Water use efficiency threshold for terrestrial ecosystem carbon sequestration in China under afforestation

Gao, Yang; Zhu, Xianjin; Yu, Guirui; He, Nianpeng; Wang, Qiufeng; Tian, Jing

doi:10.1016/j.agrformet.2014.04.010

Cited by 127 publications

(49 citation statements)

References 28 publications

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“…Both MODIS-and eddy covariance-derived WUE values were within the range of previous studies (0.36-6.07 g·C·kg −1 H2O) [9,32]. They also show higher values in forest ecosystems than grassland ecosystems, which were consistent with previous studies of the variation of WUE across different ecosystem types [7,8,33]. Because we defined WUE as the ratio of GPP and ET, the performance of MODIS WUE depends on the accuracy of both GPP and ET estimation.…”

Section: Discussionsupporting

confidence: 78%

Evaluation of Water Use Efficiency Derived from MODIS Products against Eddy Variance Measurements in China

Zhang

Tian

et al. 2015

Remote Sensing

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Water use efficiency (WUE) is a useful indicator to illustrate the interaction of carbon and water cycles in terrestrial ecosystems. MODIS gross primary production (GPP) and evapotranspiration (ET) products have been used to analyze the spatial and temporal patterns of WUE and their relationships with environmental factors at regional and global scales. Although MODIS GPP and ET products have been evaluated using eddy covariance flux measurements, the accuracy of WUE estimated from MODIS products has not been well quantified. In this paper, we evaluated WUE estimated from MODIS GPP and ET products against eddy covariance measurements of GPP and ET during 2003-2008 at eight sites of the Chinese flux observation and research network (ChinaFLUX) and conducted sensitivity analysis to investigate the possible key contributors to the bias of MODIS products. Results show that MODIS products underestimate eight-day water use efficiency in four forest ecosystems and one cropland ecosystem with the bias from −0.36-−2.28 g·C·kg H2O.Mean annual WUE was underestimated by 14%-54% at four forest sites, 45% at one OPEN ACCESSRemote Sens. 2015, 7 11184 cropland site and 7% at an alpine grassland site, but overestimated by 66% and 9% at a temperate grassland site and an alpine meadow site, respectively. The underestimation of WUE by MODIS data results from underestimated GPP and overestimated ET at four forest sites, while MODIS WUE values are significantly overvalued mainly due to underestimated ET in the three grassland ecosystems. The maximum light use efficiency and fraction of photosynthetically-active radiation (FPAR) were the two most sensitive factors to the estimation of WUE derived from the MODIS GPP and ET algorithms. The error in meteorological data partly caused the overestimation of ET and accordingly underestimation in WUE in subtropical and tropical forests. The bias of MODIS-produced WUE was also derived from the uncertainties in eddy flux data due to gap-filling processes and unbalanced surface energy issue. Their contributions to the uncertainty in estimated WUE at both eight-day and annual scales still need to be further quantified.

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Section: Discussionsupporting

confidence: 78%

Evaluation of Water Use Efficiency Derived from MODIS Products against Eddy Variance Measurements in China

Zhang

Tian

et al. 2015

Remote Sensing

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“…However, the increasing trend of NDVI in Loess Plateau after 2001 was much higher than any other regions in China that it can hardly be only explained by temperature rise. The study by Gao et al [61] showed that from 1999 to 2010, the total afforestation area was 5165 × 103 hm 2 in Shanxi province, mainly located in Loess Plateau, ranked the second in all provinces of China, which can partly explain the extremely high increasing rate of NDVI in this area. Therefore in Loess Plateau, NDVI increased rapidly after 2001 due to temperature rise and afforestation.…”

Section: Temporal Variation In Ndvi In Typical Regionsmentioning

confidence: 99%

Responses of Natural Vegetation Dynamics to Climate Drivers in China from 1982 to 2011

Liu

Lei

2015

Remote Sensing

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This study investigated the spatiotemporal variation of vegetation growth and the influence of climatic drivers from 1982 to 2011 across China using datasets from the Normalized Difference Vegetation Index (NDVI) and climatic drivers. Long term trends, significance and abrupt change points of interannual NDVI time series were analyzed. We applied both simple regression and multi-regression models to quantify the effects of climatic drivers on vegetation growth and compare their relative contributions. Results show that on average, the growing season NDVI significantly increased by 0.0007 year −1 , with 76.5% of the research area showed increasing NDVI from 1982 to 2011. Seasonally, NDVI increased at high rates during the spring and autumn while changed slightly during the summer. At a national scale, the growing season NDVI was significantly and positively correlated to temperature and precipitation, with temperature being the dominant factor. At regional scales, the growing season NDVI was dominated by increasing temperature in most forest-covered areas in southern China and dominated by precipitation in most grassland in northern China. Within the past three decades, the increasing trend of national mean NDVI abruptly changed in 1994, slowing down from 0.0008 year −1 to 0.0003 year −1 . To be regional specific, the growing season NDVI in forest covered southern China has accelerated together with temperature since mid 1990s, while parts of the grassland in northern China have undergone stalled NDVI trends corresponding to slowed temperature increment and dropped precipitation since around 2000. Typical region analysis suggested that apart from

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“…For example, the use of poplars in water-limited regions may increase the risk of environmental degradation, soil moisture deficit, hydrologic and vegetation changes (Gao et al, 2014).…”

Section: Kang Et Al: Energy Partitioning and Surface Resistance Omentioning

confidence: 99%

Energy partitioning and surface resistance of a poplar plantation in northern China

et al. 2015

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Abstract. Poplar (Populus sp.) plantations have been, on the one hand, broadly used in northern China for urban greening, combating desertification, as well as for paper and wood production. On the other hand, such plantations have been questioned occasionally for their possible negative impacts on water availability due to the higher water-use nature of poplar trees compared with other tree species in water-limited dryland regions. To further understand the acclimation of poplar species to semiarid environments and to evaluate the potential impacts of these plantations on the broader context of the region's water supply, we examine the variability of bulk resistance parameters and energy partitioning in a poplar (Populus euramericana cv. "74/76") plantation located in northern China over a 4-year period, encompassing both dry and wet conditions. The partitioning of available energy to latent heat flux (LE) decreased from 0.62 to 0.53 under mediated meteorological drought by irrigation applications. A concomitant increase in sensible heat flux (H ) resulted in the increase of a Bowen ratio from 0.83 to 1.57. Partial correlation analysis indicated that surface resistance (R s ) normalized by leaf area index (LAI; R s :LAI) increased by 50 % under drought conditions and was the dominant factor controlling the Bowen ratio. Furthermore, R s was the main factor controlling LE during the growing season, even in wet years, as indicated by the decoupling coefficient ( = 0.45 and 0.39 in wet and dry years, respectively). R s was also a major regulator of the LE / LE eq ratio, which decreased from 0.81 in wet years to 0.68 in dry years. All physiological and bioclimatological metrics indicated that the water demands of the poplar plantation were greater than the amount available through precipitation, highlighting the poor match of a water-intensive species like poplar for this water-limited region.

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Water use efficiency threshold for terrestrial ecosystem carbon sequestration in China under afforestation

Cited by 127 publications

References 28 publications

Evaluation of Water Use Efficiency Derived from MODIS Products against Eddy Variance Measurements in China

Evaluation of Water Use Efficiency Derived from MODIS Products against Eddy Variance Measurements in China

Responses of Natural Vegetation Dynamics to Climate Drivers in China from 1982 to 2011

Energy partitioning and surface resistance of a poplar plantation in northern China

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