Abstract
Abstract. Attributing changes in evapotranspiration (ET) and gross primary productivity (GPP) is crucial for impact and adaptation assessment of the agro-ecosystems to climate change. Simulations with the VIP model revealed that annual ET and GPP slightly increased from 1981 to 2013 over the North China Plain. The tendencies of both ET and GPP were upward in the spring season, while they were weak and downward in the summer season. A complete factor analysis illustrated that the relative contributions of climatic change, CO2 fertilization, and management to the ET (GPP) trend were 56 (−32) %, −28 (25) %, and 68 (108) %, respectively. The decline of global radiation resulted from deteriorated aerosol and air pollution was the principal cause of GPP decline in summer, while air warming intensified the water cycle and advanced the plant productivity in the spring season. Generally, agronomic improvements were the principal drivers of crop productivity enhancement.
Highlights
Terrestrial hydrological and carbon cycles are intimately coupled via transpiration and photosynthesis processes which are regulated by plant leaf stomata
In view of the complementary relationship hypothesis (Hobbins et al, 2001), alteration of available energy partitioned into latent heat flux is dominated by the atmospheric water vapour deficit, namely, while more vapour is evaporated into the atmosphere boundary layer, its water vapour deficit is relaxed, resulting in a lower rate of ETp
As the trends of both ETp and ETw were dominated by the radiation trend, the ETa estimated from the complementary relationship definitely followed the negative trend of radiation, because the positive trend of aerodynamic evaporation was weak as a tradeoff of the positive effect of rising water vapour deficit and the negative effect of decreasing wind speed
Summary
Terrestrial hydrological and carbon cycles are intimately coupled via transpiration and photosynthesis processes which are regulated by plant leaf stomata. Due to land use/cover changes, intensified agricultural management, and climatic change, terrestrial eco-hydrological processes have been noticeably shifted on multiple spatiotemporal scales (Tian et al, 2011; Douville et al, 2013); for example, prevailing irrigation and application of chemical fertilizers have raised soil moisture, evapotranspiration (ET), and crop productivity, etc. Global consumptive water use and carbon fixation by terrestrial ecosystems have been demonstrated to slightly increase with more efficient water use, corresponding to changes in climatic factors and the fertilization effect of elevated atmospheric CO2 concentration (Yan et al, 2013; Nayak et al, 2013). Over the North China Plain (NCP) the changes in ETp are mainly attributed to declines in global radiation and nearsurface wind speed (Tang et al, 2011; Song et al, 2009).
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