Higher dung seedling density increases livestock dung greenhouse gas emissions in an alpine meadow

Abstract

The dung seed bank (i.e. vegetation renewal) and greenhouse gas (GHG, e.g. carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), which contributing to global warming) emissions (i.e. materials circulation) are two of the most important ecological functions of livestock dung in grassland ecosystems. With decomposition of faeces, dung seedling density (e.g. increase) and GHG emission (e.g. decrease) changes proceeded simultaneously. Although these two processes have so far been studied in isolation, almost no studies have explored the effects of dung seedlings on GHG emissions. We collected the dung of three livestock species—yak, sheep and horse—during late April (i.e. early warm season) in an alpine meadow in the northeastern Qinghai‐Tibetan Plateau (QTP). The livestock dung seedling composition and GHG fluxes were determined on Days 1, 6, 11, 16, 21, 26, 31, 37, 53 and 60 of germination, and we used frozen and ground faeces as the control group. The average seedling density of horse dung was significantly greater than that of yak and sheep. The GHG fluxes in the collected native dung samples were significantly greater than those of the dung controls, and the fluctuations in CO2, CH4 and N2O all showed a pattern of yak dung > horse dung > sheep dung. Over the course of the experiment, the GHG fluxes of both the experimental and control groups gradually decreased; however, the GHG emissions of the experimental group declined faster than those of the control group. There was a significant negative correlation between dung seedling density and GHG fluxes. Dung seedlings provide a reference for estimation of GHG emissions from livestock faeces. Synthesis and applications. Our research has revealed the features of and interactions between two important ecological functions of livestock dung in the grazing system. Furthermore, dung seedlings could substantially affect GHG fluxes and emission rates of livestock dung patches. The contributions of dung seeds to GHG emissions should be considered when estimating global warming potential from grazing livestock on the QTP for the purposes of determining national and regional land use policies and compiling global GHG inventories.