Long-Term Glades in Acacia Bushland and Their Edge Effects in Laikipia, Kenya
Long-Term Glades in Acacia Bushland and Their Edge Effects in Laikipia, Kenya
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肯尼亚莱基皮亚的金合欢丛林中的长期空地及其边缘效应
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
A. Macrae
中科院分区：
文献类型：
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作者：
T. Young;Nathaniel Patridge;A. Macrae
在肯尼亚的莱基皮亚生态系统中，孤立的林中空地出现在金合欢灌木和林地群落中。这些空地至少有几十年的历史了。据报道，它们是不再存在的传统牧民的旧定居点，它们的大小、位置和方向与其他地方研究的相关牧民的定居点一致。这项研究的目的是记录这些空地在当地和景观层面的影响。在莱基皮亚中部工作时，我们记录了其中四个林中空地的植被、动物利用和土壤的差异，并且距离林中空地边缘的距离越来越远。四种“沼泽专家”在沼泽植物群落中占主导地位，而在沼泽植物群落之外非常罕见。狼尾草（Pennisetum stramineum）是六个林间空地边缘种之一，在大多数林间空地边缘形成茂密的高草环。林间空地边缘向金合欢灌木林的过渡并不总是突然的（取决于所考虑的性状），导致边缘效应在深度和锐度上有所不同。边缘深度，定义为达到某性状背景水平的三分之二所需的距离，范围从0到200米。林下植物物种丰富度和多样性在林地内最低，随距离增加而逐渐增加。然而，由于林中空地支持其他地方没有的物种，因此林中空地的存在增加了整体物种多样性。野生和家养大型哺乳动物粪便密度在林间空地内最高可达10倍，且随距离林间空地边缘的远近而减小。同样，在林中空地中，土壤中的氮、钾、碳、钙和钠含量最高。土壤磷、镁和锰在林中空地及其100米范围内没有升高，但在背景样品中含量要高得多。这些林中空地可能是由高密度的大型哺乳动物维持的，要么是通过食草动物，要么是通过土壤化学的变化。林中空地可能对哺乳动物有吸引力，因为那里有高质量的食物，或者是作为对抗捕食者策略的一部分。其结果是形成了一个相对永久的群落马赛克，增加了生态系统的异质性和家畜和野生动物对资源的利用。这种异质性的空间性质在不同物种之间是不同的，这取决于它们相对于林中空地的分布。
Throughout the Laikipia ecosystem in Kenya, isolated glades occur within acacia bushland and woodland communities. These glades are at least several decades old. They are reported to be old settlement sites of traditional pastoralists no longer present, and their size, location, and orientation are consistent with the settlement sites of related pastoralists studied elsewhere. The purpose of this study was to document the effects of these glades at the local and landscape levels. Working in central Laikipia, we documented differences in vegetation, animal use, and soils at four of these glades, and at increasing distances from glade edges. Four "glade specialists" dominated the plant communities within glades, and were very rare outside of glades. Pennisetum stramineum, one of six glade edge species, formed a ring of dense tall grass around most glade edges. The transition to acacia bushland at the glade edges was not always abrupt (depending on the trait con- sidered), resulting in edge effects that differed in depth and sharpness. Edge depth, defined as the distance required to attain two-thirds of background levels for a trait, ranged from 0 to 200 m. Understory plant species richness and diversity were lowest inside glades, and gradually increased with distance from glades. However, because glades supported species not found elsewhere, the presence of glades increased overall species diversity. The density of wild and domestic large mammal dung was up to 10 times greater inside the glades, and declined with distance from glade edges. Similarly, soil nitrogen, potassium, carbon, calcium, and sodium were greatest inside glades. Soil phosphorus, magnesium, and man- ganese were not elevated inside glades or within 100 m of glades, but instead were much more abundant in background samples. These glades may be maintained by high densities of large mammals, either through herbivory or through changes in soil chemistry. Glades may be attractive to mammals because of the high quality of food there, or as part of an anti-predator strategy. The result is a relatively permanent community mosaic that increases ecosystem heterogeneity and resource use by domestic and wild animals. The spatial nature of this heterogeneity differs among species, depending on their distributions relative to the glades.