The geographical environment of lishi district

The geological structure of lishi district is dominated by Lvliang-Taihang fault block, and only the northwest (west of Matoushan) belongs to the eastern edge of Ordos fault block. During this period, folds and faults developed very well. The upper Ordovician, Silurian, Devonian, Jurassic and Cretaceous strata are missing in this area, but there are Archaean (Jiedaokou Group and Luliangshan Group), Proterozoic (Yejishan Group), Paleozoic (Cambrian, Lower Ordovician, Middle Ordovician, Carboniferous and Permian) and Cenozoic (Tertiary and Quaternary).

Lishi district is located in the hinterland of Luliang Mountain. Its terrain is high in the east and wide in the west, low in the west and narrow in the west. There are many mountains and few rivers in the territory. Beichuan River flows from north to south, Dongchuan River flows through the whole territory from east to west, and the two rivers meet in the southwest of the city, then go to Jiaokou Street, and then the Chuanhe River in Henan Province leaves the country and flows into the Yellow River. The highest point is Jigu Mountain in the northeast of the area, with an altitude of 2535 meters, and the lowest point is Sanchuan River Basin, with an altitude of 889 meters. The eastern part of the territory is an alpine mountain area with an area of 266.6 square kilometers, accounting for 20% of the total area of the region. It is the main forest area in China, suitable for developing forestry and animal husbandry. In the northeast of the city, there is a continuous mountainous area of Mao Liang, covering an area of 398.4 square kilometers, accounting for 30% of the total area. Matou Mountain and Wanglaopo Mountain in the west of the city span the north and south, and are hilly and gully regions of loess, covering an area of 660 square kilometers, accounting for 50% of the total area. The rocky mountainous areas and loess hilly areas account for 80% of the total area of the whole region, with mild climate and little rain, but great potential for development and production, and are domestic miscellaneous grain producing areas; The central part is a valley area dominated by Beichuan and Dongchuan, with fertile land, abundant water resources and concentrated population. It is an important grain and vegetable base in China.

From the southeast to the northeast edge of the area, Luliang Mountain runs through the north and south as a barrier, mainly the "Guandi Mountain Dome Uplift", which starts from Jigushan in the north and reaches Xuegongling in the south, and is connected with single mountain Slope Mountain in Zhongyang County, with a length of about 80 kilometers, all of which are branches or residual veins of Luliang Mountain. The branches of Jianshan Mountain are Xiaoshentou and the mountain in the south of Xinyi. It is east-west, starting from Song Houmao in the east and reaching Wangyingzhuang in the west. It is about 30 kilometers long and is opposite to Beihai Mountain in the south across the Beihai Trench. It has forest vegetation in the east and sparse forests and intensive irrigation in the west. A branch of the Beihai Mountain System, which runs in the northeast direction, is located to the west of Chenjiata and Wangzhizhuanggou (Wucheng Fault) and extends to the north ridge of Youfangping in the southwest. It passes through the branch of Jianshan Mountain, about15km long, with dense forest and shrub vegetation. Starting from the branch of Yunshan, it is the mountain range south of Dadongchuan, which runs east and west. It starts from Xuegongling in the east, extends to Rutian Mountain in the southwest of Donggou, Wangyingzhuang, and is bounded by Zhongyang in the south, with a length of about 35 kilometers. Mostly dense shrub and grass vegetation. In the north-central part of this area, North Street is in the north, with Yulin Mountain and Shuangshan Mountain, which run north and south and extend to fangshan county. There are Matou Mountains in the northwest of the territory, from north to south to west, from north to fangshan county, and from south to Zaolin fairy mountain. At the junction of the west and Liulin County, there are Wanglaopo Mountain and Wutongyan Mountain, both of which are east-west. hydrology

