Modeling of the potential vegetation index of steppe in the western part of the Chinese Loess Plateau

2011 ◽  
Author(s):  
Pengcheng Qi ◽  
Yan Cui
Keyword(s):  
Loess Plateau ◽  
Vegetation Index ◽  
Chinese Loess Plateau ◽  
Chinese Loess ◽  
Potential Vegetation ◽  
The Chinese Loess Plateau

scholarly journals Soil Moisture Estimation for the Chinese Loess Plateau Using MODIS-derived ATI and TVDI

2020 ◽  
Vol 12 (18) ◽  
pp. 3040
Author(s):  
Lina Yuan ◽  
Long Li ◽  
Ting Zhang ◽  
Longqian Chen ◽  
Jianlin Zhao ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Loess Plateau ◽  
Vegetation Index ◽  
Joint Model ◽  
Iteration Procedure ◽  
Chinese Loess Plateau ◽  
Vegetation Coverage ◽  
Chinese Loess ◽  
The Chinese Loess Plateau

Timely and effective estimation and monitoring of soil moisture (SM) provides not only an understanding of regional SM status for agricultural management or potential drought but also a basis for characterizing water and energy exchange. The apparent thermal inertia (ATI) and Temperature Vegetation Dryness Index (TVDI) are two widely used indices to reflect SM from remote sensing data. While the ATI-based model is routinely used to estimate the SM of bare soil and sparsely vegetated areas, the TVDI-based model is more suitable for areas with dense vegetation coverage. In this study, we present an iteration procedure that allows us to identify optimal Normalized Difference Vegetation Index (NDVI) thresholds for subregions and estimate their relative soil moisture (RSM) using three models (the ATI-based model, the TVDI-based model, and the ATI/TVDI joint model) from 1 January to 31 December 2017, in the Chinese Loess Plateau. The initial NDVI (NDVI0) was first introduced to obtain TVDI value and two other thresholds of NDVIATI and NDVITVDI were designed for dividing the whole area into three subregions (the ATI subregion, the TVDI subregion, and the ATI/TVDI subregion). The NDVI values corresponding to maximum R-values (correlation coefficient) between estimated RSM and in situ RSM measurements were chosen as optimal NDVI thresholds after performing as high as 48,620 iterations with 10 rounds of 10-fold cross-calibration and validation for each period. An RSM map of the whole study area was produced by merging the RSM of each of the three subregions. The spatiotemporal and comparative analysis further indicated that the ATI/TVDI joint model has higher applicability (accounting for 36/38 periods) and accuracy than the ATI-based and TVDI-based models. The highest average R-value between the estimated RSM and in situ RSM measurements was 0.73 ± 0.011 (RMSE—root mean square error, 3.43 ± 0.071% and MAE—mean absolute error, 0.05 ± 0.025) on the 137th day of 2017 (DOY—day of the year, 137). Although there is potential for improved mapping of RSM for the entire Chinese Loess Plateau, the iteration procedure of identifying optimal thresholds determination offers a promising method for achieving finer-resolution and robust RSM estimation in large heterogeneous areas.

scholarly journals Improving Soil Moisture Estimation by Identification of NDVI Thresholds Optimization: An Application to the Chinese Loess Plateau

2021 ◽  
Vol 13 (4) ◽  
pp. 589
Author(s):  
Lina Yuan ◽  
Long Li ◽  
Ting Zhang ◽  
Longqian Chen ◽  
Jianlin Zhao ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Loess Plateau ◽  
Vegetation Index ◽  
Climate Models ◽  
Irrigation Management ◽  
Chinese Loess Plateau ◽  
Chinese Loess ◽  
Thresholds Optimization ◽  
Moisture Estimation ◽  
The Chinese Loess Plateau

Accuracy soil moisture estimation at a relevant spatiotemporal scale is scarce but beneficial for understanding ecohydrological processes and improving weather forecasting and climate models, particularly in arid and semi-arid regions like the Chinese Loess Plateau (CLP). This study proposed Criterion 2, a new method to improve relative soil moisture (RSM) estimation by identification of normalized difference vegetation index (NDVI) thresholds optimization based on our previously proposed iteration procedure of Criterion 1. Apparent thermal inertia (ATI) and temperature vegetation dryness index (TVDI) were applied to subregional RSM retrieval for the CLP throughout 2017. Three optimal NDVI thresholds (NDVI0 was used for computing TVDI, and both NDVIATI and NDVITVDI for dividing the entire CLP) were firstly identified with the best validation results (R¯) of subregions for 8-day periods. Then, we compared the selected optimal NDVI thresholds and estimated RSM with each criterion. Results show that NDVI thresholds were optimized to robust RSM estimation with Criterion 2, which characterized RSM variability better. The estimated RSM with Criterion 2 showed increased accuracy (maximum R¯ of 0.82 ± 0.007 for Criterion 2 and of 0.75 ± 0.008 for Criterion 1) and spatiotemporal coverage (45 and 38 periods (8-day) of RSM maps and the total RSM area of 939.52 × 104 km2 and 667.44 × 104 km2 with Criterion 2 and Criterion 1, respectively) than with Criterion 1. Moreover, the additional NDVI thresholds we applied was another strategy to acquire wider coverage of RSM estimation. The improved RSM estimation with Criterion 2 could provide a basis for forecasting drought and precision irrigation management.

