A meta-analysis and modeling approach to understanding climate warming impacts on ecosystem rain use efficiency

Background/Question/Methods

The relative impact of global warming on ecosystem water use efficiency (ERUE = the amount of carbon sequestered per unit of rainfall) has not been explored in multiple biomes. In this study, we used a terrestrial ecosystem (TECO) model to explain the meta-analysis result of climate warming’s impact on ecosystem rain use efficiency. We examined 4 biomes (grassland, shrubland, tundra, and wetland) that had at least an experimental warming of 2°C. From our meta-analysis results, we concluded that there was a positive increase in ecosystem rain use efficiency across all biomes with experimental warming. Based on these results the TECO model was then used to determine the change in the total ecosystem hydrologic cycle. This was done by increasing the atmospheric temperature of the TECO model by 2°C and then evaluating the performance of the model with actual field observations. From our analysis we were able to show that the model’s soil moisture and ecosystem rain use efficiency responded in congruence with observational data.

Results/Conclusions

We then evaluated the model output of runoff, evaporation, transpiration, and plant water use efficiency to the 2°C change in temperature. According to the TECO model, runoff decreased by 25%, evaporation decreased by 3%, and plant water use efficiency decreased by 2.73%; however, there was an increase in transpiration of 16.77%. From our results we are able to conclude that temperature is a limiting factor to ecosystem water use efficiency and with an increase in temperature there will be changes in all other components of the hydrologic cycle. In particular, runoff, a major element to replenishing freshwater, changed in a distinct fashion to an increase in ecosystem rain use efficiency; this change could lead to a direct impact on hydrological modeling and policy decisions.