Surface water in the territory belongs to the Yellow River system. Except the area west of Matoushan in the west belongs to Suishui River, and Xihua Town in the east belongs to Sanchuan River, the rest belong to Sanchuan River. Because it is located in the loess plateau in western Shanxi, the terrain is high in the northeast and low in the southwest. Dadongchuan, Xiaodongchuan and Beichuan are fan-shaped and the valleys are dendritic. Under the cutting of nature, shallow ditches, deep valleys and rivers have developed water systems and dense water networks, forming a natural landscape with continuous mountains, undulating ridges, criss-crossing gullies and orderly valleys. There are 387 ditches over 1 km, including 307 ditches under 3 km, 43 ditches over 3-5 km, 28 ditches over1km and 9 ditches over1km. The basin area of Sanchuan River accounts for 7 1% of the total basin area of the whole region, reaching 946.6 square kilometers. There are 6/kloc-0 springs with water volume less than 2L/ s in the whole region, which are mainly distributed in Pingtou Township (1 1), Zaolin Township (8), Xishuba Street (4), Chengbei Street (6), Lianhua Street (1) and Hongyan Chuan Township. There are 7 springs with water volume greater than 2 liters/second, namely Wucheng Grottoes Spring, Youfang Pingquan, Lianhuachi Spring, Mamaozhuang Spring, Xiangshuiyan Spring, Beihai Spring and Longshan Spring.

land

According to 1980 soil survey, the total soil area in the whole region is 187370 mu, which can be divided into 5 soil types, 13 subcategories, 44 soil genera and 93 soil species. Subalpine meadow soil is distributed in Nanyunding Mountain, which is above 2200m above sea level in the northeast of this area, at the top platform and gentle slope of Shili Saima soil, with a total area of 1700 mu. There is only one subclass of this soil in this area, which is divided into one soil genus and one typical soil species according to the parent material type, namely limestone subalpine meadow soil. Brown soil is widely distributed in mountainous areas such as Jigu, Beihai and Genting. The altitude is about 1, 800 ~ 1, 850m. The sunny slope is slightly higher, and the outer position of gully and shady slope is lower, with a total area of 96,500 mu. The soil types in this area are divided into three subtypes, including 12 soil genera and 12 soil species. Loessial soil is located in the loess hills and some low mountain valleys, with an altitude of about 800 ~ 1800 meters, which is an important agricultural soil in this area. The soil is divided into 3 subtypes, 24 soil genera and 60 soil species, with a total area of 1747650 mu. Cinnamon is distributed in Xihua Town, Miaodi and Zhuanger to the east of Luliang Mountain, with an altitude of about 1, 690 ~ 1, 850m. There are only two typical soil genera in this area, which are divided into three soil species with a total area of 6630 mu. Meadow soil is distributed in the floodplain and the first terrace on both sides of the East and Beichuan rivers, which is an excellent agricultural soil in this area. Indigenous species are divided into 3 subtypes, 5 soil genera and 17 soil species, including loessial soil, light meadow soil and salinized light meadow soil, with a total area of 2 1 190 mu. The surface vegetation in lishi district is influenced by many factors such as topography, climate, hydrology and altitude. Moreover, the geomorphic units are very different, and the distribution of vegetation communities is complex. Vegetation is good in the northeast, but poor in the central and western regions. The vegetation coverage rate in the whole region is less than 30%.

Forest vegetation is mainly distributed in the bedrock mountainous areas in the northeast, mainly in Jigu Mountain, Genting Mountain, Jianshan Mountain, Beihai Mountain and other mountainous areas, mostly in Xinyi and wucheng town, with a forest coverage rate of 29.6%. It is the best place in the county, with an area of 266.6 square kilometers, accounting for 20% of the total area. It is the main forest area and forestry base in the whole region. Above the altitude of 1800 m, it is mainly covered by coniferous forests, and at the altitude of 1400 ~ 1800 m, it is a mixed forest of coniferous trees and dense shrub vegetation.

Shrub vegetation is mainly distributed in the rocky mountainous areas in the central and western regions. Except Matou Mountain, fairy mountain Mountain, Yulin Mountain, Shuangshan Mountain and Qiyun Mountain in the southeast, the rest are on steamed bread-shaped and circular undulating beams. The shrubs are mostly Vitex negundo, vinegar willow, Lespedeza, Daouri and so on. Grass is a xerophytic weed, including Artemisia, Phragmites communis, bothriochloa ischaemum and Setaria viridis.

Sporadic grass shrub vegetation is mainly distributed in loess plateau and Sichuan valley, accounting for half of the total area, which is the key farmland cultivation area in the whole region. There are mugwort, Shapong, Setaria viridis, reed, bothriochloa ischaemum, amaranth and Xanthium sibiricum. Common shrubs on cliffs, ditches and graves are Vitex negundo, Lycium barbarum, jujube, papaya and Lespedeza. Vegetation coverage is small, generally between 5 ~ 10%, and the highest can reach 20%.