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1.
Factors Influencing Succession: Lessons from Large, Infrequent Natural Disturbances 总被引:16,自引:5,他引:11
Monica G. Turner William L. Baker Christopher J. Peterson Robert K. Peet 《Ecosystems》1998,1(6):511-523
Disturbance events vary in intensity, size, and frequency, but few opportunities exist to study those that are extreme on
more than one of these gradients. This article characterizes successional processes that occur following infrequent disturbance
events that are exceptional in their great intensity or large size. The spatial variability in disturbance intensity within
large, infrequent disturbances (LIDs) often leads to a heterogeneous pattern of surviving organisms. These surviving organisms
dictate much of the initial successional pattern on large disturbances where the opportunities for seeds to disperse into
the middle of the disturbance are limited. The traditional distinction between primary and secondary succession is insufficient
to capture the tremendous variability in succession following LIDs. Disturbance size influences succession where long-distance
colonization by propagules is important. Observations from LIDs suggest the following interrelated hypotheses about trends
in succession with increasing distance from seed sources when disturbanceintensity is high: (a) initial densities of organisms
will be lower; (b) nucleation processes, in which recovering patches serve as foci for additional colonization and expand
spatially, will be more important; (c) competitive sorting will be less important relative to chance arrival in determination
of community composition, and (d) community composition will be initially less predictable; and (e) the rate of recovery of
community composition will be slower. Prediction of succession following LIDs without considering contingencies such as the
abundance, types, and spatial distribution of residuals, and distance to seed sources is likely to be unsuccessful for large
portions of the landscape. Abundance and spatial arrangement of survivors and arrival patterns of propagules may be the pivotal
factors determining how succession differs between intense disturbances of large and small extent.
Received 14 July 1998; accepted 18 September 1998 相似文献
2.
Compounded Perturbations Yield Ecological Surprises 总被引:20,自引:5,他引:15
All species have evolved in the presence of disturbance, and thus are in a sense matched to the recurrence pattern of the
perturbations. Consequently, disturbances within the typical range, even at the extreme of that range as defined by large,
infrequent disturbances (LIDs), usually result in little long-term change to the system's fundamental character. We argue
that more serious ecological consequences result from compounded perturbations within the normative recovery time of the community
in question. We consider both physically based disturbance (for example, storm, volcanic eruption, and forest fire) and biologically
based disturbance of populations, such as overharvesting, invasion, and disease, and their interactions. Dispersal capability
and measures of generation time or age to first reproduction of the species of interest seem to be the important metrics for
scaling the size and frequency of disturbances among different types of ecosystems. We develop six scenarios that describe
communities that have been subjected to multiple perturbations, either simultaneously or at a rate faster than the rate of
recovery, and appear to have entered new domains or “ecological surprises.” In some cases, three or more disturbances seem
to have been required to initiate the changed state. We argue that in a world of ever-more-pervasive anthropogenic impacts
on natural communities coupled with the increasing certainty of global change, compounded perturbations and ecological surprises
will become more common. Understanding these ecological synergisms will be basic to environmental management decisions of
the 21st century.
Received 14 July 1998; accepted 18 September 1998. 相似文献
3.
Landscape Patterns and Legacies Resulting from Large, Infrequent Forest Disturbances 总被引:15,自引:6,他引:9
We review and compare well-studied examples of five large, infrequent disturbances (LIDs)—fire, hurricanes, tornadoes, volcanic
eruptions, and floods—in terms of the physical processes involved, the damage patterns they create in forested landscapes,
and the potential impacts of those patterns on subsequent forest development. Our examples include the 1988 Yellowstone fires,
the 1938 New England hurricane, the 1985 Tionesta tornado, the 1980 eruption of Mount St. Helens, and the 1993 Mississippi
floods. The resulting landscape patterns are strongly controlled by interactions between the specific disturbance, the abiotic
environment (especially topography), and the composition and structure of the vegetation at the time of the disturbance. The
very different natures of these interactions yield distinctive temporal and spatial patterns and demand that ecologists increase
their knowledge of the physical characteristics of disturbance processes. Floods and fires can occur over a long period, whereas
volcanic eruptions and wind-driven events often last for no more than a few hours or days. Tornadoes and floods produce linear
patterns with sharp edges, but fires, volcanic eruptions, and hurricanes can affect broader areas, often with gradual transitions
of disturbance intensity. In all cases, the evidence suggests that LIDs produce enduring legacies of physical and biological
structure that influence ecosystem processes for decades or centuries.
