Short-term study on the yak dung seed bank on the Qinghai-Tibetan Plateau: effects of grazing season, seed characteristics and forage preferences

Abstract

Aims Viable seeds in herbivore dung constitute the dung seed bank, and the contribution of livestock dung to this seed bank in grazing pastures is often overlooked. Grazing season (warm and cold), seed characteristics (size and shape), and forage preference are the main factors that affect the size and composition of the dung seed bank and ultimately affect grassland ecology. However, how these three factors interact is unclear. Methods We collected yak dung as well as seeds of the common plant species from warm- and cold-season alpine meadows in northeastern Qinghai-Tibetan Plateau, and explored how grazing season (warm and cold), seed characteristics (size and shape) and foraging preferences (temporary cages method) affects yak dung seedling density, richness and diversity in an alpine pasture. Results Forty-three plant species (mainly perennials) germinated from yak dung. Dung seedling density, richness, and diversity did not differ significantly between the two grazing seasons. Small to medium-sized spherical seeds (seed size < 10 mg, shape index < 0.5) had the greatest germination potential. Conclusions Yaks vary their forage preference depending on the season (phenological period), and endozoochory occurs throughout both grazing seasons. Seed shape and size directly regulate the dung seedling density, richness, and diversity. Dung seedlings increase the heterogeneity of the aboveground vegetation near the microsites of the dung pieces and therefore promote grassland patching. Our study demonstrates that grazing season, seed characteristics, and yak forage preferences affect the dung seed bank in grazing ecosystems.

Precipitation regulates the livestock dung seed bank through above ground vegetation productivity in the Qaidam basin

“…Wang et al (2019) found that the relationship between the tan sheep DSB and AGV was weak on the Loess Plateau of China. The present study showed a high dissimilarity between the DSB for each of the three livestock species and the AGV during the 3‐year experimental period (Figure 5), indicating that the DSB had the potential to increase the heterogeneity of the AGV near the microsites of the dung pieces (Wang & Hou, 2021b; Yu, Xu, Muhammad, & Long, 2013). Meanwhile, the livestock has long gut retention times and can move several kilometres every day (Manzano et al, 2005; Wang et al, 2016), so at least some of the dung seeds delivered near our quadrats would be expected to be from plants located several kilometres away—a potential explanation for the differences between the composition of the vegetation and that of the dung.…”

“…For example, in grazing ecosystems, because of livestock feeding preferences, a large number of plant seeds accumulate in faeces (the ‘fertile island effect’) (Cai et al, 2020). The heterogeneity in the composition between the DSB and that of AGV indicates that the DSB is a potential driving force for the formation of grassland patching due to grazing (Fulgoni et al, 2020; Wang & Hou, 2021a, 2021b; Yu et al, 2012; Yu, Xu, Wang, Shang, & Long, 2013). Moreover, in arid environments such as the desert grassland of the study site, seed dispersal via dung pellets provides substantial protection for seeds until sufficient rainfall occurs to allow germination and seedling establishment, thus representing an adaptation for survival in this type of harsh environment.…”

“…These viable seeds in herbivore faeces constitute the dung seed bank (DSB) (Wang & Hou, 2021a). The composition of the DSB depends on the rangeland composition and the selective feeding by livestock and can benefit plant species in various ways (Wang & Hou, 2021b).…”

Effect of sheep grazing on seed circulation on the Loess Plateau

“…When mature plant seeds are consumed by foraging livestock, some of these seeds survive passage through the digestive tract and are ultimately deposited in dung. These viable seeds in herbivore feces constitute the dung seed bank (DSB; Wang & Hou, 2021; Wang, Hu, et al, 2019), which defined as a subset of the SSB and is an important source of vegetation renewal. The structure of the DSB depends on rangeland composition and selective feeding by livestock (Wang & Hou, 2021).…”

“…These viable seeds in herbivore feces constitute the dung seed bank (DSB; Wang & Hou, 2021; Wang, Hu, et al, 2019), which defined as a subset of the SSB and is an important source of vegetation renewal. The structure of the DSB depends on rangeland composition and selective feeding by livestock (Wang & Hou, 2021). The DSB is a special form of the SSB, as once dung decomposes, seeds in the feces are eventually incorporated into the soil, contributing to the SSB.…”