Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest

Abstract

. 2016. Static and dynamic controls on fire activity at moderate spatial and temporal scales in the Alaskan boreal forest. Ecosphere 7(11):e01572. 10.1002/ ecs2.1572Abstract. Wildfire, a dominant disturbance in boreal forests, is highly variable in occurrence and behavior at multiple spatiotemporal scales. New data sets provide more detailed spatial and temporal observations of active fires and the post-burn environment in Alaska. In this study, we employ some of these new data to analyze variations in fire activity by developing three explanatory models to examine the occurrence of (1) seasonal periods of elevated fire activity using the number of MODIS active fire detections data set (MCD14DL) within an 11-day moving window, (2) unburned patches within a burned area using the Monitoring Trends in Burn Severity fire severity product, and (3) short-to-moderate interval (<60 yr) fires using areas of burned area overlap in the Alaska Large Fire Database. Explanatory variables for these three models included dynamic variables that can change over the course of the fire season, such as weather and burn date, as well as static variables that remain constant over a fire season, such as topography, drainage, vegetation cover, and fire history. We found that seasonal periods of high fire activity are associated with both seasonal timing and aggregated weather conditions, as well as the landscape composition of areas that are burning. Important static inputs to the model of seasonal fire activity indicate that when fire weather conditions are suitable, areas that typically resist fire (e.g., deciduous stands) may become more vulnerable to burning and therefore less effective as fire breaks. The occurrence of short-to-moderate interval fires appears to be primarily driven by weather conditions, as these were the only relevant explanatory variables in the model. The unique importance of weather in explaining short-to-moderate interval fires implies that fire return intervals (FRIs) will be sensitive to projected climate changes in the region. Unburned patches occur most often in younger stands, which may be related to a greater deciduous fraction of vegetation as well as lower fuel loads compared with mature stands. The fraction of unburned patches may therefore increase in response to decreasing FRIs and increased deciduousness in the region, or these may decrease if fire weather conditions become more severe.

Relating Spatiotemporal Patterns of Forest Fires Burned Area and Duration to Diurnal Land Surface Temperature Anomalies

“…Negative values are proportionally more prevalent in coniferous forest and sclerophyllous vegetation than in other land cover classes. The observation of this dependence was expected from literature review (e.g., [63,65]) and does not affect the quality of further findings. Indeed, evaluations of burned area and fire duration were performed conditional to LST anomaly, that is leveraging out all other parameters.…”

“…Burned area is indeed controlled by a large variety of both static and dynamic factors, essentially falling into five groups: topography, such as elevation, slope, south-westness (in the northern hemisphere) or north-westness (in the southern hemisphere); land cover, including vegetation type, composition, connectivity, fuel load, pyrodiversity; climate, for example annual average daily maximum and minimum temperature; weather (including active drivers of fuel moisture) such as cumulative antecedent precipitation, wind speed, relative humidity; anthropic activity, including land development, road density, distance to settlements, fire prevention and contrasting strategies [61][62][63][64][65][66][67]. While less studied, fire duration appears to be related to similar factors [68][69][70][71].…”

Regional variation in interior Alaskan boreal forests is driven by fire disturbance, topography, and climate

“…Furthermore, the timing and severity of the fire disturbance also introduces additional spatial and temporal variability in the balance between conifer self‐replacement and trajectories that result in widespread broadleaf dominance (Barrett et al. , ).…”

Assessment of the post-pyrogenic dynamics of tundra vegetation in the northern part of Western Siberia over the past 50 years (1968–2018) based on detailed and high resolution remote sensing data

“…Например, на Аляске половина гарей за 2002-2010 гг. образовалась суммарно всего за 36 дней горения (Barrett et al, 2016). На примере рассматриваемой территории хорошо видно, что увеличению площади гарей способствует одновременное появление многочисленных очагов, которые по мере расширения объединяются, охватывая значительные территории.…”