Effects of multiple environment stresses on evapotranspiration and runoff over eastern China Mingliang Liu 1 , Hanqin Tian ⇑ , Chaoqun Lu, Xiaofeng Xu, Guangsheng Chen, Wei Ren Ecosystem Dynamics and Global Ecology (EDGE) Laboratory, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA International Center for Climate and Global Change Research, Auburn University, Auburn, AL 36849, USA article info Article history: Received 24 April 2011 Received in revised form 24 September 2011 Accepted 10 January 2012 Available online 18 January 2012 This manuscript was handled by Andras Bardossy, Editor-in-Chief, with the assistance of K.P. Sudheer, Associate Editor Keywords: China Evapotranspiration Global change Runoff Water resources summary Little is known about how the terrestrial hydrological cycle responds to multiple environmental changes at large spatial scale and over long time period. Here, we applied a well calibrated and verified ecosystem model (the Dynamic Land Ecosystem Model, DLEM), in conjunction with newly developed data sets of multiple environmental factors including land use change, climate variability, elevated atmospheric carbon dioxide (CO 2 ), nitrogen deposition, ozone pollution, and nitrogen fertilizer application, to charac- terize the spatial and temporal patterns of evapotranspiration (ET) and runoff in eastern China during 1961–2005 and further quantified the relative contributions of multiple environmental factors to these patterns at both basin and regional scales. The simulation results indicated that annual ET in the study area had a significantly increasing trend from 1961 to 2005. Yet there were no significant changing trends for estimated runoff and net water balance (precipitation minus ET). Substantial spatial heterogeneities in ET and runoff were observed. Annual ET increased in all basins except Yellow River Basin. Runoff increased in the southern part of the study area (including Pearl River and the Southeast basin), but decreased in northern part of the study area, particularly in Haihe and Huaihe river basins. Factorial analysis showed that climate change was the dominant factor responsible for the interannual variations in ET and runoff in the past 45 years. Land use change (including land conversions and land management practices) yielded minor effects on the interannual variations in ET and runoff but caused relatively large effects over long-term period. For the accumulated change in ET at basin scale, climate change was the dominant factor in the basins of Song-Liao, Pearl River, while land use change contributed the most in the basin of Haihe, Huaihe, and Yellow River. Climate change was the dominant factor controlling runoff change in all basins except Huaihe and Yangtze River basins. Our simulated results imply that it is important to quantify relative roles of natural and anthropogenic disturbances on water fluxes for maintaining water sustainability in a changing climate. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The terrestrial hydrological cycle is essential for the functioning of land ecosystems; it plays crucial roles in maintaining the sus- tainability of the Earth system (Hutjes et al., 1998). Understanding the variations of terrestrial hydrological cycle and their underlying mechanisms are fundamental for predicting response of terrestrial ecosystems to environmental changes. Previous studies have re- vealed the changes in hydrological fluxes over the past decades; for instance, both observational data and simulations indicate an on-going intensification of the hydrological cycle since the 20th Century (Huntington, 2006). Recent data-driven analyses detected a declining trend of ET since 1998 at global scale (Jung et al., 2010); however, the underlying mechanisms for these changes are short of investigation. Many factors may contribute to the variations in ET at both tem- poral and spatial scales, such as climate variability (Arnell, 1999; Jackson et al., 2001; Milly et al., 2005; Vorosmarty and Sahagian, 2000), elevated atmospheric CO 2 (Field et al., 1995; Gedney et al., 2006), ozone (O 3 ) pollution (McLaughlin et al., 2007b), nitrogen (N) inputs (Dickinson, 1991), and human activities, especially land use/cover change (Bosch and Hewlett, 1982; Foley et al., 2005; Hut- jes et al., 1998; Liu et al., 2008; Sun et al., 2005; Vorosmarty and Sahagian, 2000). The effects of these factors on the hydrological cy- cle vary for different regions and biomes. Yet the sparse observa- tions and field experiments prohibit accurately characterizing the spatial and temporal patterns of ET and runoff over large spatial scales (Sun et al., 2005). Therefore, a bottom-up modeling approach, 0022-1694/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jhydrol.2012.01.009 ⇑ Corresponding author at: Ecosystem Dynamics and Global Ecology (EDGE) Laboratory, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36849, USA. Tel.: +1 334 844 1059; fax: +1 334 844 1084. E-mail address: tianhan@auburn.edu (H. Tian). 1 Present address: Department of Civil and Environmental Engineering, Washing- ton State University, Pullman, WA 99164, USA. Journal of Hydrology 426–427 (2012) 39–54 Contents lists available at SciVerse ScienceDirect Journal of Hydrology journal homepage: www.elsevier.com/locate/jhydrol