Project description:BackgroundPrecipitation influences the vulnerability of grassland ecosystems, especially upland grasslands, and soil respiration is critical for carbon cycling in arid grassland ecosystems which typically experience more droughty conditions.MethodsWe used three precipitation treatments to understand the effect of precipitation on soil respiration of a typical arid steppe in the Loess Plateau in north-western China. Precipitation was captured and relocated to simulate precipitation rates of 50%, 100%, and 150% of ambient precipitation.Results and discussionSoil moisture was influenced by all precipitation treatments. Shoot biomass was greater, though non-significantly, as precipitation increased. However, both increase and decrease of precipitation significantly reduced root biomass. There was a positive linear relationship between soil moisture and soil respiration in the study area during the summer (July and August), when most precipitation fell. Soil moisture, soil root biomass, pH, and fungal diversity were predictors of soil respiration based on partial least squares regression, and soil moisture was the best of these.ConclusionOur study highlights the importance of increased precipitation on soil respiration in drylands. Precipitation changes can cause significant alterations in soil properties, microbial fungi, and root biomass, and any surplus or transpired moisture is fed back into the climate, thereby affecting the rate of soil respiration in the future.
Project description:The extreme environments of the Tibetan Plateau offer significant challenges to human survival, demanding novel adaptations. While the role of biological and agricultural adaptations in enabling early human colonization of the plateau has been widely discussed, the contribution of pastoralism is less well understood, especially the dairy pastoralism that has historically been central to Tibetan diets. Here, we analyze preserved proteins from the dental calculus of 40 ancient individuals to report the earliest direct evidence of dairy consumption on the Tibetan Plateau. Our palaeoproteomic results demonstrate that dairy pastoralism began on the higher plateau by approximately 3,500 years ago, more than 2,000 years earlier than the recording of dairying in historical sources. With less than 1% of the Tibetan Plateau dedicated to farmland, pastoralism and the milking of ruminants were essential for large-scale human expansion into agriculturally-marginal regions that make up the majority of the plateau. Dairy pastoralism allowed conversion of abundant grasslands into nutritional human food, which facilitating adaptation in the face of extreme climatic and altitudinal pressures, and maximizing the land area available for long-term human occupation of the “roof of the world”.