Abstract
AimsThis study investigated the influences of herbivore grazing intensity and grazing season on decomposition and nutrient release of dung and litter, which aimed to improve our understandings of grazing affecting nutrient cycling in alpine meadows on the Qinghai-Tibetan Platean.MethodsA factorial design experiment comprising 3 grazing intensities (non-grazing, moderate grazing, and heavy grazing) and 2 grazing seasons (summer and winter), was applied to quantify the decomposition and chemistry of dung and litter in an alpine pasture using the litterbag technique. Litterbags were retrieved for analysis of mass loss and nutrient release with 180, 360, 540, and 720 days after placement.ResultsGrazing activity accelerated the decomposition of dung and litter and increased nutrient release from dung and litter by increasing soil temperature compared with non-grazing pastures, whereas grazing season had no effect on decomposition. The decomposition time was shorter for dung than that for litter.ConclusionsHerbivores grazing benefited dung and litter decomposition and nutrient cycling directly by increasing soil temperature, which is likely to promote soil microbial activity due to low temperatures in alpine meadows, and indirectly through herbage ingestion and dung deposition which increase the organic debris concentration used for microorganisms growth and reproduction. This study provides insights into the mechanisms of grazing regulating nutrient cycling in alpine ecosystems.
Highlights
Dung and litter decomposition together play a vital role in nutrient cycling in grazed pastures as well as the energy flow in grassland ecosystems
Grazing activity accelerated the decomposition of dung and litter and increased nutrient release from dung and litter by increasing soil temperature compared with non-grazing pastures, whereas grazing season had no effect on decomposition
Herbivores grazing benefited dung and litter decomposition and nutrient cycling directly by increasing soil temperature, which is likely to promote soil microbial activity due to low temperatures in alpine meadows, and indirectly through herbage ingestion and dung deposition which increase the organic debris concentration used for microorganisms growth and reproduction
Summary
Dung and litter decomposition together play a vital role in nutrient cycling in grazed pastures as well as the energy flow in grassland ecosystems. Grazing affects the litter decomposition processes by altering environmental condition and litter quality (Sun et al 2018), and the dynamics of nutrient cycling (Semmartin et al 2004, 2008). Previous publications show that grazing activity of herbivores with different grazing intensities in grazing season may induce considerable changes in the decomposition of dung or litter in grassland ecosystems (Liang et al 2018; Song et al 2017; Sun et al 2018). Shariff et al (1994) reported that moderate grazing pressure results in a higher litter decomposition compared with non-grazing and heavy grazing. Song et al (2017) found that grazing sheep significantly reduce litter decomposition rate in the local species-rich communities, whereas litter decomposition rate increases in the local species-poor communities at the meadow steppe
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