Effects of fragmentation on cattle in African savannas under variable precipitation
Effects of fragmentation on cattle in African savannas under variable precipitation
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DOI：
10.1007/s10980-007-9124-4
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发表时间：
2007-11-01
影响因子：
5.2
通讯作者：
Boone, Randall B.
中科院分区：
文献类型：
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作者：
Boone, Randall B.
牛群移动到饲料数量和质量各不相同的地方。碎片化可以阻止动物到达斑块。我使用了一个综合生态系统模型，应用于三个非洲景观，以探索不同降水模式下牛种群对破碎化的敏感性（这里，随着包裹面积的减少，种群的变化）。我假设低降水和高降水会产生对破碎化相对不敏感的种群，中等降水会产生更敏感的种群，年际降水变化更大会降低对破碎化的敏感性。降水资料改为100 ~ 1000 mm年（-1）的平均产量，年际变异系数为0 ~ 60%。每个地区1000公里（2公里）的景观被逐步划分为较小的地块，并对每个地块进行模拟。100毫米年（-1）的降雨量支持对破碎化不敏感的低种群。种群数量在与观测值相似的降雨水平下达到峰值，在高降水条件下下降，部分原因是灌木扩张。破碎的景观导致牛的数量下降了62%。当降水量高于观测值时，年际变化较大的降水量降低了对破碎化的敏感性。当降水量低于观测值时，情况正好相反。细尺度异质性景观上的牛对破碎化相对不敏感，而粗粒度异质性景观上的牛对破碎化异常敏感。在人口敏感的景观中，破碎化将需要更密集的投入来抵消损失，而与气候变化有关的极端天气频率的变化将改变一些人口对破碎化的敏感性。
Cattle move to access patches that vary in forage quantity and quality. Fragmentation can prevent animals from reaching patches. I used an integrative ecosystem model applied to three African landscapes to explore the sensitivity of cattle populations to fragmentation (here, changes in populations as parcel areas decreased) under different precipitation patterns. I hypothesized that low and high precipitation would yield populations relatively insensitive to fragmentation, intermediate precipitation would yield more sensitive populations, and more variable inter-annual precipitation would reduce sensitivity to fragmentation. Precipitation data were altered to yield averages of 100-1,000 mm year(-1) and inter-annual coefficients of variation of 0-60%. A 1,000 km(2) landscape in each area was divided into progressively smaller parcels and simulations conducted for each parcel. Rainfall at 100 mm year(-1) supported low populations that were insensitive to fragmentation. Populations peaked at rainfall levels similar to those observed, and declined under higher precipitation, due in-part to shrub expansion. Fragmenting landscapes caused up to a 62% decline in cattle. High inter-annual variation in precipitation reduced sensitivity to fragmentation when precipitation was above that observed. The pattern was opposite when precipitation was below what was observed. Cattle on the landscape with fine-scale heterogeneity were relatively insensitive to fragmentation, and those on the heterogeneous but coarse-grained landscape were extremely sensitive. Fragmentation in landscapes where populations are sensitive will require more intensive inputs to offset losses, and changes in the frequency of extreme weather associated with climate change will alter the sensitivity of some populations to fragmentation.