Study On The Landscape Features And Ecological Environment Effect Of Semi-Karst Region

Guizhou as a typical example of karst development zone, wide distribution of karst and unique ecological environment constitute the characteristics of the situation of important elements in Guizhou. Research and exploration about the karst ecological environment has always been the focus of academic circles. In this paper, based on TM, GF-1, ZY-3, ALOS, etc high resolution remote sensing image as data source, with geological lithology map, topographic map data, which based on the data of field investigation and statistical data. In comprehensive physical geography, landscape ecology and thought under the guidance of system science and other disciplines, from the karst geological lithology and the landscape pattern of development, draw lessons from academia on karst research and experience, to discuss the concept of "semi-karst", landscape characteristics and ecological environment effect etc are discussed in this paper. The paper research mainly has the following conclusion:(1) From the perspective of geological lithology, semi-karst development is mainly constituted by impure carbonate rocks and interlayer of carbonate rocks and non-carbonate rocks. Impure carbonate rocks mainly include the argillaceous limestone and argillaceous dolomite, the most typical is middle Triassic Guanling Formation(T2g). Interlayer lithology combination zone include dolomite with clay rock, clastic limestone, limestone with clay rock, clastic rock with clay rocks, Argillaceous limestone and shale, etc. The formation mainly is Daye formation(T1d), Ziyun formation(T1z) and Luolou formation(T1l). In a word, rocks mostly contain high argillaceous composition, due to a high content of acid insolubles, so corrosion rate of rocks is relatively slow, fast soil formation rate.(2) From the perspective of geomorphologic landscape, due to the inherent rock properties of semi-karst area, The main types of topographic form contain depressions, hill and valley, shallow low hills, low and middle hill, deep in the mound, shallow cutting low and middle mountain, middle mountain, etc. Terrain fluctuation and surface cutting level are relatively small; slope is nearly between 8 to 35 degree. Karst cave development degree is not high, few underground karst caves distribute, underground karst water is given priority to with carbonatite karst water, runoff modulus are relatively high, groundwater resource is rich, surface water shortage are not as serious as in typical karst area, peak cluster and peak forest are rare. A case study of a typical study area, low and middle hill has a 739.97 km2 and low and middle mountain has a 662.59 km2 in Guiyang city, accounted for 36.84%, 32.98% of the semi-karst region; Zunyi, low and middle mountain has 1107.47 km2, accounted for 69.3%, deep in the mound has 305.03 km2; however, low and middle hill has a 758.22 km2 and accounted for 59.12%, is the mainly geomorphologic types.(3) From the perspective of effect of soil vegetation, The soil layer is relatively thick and soil covered continuously in semi-karst region, the soil type is mainly include yellow soil, yellow brown soil, lime soil and paddy soil, etc. Soil acidity and alkalinity is suitable, most pH distribution between 5.2~6.9, suitable for the growth of trees and crops. Semi-karst regions have a large amount of cultivated lands, land has high agricultural value and production capacity. The vegetation is evergreen broad-leaved shrub forest, evergreen broad-leaved forest, evergreen coniferous forest and shrub, Such as Pinus massoniana a growth in acid soil, the alkaline soil on the growth of cypress and rattan thorn bushes, with drought and calciphilous characteristics. The secondary sex is stronger, the cultivated land and vegetation are distributed, the vegetation coverage is higher, the ecological effect is more obvious, and the stability of the ecosystem is relatively high.(4) From the perspective of land use transition, from 1995 to 2015, regional land use morphology changed greatly, part of the land use function transformation happened. Living land, ecological land area showed a trend of obvious increase, productive land area is reducing year by year. Main types of transformation are the conversion from agricultural productive land into urban and rural living land and forest ecological land,as the same time, The agricultural productive land also partially changed to grassland ecological land and forest land ecological land use. living land has been increased by 198.78 km2 of the semi-karst region in past 20 years, Its rate of increase of slightly faster than the typical karst region. Ecological land use in 2015 increased to 2760.42 km2, increased during 239.62 km2, While the area of agricultural productive land in a large scale reduction, reduced 438.39 km2 in a total of 20 years, year fell 21.92 km2.(5) From the perspective of ecological environment effect, the ecological environment is basically stable and the ecological environment quality index is increased year by year, the ecological environment index were 0.5402, 0.5397, 0.5523, 0.5397 and 0.5523. The typical karst region ecological environment quality is more stable on the whole, ecological environment index fell slightly last five years. From the point of view of the contribution rate of land utilization on ecological environment, there are two kinds of change trend about ecological environment improvement and ecological environment deterioration at the same time in the semi-karst region. Leading to ecological environment quality improvement is mainly agricultural productive land into woodland ecological land, grassland ecological land and water ecological land; however, caused by the deterioration of the ecological environment is mainly agricultural productive land into urban and rural living land, grassland ecological land and woodland ecological land into agricultural productive land, but the trend of ecological environment improvement is greater than that of the ecological environment deterioration.(6) The semi-karst, as a special part of karst ecological environment, is a typical ecological sensitive and ecological fragile zone, it is a transitional topographic form between typical karst and non-karst. The difference between the typical karst and semi-karst landscape difference is mainly lithologic, include carbonate rock purity and stratigraphic interlayer combination, the result of regional differentiation is not only embodied in every element of the natural geographical landscape, but also in the whole landscape appearance and structure. Semi-karst interior landscape with inpure lithology is relatively homogenous, interlayer combination of semi-karst landscape structure is relatively complex, from small scale to see its internal heterogeneity, and from the larger scale to see of semi-karst landscape effect obvious.