Comparing Large, Infrequent Disturbances: What Have We Learned?
Comparing Large, Infrequent Disturbances: What Have We Learned?
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DOI：
10.1007/s100219900045
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发表时间：
1998-11
期刊：
影响因子：
3.7
通讯作者：
M. Turner;V. Dale
中科院分区：
文献类型：
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作者：
M. Turner;V. Dale
自然干扰在形成景观和影响生态系统方面的重要性现已在生态学中得到充分认识。干扰的规模和频率范围很广，虽然对相对较小的干扰的了解迅速增加，但对空间范围大且发生频率低的干扰事件的生态影响还没有很好的了解。这些大的和罕见的扰动的例子包括火山爆发，大火，和极端的洪水或风暴。大的、不频繁的干扰是否与小的、频繁的干扰有质的不同，这在生态学中仍然是一个悬而未决的问题，部分原因是缺乏关于大规模干扰影响的长期数据。集中在几个大的自然干扰（例如，1988年黄石公园大火，1989年雨果飓风，1980年圣海伦火山爆发，1993年洪水在中西部）的密集postdisturbance研究提供了一个机会，在这些不寻常的事件之间进行比较。下面的一组文章开始综合什么是已知的生态影响的大，罕见的干扰（LID）。在这篇文章中，我们提出了这种合成的动机，定义LID和讨论其生态的重要性。LID很难客观地定义，因为干扰发生在连续的大小和频率上。我们遵循白色和Pickett（1985）对干扰的定义："任何在时间上相对离散的事件，破坏生态系统、群落或种群结构，改变资源、基质可用性或物理环境。"这一一般但灵活的定义需要具体说明系统的空间和时间尺度以及扰动。扰动的典型特征是其大小、空间分布、频率或重现间隔、可预测性和量级，包括强度和严重性。沿着扰动连续体，LID在空间范围（陆地系统）或深度/持续时间（洪水）上比"通常"影响系统的扰动大得多。我们建议用两种方法来识别LID，而不是给出一个严格的定义：第一，LID可以根据空间范围、强度或持续时间的统计分布来定义。例如，干扰事件特性的平均值、中值和标准偏差可以用于表征LID。极端洪水事件可以被认为是水深（水位）或流量（流量，以立方米每秒为单位）超过至少几十年记录期平均值的2个标准差的洪水事件（Resh等人，1988年）。由于大多数河流和溪流的深度和流量随季节变化，一年中某个季节的异常洪水可能在另一个季节平均值的2个标准差内。1993年美国中西部的洪水在一年中的任何时候都是大洪水，但其严重程度
The importance of natural disturbances in shaping landscapes and influencing ecosystems is now well recognized in ecology. Disturbances span a broad range of sizes and frequencies, and while understanding of relatively small disturbances has in-creased rapidly, the ecological effects of disturbance events that are large in spatial extent and infrequent in occurrence are not well understood. Examples of these large and infrequent disturbances include volcanic eruptions, big fires, and extreme floods or storms. Whether large, infrequent disturbances are qualitatively different from small frequent disturbances remains an unresolved issue in ecology, in part, because of a paucity of long-term data on the effects of broad-scale disturbances. The intensive postdisturbance research focused on several large natural disturbances (for example, the 1988 Yellow-stone fires, Hurricane Hugo in 1989, the eruption of Mount St. Helens in 1980, and the 1993 floods in the Midwest) provides an opportunity to develop comparisons across these unusual events. The following set of articles begins to synthesize what is known about the ecological implications of large, infrequent disturbances (LIDs). In this article, we present the motivation for this synthesis by defining LIDs and discussing their ecological importance. LIDs are difficult to define objectively because disturbances occur across a continuum of sizes and frequencies. We follow White and Pickett's (1985) definition of disturbance:" any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resource, substrate availability, or the physical environment." This general but flexible definition requires the spatial and temporal scales of the system and the disturbance to be specified. Disturbances would typically be characterized by their size, spatial distribution, frequency or return interval, predictability, and magnitude, including both intensity and sever-ity. Along the disturbance continuum, LIDs are much larger in spatial extent (terrestrial systems), or in depth/duration (floods) than the disturbances that" typically" affect the system. Rather than pro-ducing a rigid definition, we suggest two ways for identifying LIDs.First, LIDs may be defined from statistical distribu-tions of spatial extent, intensity, or duration. For example, the mean, median, and standard deviation of disturbance event characteristics can be used to characterize LIDs. Extreme flood events can be considered to be those in which water depth (stage) or flow volume (discharge, in cubic meters per second) is beyond 2 standard deviations of the mean for a period of record that spans at least several decades (Resh and others 1988). Since depth and flow vary seasonally in most rivers and streams, what constitutes an exceptional flood in one part of the year may be within 2 standard deviations of the mean during another season. The 1993 floods in the midwestern United States would have been major floods at any time of year, but the severity of their