Received 14 July 1998; accepted 6 October 1998. 相似文献
4.
While disturbances such as fire, cutting, and grazing can be an important part of the conservation of natural lands, some adjustments to management designed to mimic natural disturbance may be necessary with ongoing and projected climate change. Stressed vegetation that is incapable of regeneration will be difficult to maintain if adults are experiencing mortality, and/or if their early life‐history stages depend on disturbance. A variety of active management strategies employing disturbance are suggested, including resisting, accommodating, or directing vegetation change by manipulating management intensity and frequency. Particularly if land‐use change is the main cause of vegetation stress, amelioration of these problems using management may help vegetation resist change (e.g. strategic timing of water release if a water control structure is available). Managers could direct succession by using management to push vegetation toward a new state. Despite the historical effects of management, some vegetation change will not be controllable as climates shift, and managers may have to accept some of these changes. Nevertheless, proactive measures may help managers achieve important conservation goals in the future. 相似文献
5.
Many elasmobranchs have experienced strong population declines, which have been largely attributed to the direct and indirect effects of exploitation. Recently, however, live elasmobranchs are being increasingly valued for their role in marine ecosystems, dive tourism and intrinsic worth. Thus, management plans have been implemented to slow and ultimately reverse negative trends, including shark-specific (e.g. anti-finning laws) to ecosystem-based (e.g. no-take marine reserves) strategies. Yet it is unclear how successful these measures are, or will be, given the degree of depletion and slow recovery potential of most elasmobranchs. Here, current understanding of elasmobranch population recoveries is reviewed. The potential and realized extent of population increases, including rates of increase, timelines and drivers are evaluated. Across 40 increasing populations, only 25% were attributed to decreased anthropogenic mortality, while the majority was attributed to predation release. It is also shown that even low exploitation rates (2-6% per year) can halt or reverse positive population trends in six populations currently managed under recovery plans. Management measures that help restore elasmobranch populations include enforcement or near-zero fishing mortality, protection of critical habitats, monitoring and education. These measures are highlighted in a case study from the south-eastern U.S.A., where some evidence of recovery is seen in Pristis pectinata, Galeocerdo cuvier and Sphyrna lewini populations. It is concluded that recovery of elasmobranchs is certainly possible but requires time and a combination of strong and dedicated management actions to be successful. 相似文献
6.
7.
A 'large infrequent disturbance' in an East African savanna 总被引:1,自引:0,他引:1
Lindsey Gillson 《African Journal of Ecology》2006,44(4):458-467
There is growing interest in large infrequent disturbances (LIDs), but by definition they occur rarely and long‐term data are needed in order to study their effects and frequency. Palaeoecological records have the potential to provide information on the effects and frequency of LIDs. By comparing recent sedimentary records with known historical data, the effects of LIDs on pollen, charcoal and sedimentary sequences can be assessed. In this study, a LID in East Africa is described, and its representation in the palaeoecological record is explored. Historical records show that there was severe drought and famine in East Africa at the end of the 19th century. Fossil pollen and charcoal records from this period show evidence of a disturbance event that occurred at approximately this time. Statistical comparison of pollen and charcoal data from before, during and after the disturbance event identified it as a LID. The data also suggest that an erosion event occurred part way through the drought, indicating that an environmental threshold was exceeded. 相似文献
8.
