Wild Ungulates and Cattle Have Different Effects on Litter Decomposition as Revealed by Fecal Addition in a Northeast Asian Temperate Forest

Litter decomposition is critical for maintaining productivity and nutrient cycling in forest ecosystems. Large herbivores play an essential role in determining the processes of nutrient cycling. Asian temperate forests are becoming degraded and fragmented by the widespread intensification of anthropogenic activities, including excessive livestock grazing. However, the effects of livestock grazing and wild ungulates on forest litter decomposition remain less explored. In this study, we used a litterbag experiment to investigate the effects of the addition of cattle (<i>Bos taurus</i>) and sika deer (<i>Cervus nippon</i>) feces on litter decomposition. The study was conducted in Northeast China from July 2022 to October 2023. We found that the addition of deer feces significantly reduced litter decomposition, but the addition of cattle feces greatly increased litter decomposition. The presence of cattle and deer excrement significantly accelerated the release of C after 1 year of litter decomposition. Compared with the results of the control group (no addition of feces), the addition of cattle and sika deer feces increased C release by 37.45% and 22.69%, respectively. Fecal addition increased the release of N; however, for the three treatment groups, the maximum accumulation of N occurred in the middle of litter decomposition, which may have been due to the initial chemical quality of the leaves and snow melt as well as nutrient limitations at the sites. Compared with the results of the control group, P release in the feces of cattle increased by 4.35%, but P release in the feces of deer decreased by 27.55%. This work highlights that feces deposition by large herbivores (e.g., wild or domestic) in the forest has nonequivalent effects on litter decomposition. Such effects may further alter the nutrient cycling in temperate forest ecosystems, with far-reaching effects on the ecosystem that deserve closer attention. We suggest that conservation managers should seek evidence-based interventions to optimize livestock use of forest habitats shared with wildlife.