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The trade-offs between key functional traits in plants have a decisive impact on biomass production. However, how precipitation and nutrient deposition affect the trade-offs in traits and, ultimately, productivity is still unclear. In the present study, a mesocosm experiment was conducted to explore the relationships between biomass production and the aboveground and belowground key functional traits and their trade-offs under changes in precipitation and nutrient depositions in Leymus chinensis, a monodominant perennial rhizome grass widespread in the eastern Eurasian steppe. Our results showed that moisture is the key factor regulating the effect of nitrogen (N) and phosphorus (P) deposition on increased biomass production. Under conditions of average precipitation, water use efficiency (WUE) was the key trait determining the biomass of L. chinensis. There were obvious trade-offs between WUE and leaf area, specific leaf area, leaf thickness, and leaf dry matter. Conversely, under increasing precipitation, the effect of restricted soil water on leaf traits was relieved; the key limiting trait changed from WUE to plant height. These findings indicate that the shift of fundamental traits of photosynthetic carbon gain induced by precipitation under N and P deposition is the key ecological driving mechanism for the biomass production of typical dominant species in semi-arid grassland. [ABSTRACT FROM AUTHOR]

Background: Climate change is predicted to lead to changes in the amount and distribution of precipitation during the growing seasonal. This "repackaging" of rainfall could be particularly important for grassland productivity. Here, we designed a two-factor full factorial experiment (three levels of precipitation amount and six levels of dry intervals) to investigate the effect of precipitation patterns on biomass production in Leymus chinensis (Trin.) Tzvel. (a dominant species in the Eastern Eurasian Steppe). Results: Our results showed that increased amounts of rainfall with prolonged dry intervals promoted biomass production in L. chinensis by increasing soil moisture, except for the longest dry interval (21 days). However, prolonged dry intervals with increased amount of precipitation per event decreased the available soil nitrogen content, especially the soil NO3−-N content. For small with more frequent rainfall events pattern, L. chinensis biomass decreased due to smaller plant size (plant height) and fewer ramets. Under large quantities of rain falling during a few events, the reduction in biomass was not only affected by decreasing plant individual size and lower ramet number but also by withering of aboveground parts, which resulted from both lower soil water content and lower NO3−-N content. Conclusion: Our study suggests that prolonged dry intervals between rainfall combined with large precipitation events will dramatically change grassland productivity in the future. For certain combinations of prolonged dry intervals and increased amounts of intervening rainfall, semi-arid grassland productivity may improve. However, this rainfall pattern may accelerate the loss of available soil nitrogen. Under extremely prolonged dry intervals, the periods between precipitation events exceeded the soil moisture recharge interval, the available soil moisture became fully depleted, and plant growth ceased. This implies that changes in the seasonal distribution of rainfall due to climate change could have a major impact on grassland productivity. [ABSTRACT FROM AUTHOR]

Extreme drought events can directly decrease productivity in perennial grasslands. However, for rhizomatous perennial grasses it remains unknown how drought events influence the belowground bud bank which determines future productivity. Ninety‐day‐long drought events imposed on Leymus chinensis, a rhizomatous perennial grass, caused a 41% decrease in the aboveground biomass and a 28% decrease in belowground biomass. Aboveground biomass decreased due to decrease in both the parent and the daughter shoot biomass. The decreases in daughter shoot biomass were due to reductions in both the shoot number and each individual shoot weight. Most importantly, drought decreased the bud bank density by 56%. In addition, drought induced a bud allocation change that decreased by 41% the proportion of buds that developed into shoots and a 41% increase in the buds that developed into rhizomes. Above results were supported by our field experiment with watering treatments. Thus, a 90‐day‐long summer drought event decreases not only current productivity but also future productivity, because the drought reduces the absolute bud number. However, plasticity in plant development does partly compensate for this reduction in bud number by increasing bud development into rhizomes, which increases the relative allocation of buds into future shoots, at the cost of a decrease in current shoots. [ABSTRACT FROM AUTHOR]

• The relationship between soil pH and plant-diversity is unimodal. • The correlation between soil pH and vegetation nitrogen storage is unimodal. • Slight increases in soil pH induced high plant-diversity then enhanced SOC and SNC storage. Grassland soil organic carbon and nitrogen storage (SOC storage and SNC storage) have been regarded as indicators to evaluate impacts of global climate change on ecosystem functions due to their significant impact on atmospheric carbon (C) concentration. The variations in vegetation and soil properties in diverse vegetation patch types may change soil C and nitrogen (N) sequestration capacity. However, the quantities of SOC and SNC stored and the mechanisms behind the variation in this storage under diverse vegetation patches in grassland ecosystems are still unclear. Here we conducted a field experiment to measure the variations in vegetation composition, soil properties and SOC storage and SNC storage among five common vegetation patch types in the Eastern Eurasian steppe. Then we investigated the link between vegetation variation and the SOC and SNC storage. The results showed that (1) the combined effects of competitive ability and physiological stress drove the unimodal relationship between species diversity and soil pH. (2) Biomass production did not reach its maximum in patch types with the greatest plant diversity due to saline-alkaline stress, but the live vegetation N storage reached its maximum in these highly diverse patches due to complementary resource utilization effects. (3) Although biomass production of patches with the greatest biodiversity did not reach a maximum due to a slight increase in soil pH, the largest SOC and SNC storage values were found in the highly diverse patches. Our study implies that in natural grassland, high levels of species diversity may accelerate the decomposition rate, resulting in more recalcitrant organic C and N are released into the soil. At the same time, our observation that reductions in the area of the originally dominant patch type due to the expansion of other species during grassland degradation suggests that comprehensive measurements of SOC and SNC storage in different vegetation patches should be undertaken for accurate evaluation of the C and N sequestering capacity of grasslands. Our results can also help policy makers determine how to achieve sustainable development of grasslands based on C and N sequestration. [ABSTRACT FROM AUTHOR]