Soil Fauna Accelerate Dung Pat Decomposition and Nutrient Cycling into Grassland Soil

Soil fauna play critical roles in various ecosystem functions and services, but empirical data measuring their impact on dung pat decomposition and subsequent nutrient cycling into rangeland soils are limited. The objective of this study was to quantify the effect of soil fauna, using dung beetle as an indicator, on dung decomposition and subsequent translocation of dung nutrients into grassland soil over time. A field experiment was conducted early in the summer season and late in the summer season of 2014 and 2015. In each season, dung beetle abundance, changes in dung properties, and subsequent translocation of dung nutrients into soils were evaluated at 1, 3, 7, 14, 28, and 56 d after placement (DAPs) of exposed dung and nonexposed dung to beetles. Analysis of no-dung control soil was included for comparison. Dung beetles contributed 7% and 4% in the losses of dung moisture and dry matter (DM), respectively; however, dung beetles had no effect on dung pat nutrients. Losses of dung nutrients—42% of water-extractable organic carbon, 46% of water-extractable phosphorus, and 65% of NH₄—occurred during the first 14 DAPs. Dung beetles increased soil nutrients in the top 10-cm depth beneath the dung. No effect of beetles was observed in deeper (> 10-cm) soil depth or in soil 30 cm away from the dung. This study concluded that soil fauna, such as dung beetles, accelerated dung moisture and DM losses and subsequent nutrient increase into the top 10 cm of soil.