Impact of grassland saline-alkaline degradation on domestic herbivore rumen microbiota and methane emissions.

Abstract

INTRODUCTION: Grazing ruminant production has the risk of degrading the environment beyond natural recovery due to their production of enteric methane (CH) which is the main contributor to the increase in global CH4 emissions. In particular, grasslands are currently experiencing severe saline-alkaline degradation that is prevalent in arid and semi-arid grassland areas globally. Yet, the impact of grassland saline-alkaline degradation-induced alterations in plant resources on herbivore, and subsequent CH4 emissions, remain underexplored. METHODS: Here we examined these effects by feeding domestic ruminant-sheep with plants from undegraded (UG), moderately degraded (MG), and severely degraded grasslands (SG), focusing on rumen key microbes and nutrition process. RESULTS: Our results showed that moderately and severely saline-alkaline degradation of grasslands differently influences rumen key microbes associated with CHsynthesis, thereby affecting CHemissions of ruminants. Specifically, the relative abundance ofthat can competitively inhibit the CHproduction was significantly increased in MG-fed sheep, which resulted in reduced CHemissions. Conversely, the relative abundance ofthat positively related to CHproduction was significantly increased in SG-fed sheep, which resulted in increased CHemissions. Forage resources in severely degraded grasslands exhibited extremely high sodium (Na) content, while high forage diversity was found in moderately degraded grassland. Further, we found that increased Na intake has a significant influence on the abundance of. DISCUSSION: Taken together, our study provides novel insights into the underlying mechanism of the CHemissions induced by saline-alkaline degradation in ruminant herbivores; the increase in Na intake induced by grassland saline-alkaline degradation could be an important factor affecting rumen Methanosphaera thereby CHemissions by livestock. Our findings suggest that increasing grassland saline-alkaline degradation worldwide will greatly change the risk of CHemissions from grazing ruminants depending on the degree of degradation, which should be incorporated into future consideration of grassland carbon budgets.