Center for Forest Disturbance Science USDA Forest Service Athens, Georgia, USA
Afforestation is conducted to meet diverse environmental objectives that include water resource conservation and water quality improvement, land degradation reverse, and wildlife habitat enhancement. Afforestation may also be advanced as a tool of social policy, for example to retire land from active agriculture or to sequester carbon. This talk provides studies on the impacts of afforestation on regional water resources using regional climate modeling technique. One focus is comparison between afforestation events in the southern United States and the northern China. The former region experienced deforestation due to the agricultural exploitation beginning in the 17th century and the timber exploitation during the first part of the 20th century. A 40 year period of regrowth of forests started after the Great Depression by both natural restoration and pine plantation. The latter region started a forest shelterbelt project in northern China in the late 1970s, which will last until 2050. The tree belt stands along the southern edge of the sandy lands, nearly paralleling to the Great Wall. Simulations with a regional climate model were conducted to examine the changes in water resources induced by these afforestation events. The results for the southern U.S. indicate large increase in soil moisture, but overall decreases in summer precipitation and evapotranspiration. The precipitation change is mainly caused by the reduction in moisture transport by the prevailing airflows. The northern China forest shelterbelt project, on the other hand, is found likely to improve overall hydroclimate conditions by increasing precipitation, relative humidity and soil moisture, and reducing prevailing winds and air temperature. The hydroclimate effects are also found in the surrounding areas, featured by noticeably moister conditions in the area south of the afforestation project. 
Yongqiang Liu is a Research Meteorologist in Center for Forest Disturbance Science, USDA Forest Service, Athens, Georgia. He is also an adjunct faculty member of George Mason University and Adjunct Associate Professor of Georgia Institute of Technology. He got his Ph.D. in Atmospheric Dynamics in 1990 from Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China and postdoc training in Rutgers University, New Jersey, U.S. He had worked in the National Center for Atmospheric Research, Rutgers University, and Georgia Institute of Technology before joining the US Forest Service in 2002. His research interests include regional climate and hydrology modeling, global change, atmosphere-vegetation-soil interactions, and forest disturbances including wildfire and hurricane. He is a member of
American Meteorological Society, American Geophysical Union and some other professional associations. He currently serves as an editor of a forest journal. He has published over 60 research papers, including over 40 in peer reviewed journals.