Biotic and abiotic controls in determining exceedingly variable responses of ecosystem functions to extreme seasonal precipitation in a mesophytic alpine grassland

Abstract

a b s t r a c tAs a result of global climate change, frequent and intensive extreme climate events are observed and predicted. These extreme climate events can change ecosystem functions through driving plant growth and mortality, as well as ecological and evolutionary processes into different directions. We simulated a 1-in-100-year extreme precipitation event in different plant growth seasons (i.e. spring, summer, or autumn) to investigate the functional responses of a mesophytic alpine grassland ecosystem to climate change in the Tibetan plateau. The results demonstrated that the seasonal distribution of extreme precipitation is a critical factor in determining soil microbial-and plant-productivity. The response of vegetation net primary productivity (NPP) to extreme precipitation depends on the growth seasons and plant types. Total NPP in the treatments experienced extreme precipitation in the early (spring), mid-(summer) and late-(autumn) plant growth seasons were significant lower, higher, and no difference, respectively, compared with the control. Soil temperature and moisture were the key abiotic factors that affected ecosystem functions. For example, in the early plant growth season, no changes of soil moisture and the decreased temperature in response to the extreme precipitation resulted in a substantial decline in NPP. By contrast, in the mid-plant growth season, higher temperature and soil moisture elicited positive synergistic effects on plant growth and soil microbial processes. The increased sensitivity of above-ground NPP and the shift of dominant species from sedges to less palatable forbs might inevitably exaggerate the degradation of this grassland. Nevertheless, a high resilience index in the related ecological processes could potentially contribute to the grassland acclimation and stability, as most parameters returned to the similar levels as in the control after the extreme events ceased. Therefore, several synergistic or antagonistic mechanisms are hypothesized to operate in parallel or at different levels of organization and timescales. Further studies involving a range of different potential scenarios and longer periods are needed to predict the future climate change impacts on mesophytic grassland.

The response of the soil microbial food web to extreme rainfall under different plant systems

“…In China, a significant increase in extreme precipitation has occurred in the west, in the mid–lower reaches of the Yangtze River, and in parts of the southwest2. The changes in precipitation regimes will be more spatially heterogeneous and less predictable than other climate changes and will leads to more intense flooding occur at local and regional scales3. Scientists have been committed to ecosystem properties to stabilize and increase community stability under climate change45.…”

Spatiotemporal Variations of Extreme Precipitation under a Changing Climate in the Three Gorges Reservoir Area (TGRA)

“…The frequent occurrence of rainfall extremes produces multiple disasters, including urban flooding, server soil erosion, landslides and debris flows [1]. Moreover, rainfall extremes affect the ecological process of the terrestrial ecosystem [2,3]. The spatial patterns of extreme precipitation trends exhibit heterogeneous characteristics, especially at a smaller scale, due to factors including warming, water vapor trends and topography differences [4,5].…”

Impacts of Precipitation on Ecosystem Carbon Fluxes in Desert‐Grasslands in Inner Mongolia, China

“…It was reported that increased precipitation led to higher SWC (Gherardi & Sala, ), which increased nutrient (nitrogen) availability by promoting microbial processes (Brito et al, ; Guo et al, ; Sun et al, ) and ultimately enhanced plant growth (Plestenjak et al, ; Ye et al, ). However, in the present study, SWC did not increase with increased precipitation in June, August, and September.…”

“…These findings indicated that the desert‐grassland ecosystem carbon sink would be enhanced by increased precipitation and reduced by decreased precipitation by altering above‐ground biomass. This was a result of the increase in SWC due to increased precipitation (Gherardi & Sala, ), which improved the soil environment (Brito et al, ; Sun et al, ) and enhanced microorganism growth and development (Conant et al, ), and ultimately, affected carbon fluxes (Guo et al, ). Consequently, precipitation influenced carbon fluxes by altering SWC, species composition and biological growth.…”