Spatiotemporal variations of soil salinization in China's West Songnen Plain

Abstract

Preventing soil salinization and improving soil productivity play vital roles in achieving the Sustainable Development Goals (SDGs), the premise of which is understanding the spatiotemporal patterns of soil salinity in various ecosystems. To improve regional ecosystem management decisions, we examined the spatial variations and temporal changes of soil salinity in China's West Songnen Plain by separately developing prediction models of soil salinity for vegetated and nonvegetated areas (VEA and NEVA) through the combination of field samples, LAND-SAT series images, and the partial least square regression (PLSR) method. Twelve variables, encompassing spectral bands, vegetation, and soil salinity indices, were extracted from LANDSAT satellite images. Among the investigated variables, the enhanced vegetation index (EVI), red band, and digital elevation model (DEM) yielded the best results for assessing the soil salinity in VEA. In contrast, the green band and SI2 exhibited the most significant correlation with soil salinity for NEVA.Based on 10-fold cross-validation, models predicted soil salinity with R 2 values of 0.812 and 0.803. Results reveal that the salt-affected areas in the West Songnen Plain were estimated at 1.23 Â 10 6 hm 2 in 2016 with evident heterogeneous distribution. Intensively salt-affected area (IA) and moderately salt-affected area (MA) are mainly distributed in the low-lying central and northern regions of the plain. From 1991 to 2016, the salt-affected area experienced a rapid increase followed by a slight decline with a peak in 2000. This suggests effective soil amelioration due to ecological projects and a wetter climate, however, the salt-affected area still had a net increase of 0.32 Â 10 6 hm 2 . The variation of different saltaffected levels was characterized by an increase in slightly salt-affected area (SA), MA, and IA. Cropland was the dominant land cover type affected by soil salinization, with the affected area expanding from 0.39 Â 10 6 hm 2 in 1991 to 0.57 Â 10 6 hm 2 in 2016. MA and SA were the dominant levels of soil salinization in grassland, with MA expanding by 1.3-times from 1991 to 2016. Although the area of soil salinization increased from 1991 to 2016, the salt-affected area was reduced, and the salt-affected level was downgraded in some parts of the study area after 2000. These results could provide support for monitoring soil salinization in other regions, with the findings expected to benefit ecosystem conservation and

Reclaimed saline‐alkali paddy field may be a hotspot of methane and ammonia emissions

“…According to the previous investigation on grades (light, moderate and heavy) and distribution of saline‐alkali land in Songnen Plain, (Yu et al, 2021; Yu et al, 2023), saline‐alkali paddy soils with different reclamation years developed from areas with similar initial saline‐alkali levels before reclamation, were collected from Da'an City, Jilin Province, China, which is located in the Songnen Plain hinterland. The saline‐alkali levels of the soil in Songnen Plain generally decrease with increasing reclamation years due to the downward migration of salt dissolved from surface water and the removal of salt by field drainage (Xu, Shao, et al, 2020).…”

“…As one of the three most important saline‐alkali soil areas in the world, the Songnen Plain in Northeast China occupies an area of 1.70 × 10 7 ha, accounting for more than 19% of total saline‐alkali soils (Wang et al, 2003). In 2016, light, moderate and heavy saline‐alkali areas accounted for 69.02%, 11.59%, and 19.39% of the saline‐alkali areas in Songnen Plain, respectively (Yu et al, 2023). Rice cultivation, with a history of 70 years in the western Songnen Plain, is considered as the most acceptable strategy for the rational use of saline‐alkali soils (Huang et al, 2016; Zhao et al, 2018), and the reclaiming of saline‐alkali land into paddy fields has been increasing in recent years (Yu et al, 2021).…”

Soil Salinity Estimation by 3D Spectral Space Optimization and Deep Soil Investigation in the Songnen Plain, Northeast China

“…In contrast, it is warm and rainy during the summer-autumn seasons. The annual average precipitation is 400~500 mm, but the annual average sunshine time is 3000 h, and the annual evaporation discharge is more than 1200 mm [39,40]. These special geographical and climate conditions (flat terrain, low precipitation, intense evaporation, high groundwater level, and freeze-thaw action) lead to the enriched accumulation of soil salinity, and anthropogenic activities seem to make it worse.…”