Abstract
The goal of this research was to characterize the impact of invasive riparian vegetation on burn severity patterns and fluvial topographic change in an urban Mediterranean riverine system (Med-sys) after fire in San Diego, California. We assessed standard post-fire metrics under urban conditions with non-native vegetation and utilized field observations to quantify vegetation and fluvial geomorphic processes. Field observations noted both high vegetation loss in the riparian area and rapidly resprouting invasive grass species such as Arundo donax (Giant Reed) after fire. Satellite-based metrics that represent vegetation biomass underestimated the initial green canopy loss, as did volumetric data derived from three-dimensional terrestrial laser scanning data. Field measurements were limited to a small sample size but demonstrated that the absolute maximum topographic changes were highest in stands of Arundo donax (0.18 to 0.67 m). This work is the first quantification of geomorphic alterations promoted by non-native vegetation after fire and highlights potential grass–fire feedbacks that can contribute to geomorphic disruption. Our results support the need for ground-truthing or higher resolution when using standard satellite-based indices to assess post-fire conditions in urban open spaces, especially when productive invasive vegetation are present, and they also emphasize restoring urban waterways to native vegetation conditions.
Highlights
Across the world, wildfires are increasing in frequency and magnitude under a changing climate and increased human interaction, which in turn impacts natural resources, infrastructure, and millions of people [1]
While the containment-type management strategies for Arundo donax as presented in the Regional Implementation for San Diego County may mitigate the spatial spread of Arundo donax, the extreme fire and geomorphic hazards associated with this invasive vegetation often found in Mediterranean riverine system (Med-sys) Wildland–Urban Interface (WUI) may not be thoroughly addressed [84]
We applied terrestrial laser scanning (TLS) to document the morphological dynamics of the land surface terrain and the quantification of volumetric change of vegetation biomass and growth forms
Summary
Wildfires are increasing in frequency and magnitude under a changing climate and increased human interaction, which in turn impacts natural resources, infrastructure, and millions of people [1]. Continuous and extreme landscape conversion due to the expansion of the human population and establishments in southern California (United States) has fragmented chaparral ecosystems and proliferated the Wildland–Urban Interface (WUI). This has increased the potential for ignition and damages to human communities and surrounding ecosystems [2,3]. The magnitude of fire effects on Mediterranean riverine systems is often related to fire frequency, severity, and timing, which are driven by climate conditions, vegetation type, fuel loads, and landscape conditions [4]. In Mediterranean systems, it is well documented that wildfire initiates sedimentation and flooding due to the loss of vegetation [5,6], reduced infiltration [7], soil cohesion [8], and soil water repellency [9]
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