Soil redistribution and seed availability after fire events in mixed Austrocedrus chilensis forests in Northern Patagonia (Argentina)

Abstract Background Severe wildfires in forest ecosystems promote soil erosion and the loss of fertile soil as a scarce natural resource. Our objective was to quantify post-fire ecosystem response in terms of soil accumulation and seed availability through redistribution. Within our study area in Northern Patagonia, Argentina, we chose three study sites at which forest fire events occurred in different years, namely 1 year post-fire (2022), 2 years post-fire (2021), and 8 years post-fire (2015). At each of the sites, we recorded both burned and control slope transects. Along these transects, three accumulation zones were differentiated, at each zone the amount of accumulated soil material as well as the number of seeds in it were determined. Results We observed significant amounts of accumulated soil material along the slopes with the highest annual rates in the first year after the forest fire. The mean accumulated soil material (± standard deviation) over all slope accumulation zones increased from 9.5 ± 2.6, 15.9 ± 4.6 to 42.9 ± 14.0 kg*m −2 , at the 1 year-old, 2 years-old, and 8 years-old forest fires sites. Despite the generally high spatio-temporal variability of seed dispersal, the transects at the burned forest sites show significantly lower numbers of seeds than control transects. In the investigated burned forest sites, the total number of seeds of the four tree species found was 64, 250, and 252 seeds*m −2 in the 1 year-old, 2 years-old, and 8 years-old site, respectively. In general, the more recent fire events had lower number of seeds, which increased with accumulated soil material and time. We also observed a greater number of shrub seeds in the burned sites, but these did not show a pattern with time since the wildfire events. Conclusion Among the 14 species recorded, the tree Austrocedrus chilensis and the shrub Aristotelia chilensis emerge as key players in post-fire recovery, with the highest number of seeds at all study locations. Forest restoration after disturbance is a global challenge, especially in the context of large-scale forest fires. Understanding the risk of soil redistribution and seed availability will assist restoration efforts and ecosystem management.