Gould William A, González Grizelle, Hudak Andrew T, Hollingsworth Teresa Nettleton, Hollingsworth Jamie
USDA Forest Service, International Institute of Tropical Forestry, Río Piedras, Peurto Rico 00926-1115, USA.
Ambio. 2008 Dec;37(7-8):577-87. doi: 10.1579/0044-7447-37.7.577.
Forest fragmentation affects the heterogeneity of accumulated fuels by increasing the diversity of forest types and by increasing forest edges. This heterogeneity has implications in how we manage fuels, fire, and forests. Understanding the relative importance of fragmentation on woody biomass within a single climatic regime, and along climatic gradients, will improve our ability to manage forest fuels and predict fire behavior. In this study we assessed forest fuel characteristics in stands of differing moisture, i.e., dry and moist forests, structure, i.e., open canopy (typically younger) vs. closed canopy (typically older) stands, and size, i.e., small (10-14 ha), medium (33 to 60 ha), and large (100-240 ha) along a climatic gradient of boreal, temperate, and tropical forests. We measured duff, litter, fine and coarse woody debris, standing dead, and live biomass in a series of plots along a transect from outside the forest edge to the fragment interior. The goal was to determine how forest structure and fuel characteristics varied along this transect and whether this variation differed with temperature, moisture, structure, and fragment size. We found nonlinear relationships of coarse woody debris, fine woody debris, standing dead and live tree biomass with mean annual median temperature. Biomass for these variables was greatest in temperate sites. Forest floor fuels (duff and litter) had a linear relationship with temperature and biomass was greatest in boreal sites. In a five-way multivariate analysis of variance we found that temperature, moisture, and age/structure had significant effects on forest floor fuels, downed woody debris, and live tree biomass. Fragment size had an effect on forest floor fuels and live tree biomass. Distance from forest edge had significant effects for only a few subgroups sampled. With some exceptions edges were not distinguishable from interiors in terms of fuels.
森林破碎化通过增加森林类型的多样性和森林边缘数量，影响了累积燃料的异质性。这种异质性对我们管理燃料、火灾和森林的方式具有重要意义。了解在单一气候条件下以及沿气候梯度，破碎化对木质生物量的相对重要性，将提高我们管理森林燃料和预测火灾行为的能力。在本研究中，我们评估了不同湿度（即干燥森林和湿润森林）、结构（即开阔冠层（通常较年轻）与封闭冠层（通常较老）林分）以及大小（即小（10 - 14公顷）、中（33至60公顷）和大（100 - 240公顷））的林分在北方、温带和热带森林气候梯度上的森林燃料特征。我们沿着从森林边缘外侧到片段内部的样带，在一系列样地中测量了腐殖质、凋落物、细木质和粗木质碎屑、立枯木以及活生物量。目标是确定森林结构和燃料特征沿此样带如何变化，以及这种变化是否因温度、湿度、结构和片段大小而异。我们发现粗木质碎屑、细木质碎屑、立枯木和活树生物量与年平均中位温度呈非线性关系。这些变量的生物量在温带地区最大。林地燃料（腐殖质和凋落物）与温度呈线性关系，生物量在北方地区最大。在一项五元多变量方差分析中，我们发现温度、湿度和年龄/结构对林地燃料、倒下的木质碎屑和活树生物量有显著影响。片段大小对林地燃料和活树生物量有影响。离森林边缘的距离仅对少数抽样亚组有显著影响。除了一些例外情况，在燃料方面，边缘与内部没有明显区别。
