Influence of climate, post-treatment weather extremes, and soil factors on vegetation recovery after restoration treatments in the southwestern US.
Aims: Understanding the conditions associated with dryland vegetation recovery after restoration treatments is challenging due to a lack of monitoring data and high environmental variability over time and space. Tracking recovery trajectories with satellite-based vegetation indices can strengthen predictions of restoration outcomes across broad areas with varying environmental conditions. Location: Southwestern United States. Methods: We quantified the recovery trajectories of spring and summer soil-adjusted total vegetation index (SATVI) for 5-10 year periods following post-wildfire seeding or prescribed burns for 241 treatment sites and related SATVI to ground-based vegetation cover. We modeled SATVI based on time since treatment, yearly temperature and precipitation, weather extremes following treatment, soil available water capacity, invasive species presence, and treatment type. We also tested for the effects of environmental variables on trajectories, by examining interactions with years post-treatment. Results: Ground-based vegetation cover and SATVI were highly correlated. Most treatment sites had positive recovery rates for spring (82%) and summer (85%) SATVI. Several environmental variables affected vegetation recovery trajectories as indicated by interactions with time since treatment. Yearly warm season precipitation had a positive effect on SATVI recovery that increased over time, whereas the positive effect of extreme high warm season precipitation following treatment decreased over time for both seasons of vegetation measurements. For spring SATVI, the positive effect of cool season yearly precipitation increased over time while the negative effect of extreme high temperatures following treatment became more negative over time. Invasive species presence led to higher spring, but not summer, SATVI. Conclusions: Satellite-based remote sensing is a promising tool to assess vegetation recovery following restoration treatments, particularly when it is combined with ground-based monitoring. Our results suggest that weather extremes following restoration treatments can affect vegetation recovery trajectories and may be considered in management decisions such as the timing of restoration treatments.