Climate change has direct and indirect effects on the watershed hydrology and ecosystem productivity through complex short-term and long-term influences on the hydrological and biological processes in forests. Across much of the southern U.S., climate projections predict warmer air temperatures and precipitation patterns that are more variable in space, time and intensity. Empirical evidence on the effects of climate change on watershed water yield (i.e., streamflow) and forest productivity is often mixed with natural or anthropogenic disturbances (e.g., harvest, regeneration, fire, and urbanization), making it difficult to disentangle the effect of different factors. Additionally, the magnitude of climate change of historical records is still relatively small compared to projected changes in the next 100 years, and observations of climate change impacts on forests are incomplete. Therefore, scientists rely on experimental setups, such as in situ warming, throughfall exclusion and Free-Air Carbon dioxide Enrichment (FACE) experiments to understand the likely impacts of future climate change. This empirical knowledge gained from the field must be incorporated into theoretical ecosystem simulation models to project the ecosystem response under hypothetical climate and management scenarios. This presentation presents key findings from the literature and recent studies from the Pine Integrated Network: Education, Mitigation, and Adaptation project (PINEMAP) project that examines the combined impacts of climate change (atmospheric [CO2], drought) and management (fertilization) on water and carbon balances across the region where loblolly pine forests are found.
Results/Conclusions
Throughfall exclusion experiments suggested that the effect of a 30% reduction of annual precipitation on forest growth differed due to variation in climatic and edaphic conditions across sites. Fertilization, a key silvicultural practice in loblolly pine management, could increase the vulnerability of pines to drought due to shifts in biomass allocation above and belowground. Regional modeling using the Water Supply Stress Index (WaSSI) model coupled with an ensemble of 20 Global Circulation Models (GCMs) and two future greenhouse gas emissions scenarios indicates that water yield could decrease regionally, while productivity could increase as a result of increased precipitation and air temperature by 2030 and 2080. The tradeoffs between carbon gain and water loss are expected to increase under the future climate in the Southeastern United States. Forest management must consider climate change impacts on both water and carbon resources to achieve sustainable forestry in the region.