1/21/2024 0 Comments Landscape definition ecology![]() Thus, particularly in landscape studies, it is useful to consider that severity and recovery, though possibly represented by just one effect, actually encompass all the responses within some defined area to gauge the overall condition and summarize fire’s ecological impact on the site. Some are more sensitive, while others are more resistant to fire, even to the point of being enhanced by fire. Thus, the acceptability of an approach depends on the intended content, quality and detail of desired information.Ī second context is that responses are trends of individual ecological components. Often coincident with information specificity is increasing difficulty, cost, effort and modeled inference that can be accompanied by decreasing reliability or coverage. Constraints on such efforts depend upon objectives, which can vary from quite general and simple to very specific and complex (Table 1). The discussion is intended to be conceptual and apply generally across a broad spectrum of methodologies, recognizing that some approaches have unique properties or limitations that go beyond these considerations.īurn assessments have a basic goal to gather reliable site-specific information over at least significant portions of impacted areas. Since remote sensing is a primary means to collect information across large burned areas, a focus is on how factors influence those results and the ecological conclusions drawn from them. Such factors result from the ecological conditions and dynamics that arise following fire, which largely determine the limitations and appropriate uses of derived information. This paper concerns basic spatial and temporal factors that generally affect detection and definition of fire severity in a landscape context. Though commonly overlooked, such considerations determine the objectives and hypotheses that are appropriate for each application, and are especially important when building comparative studies or long-term reference databases on fire severity. Spatial and temporal conditions of sampling strategies constrain data quality and ecological information obtained about fire severity. Based on such implications, three sampling intervals for short-term burn severity are identified rapid, initial, and extended assessment, sampled within about two weeks, two months, and depending on the ecotype, from three months to one year after fire, respectively. Both responses can lead initially to either over- or underestimating severity. Both responses depend on fire behavior and various species-specific adaptations to fire that are unique to the pre-fire composition of each burned area. ![]() Conversely, delayed mortality increases the severity estimate when apparently healthy vegetation is in fact damaged by heat to the extent that it dies over time. Survivorship diminishes the detected magnitude of severity, as burned vegetation remains viable and resprouts, though at first it may appear completely charred or consumed above ground. Lag timing, or time since fire, notably shapes the ecological character of severity through first-order effects that only emerge with time after fire, including delayed survivorship and mortality. ![]() Thus, a need exists to supersede many rapid response applications when remote sensing conditions improve. Detection sensitivity can degrade toward the end of many fire seasons when low sun angles, vegetation senescence, incomplete burning, hazy conditions, or snow are common. Seasonal timing impacts the quality of radiometric data in terms of transmittance, sun angle, and potential contrast between responses within burns. As resolution decreases, alpha variation increases, extracting beta variation and complexity from the spatial model of the whole burn. Resolution determines the aggregation of effects within a sampling unit or pixel (alpha variation), hence limiting the discernible ecological responses, and controlling the spatial patchiness of responses distributed throughout a burn (beta variation). Ecological definition and detection of fire severity are influenced by factors of spatial resolution and timing.
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