The importance of core habitat for a threatened species in changing landscapes
The importance of core habitat for a threatened species in changing landscapes
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受威胁物种的核心栖息地在景观变化中的重要性
DOI：
10.1111/1365-2664.13234
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发表时间：
2018
影响因子：
5.7
通讯作者：
W. A. Boyle
中科院分区：
文献类型：
--
作者：
Mark R. Herse;Kimberly A. With;W. A. Boyle
栖息地的丧失、碎片化和景观基质的改变是相互依存的过程，共同导致了最近的物种灭绝。因此，确定这些景观过程对动物的影响程度对保护至关重要。然而，研究人员经常假设相互依赖的影响与动物的反应独立相关，低估了一个或几个景观过程在推动物种衰退方面的重要性。我们通过评估美国堪萨斯州东部一种快速衰落的草原鸣鸟物种(草原蝗虫)的丰度，展示了如何理清栖息地数量、碎片化程度和边缘环境对种群规模的相互依赖影响。我们在两个繁殖季节对2,000个地点进行了7,000点计数调查，然后模拟了与我们的重点物种的扩散行为相关的空间尺度(200、400、800和1600米半径)内的景观因素对丰度的直接、交互和间接影响。在400 m半径范围内，麻雀丰度与景观结构的相关性最强，随草地面积的增加而非线性增加，随耕地或林缘草地所占比例的增加而减少。麻雀对农田边缘的负面反应主要是草地面积减少的附加间接结果，而麻雀对木质边缘更强的负面反应不是由于草原面积的变化。在约50%-80%的草地景观中，破碎化和边缘背景最重要。合成与应用。在我们的研究中，受威胁的草原鸣鸟的数量更多地受到核心草原面积(草地总面积、破碎度和边缘环境的函数)的影响，而不是草地总面积本身。此外，约50%草原的局部灭绝阈值表明，无论生境配置或基质类型如何，少量的栖息地都不适合我们的重点物种。针对生境面积的局部灭绝阈值为土地管理者提供了明确的基线目标；超过这些阈值，可以修改配置和矩阵，以增加边缘敏感型动物的丰度。文献中关于碎片化和基质特征重要性的相互矛盾的证据可以部分地解释为物种水平的特征，或方法学问题，如在生态上任意的空间尺度上定义景观，使用物种丰富度来评估景观质量，以及忽视相互作用和间接影响。
Habitat loss, fragmentation, and alteration of the landscape matrix are interdependent processes, collectively responsible for most recent species extinctions. Thus, determining the extent to which these landscape processes affect animals is critical for conservation. However, researchers have often assumed that interdependent effects are independently related to animals’ responses, underestimating the importance of one or several landscape processes in driving species declines. We demonstrate how to disentangle the interdependent effects of habitat amount, fragmentation, and edge context on population size by assessing abundance of a rapidly declining grassland songbird species (grasshopper sparrow Ammodramus savannarum) in eastern Kansas (USA). We conducted >7,000 point count surveys at >2,000 sites over two breeding seasons, then modelled the direct, interactive, and indirect effects of landscape factors on abundance within spatial scales (200‐, 400‐, 800‐, and 1,600‐m radii) relevant to our focal species’ dispersal behaviour. Sparrow abundance correlated most strongly with landscape structure within 400‐m radii, increasing nonlinearly with grassland area and decreasing with the proportion of grassland near cropland or woody edges. Sparrows’ negative response to cropland edges was mostly an added, indirect consequence of reduced grassland area, whereas sparrows’ stronger negative response to woody edges was not attributable to variation in grassland area. Fragmentation and edge context mattered most in landscapes comprising c. 50%–80% grassland. Synthesis and applications. In our research, abundance of a threatened grassland songbird was influenced more by core grassland area (a function of total grassland area, fragmentation, and edge context) than total grassland area per se. Moreover, a local extinction threshold of c. 50% grassland indicated that small amounts of habitat were unsuitable for our focal species regardless of habitat configuration or matrix type. Local extinction thresholds in response to habitat area provide clear baseline targets for land managers; above those thresholds, configuration and the matrix can be modified to increase abundance of edge‐sensitive animals. Conflicting evidence in the literature regarding the importance of fragmentation and matrix features could be partially explained by species‐level traits, or methodological issues such as defining landscapes at ecologically arbitrary spatial scales, assessing landscape quality using species richness, and ignoring interactive and indirect effects.