The geographical environment of Dailing District

Dailing District is affiliated to Yichun City, and Dailing Forestry Experimental Bureau is an enterprise directly under the Heilongjiang Provincial Forest Industry Administration. Dailing District is located in the south of Yichun City, at the southern foot of Xiaoxing'an Mountains. The geographical coordinates are 128°37′46″~129°17′50″ east longitude and 46°50′8″~47°21′32″ north latitude. The territory is generally spindle-shaped. The southeast and northwest directions of Dailing District are 78 kilometers long, and the southwest and northeast directions are narrow, only 8 kilometers, with an average width of 12 kilometers. As of 2012, the administrative division area of ??Dailing District is 1,041 square kilometers, and the forestry operation area is 96,742 hectares.

Dailing has become land as early as ancient times (about 800 million years ago). After many crustal ups and downs, changes in sea and land, and after the Yanshan Movement and Himalayan Orogeny, the landform outline was formed.

The geological structures of Dailing are mostly folds; from the cross-section, the fold lines are mostly northeast-southwest, and there are micro-faults in some parts of the southwest.

Dailing is divided into the northern mountains of the Yongcui River Basin and the southern mountains of the Daqingchuan River Basin. According to the type of landform formation, it can be divided into erosion-accumulation terrain, slope skirt and accumulation terrain, and floodplain. The local area is covered by Quaternary strata. The upper part is dominated by loamy clay, and the lower part has more gravel. This layer is in pseudo-conformity contact with granite and is distributed in rock layers in the floodplain zone. It is divided into loamy clay, medium-fine sand, gravel and pebbles.

The mountains in the northern part of Dailing have deep rivers, narrow ditches and gentle terrain. There is Luchui Mountain with an altitude of 1090 meters. The mountain range is 120-173.2 meters. The flat slope below 5 degrees is 10.8%, the gentle slope is 88.4%, and the steep slope is 0.8%. The southern mountains have wide ravines and shallow rivers, and the terrain varies greatly. There are four high mountains with an altitude of more than 1,000 meters, including Daqing Mountain and Laohuang Mountain. The mountainous terrain is undulating from 143.8 meters to 182.2 meters, with flat slopes below 5 degrees accounting for 17.2%, gentle slopes accounting for 74.6%, and steep slopes accounting for 8.2%. Although there are many high-slope areas, there are no mid-to-high mountain areas. Dailing is located in the mid-temperate zone and has a continental humid monsoon climate. Affected by the dual influence of Siberian cold air and the Pacific monsoon, winters are long, dry, cold, and snowy; summers are humid and warm.

Temperature

The annual temperature in Dailing varies greatly. The annual average temperature is 1.4℃, and the monthly average minimum temperature is -19.4℃. The annual minimum temperature is in January, with the lowest temperature reaching -40℃, the monthly average maximum temperature is 20.9℃, and the annual maximum temperature is in July, with a maximum temperature of 37℃. The frost-free period is about 115 days throughout the year. Generally, the first frost is after September 14th, and the last frost is before May 20th of the following year. However, there are also years when freezing damage occurs until the end of May.

Rain and Snow Amount

The annual average rainfall in Dailing is 661 mm, and the maximum annual rainfall is 836.5 mm. The rainfall period lasts about 130 days throughout the year, mostly concentrated in July, August and September, accounting for more than half of the annual rainfall. The precipitation from January to February is relatively low, generally between 44 and 46 mm, while the precipitation from July to August is relatively high, generally between 160.5 and 174.8 mm. Winter is snowy, and the snow gradually thickens from November and begins to melt at the end of March the following year. The maximum snow thickness sometimes exceeds 100 cm.

Wind direction

Dailing winds mostly blow from the northwest in winter and southwesterly in spring and summer. The average wind speed is 1.38 meters per second, and the maximum wind speed is 10 meters per second. The windiest season is mostly in April and May in spring.

Sunshine

Dailing has 2156 hours of sunshine throughout the year, with the longest sunshine time in June and the shortest sunshine time in January.

Soil

Due to the cold winter in Dailing, the soil freezes in mid-November every year and thaws in mid-April of the following year. The frozen layer is thickest in January, with a maximum depth of 2.15 meters, and begins to thaw in early April. Due to the influence of air temperature and deep ground temperature, the upper and lower layers of frozen soil thaw at the same time, but the upper layer thaws faster. By June, most areas have completely thawed. Island-shaped permafrost appears on some shady slopes and in the birch forest area at the head of the tower.