The northern line of mountain and national orchid distribution

Kunlun-Qinling Mountains is a complete mountain system of 5OO0km across China. Kunlun Mountains are full of snowy peaks, glaciers, volcanoes and hot springs. From Pamir to Sichuan Basin up to 2500km, elevation 500O-7000m, the main peak Muzitag Mountain 7723m high, snow line high 55O0m, ice thickness 200m, known as the "father of icebergs", Guolan can not survive.

Qinling Mountains, from the border between Gansu and Qinghai provinces in the west, and central Henan in the east, with a full length of 15OOkm. The topography at the top of the mountain is smooth, showing the shape of a plateau, indicating that it is a flat land, and the weathering layer is also very deep. The mountain is high 22O-3000m, and the main peak Taibai Mountain is 3767m high. The fault falls on the north side and the mountain is majestic. There are glaciers, trough valleys, corner peaks and so on. Like a wall against the wind, it intercepts the cold current going south and turns the Sichuan Basin in the south into a warm area. For example, although the elevation of Chengdu (30 degrees 40 degrees N) is 5O8m, it is the same as Hangzhou (30 degrees 14 degrees N) where the elevation is only 43m, with an annual average of 16.2 degrees. It also blocks the moist air going northward, making the north of the mountain an arid area. For example, the annual precipitation in Xi'an (34 degrees 18N) is only 580.2mm, while that in Xuzhou (34 degrees 17n) is 848.1mm. Therefore, the Qinling Mountains is the dividing mountain between the north and the south. The south of the mountain is warm and suitable for the growth of the orchid, while the north of the mountain is dry and cold (the annual precipitation in Xi'an is 580.2mm, the average annual precipitation is 13.3 degrees), which is not suitable for the growth of the orchid, which is consistent with the regionalization of Chen Xinqi.

The hills of central Shandong were formed by a dome on the basis of crustal thickness 35km 500 thousand years ago and gradually plunged into the flat North China Plain. At the top of the dome is Mount Tai (elevation 1524m). Mengshan (1156), Lushan (1108), Yishan (1032) and other fault block mountains. The most famous Mount Tai is composed of gneiss, granite and limestone. The composition of gneiss and granite is the same, and the weathered soil is acidic, such as the chestnut garden on the west slope of Mount Tai. The weathered soil in lime is alkaline. However, the mountains in central Shandong are mainly limestone, so there is a lack of acidic soil. Only acidic soil is suitable for orchid growth (editor's note: both weakly acidic and neutral soil can produce orchid, alkaline is not suitable).

There are mountains in Liangshan County and Jiaxiang County in Shandong Province. These two counties may be the places where Confucius returned to Lu from northern Henan. The mountain area is limestone formed by long-term deposition under the water depth of 60m. The soil formed by this kind of rock weathering is alkaline, which is not conducive to the growth of national orchid. (Wang Tao)