Characterizing ecosystem water-use efficiency of croplands with eddy covariance measurements and MODIS products

Abstract

a b s t r a c tHow to quantify the variability in ecosystem water use efficiency (WUE) of croplands is of vital importance. Especially in the context of changing hydrologic environment, much attention need to be paid on how to use limited water to improve crop yield. However, the biophysical performances of environmental/biological controls, crop types, and effects of diverse farming practices on WUE remain unclear. Therefore, this study aims to address these questions through tower-based measurements from eddy covariance and satellite-based estimates from MODIS GPP and ET products at the two annual soybean/corn rotation fields. The results exhibited that temperature and solar radiation are the most important meteorological factors. MODIS WUE estimates captured the broad trend of 8-day tower-based observations. However, ecosystem WUE was overpredicted at the seedling stage and after harvest, and was severely underestimated at the peak periods of maize, which was mainly ascribed to the uncertainties in MODIS GPP. Finally, we evaluated the effects of two farming practices (conventional vs alternative) on WUE and carbon sequence (NEE). On annual time scale, WUE of both soybean and maize are improved obviously under the alternative management whereas contrasting effects are observed on NEE. But the overall carbon balance for both treatments is nearly identical over 2-year rotation.

Potential of MODIS data to track the variability in ecosystem water-use efficiency of temperate deciduous forests

“…6, in general, GPP MOD showed a poor agreement whereas ET MOD performed relatively well at the four forest sites except several 8-day periods. Previous studies also confirmed the reliable ET MOD for croplands relying completely on rainfall (Cammalleri et al, 2014;Tang et al, 2015a) and evergreen forests (Liu et al, 2015). The large underestimation of GPP MOD during the vegetation periods may lead to a similar pattern in ecosystem WUE.…”

“…Nevertheless, tower-based observations are spatially limited for adequate sampling of natural ecosystems. The spatiotemporal variability of WUE in large areas has been rarely quantified mainly owing to the complicated interactions between water and carbon as well as the uncertainty in the interactive influences of multiple environmental controls (Tian et al, 2010;Tang et al, 2015a). Although it can be estimated using empirical models driven by highly-related meteorological inputs (Wang et al, 2007;Beer et al, 2009;Yang et al, 2013a), it is worthwhile exploring methods to quantify WUE entirely from remotely sensed information as this could greatly reduce the difficulty in acquiring infrequently meteorological data.…”

Impacts of land use changes on net ecosystem production in the Taihu Lake Basin of China from 1985 to 2010

“…Some reliable remote sensing data on vegetation, such as MODIS products of leaf area index (LAI), gross primary production (GPP), and net primary production (NPP), can be further incorporated to calibrate the model [ Zhu and Zhuang , ]. The observed water flux (evapotranspiration, ET) and latent heat flux (based on the eddy covariance technique) can also be included in the calibration [ Tang et al, ; Trusilova et al , ; Ueyama et al, ]. The ecosystem flux data will help refine model parameters to quantify NEP more precisely on regional scale in the future.…”

Alterações na eficiência do uso da água relacionadas com fatores climáticos e uso e ocupação do solo, na região do MATOPIBA

“…A eficiência do uso da água (WUE) utiliza a relação entre a produtividade primária bruta (PPB) da cultura ou vegetação e a evapotranspiração (ET), já que as trocas de carbono e água entre a vegetação e a atmosfera (fotossíntese), desempenham papel importante no ecossistema (Dalastra et al, 2020;Yamori, 2020). Além de ser uma informação importante utilizada para a avaliação dos impactos referentes as mudanças climáticas, deficiência da irrigação e gestão das estratégias afins de produtividades do ecossistema (Tang et al, 2015a;Tang et al, 2015b).…”