Landscape Pattern Changes At County Scale And Relationship Between Landscape Types And Soil Characters

Studying on landscape pattern change and its environment effect play an important role in correlation study field , and the importance are ever increasing. The thesis focused on the response to the landscape pattern on the land use pattern and the driving factors in terrain transition belt of western Sichuan, Minshang County, which is combination of the relative integrity of landform types, and economic development mainly in agriculture. Study effects of landscape pattern change on topography with taking Minshang county administrative district for a case. Meanwhile, taking the county's tea plantation as an example to study soil fertility and soil organic carbon after land use change.The main results were as follows:(1) It was a typical agricultural country of Mingshan County, and forestland paddy and dry land were the main land use types. However, the land use structure changed greatly from 1975 to 1999, especially from 1999 to 2005. The garden plot , residents and construction respectively increased gradually, forest land and aaters decreased gradually ,but dry land first increased and then decreased from 1975 to 2005.The garden plot change percentage was10.96%, which is the biggest number of all the land use types, the second was residents and construction.The number of large landscape patches more and more redued, which of control effect increasingly weak on the hole landscape, while patch numbers more and more incresed.Then the landscape structure compex and fragmentation strengthened year by year from 1975 to 1999, but weakened from 1999 to 2005.Topography, climate precipitation were the important natural driving factors of landscape pattern changes in Mingshan, residents saving balance,the primary,secondary and tertiary industries , construction investment and total retail sales of consumer goods were the important social driving factors.(2) The distribution characteristics of landscape elements in different geomorphology region changed much in Minshang county administrative district from 1975 to 1999. Forest land area is 43.787 percent of the whole study area in 1975, which of landscape background ranked respectively first in the distribution of other landscape types in low mountain areas, high hill areas and middle hill areas. Paddy fields dominated the landscape in low hill areas.Paddy fields dominated the landscape in low hill areas. Substantial expansions of the city Mingshan County, which of this area became an important factor in landscape pattern. Agricultural activities expand to the terrain higher regional. The middle hill areas in the landscape of paddy fields and dry land increased rapidly, and became for the major land use. The distribution of dry land occupied the first, followed by paddy fields, the garden plot also had a certain amount of distribution in high hill areas. The garden plot had been a larger expansion in the lower hill areas. Conclusively, Human disturbance interference of land system became more ferocity, and the landscape was complex structure, and the pattern broken during this period. Landscape pattern from 1999 to 2005 was to maintain the basic pattern state in 1999. Residents and construction continued to grow, particularly significantly in low hill areas. The total patch number reduced, and the mean patch area increased, with patch shape index and patch fractal dimension decreased in low and middle hill areas. Paddy field and dry land reduced, but the garden plot increased in high hill and low mountain areas. The trend of breaking fragmentation decreased.(3) Land use changed into tea plantations in lowmountain and hilly region, Minshang County. Grit in the soil of tea plantation which accounted for 39.13% is highest, next is the clay, the third is the silt. The average value of pH in soil is lower than 4.5, which numerical value is below the standard of the soil in high quality tea plantation. The soil is enriched in available N with low content of soil organic matter, total N, and available P. There is not significant change in available K. Contents of soil particle and available nutrient have no significant law compared with waste land and forest land. Organic matter and total nitrogen of tea plantation is lower than waste land and forest land respectively except which is higher than waste land on lower slope. The soil fertility quality of tea plantation is changing dramatically with the change of slope position. The value of PI (-13.64 %) on middle slope position is lower than upper slope (0 %) and lower slope (14.39 %) with taking the uphill position as the datum. The value of QI in tea plantation is lowest compared with waste land and forest land. It for tea plantation, waste land, forest land is 0.56, 1.11 and 2.73 respectively.(4) The content of soil total organic carbon (TOC) in tea plantation followed the variety trend of middle slope < upper slope < lower slope, existing difference significantly (p<0.05) between middle slope and lower slope. TOC of middle slope was lower than that of upper slope and lower slope 9.38 %,13.95 % respectively. The content of water-soluble organic carbon (WSOC) was significantly (p<0.05) lowest in middle slope. Meanwhile, WSOC of middle slope was lower than that of upper slope and lower slope 33.33 %,38.82 % respectively. The variety trend of easily oxidized organic carbon (EOC) was the same as that of WSOC .EOC of middle slope was lower than that of upper slope and lower slope12.25 %,18.83 % respectively. There were significant positive correlation between WSOC and TOC, TN(r=0.940,p<0.01,r=0.966,p<0.01), EOC and TOC, TN(r=0.995,p<0.01,r=0.960,p<0.01),WSOC and EOC(r=0.947,p<0.01). Most of humus composed of loosely and tightly combined forms, following the order of middle slope < upper slope < lower slope. The ratio of loosely combined humus to tightly combined humus was higher than which of forest land on the same slope. The fulvic acid (FA) of loosely combined humus showed lowest on middle slope, but little higher than humin acid (HA) on other slopes. HA of tightly combined humus was higher on slope, while the maximum appeared on middle slope. The value of HA / FA of tightly combined humus was higher than that of loosely combined humus.