Mapping the Soil Salinity Distribution and Analyzing Its Spatial and Temporal Changes in Bachu County, Xinjiang, Based on Google Earth Engine and Machine Learning
Abstract
:1. Introduction
2. Materials and Methods
2.1. Overview of the Study Area
2.2. Technological Approach
2.3. Data Sources and Processing
2.3.1. Ground-Truth Data
2.3.2. Remote Sensing Data
2.3.3. Spectral Indices
2.3.4. Salinity Indices
2.3.5. Composite Indices
2.3.6. Topographic Factors
2.3.7. Climatic Factors
2.4. Predictive Model
2.5. Evaluation of Model Accuracy
3. Results and Analysis
3.1. Soil Salinity Predictors
3.2. Model Accuracy Validation and Selection
3.3. Spatial and Temporal Variability of Salinization in Bachu County
3.3.1. Analysis of Spatial and Temporal Variations at the 0–20 cm Depth
3.3.2. Analysis of Spatial and Temporal Variations at the 20–40 cm Depth
3.4. Validation of Model Prediction Classification Errors
4. Discussion
4.1. Selection of Model Indices
4.2. Validation of the Model Accuracy and Classification Error
4.3. Analysis of Spatial and Temporal Changes in Soil Salinization and Their Influencing Factors in Bachu County
4.4. Future Prospects and Challenges
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Data Availability Statement
Conflicts of Interest
References
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Soil Impregnation Class | Non-Saline Soil | Weakly Saline Soil | Moderately Saline Soils | Highly Saline Soil | Saline Soil |
---|---|---|---|---|---|
Soil salinity (g·kg−1) | <3 | 3–6 | 6–10 | 10–20 | ≥20 |
Serial Number | Pseudolaric Acid | Extract Data | Resolution (m) | Time Range of Values |
---|---|---|---|---|
1 | Landsat7/9 | Single band, vegetation index, salinity index, composite index | 30 | April 2022, April 2012, April 2002 |
2 | MOD16A2 | Evapotranspiration | 500 | 2022 |
3 | CHIRPS Daily 2.0 Final | Precipitation | 500 | 2022 |
4 | SRTM | Elevation, slope, direction of slope | 30 | 2001 |
Index | Formula | Reference |
---|---|---|
NDVI (normalized difference vegetation index) | [36] | |
DVI (difference vegetation index) | [37] | |
ERVI (enhanced red vegetation index) | [38] | |
ENDVI (enhanced normalized difference vegetation index) | [39] | |
CRSI (canopy redness index) | [19] | |
MSAVI (modified soil-adjusted vegetation index) | [40] |
Index | Formula | Reference |
---|---|---|
SI1 | [42] | |
SI2 | [43] | |
SI3 | [44] | |
SI4 | [45] | |
SI5 | [46] | |
SI6 | [47] | |
SI7 | [48] | |
SI8 | [48] | |
SI9 | [48] | |
NDSI | [49] | |
SI-T | [50] |
Soil Depth | Model | R2 | RMSE/(g·kg−1) | MAE/(g·kg−1) |
---|---|---|---|---|
SSC (0–20 cm) | RF | 0.723 | 2.604 | 1.950 |
SVM | 0.459 | 3.829 | 3.494 | |
CART | 0.515 | 3.818 | 3.254 | |
PLS | 0.678 | 2.666 | 2.278 | |
SSC (20–40 cm) | RF | 0.64 | 3.620 | 2.728 |
SVM | 0.316 | 3.940 | 3.501 | |
CART | 0.503 | 3.820 | 3.390 | |
PLS | 0.628 | 3.670 | 2.790 |
Soil Salinity Class | 2012 Non-Saline Soil | 2012 Weakly Saline Soil | 2012 Moderately Saline Soils | 2012 Highly Saline Soil | 2012 Salted Soil |
---|---|---|---|---|---|
2002 non-saline soil | 8779.19 km2 | 178.93 km2 | 2586.03 km2 | 355.94 km2 | 207.64 km2 |
