LTREB: Long-Term Studies of Population and Community Ecology in an Experimentally Fragmented Landscape

[00:76064]理解斑块性和空间动力学的含义是生态学中许多问题的基础，包括许多应用问题。生境破碎化尤其如此，这是全球变化的一个主要特征。一项关于栖息地破碎化的长期实验正在堪萨斯州东部的草原-森林过渡带进行，目的是研究破碎化对次生演替的影响，次生演替被广泛地定义为包括关键的消费者群体，以及植物动态。实验的物理布局（开始于1984年）是在一个大的割过的田地里的栖息地斑块群岛。在项目的第一阶段，斑块大小对小型哺乳动物的分布有显著的影响，但斑块大小对演替没有总体影响。到1993年，木本植物的殖民化开始加速。假设这将导致斑块大小对演替的影响。这一假设已被证实：向木本植被的演替速率随斑块大小而增加，随距离林地源池的距离而减少。小型哺乳动物群落发生了相应的演替和空间变化，对木本植物幼苗造成了相当大的损害。1998年，17年一次的蝉偶然出现，造成了严重的破坏，大面积的破坏更严重。对植物和小型哺乳动物动态的监测将继续确定斑块大小和距离对演替轨迹的影响的持久性。由于存在大量单独标记的木本样本，因此可以表征演替对木本物种的人口统计学后果，包括蝉出苗事件对树苗人口统计学的潜在影响。这个项目的独特之处在于，目前还没有关于演替的实验研究测量过斑块大小对植物和动物动态的影响。

0076064HoltUnderstanding the implications of patchiness and spatial dynamics is fundamental to many issues in ecology, including many applied problems. This is particularly true of habitat fragmentation, which is a dominant feature of global change. A long-term experiment on habitat fragmentation is underway in the prairie-forest ecotone of eastern Kansas aimed at examining the impact of fragmentation on secondary succession, defined broadly to include key consumer groups, as well as plant dynamics. The physical layout of the experiment (initiated in 1984) is an archipelago of habitat patches in a large mown field. During the first phases of the project, there wre dramatic patch size effects on the distribution of small mammals, but no overall effect of patch size on succession. By 1993, colonization of woody plants was beginning to accelerate. It was hypothesized that this would lead to patch size effects on succession. This hypothesis has been borne out: the rate of succession towards woody vegetation has increased with patch size and decreased with distance from woodland source pools. There has been corresponding succession and spatial shifts in the small mammal community, and small mammals have been shown to inflict considerable damage on woody seedlings. In 1998 there was a serendipitous emergence of 17-year periodical cicadas, which imposed high levels of damage, with more damage in large patches. Monitoring of plant and small mammal dynamics will continue to determine the persistence of patch size and distance effects on successional trajectories. Because a large number of individually marked woody samplings exists, the demographic consequences of succession on woody species can be characterized, including the potential impact of the cicada emergence event on sapling demography. This project is unique in that no experimental studies of succession exist in which patch size effects on plant and animal dynamics have been measured.