What is the range of tropical and southern subtropics in China?

According to the second division standard of climatology in China, climatic zones are divided by temperature indexes such as heat, and climatic zones are divided by dryness. Therefore, China's subtropics are divided into north subtropics, middle subtropics and south subtropics; The tropics are divided into north tropics, middle tropics and south tropics. See table 0- 1 for the heat and temperature indexes of each district.

Generally speaking, the accumulated temperatures of ≥ 10℃ and 6500℃ can meet the heat demand of perennial thermophilic plants in the south subtropical zone to successfully complete a growth cycle within one year, so they can be used as the starting point for dividing hot zones. Due to the topographical characteristics, the thermal efficiency in southwest China is high, with the starting point of its hot zone ≥ 10℃ and the accumulated temperature of 6000℃. The starting and ending period of ≥ 10℃ is similar to the starting and ending period of frost-free period, and it is also the starting and ending period of warm-loving plants, so the length of growth period can be measured by the number of days with accumulated temperature ≥ 10℃. The average temperature in Leng Yue is ≥ 10℃, which shows that the temperate plants in the south subtropical zone are basically not inhibited by low temperature and can grow normally in winter. The extreme low temperature in 2008 reflects the extent to which warm-loving plants may suffer from low temperature damage in winter. China belongs to monsoon climate zone, with hot summer and cold winter. Many areas are not due to insufficient accumulated temperature, but because the winter temperature is too low to be classified as hot areas. Therefore, the most Leng Yue average temperature (inhibitory low temperature) and the annual extreme minimum temperature (lethal low temperature) are taken as restrictive indicators.

Table 0- 1 division index of climate zones in South China and Southwest China

Note: According to the climate of South China and Southwest China.

According to the above criteria, the northern boundary of China's tropics and south subtropics is roughly located in Fuzhou-Yongchun-Hua 'an-Longyan in Fujian, Jiaoling-Heping-Qujiang-Lianshan South in Guangdong, Hexian Central-Xiangzhou-Luzhai-Donglan-Tianlin in Guangxi and Guangnan East-Funing-Kaiyuan-Huaning in Yunnan. In addition, there are two "enclaves" to the north of this line, namely, the dry-hot valley of Jinsha River at the junction of Sichuan and Yunnan and the north-south valley of Hongshui River in southwest Guizhou.

The dividing line between the south subtropical zone and the north subtropical zone is roughly along the lines of Dongshan-Zhangzhou-Nanjing-Xiao Yun in Fujian, Chaozhou-Puning-Huizhou-Huadu-Zhaoqing in Guangdong and Rongxian-Hepu-Nanning-Baise-Daxin-Longzhou in Guangxi. The vertical change of altitude in Yunnan has greater influence on climate than latitude, and it is no longer divided into north and south.

The dividing line between south subtropics and tropics is located in the south of Taiwan Province Province in the east, in the north of Leizhou Peninsula in Guangdong Province in the middle, and in the west, it is scattered on the contour lines of some low-heat valleys in southern Yunnan at an altitude of 300m (east) to 750m (west).

The tropics include the southern part of Leizhou Peninsula, Hainan, Xisha and Nansha.

The climate in Yunnan is mainly influenced by horizontal zonality and vertical zonality. Generally speaking, areas below 300 ~ 750 m above sea level are hot spots. The measured hot spots are distributed in the valleys, flat dams and low-altitude mountains of the six major river basins, and most of them extend upward along the river valleys in a tree shape. Any place above a certain height is not a hot spot. Some counties and cities outside the hot zone (north) will also have some sporadic small environments with hot zone climate types, such as dozens of counties such as Luxi, Yuxi and Chuxiong in central and northern Yunnan; Jinyang and other counties in Sichuan in Jinsha River basin; Zhenfeng and other counties in southern Guizhou. A small area of hot soil is small and scattered, and it is not marked on the map.

There is a transition zone with a certain width between climatic zones. When developing fruit trees with high growth conditions in the transitional zone, we should pay special attention to microclimate changes caused by topography, choose favorable topography and take all measures to avoid or mitigate natural disasters.

The hot area in China is about 480,000 km2, accounting for about 5% of the national territory. See Table 0-2 for the area and proportion of hot zones in each province.

Table 0-2 Statistics of Hot Areas in China Provinces

Note: 1. According to the statistics of the provinces; 2 * Counties containing land in tropical areas are counted.