Climate models project significant changes in precipitation amount, timing, and frequency for the next 50 years. These changes should influence the productivity and carbon sequestration of terrestrial ecosystems. Changes in timing and amount of precipitation would differentially modify ecosystem carbon fluxes and hydrological cycles in ecosystems. Our hypothesis is, changes in growing and non-growing season precipitation redistribution would differentially modify ecosystem carbon fluxes and hydrological cycles in a grassland ecosystem when keeping total precipitation amount and frequency constant. As site manipulated experiments testing responses of productivity and carbon sequestration with various changes in precipitation require high financial and temporal investment, here we used a process-based ecosystem model, TECO model (designed to examine ecosystem responses to changes in global climate change factor such as precipitation, temperature, and CO2 concentration), to simulate how carbon fluxes and hydrological cycles respond to simulated seasonal redistribution of precipitation in an old-field tall grass prairie site in central Oklahoma. We used data from a 16-year field experiment, in which a grassland was warmed and clipped.
Results/Conclusions
Our results show that reallocating precipitation from other seasons to summer enhances annual NPP, GPP, Rh and NEE. Moreover, changes in summer precipitation has larger controlling effects on annual carbon fluxes. Ecosystem annual carbon fluxes changes is more sensitive to summer drought, comparing to an increment in precipitation in summer. We also found that autumn drought offset the positive effect of summer precipitation increment on carbon fluxes. There are legacy effects of precipitation change on soil moisture, which could be explained by extra run off in the main precipitation change seasons. Future investigations should focus on testing the ability of this model to reproduce existing manipulated experiment data, which in turn could provide guidance to the experimental setup for the future changing precipitation scenarios.