scholarly journals Spatiotemporal Patterns of Terrestrial Evapotranspiration in Response to Climate and Vegetation Coverage Changes across the Chinese Loess Plateau

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1625 ◽  
Author(s):  
Han Zheng ◽  
Henry Lin ◽  
Xianjin Zhu
Keyword(s):  
Climate Variability ◽  
Interannual Variability ◽  
Loess Plateau ◽  
Vegetation Index ◽  
Growing Season ◽  
Spatiotemporal Patterns ◽  
Chinese Loess Plateau ◽  
Vegetation Coverage ◽  
Chinese Loess ◽  
The Chinese Loess Plateau

Spatiotemporal patterns of evapotranspiration (ET) and its controlling factors are important for ecosystem services and water resources management in the Chinese Loess Plateau (CLP). In this study, we assessed the spatial patterns of ET and then investigated the interannual variability of ET and its relationships with climate variability and vegetation coverage changes at the timescales of annual, active growing season, as well as different seasons across the entire CLP from 2000 to 2014. A MODIS-derived ET dataset, ground-based datasets of precipitation and atmospheric evaporative demand (AED), and a remote-sensing dataset of Normalized Difference Vegetation Index (NDVI) were comprehensively analyzed. Results showed that mean annual ET varied distinctly among different vegetation zones, generally higher in the more humid southeastern parts of the CLP. Summer ET and ET over active growing season significantly increased for more than 40% of the entire CLP area, and winter ET significantly decreased over ~70% of the entire CLP region, while annual ET, spring ET, and autumn ET remained quite stable during 2000–2014. Per-pixel interannual variability of ET was mainly positively correlated with that of precipitation and NDVI except for winter, but negatively correlated with AED trends. Our study also demonstrated that ET variation trends were exactly consistent for the entire CLP region, the areas mainly implemented with the Grain for Green (GFG) project, and other CLP areas not implemented with the GFG project during 2000–2014. Our findings suggest that the spatiotemporal patterns of CLP ET were mainly water-limited, and climate variability played an essential role in shaping the interannual variability of ET in the CLP. This study will improve our understanding on the ET variations over water-limited areas under climate and vegetation coverage changes.

scholarly journals Changes in soil water holding capacity and water availability following vegetation restoration on the Chinese Loess Plateau

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yong-wang Zhang ◽  
Kai-bo Wang ◽  
Jun Wang ◽  
Changhai Liu ◽  
Zhou-ping Shangguan
Keyword(s):  
Land Use ◽  
Soil Water ◽  
Loess Plateau ◽  
Soil Layer ◽  
Soil Physical Properties ◽  
Chinese Loess Plateau ◽  
Land Use Type ◽  
Chinese Loess ◽  
Water Holding ◽  
The Chinese Loess Plateau

AbstractChanges in land use type can lead to variations in soil water characteristics. The objective of this study was to identify the responses of soil water holding capacity (SWHC) and soil water availability (SWA) to land use type (grassland, shrubland and forestland). The soil water characteristic curve describes the relationship between gravimetric water content and soil suction. We measured the soil water characteristic parameters representing SWHC and SWA, which we derived from soil water characteristic curves, in the 0–50 cm soil layer at sites representing three land use types in the Ziwuling forest region, located in the central part of the Loess Plateau, China. Our results showed that the SWHC was higher at the woodland site than the grassland and shrubland, and there was no significant difference between the latter two sites, the trend of SWA was similar to the SWHC. From grassland to woodland, the soil physical properties in the 0–50 cm soil layer partially improved, BD was significantly higher at the grassland site than at the shrubland and woodland sites, the clay and silt contents decreased significantly from grassland to shrubland to woodland and sand content showed the opposite pattern, the soil porosity was higher in the shrubland and woodland than that in the grassland, the soil physical properties across the 0–50 cm soil layer improved. Soil texture, porosity and bulk density were the key factors affecting SWHC and SWA. The results of this study provide insight into the effects of vegetation restoration on local hydrological resources and can inform soil water management and land use planning on the Chinese Loess Plateau.

Drought variation trends in different subregions of the Chinese Loess Plateau over the past four decades

2012 ◽  
Vol 115 ◽  
pp. 167-177 ◽  
Author(s):  
Baoqing Zhang ◽  
Pute Wu ◽  
Xining Zhao ◽  
Yubao Wang ◽  
Jiawen Wang ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Chinese Loess Plateau ◽  
Chinese Loess ◽  
The Past ◽  
Variation Trends ◽  
The Chinese Loess Plateau
Sign in / Sign up

Export Citation Format

Share Document