然而，周围景观中采伐和火灾的数量对大型老树木倒塌风险的影响还不是很清楚。本研究使用维多利亚州中部高山山灰（Eucalyptus regnans）森林的 18 年研究，量化了一个地点大型老空心树倒塌概率与周围景观中采伐量和火灾量之间的关系。我们发现，随着周围景观中采伐森林面积的增加，倒塌的概率也随之增加。周围景观中燃烧面积的增加也会增加倒塌的概率，尤其是对于处于高度腐烂阶段的树木。随着周围景观中采伐或燃烧区域的增加，树木倒下的可能性增加的最可能解释是与采伐区或燃烧区相关的风运动模式发生了变化。先前的研究表明，在我们的研究区域，大型空心树木已经处于高倒塌风险之中。这里提出的新分析表明，周围景观中的额外采伐作业将进一步提高这种风险。当前的采伐法规要求在采伐区保护大型空心树木。我们建议，为了降低未采伐地点大型空心树木倒塌的概率，需要进行仔细的景观规划，以限制周围景观中的木材采伐量。
