Ecohydrological Optimality in Northeast China Transect
Zhentao Cong1,2, Qinshu Li1,2, Kangle Mo1,2, and Lexin Zhang1,21Department of Hydraulic Engineering, Tsinghua University, Beijing, 100084, China 2State Key Laboratory of Hydroscience and Engineering, Beijing, 100084, China
Received: 26 Jan 2017 – Accepted for review: 26 Jan 2017 – Discussion started: 27 Jan 2017
Abstract. Northeast China Transect (NECT) is one of International Geosphere-Biosphere Program (IGBP) terrestrial transects., where there is a significant precipitation gradient from east to west, as well as a vegetation transition of forest-grasslands-dessert. It is interesting to understand vegetation distribution and dynamics under water limitation in this transect. We take canopy cover (M), derived from Normalized Difference Vegetation Index (NDVI), as an index to describe the properties of vegetation distribution and dynamics in NECT. In Eagleson's ecohydrological optimality theory, the optimal canopy cover (M*) is determined by the trade-off of water supply depending on water balance and water demand depending on canopy transpiration. We apply Eagleson’s ecohydrological optimality method in NECT based on data from 2000 to 2013 to get M*, then compare with M from NDVI, furthermore to discuss the sensitivity of M* to vegetation properties and climate factors. The result indicates that the average M* fits the actual M well (for forest, M* = 0.822 while M = 0.826 for grassland, M* = 0.353 while M = 0.352; the correlation coefficient between M and M* is 0.81). The result of water balance also matches the field-measured data in references. The sensitivity analyses show that M* decreases with the increase of LAI, stem fraction, temperature, while increases with the increase of leaf angle and precipitation amount. The Eagleson's ecohydrological optimality method offers a quantitative way to understand the impacts of climate change to canopy cover quantitatively, and provides guidelines for eco-restoration projects.
Cong, Z., Li, Q., Mo, K., and Zhang, L.: Ecohydrological Optimality in Northeast China Transect, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2017-42, in review, 2017.