Disturbance frequency and community structure in a twenty-five year intervention study
Disturbance frequency and community structure in a twenty-five year intervention study
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DOI：
10.1007/s00442-005-0094-4
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发表时间：
2005-07
期刊：
影响因子：
2.7
通讯作者：
J. Trexler;W. Loftus;S. Perry
中科院分区：
文献类型：
--
作者：
J. Trexler;W. Loftus;S. Perry
群落调节模型通常包含与生物相互作用在调节中间营养水平中的作用成反比的扰动梯度。据预测，较高营养水平的生物比它们所消耗的生物更容易受到中等水平干扰的限制。我们在干预分析中使用了对水文干扰频率的操纵，以检查其对美国大沼泽地小鱼群落的影响。从1978年到2002年，我们在一个长水期（平均350天）和一个短水期（平均259天，1985年开始监测）地点监测鱼类。在第三个地点，管理人员于1985年进行干预，以减少沼泽干燥的频率和持续时间。到20世纪90年代末，干预地点的密度和相对丰度的演替动态与长水期地点趋同。如果一个地点仍然被淹没，那么在干枯后的3到5年内，社区的变化就会显现出来；从最近一次干燥事件开始的天数和之前干燥期的长度对预测种群动态是有用的。群落差异度与末次干旱时间呈正相关。群落动态是由三组物种相对丰度的变化引起的，这些物种通过生活史对干旱的响应而联系在一起。在景观尺度上，干旱发生频率和强度随水文调控而共变；当干旱回归时间超过4年时，群落水平的演替动态集中在相对较小的物种组成范围内。小鱼密度随干旱频率的减少而增加，符合干扰有限的群落结构；与本研究相比，干旱的频率较低（即返回时间较长），在大沼泽地的某些地区，捕食者主导了小鱼群落的调节。
Models of community regulation commonly incorporate gradients of disturbance inversely related to the role of biotic interactions in regulating intermediate trophic levels. Higher trophic-level organisms are predicted to be more strongly limited by intermediate levels of disturbance than are the organisms they consume. We used a manipulation of the frequency of hydrological disturbance in an intervention analysis to examine its effects on small-fish communities in the Everglades, USA. From 1978 to 2002, we monitored fishes at one long-hydroperiod (average 350 days) and at one short-hydroperiod (average 259 days; monitoring started here in 1985) site. At a third site, managers intervened in 1985 to diminish the frequency and duration of marsh drying. By the late 1990s, the successional dynamics of density and relative abundance at the intervention site converged on those of the long-hydroperiod site. Community change was manifested over 3 to 5 years following a dry-down if a site remained inundated; the number of days since the most recent drying event and length of the preceding dry period were useful for predicting population dynamics. Community dissimilarity was positively correlated with the time since last dry. Community dynamics resulted from change in the relative abundance of three groups of species linked by life-history responses to drought. Drought frequency and intensity covaried in response to hydrological manipulation at the landscape scale; community-level successional dynamics converged on a relatively small range of species compositions when drought return-time extended beyond 4 years. The density of small fishes increased with diminution of drought frequency, consistent with disturbance-limited community structure; less-frequent drying than experienced in this study (i.e., longer return times) yields predator-dominated regulation of small-fish communities in some parts of the Everglades.