Abstract

The primary forests in southern Chile harbor unique endemic plants and diverse soil invertebrates that are vital for nutrient cycling. These forests face an atypical fire regime because fire is not a natural component of their ecology. Consequently, we hypothesize that human-caused wildfires could significantly affect soil invertebrate communities, with cascading impact on ecosystem processes provided by these communities, such as litter decomposition. We studied invertebrate diversity in the China Muerta National Reserve (38 degrees S) eight years after a high-severity wildfire. The goal was to assess how community structure changed after different wildfire severities and their effect on litter decomposition. We used litterbags with two mesh sizes: 1 mm to prevent and 5 mm to allow invertebrate access. These were placed in areas affected by high- and low-severity wildfires, as well as an unburned control site. Significant declines in invertebrate richness, abundance, and diversity were seen in both high- and low-severity plots compared to the control plots. Control plots contained 2.2 and 1.9 times more taxonomic groups than high- and low-severity fire plots, respectively. Similar patterns were observed in abundance and diversity. Predators, omnivores, and phytophagous species were less abundant in burned plots. Although soil properties changed between burned and unburned plots, these changes were not significantly related to soil invertebrate composition and trophic groups. Wildfire significantly influenced the litter decomposition rate, with low-severity plots showing the slowest rates (0.041 year-1), followed by high-severity plots (0.086 year-1), and control plots (0.114 year-1). Decomposition rates decreased even further in litter bags inaccessible to invertebrates. Therefore, changes in the soil invertebrate community caused by fires contributed to the decline in litter decomposition, which could ultimately affect nutrient cycling within vulnerable forest ecosystems.