Using Modified Remote Sensing Imagery to Interpret Changes in Cultivated Land under Saline-Alkali Conditions

Abstract

Abstract:Managing the rapidly changing saline-alkali land under cultivation in the coastal areas of China is important not only for mitigating the negative impacts of such land on the environment, but also for ensuring long-term sustainability of agriculture. In this light, setting up rapid monitoring systems to assist decision-making in developing sustainable management plans is therefore an absolute necessity. In this study, we developed a new interpretation system where symbols are used to grade and classify saline-alkali lands in space and time, based on the characteristics of plant cover and features of remote sensing images. The system was used in combination with the maximum likelihood supervised classification to analyze the changes in cultivated lands under saline-alkali conditions in Huanghua City. The analysis revealed changes in the area and spatial distribution of cultivated under saline-alkali conditions in the region. The total area of saline-alkali land was 139,588.8 ha in 1992 and 134,477.5 ha in 2011. Compared with 1992, severely and moderately saline-alkali land areas decreased in 2011. However, non/slightly saline land areas increased over that in 1992. The results showed that the salinization rate of arable lands in Huanghua City decreased from 1992 to 2011. The moderately saline-alkali land southeast of the city transformed into non/slightly saline-alkaline. Then, severely saline-alkali land far from the coastal zone west of the city became moderately saline-alkaline. Spatial changes in cultivated saline-alkali lands in Huanghua City were such that the centers of gravity (CG) of severely and non/slightly saline-alkali land moved closer the coastline, while that of the moderately saline-alkali land moved from southwest coastal line to northwest. Factors influencing changes in cultivated lands in the saline-alkali ecosystem included climate, hydrology and human activity. Thus, studies are required to further explore these factors in order to build a better understanding into the relative contributions of the changes saline-alkali state on the functions of coastline ecosystems.

Dynamic changes in water and salinity in saline-alkali soils after simulated irrigation and leaching

“…These indoor experiments simulating the dynamic changes in water and salinity in saline-alkali soil revealed that after multiple irrigations of the soil column, the pH, conductivity, and total soluble salt content of the percolation samples were all higher than those of the initial water samples. With additional irrigation applications, these parameters gradually decreased in the percolation samples, consistent with the results in [ 23 ].…”

“…The pH, conductivity, and total soluble salt content values decreased overall, reflecting desalination in the simulation. When the 20–70 cm layer of the soil column was irrigated, the total salt content in the bottom layer of the soil column became 2.21–3.42 mg/L, representing a general decrease from initial values of 2.35–3.84 mg/L [ 23 ]. With increasing irrigation applications, the contents of all salt ions in the soil from Huanghua increased initially then decreased, reflecting resalinization and the considerable impact of soil moisture transport on K + , Na + , and Cl - .…”

Can Arable Land Alone Ensure Food Security? The Concept of Arable Land Equivalent Unit and Its Implications in Zhoushan City, China

“…However, from the history of reclamation in Zhoushan City, salt land or breeding ponds were built first and they gradually evolved into arable land thereafter with the improvement of soil. The tidal flats developed through concentrated reclamation in recent years may only be used for aquaculture [21,32]. Therefore, the newly increased aquaculture waters from tidal flats developed by reclamation should be identified beforehand as newly increased arable land.…”

Land Use Change Impact on Flooding Areas: The Case Study of Cervaro Basin (Italy)

“…Incorporating processed satellite data within hydrological models has become a promising approach for better and accurate quantifications of water resources in river basins [8,9].…”