Where does Longnan belong?

Longnan is a prefecture-level city under the jurisdiction of Gansu Province. Located in the southeast of Gansu Province, Qinba Mountain area, bordering Shaanxi, Nantong and Sichuan in the east and Shaanxi, Gansu and Sichuan provinces in the east. Known as "the key of Qin Long, the throat of Bashu".

Longnan is the only region in Gansu Province with the Yangtze River system and subtropical climate, and is known as "Longshang Jiangnan". Mountains, valleys, hills and basins crisscross the territory, and the climate is vertically distributed, with obvious regional differences. There are national protected plants such as Metasequoia glyptostroboides and Taxus chinensis, and more than 20 rare animals such as giant pandas and golden monkeys. There are 2 national nature reserves (Baishuijiang National Nature Reserve in Gansu and Yu He National Nature Reserve), 1 provincial nature reserve/kloc-0 (Jianshan Giant Panda Nature Reserve in Wenxian County), 3 national forest parks (Tianchi in Wenxian County, Guan 'egou in Tanchang County and Jifeng Mountain in Chengxian County) and 2 national wetland parks (Huang Lin Gou National Wetland Park in Wenxian County and Meiyuanhe National Wetland Park in Kangxian County).

Longnan climate

The climate in Longnan city is divided into three types in horizontal distribution: north subtropical zone, warm temperate zone and middle temperate zone. The northern subtropical zone includes the southern part of Kangxian, the southern part of Wudu, the eastern part of Wenxian and the shallow mountainous areas of Bailong River, Baishui River and Jialing River basins. In this area, there are two high calorific value areas in the city. One is the valleys and shallow mountainous areas along the Bailong River and Baishui River. The annual average temperature is 2 ~ 14℃ ≥ 10℃, the accumulated temperature is 4,000 ~-4,800℃, the precipitation is about 600 mm, and the cultivated land area is about 300,000 mu, accounting for 6.7% of the total land area of the city. It is a two-hot agricultural area. The other is Jialing River Basin and Huicheng Basin; Annual average temperature 10- 12℃, accumulated temperature ≥ 10℃, 3500-4000℃. The cultivated land area is about 1.7 million mu, accounting for 37.8% of the total cultivated land area in the city. This is an agricultural area with three crops in two years.

The warm temperate zone includes the central, eastern and southern parts of the city, with an altitude of1/kloc-0-2,000m, an accumulated temperature of ≥ 10℃ of 2100-4,000℃, rainfall of 500-800mm and the curvature of cultivated land of about1.

The middle temperate zone includes the northern and western parts of the city, mainly in most areas of Dangchang and Xihe County, Jinchang, Maying and Chiba in Wudu District, and the lower four districts of Lixian County. The cultivated land in this area is generally over 2000 meters, the accumulated temperature is ≥ 10℃ and less than 2 100℃, and the annual minimum temperature is below -20℃. The cultivated land area is about 6.5438+100,000 mu, accounting for 22.2% of the total cultivated land area in the city. It is an agricultural area with three crops.

The topography of Longnan:

According to the overall difference of landforms and the different degree of regional cutting, the whole territory of Longnan can be divided into three types of landforms:

Shallow-middle cutting landform area of hilly basin in shallow mountain area

This area includes Chengxian, Huixian and all counties in liangdang county in Huicheng Basin. The west Qinling is divided into two branches, north and south, which extend into this area, forming a long trough-shaped fault basin with an altitude of 800-2700 meters. The northern part of the mountain is cut by the North Qinling fault, with an altitude of1500 ~ 2,700 meters and a relative height difference of about 500 meters. This is a shallow mountain area with gentle terrain. Shallow mountains have been reclaimed as farmland, while deep mountains have dense water conservation forests with good vegetation coverage. The southern part belongs to the south Qinling horst-type mountain area, with an altitude of about1900 ~ 2,400 meters and a relative height difference of about 500~ 1000 meters. It is a cutting mountain area in the middle. The gentle slope hilly basin in the middle is 800 ~1300m above sea level, with a relative height difference of less than 200m and a slope of less than 20 degrees. Sichuan dam land is scattered among hills, with thick soil and abundant water resources, which is a concentrated grain producing area in history.

Cut the middle-high mountain landform area in the middle depth.

This area is a crisscross between the western extension of South Qinling and the eastern extension of Minshan Mountain, including the whole territory of Kangxian, Wudu and Wenxian, with an altitude of about 900 ~ 2,500m, most of which are located south of 33 degrees north latitude and belong to the subtropical marginal zone. Due to the staggered distribution of mountains, ravines and valleys, most of the cultivated land in this area is sloping farmland, with thin soil layer and many stones, and poor water and fertilizer conservation ability. However, the climate is good, belonging to the transitional zone between north and south, with warm temperate zone and tropical climate in North Asia. It can not only produce grain, but also be an ideal suitable area for rare medicinal materials and rare tree species such as Wendan, Angelica sinensis, Astragalus membranaceus, olives, tea, and Dahongpao pepper.

All-cut middle-high mountain landform area

The area includes three counties: Dangchang County, Lixian County and Xihe County, with an altitude of 968~4 100 meters and a relative height difference of 300~500 meters in Gu Feng. Hadapu, Lichuan and Nanyang in Tanchang County, banks of the Western Han River and its tributaries in Lixian County, and banks of Shui Yang and its tributaries in Xihe County. The relative height difference is small, the terrain is gentle, the river valley is wide, the contiguous land area is large, and there are many small mountain plains, among which Xili Basin is located. In the lower reaches of the Western Han Dynasty, the mountains are steep and narrow, with many dry lands and scattered land, but there are more cultivated land, with a large area of grassland and land resources that can be developed and utilized.