Changes in Patch Features May Exacerbate or Compensate for the Effect of Habitat Loss on Forest Bird Populations
Changes in Patch Features May Exacerbate or Compensate for the Effect of Habitat Loss on Forest Bird Populations
复制标题
斑块特征的变化可能会加剧或补偿栖息地丧失对森林鸟类种群的影响
作者：
Ainhoa Magrach;A. Larrinaga;L. Santamaría
在达尔文访问奇洛埃岛一个半世纪后，他所描述的“.一个被一片大森林覆盖的岛屿.”已经失去了三分之二的森林面积。在这个生物多样性热点地区，由于不受管制的伐木、清理牧场和被外来树木种植园取代，森林表面正变得越来越支离破碎。斑块大小的减少、隔离的增加和“边缘效应”会影响森林物种在残余碎片中的持久性。我们评估了这些变量如何影响当地密度的6种森林鸟类，选择包括最重要的种子传播者（4种）和鸟类传粉者（2种，其中之一也作为种子传播者），再加上最常见的食虫动物（Aphrastura spinicauda）。基于线索计数点调查（每个片段8个点），我们估计鸟类密度为每个物种在22个森林片段的大小，形状，隔离和内部栖息地结构（如树木大小和附生植物覆盖）。鸟类密度与片段连接（三个物种）和形状（三个物种），但没有一个物种的斑块大小的显着影响。卫星图像分析显示，从1985年到2008年，森林面积减少了8.8%，剩余的森林碎片变得更小16%，更孤立58-73%，更规则11-50%。在此期间，奇洛埃北方地区（面积为1 214.75平方公里）的鸟类密度估计数中，有一种（elaenia）减少，另外两种（chucao和蜂鸟）增加，三种（rayadito、推力和黑鸟）没有变化。对于前三个物种，斑块特征的变化分别加剧，平衡和克服了森林损失对鸟类种群规模的影响（鸟类水平丰度）。因此，斑块特征的变化可以调节栖息地破碎化对森林鸟类的影响，这表明空间规划（由空间明确的模型指导）可以是一种有效的工具，以促进其保护。
One and a half centuries after Darwin visited Chiloe Island, what he described as “…an island covered by one great forest…” has lost two-thirds of its forested areas. At this biodiversity hotspot, forest surface is becoming increasingly fragmented due to unregulated logging, clearing for pastures and replacement by exotic tree plantations. Decrease in patch size, increased isolation and “edge effects” can influence the persistence of forest species in remnant fragments. We assessed how these variables affect local density for six forest birds, chosen to include the most important seed dispersers (four species) and bird pollinators (two species, one of which acts also as seed disperser), plus the most common insectivore (Aphrastura spinicauda). Based on cue-count point surveys (8 points per fragment), we estimated bird densities for each species in 22 forest fragments of varying size, shape, isolation and internal-habitat structure (e.g. tree size and epiphyte cover). Bird densities varied with fragment connectivity (three species) and shape (three species), but none of the species was significantly affected by patch size. Satellite image analyses revealed that, from 1985 to 2008, forested area decreased by 8.8% and the remaining forest fragments became 16% smaller, 58–73% more isolated and 11–50% more regular. During that period, bird density estimates for the northern part of Chiloé (covering an area of 1214.75 km2) decreased for one species (elaenia), increased for another two (chucao and hummingbird) and did not vary for three (rayadito, thrust and blackbird). For the first three species, changes in patch features respectively exacerbated, balanced and overcame the effects of forest loss on bird population size (landscape-level abundance). Hence, changes in patch features can modulate the effect of habitat fragmentation on forest birds, suggesting that spatial planning (guided by spatially-explicit models) can be an effective tool to facilitate their conservation.