2002 weakly saline soil | 437.08 km2 | 251.43 km2 | 200.60 km2 | 33.61 km2 | 40.24 km2 |
2002 moderately saline soil | 167.78 km2 | 226.38 km2 | 445.12 km2 | 175.19 km2 | 285.40 km2 |
2002 highly saline soil | 316.09 km2 | 84.89 km2 | 2308.85 km2 | 639.46 km2 | 386.43 km2 |
2002 salted soil | 27.18 km2 | 0.64 km2 | 95.68 km2 | 11.89 km2 | 6.99 km2 |
Soil Salinity Class | 2022 Non-Saline Soil | 2022 Weakly Saline Soil | 2022 Moderately Saline Soil | 2022 Highly Saline Soil | 2022 Salted Soil |
---|---|---|---|---|---|
2012 non-saline soil | 5843.76 km2 | 3541.94 km2 | 146.98 km2 | 62.48 km2 | 141.75 km2 |
2012 weakly saline soil | 218.78 km2 | 261.55 km2 | 161.08 km2 | 77.74 km2 | 13.73 km2 |
2012 moderately saline soils | 789.58 km2 | 2690.16 km2 | 308.75 km2 | 580.86 km2 | 1228.03 km2 |
2012 highly saline soil | 241.46 km2 | 168.14 km2 | 99.42 km2 | 276.02 km2 | 470.35 km2 |
2012 salted soil | 121.84 km2 | 79.79 km2 | 151.54 km2 | 358.35 km2 | 214.78 km2 |
Soil Salinity Class | 2012 Non-Saline Soil | 2012 Weakly Saline Soil | 2012 Moderately Saline Soils | 2012 Highly Saline Soil | 2012 Salted Soil |
---|---|---|---|---|---|
2002 non-saline soil | 7623.87 km2 | 136.01 km2 | 1377.66 km2 | 1106.79 km2 | 412.99 km2 |
2002 weakly saline soil | 1186.64 km2 | 19.45 km2 | 127.25 km2 | 116.12 km2 | 12.19 km2 |
2002 moderately saline soils | 373.05 km2 | 200.29 km2 | 136.03 km2 | 31.24 km2 | 40.11 km2 |
2002 highly saline soil | 529.88 km2 | 349.18 km2 | 2031.07 km2 | 1014.47 km2 | 1135.41 km2 |
2002 salted soil | 49.47 km2 | 1.26 km2 | 130.19 km2 | 85.04 km2 | 22.94 km2 |
Soil Salinity Class | 2022 Non-Saline Soil | 2022 Weakly Saline Soil | 2022 Moderately Saline Soils | 2022 Highly Saline Soil | 2022 Salted Soil |
---|---|---|---|---|---|
2012 non-saline soil | 135.22 km2 | 7245.48 km2 | 223.38 km2 | 353.55 km2 | 1771.51 km2 |
2012 weakly saline soil | 40.78 km2 | 379.57 km2 | 230.27 km2 | 45.22 km2 | 5.26 km2 |
2012 moderately saline soils | 22.93 km2 | 454.47 km2 | 464.74 km2 | 392.75 km2 | 2462.10 km2 |
2012 highly saline soil | 3.35 km2 | 81.27 km2 | 599.63 km2 | 844.82 km2 | 804.23 km2 |
2012 salted soil | 5.31 km2 | 118.93 km2 | 638.33 km2 | 653.48 km2 | 200.79 km2 |
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Zhang, Y.; Wu, H.; Kang, Y.; Fan, Y.; Wang, S.; Liu, Z.; He, F. Mapping the Soil Salinity Distribution and Analyzing Its Spatial and Temporal Changes in Bachu County, Xinjiang, Based on Google Earth Engine and Machine Learning. Agriculture 2024, 14, 630. https://doi.org/10.3390/agriculture14040630
Zhang Y, Wu H, Kang Y, Fan Y, Wang S, Liu Z, He F. Mapping the Soil Salinity Distribution and Analyzing Its Spatial and Temporal Changes in Bachu County, Xinjiang, Based on Google Earth Engine and Machine Learning. Agriculture. 2024; 14(4):630. https://doi.org/10.3390/agriculture14040630
Chicago/Turabian StyleZhang, Yue, Hongqi Wu, Yiliang Kang, Yanmin Fan, Shuaishuai Wang, Zhuo Liu, and Feifan He. 2024. "Mapping the Soil Salinity Distribution and Analyzing Its Spatial and Temporal Changes in Bachu County, Xinjiang, Based on Google Earth Engine and Machine Learning" Agriculture 14, no. 4: 630. https://doi.org/10.3390/agriculture14040630