Spatio-temporal Coupling Relationship Between Fractional Vegetation Cover And Soil Salinity On Saline-alkali Land

Soil salinization is one of the world's five disasters causing great damages to economic development and ecological environment, and China is one of the most affected countries sufferring from land salinization, which totally contains an area of about 3.5 × 107hm2 saline land, while Bohai low plains have 2.67 million hm2 in low-yielding fields and 666,700 hm2 saline wasteland that needs to be reformed and improved. To acquaintance the status of soil water and salinity, characteristics of vegetation distribution and coupling relationship of temporal pattern for the transformation of saline means a lot to improve saline efficiency, protect arable land and secure food supply.This study selects Wudi County in Shandong Province as investigation area by using methods of datum inquiring, field surving, RS&GIS and statistical analysing.By analysing the fractional vegetation coverage(FVC), and spatiotemporal variation of temporal soil salinity variability in study area 2013-2015, it mainly investigates the temporal coupling relationship between soil water&salinity and FVC. The results are as follows:(1) The result of FVC RS temporal variability analysis shows, within the studying area FVC levels from southwest(high) to northeast(low), consistent with the topography and soil spatial pattern of the county. From 2013 to 2015, it shows overall normal FVC features in summer(high) and winter(low), but for the abnormal climate changing impacts, the year 2013&2015 each presents abnormal phenomenon of high level in winter and low level in spring. According to the magnitude of the change of vegetation coverage changes during the year of a comprehensive index the study built a ratio, it divides the type of FVC into 5 types(highly stable, moderate stability, low and stable, unstable and extremely unstable) and each of them shows unique characteristic obviously.(2) Based on the grid method, according to research purpose and the characteristics of studying area presents ideas of soil water and sal sampling point laying out in accordance with local reality, using of field and laboratory check-speed measurement method of combining soil water and salt to obtain data.Soil surface salinity 2013-2014 in Wudi County statistics shows that soil salinization totally is moderate, but there exists a strong variation in the horizontal direction. By abnormal weather and waterfall inteferencing, soil salinity appeared ?high in spring while low in winter ?. Spatial analysis of soil salinity using inverse distance interpolation(IDW) method shows that soil salinity levels from high northeast territory to low southwest generally, meanwhile the local topography, groundwater depth, fresh water sources and use patterns could also cause different characteristics. Later fall in 2013 to winter in 2014, it shows a generally upward trend in soil salinity, varying degrees of salinity with the regional distribution of hydrothermal conditions render sizing phenomenon. Under the conditions of floods in summer & autumn 2013 and prolonged drought 2014 while the Yellow River water supply no longer contents, it occurs the boundary area of mild salinization and moderate to severe salinization area moves southward on the occasion of the 2014 summer&autumn, while mild saline area of is greatly reduced and severe salinization area presents to increase.(3) Quantitative analysis of soil water and salt and FVC show temporal coupling changes between different vegetation types based on distinct salinity contents according to the rank in order "bare land> S.salsa> reed> grass> cotton, jujube> wheat-corn" from high to low. Correlation analysis showes that the FVC and soil salinity are negative correlated, and its degree of negative correlation was not significant change in different seasons. The Arcgis principal component analysis(PCA) of soil water and salt and FVC shows a negative correlation curve fitting vegetation coverage and salinity content is exponential(R2 = 0.9931).This paper analyses the change and the coupling variation law of temporal Wudi County saline land FVC and water-salt correlation, resulting in consistent with the findings of field investigations. This study could provide information support and references to regional saline soil improvement and land use&land cover change(LUCC), assessment and management.