Long-term warming alters the climate sensitivity of plant and microbial processes in the Boston-Area Climate Experiment
To improve our understanding of ecosystem process responses to long-term changes in climate, we exposed an old-field ecosystem to twelve combinations of warming and precipitation change over five years. Four warming treatments (up to +4 degrees C) were applied using infrared heaters, and precipitation was manipulated using rainout shelters (-50%) and sprinklers (+50% during the growing season). We recorded the responses of plant growth, including tree seedlings and the herbaceous community, and microbe-driven processes, including heterotrophic respiration and nitrogen transformations, to the various climate treatments to characterize the nature of the responses to warming, and to understand how these warming responses were modified by water availability.
In a warmed climate, some plant processes became more sensitive to precipitation treatments. For instance, the precipitation treatments did not affect plant growth in unwarmed plots, but precipitation removal suppressed growth (and precipitation addition sometimes increased it) in the warmed plots. Microbial processes also responded to long-term warming, through acclimation-type responses. For instance, nitrogen transformations became less sensitive to temperature in warmed plots. Understanding how long-term warming affects the character of short-term ecosystem process responses such as this can help improve the representation of ecosystem processes in models.