Studying Effects of Evapotranspiration and Precipitation on Hydrological Cycles of Forest and Grassland( I )( II )

Evapotranspiration (ET) and rainfall infiltration (RI) are important fluxes of Earth hydrological cycles. Both are critical to water exchanges between land and atmosphere to affect Earth critical zone’s services and water resources, and their dynamics are affected by atmospheric conditions, land cover types, and hydrogeology characteristics. In view of energy exchanges between land and atmosphere, ET represents latent heat fluxes along with sensible het fluxes to balance surface available energy. Therefore forest plays a role in addition to provide functions of carbon sequestrations, but also to reduce global warming due to capable of lowering surface temperature via ET. Based on our long-term research planning, this study proposes the second phase plan with three-year of action themes mainly on the Lien-Hua-Chih (LHC) hydrometeorological site with continuing operation of the grassland site. Objectives of the first year study are to investigate forest ET variations with different temporal scales. Major tasks include: (1) testing skills of complimentary theory on estimating forest ET with different temporal scale; (2) analyzing effects of forest ET on soil moisture variations; (3) developing gap-filling models for eddy variance carbon fluxes; (4) calibrating and validating land surface models for forest. Objectives of the second year study are to investigate forest RI variations with different temporal scales. Major tasks include: (1) analyzing effects of RI on soil moisture variations with surface covered by forests; (2) investigating contributions of RI to groundwater variations with surface covered by forests; (3) improving water, energy, and carbon exchanges mechanisms described by land surface models; (4) analyzing characteristics of forest hydrological cycles. Objectives of the third year study are to compare hydrological characteristics and variations between forest and grassland due to ET and RI. Major tasks include: (1) comparing variations of ET dynamics between forest and grassland due to different surface roughness; (2) analyzing variations of RI dynamics between forest and grassland due to different land covers; (3) investigating characteristics of hydrological cycles between forest and grassland due to different land cover and weather conditions under different temporal scales; (4) preliminary selecting of riparian test site for the third phase research theme. To promote international collaborations, the LHC has been recognized by the AsiaFlux in Asian region and the global FLUXNET. Both grassland site (NAHOs) and LHC Flux site have been registered as sites of international Critical Zone Exploration Network. During the second phase study, we will try to build up international collaborations and share our data to both domestic and international communities. The expected contributions of the second phase study is to provide solid scientific supports for solving complicated water, energy, and carbon interactions between land and atmosphere based on field observations, analyzing, and simulations tasks. On the practical aspects, outcomes of this study will provide critical knowledge to support decision making on facing challenges by climate change, water resources management, and land use management.