Mapping and exploring variation in post‐fire vegetation recovery following mixed severity wildfire using airborne LiDAR

Abstract

There is a public perception that large high-severity wildfires decrease biodiversity and increase fire hazard by homogenizing vegetation composition and increasing the cover of mid-story vegetation. But a growing literature suggests that vegetation responses are nuanced. LiDAR technology provides a promising remote sensing tool to test hypotheses about post-fire vegetation regrowth because vegetation cover can be quantified within different height strata at fine scales over large areas. We assess the usefulness of airborne LiDAR data for measuring post-fire mid-story vegetation regrowth over a range of spatial resolutions (10 × 10 m, 30 × 30 m, 50 × 50 m, 100 × 100 m cell size) and investigate the effect of fire severity on regrowth amount and spatial pattern following a mixed severity wildfire in Warrumbungle National Park, Australia. We predicted that recovery would be more vigorous in areas of high fire severity, because park managers observed dense post-fire regrowth in these areas. Moderate to strong positive associations were observed between LiDAR and field surveys of mid-story vegetation cover between 0.5-3.0 m. Thus our LiDAR survey was an apt representation of on-ground vegetation cover. LiDAR-derived mid-story vegetation cover was 22-40% lower in areas of low and moderate than high fire severity. Linear mixed-effects models showed that fire severity was among the strongest biophysical predictors of mid-story vegetation cover irrespective of spatial resolution. However much of the variance associated with these models was unexplained, presumably because soil seed banks varied at finer scales than our LiDAR maps. Dense patches of mid-story vegetation regrowth were small (median size 0.01 ha) and evenly distributed between areas of low, moderate and high fire severity, demonstrating that high-severity fires do not homogenize vegetation cover. Our results are relevant for ecosystem conservation and fire management because they: indicate that native vegetation are responsive and resilient to high-severity fire, and show the usefulness of remote sensing tools such as LiDAR to monitor post-fire vegetation recovery over large areas in situ.

Testing the assumptions of the pyrodiversity begets biodiversity hypothesis for termites in semi-arid Australia

“…This reiterates findings from studies to the north of our study region (the Mallee Fire and Biodiversity Project [54]), which showed that many habitat attributes continue to change for over a century following fire [19,55]. Also consistent with those and other studies [56][57][58] was the finding that the response of habitat attributes to fire is context dependent-in this instance, different rates of recovery of habitat attributes were apparent in different vegetation types. Despite differences between vegetation types, the strong influence of fire on several habitat attributes and the longevity of these effects mean that, in our study region, assumption 1 of the pyrodiversity hypothesis is supported.…”

Remarkable Resilience of Forest Structure and Biodiversity Following Fire in the Peri-Urban Bushland of Sydney, Australia

“…However, research in nearby IF that had not burned for 35 years found denser canopies, with understory species composition dominated by shade-tolerant sedges and grasses [57]. The agreement between ground-based LAI and airborne lidar estimates of canopy density (R 2 of 0.11; data not shown) demonstrates the suitability of lidar technology for broader surveys of vegetation recovery from disturbance [25] and simpler and cheaper LAI methods appropriate at smaller scales.…”

“…High resolution maps of the three-dimensional structure of forest canopies can inform biodiversity conservation efforts [23], because structurally complex canopies (such as those with several layers, or with a high variance of heights) indicate diverse species composition and plant ages and create a wide range of habitats supporting wildlife [24]. Spatially explicit maps of forest structure recovery following fires of different age, severity or intensity at high spatial resolution are increasingly used to inform fire management planning [25,26].…”

A Review of the Applications of Remote Sensing in Fire Ecology

“…Lidar's ability to provide data on important vegetation structure parameters makes the system ideal for monitoring vegetation recovery. Gordon et al [76] used lidar data to measure post-fire mid-story vegetation regrowth. They found that the metrics computed with the lidar data agreed with field derived metrics and provided a suitable representation of post-fire vegetation cover.…”