Modeling the impact of drought on canopy carbon and water fluxes for a subtropical evergreen coniferous plantation in southern China through parameter optimization using an ensemble Kalman filter

Abstract

Abstract. Soil and atmospheric water deficits have significant influences on CO 2 and energy exchanges between the atmosphere and terrestrial ecosystems. Model parameterization significantly affects the ability of a model to simulate carbon, water, and energy fluxes. In this study, an ensemble Kalman filter (EnKF) and observations of gross primary productivity (GPP) and latent heat (LE) fluxes were used to optimize model parameters significantly affecting the calculation of these fluxes for a subtropical coniferous plantation in southeastern China. The optimized parameters include the maximum carboxylation rate (Vc max ), the slope in the modified Ball-Berry model (M) and the coefficient determining the sensitivity of stomatal conductance to atmospheric water vapor deficit (D 0 ). Optimized Vc max and M showed larger variations than D 0 . Seasonal variations of Vc max and Mwere more pronounced than the variations between the two years. Vc max and M were associated with soil water content (SWC). During dry periods, SWC at the 20 cm depth explained 61% and 64% of variations of Vc max and M, respectively. EnKF parameter optimization improved the simulations of GPP, LE and SH, mainly during dry periods. After parameter optimization using EnKF, the variations of GPP, LE and SH explained by the model increased by 1% to 4% at half-hourly steps and by 3% to 5% at daily time steps. Further efforts are needed to differentiate the real causes of parameter variations and improve the ability of models to describe the change of stomatal conductance with net photosynthesis rate and the sensitivity of photosynthesis capacity to soil water stress under different environmental conditions.

Impact of estimated solar radiation on gross primary productivity simulation in subtropical plantation in southeast China

“…The inputs to the BEPS model include LAI, daily meteorological variables (maximum temperature, minimum temperature, solar radiation, precipitation, and relative humidity), and soil texture. Parameters here are referenced Ju et al (2010b).…”

Construction and progress of Chinese terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation

“…ChinaFLUX community modified several process-based models and remote sensing models, such as CEVSA (Cao et al, 2005;Gu et al, 2010), In-TEC , EALCO (Mi et al, 2007;Mi et al, 2009), and BEPS Ju et al, 2010), and VPM Wu et al, 2008). Meanwhile, many new models have been developed including AVIM2 (Ji et al, 2008;, CEVSA2 Gu et al, 2015), the evapo-transpiration model (Hu et al, 2013;Ren et al, 2005), a MODIS-based Photosynthetic Capacity Model , a remote sensing model for respiration ReRSM , and the statistical model GSM (Zheng et al, 2009;Zhu et al, 2014a).…”

Spatial cross‐correlation patterns of European low, mean and high flows

“…Other interesting aspects are nutrient and carbon cycling, which largely depend on average water availability [e.g. Davidson et al, 2000;Reichstein et al, 2003;Lohse et al, 2009;Ju et al, 2010]. In recent years, the influence of episodic changes in terrestrial water availability on largescale carbon cycling, including droughts [e.g.…”

“…In recent years, the influence of episodic changes in terrestrial water availability on largescale carbon cycling, including droughts [e.g. Saigusa et al, 2010;Ju et al, 2010], has received increasing attention. Theoretical [e.g.…”