Study On Temporal-Spatial Variability Of Soil Nutrient And Evolvement Of Landscape Pattern In The Wenxihe Valley

The temporal-spatial variability characteristics of landscape and soil nutrient were studied by using GIS and remote sensing technical, index of landscape and transition matrix by Markov in the Wenxihe valley in the northern Sichuan Slopes. In addition, the spatial situation and dynamic variety trend was simulated. The results showed that:From 1982a to 2004a, the diversity and fragmentation of landscape in the study area became big, the dominance of landscape diminished. In evolvement, the fragmentation of dryland, paddyland, orchard and rural decreased, but which of forestland increased and of water did not change obviously. The order of the average value of various landscape fractal dimensions was forestland> water> rural> dryland ,> paddyland>orchard. From the process of the landscape pattern evolvement, the trend of the fractal dimension of dryland, paddyland, orchard and rural was increased slowly, but the forestland was decreased. By the method of transition matrix by Markov, the trend of landscape pattern change characteristics during 2010 and 2020 was analyzed, the results show that, the proportion of the forestland was diminished; and the dryland, paddyland, orchard, water and rural were all increased during the last 22 years.This paper analyzed the content of soil organic matter (SOM) in 1982 and 2004, the results showed that, the content of SOM in northeast and southwest of study area was increased, in the middle did not change, and in local part was declined. As a whole, the content of SOM in 69.7% of total area was increased; the others were decreased during the last 22 years.In 1982 the soil total nitrogen (STN) content had the linear trend from east to west and from north to south. In additionally, it was gradually lowered from northwest to southeast. The description of the STN was parabola in 2004; the central parts of study area were slightly higher than other parts. The content of STN and SAN all were decreased, the decreased area percentages were 95.99% and 78.60%, respectively; the increased were 4.01% and 21.40%, respectively.Compared to 1982, the content of soil total phosphorus (STP) was decreased, but soil available phosphorus (SAP) was increased in 2004. During the latest 22 years, the increased area of STP and SAPwas 4.75% and 75.63%, the decreased was 95.25% and 20.37%, respectively. Among them, the increased area of STP was existed in the north region of Tuditang; the decreased area of SAP was existed in the northwest of Maohuoshan and in the north of Shangligou.Compared to the 1982, the content of soil total potassium (STK) was declined, but the content of soil available potassium (SAK) was increased. As a while, the percentage of increased and decreased area to the total area of STK was 81.82% and 18.18%, respectively; of SAK was 38.22% and 61.78%, respectively.Compared to 1982, the content of SOM, SAP and SAK was increased in forestland, and the content of STN, SAN, STP and STK was decreased. In dryland, the content of SOM, STN, SAN, STP and STK was declined, and the content of SAP and SAK was increased. In paddyland, the content of SOM, SAP and SAK was increased obviously, but the content of STN, SAN, STP and STK decreased.The change of the landscape would bring on the change of soil nutrient content. When the type of the landscape was transformed form forestland to dryland, the content of STP and STK was decreased; the content of SOM, STN, SAN, SAP and SAK was increased. When it was changed to paddyland, the content of SAN, STP and STK was decreased; the content of SOM, STN, SAP and SAK was increased.Along with the increase of landscape variety and fragmentation and the decrease of domination, the storages of SOM, SAP and SAK in the study area were increased; the storages of SAK, STN, SAN, STP and STK were decreased. Compared to 1982, the isolation diversities of forestland and paddyland were increased, and the fractal dimension of them were decreased; the isolation diversity of dryland decreased 19.00%, and the fractal dimension increased. The storages of soil nutrient were decreased in forestland except SAP. In dryland, the storages of soil nutrient were increased except STN and STP. In paddyland, the storages of STN, STP and STK were decreased, and others were increased.