William H. Romme Edwin H. Everham Lee E. Frelich Max A. Moritz Richard E. Sparks 《Ecosystems》1998,1(6):524-534
In this article, we develop a heuristic model of ecosystem-disturbance dynamics that illustrates a range of responses of
disturbance impact to gradients of increasing disturbance extent, intensity, or duration. Three general kinds of response
are identified and illustrated: (a) threshold response, (b) scale-independent response, and (c) continuous response. Threshold responses are those in which the response curve shows a discontinuity or a sudden change in slope along the axis of increasing disturbance
extent, intensity, or duration. The response threshold occurs at a point where the force of the disturbance exceeds the capacity
of internal mechanisms to resist disturbance, or where new mechanisms of recovery become involved. Within this conceptual
framework, we find that some unusually large or intense disturbances, but not all, produce qualitatively different responses
compared with similar disturbances of lesser magnitude. If disturbance impact does not increase with increasing disturbance
extent, intensity, or duration, or if the response curve changes monotonically, then large disturbances are not qualitatively different from small ones. For example, jack pine tends to become reestablished after stand-replacing fire
in boreal forests, regardless of fire size, because its serotinous cones provide an adequate seed source throughout the burned
area. Thus, large fires are not qualitatively different from small fires in terms of jack pine reproduction. However, if disturbance
impact does increase abruptly at some point with increasing disturbance extent, intensity, or duration, often because of thresholds
in the capacity of internal mechanisms to resist or respond to disturbance impact, then large disturbances are qualitatively different from small ones, at least for some parameters of ecological response. For example, balsam fir and
white cedar can recolonize a small burned patch of boreal forest in close proximity to surviving individuals of these species,
but they will be eliminated from a large burn because of their susceptibility to fire-caused mortality and their inability
to disperse their seeds over long distances. The conceptual framework presented here permits some new insights into the dynamics
of natural systems and may provide a useful tool with which managers can assess the potential for catastrophic damages resulting
from large, infrequent disturbances.
Received 14 July 1998; accepted 29 September 1998 相似文献
9.
Richard P. Shefferson Chase M. Mason Kimberly M. Kellett Eric W. Goolsby Erin Coughlin R. Wes Flynn 《Population Ecology》2018,60(1-2):49-59
Conservation management for environmental sustainability is now ubiquitous. The ecological effects of these actions are well-intentioned and well-known. Although conservation biologists and managers increasingly incorporate evolutionary considerations into management plans, the evolutionary consequences of management strategies have remained relatively unexplored and unconsidered. But what are the evolutionary consequences? Here, we advocate a new research agenda focused on identifying, predicting, and countering the evolutionary consequences of conservation management. We showcase the examples of park creation and invasive species management, and speculate further on five other major methods of management. Park creation may cause selection for altered dispersal and behavior that utilizes human foods and structures. Management of invasive species may favor the evolution of resistance to or tolerance of control methods. In these and other cases, evolution may cause deviations from the predicted consequences of management strategies optimized without considering evolution, particularly when management results in or coincides with major environmental change, if population size change strongly, or if life histories are short enough to allow more rapid evolution. We call for research focused on: (1) experimental predictions and tests of evolution under particular management strategies, (2) widespread monitoring of managed populations and communities, and (3) meta-analysis and theoretical study aimed at simplifying the process of evolutionary prediction, particularly at systematizing a means of identifying traits likely to evolve due to likely existing genetic variance or high mutation rates. Ultimately, conservation biologists should incorporate evolutionary prediction into management planning to prevent the evolutionary domestication of the species that they are trying to protect. 相似文献
10.
C. MORITZ 《Molecular ecology》1994,3(4):401-411
Patterns of variation in mitochondrial DNA (mtDNA) increasingly are being investigated in threatened or managed species, but not always with clearly defined goals for conservation. In this review I identify uses of mtDNA analysis which fall into two different areas: (i) 'gene conservation' - the identification and management of genetic diversity, and (ii) 'molecular ecology' - the use of mtDNA variation to guide and assist demographic studies of populations. These two classes of application have different conceptual bases, conservation goals and time-frames. Gene conservation makes extensive use of phylogenetic information and is, in general, most relevant to long-term planning. Appropriate uses here include identification of Evolutionarily Significant Units and assessment of conservation priority of taxa or areas from an evolutionary perspective. Less appropriate are inferences about fitness from within-population diversity and about species boundaries. Molecular ecology makes more use of allele frequencies and provides information useful for short-term management of populations. Powerful applications are to identify Management Units and to define and use naturally occurring genetic tags. Estimating demographic parameters, e.g migration rate and population size, from patterns of mtDNA diversity is fraught with difficulty, particularly where populations are fluctuating, and is unlikely to produce quantitative estimates sufficiently accurate to be useful for practical management of contemporary populations. However, through comparative studies, mtDNA analysis can provide qualitative signals of population changes, allowing efficient targeting of resource-intensive ecological studies. Thus, there are some relatively straightforward uses of mtDNA, preferably in conjunction with assays of nuclear variation, that can make a significant contribution to the long-term planning and short-term execution of species recovery plans. 相似文献