What is tropical monsoon forest?

(Zheng)

Forests distributed in tropical areas with periodic alternation of dry and wet. It belongs to the zonal vegetation type in tropical monsoon climate zone. Also known as monsoon forest, moist semi-deciduous forest, semi-evergreen monsoon forest, etc.

Be distributed

Intermittently distributed in the monsoon tropical regions of Asia, Africa and America. Tropical monsoon forest is the largest area in Asia, and the community reproduction in Southeast Asia is the most developed. It is distributed in Deccan Plateau in India, dry-hot valleys and basins in Myanmar, Thailand, Laos and Vietnam, and places affected by dry monsoon in Kalimantan, Sulawesi, Irian and Timor. In Africa, the distribution is scattered, and the eastern and northern parts are often scattered between dry thorn forests and tropical grasslands, or form "corridor forests", which remain in local low-humidity valleys. In America, it is distributed in the La Plata Plain in the upper reaches of the parana river in South America and the Borborema Platform in Kayangas, along the coasts of the West Indies, Panama and Mexico. Under the special habitat conditions such as low-lying land and limestone in the south subtropical zone, the distribution of tropical monsoon forest often partially crosses this zone and becomes a non-zonal vegetation type. The northern boundary of China is basically near the Tropic of Cancer, that is, from the south of Taiwan Province Province to the south of Yangjiang, Gaozhou, Huazhou and Lianjiang in Guangdong, including the low-lying areas of Leizhou Peninsula and the plateau hills in the north, west and southwest of Hainan Island. Limestone hills, hills and valleys below 700 meters above sea level, such as Longzhou, Tian Yang and Napo in the south and southwest of Guangxi, and the valleys along the upper reaches of Hongshui River to the south of Guizhou; The wide valleys and valley terraces in the lower reaches of Mengding Sifang Well, Jinping Mengla, Xishuangbanna, Menglun, Nanding River, Honghe River, Lancang River and Nujiang River in southwest and south Yunnan are sunny slopes with an altitude of 700 ~ 1200m. It is also distributed in the south of Medog in southern Tibet. The annual average temperature in the region is 20 ~ 25℃, and the highest average temperature in Leng Yue is 10 ~ 13℃, with occasional light frost. Annual precipitation 1 0,000 ~1800 mm, and the seasonal distribution of rainfall is uneven. The monthly precipitation from May (4) to September (65,438+00) accounts for more than 80% of the annual precipitation. Dry and wet seasons alternate obviously, and evaporation is greater than precipitation. The soil is mainly latosol, red brown soil and various calcareous soils. The organic matter content is high, the decomposition is not as strong as that of tropical rain forest, and there is a thick deciduous layer.

trait

The dry season is obvious, the precipitation is less than that of tropical rain forest, and the annual temperature difference is large. The community height is low and the species composition is poor, but it belongs to the tropics. About 80% of the species in tropical monsoon forest of China belong to pantropical elements. Life-form plants with high buds account for about 70 ~ 80%, and deciduous trees account for a certain proportion in dry season. Lianas are mainly woody lianas, and most trees are climbed by lianas, mostly dicotyledonous plants in Xiyang. Herbs are the most common epiphytes, while orchids, ferns and woody epiphytes common in tropical rainforests are rare. The leaf area of trees is smaller than that of tropical rain forest, and the medium-leaved trees account for more than 60% (tropical rain forest accounts for more than 80%), but they still show the characteristics of tropical types (subtropical evergreen broad-leaved forest is dominated by lobules). The seasonal changes in tropical monsoon forest are obvious. Although some species bloom and bear fruit many times a year, most plants bloom and bear fruit once a year. About two-thirds of plants bloom in February-May, and the fruit ripens in August-September or11~ March. In the vertical structure, the tree layer can be divided into three layers, the tree height is generally below 25 meters, and individual trees can reach 37 meters. The first layer has a broad, sparse and unconnected crown, slightly straight trunk, low branches, short and curved branches, thick and rough bark and underdeveloped roots. The height of the second layer is10 ~15m, the number of species and planting density are larger than those of the first layer, the crowns are interconnected and the bark is smooth. The trees in the third layer are well developed in evergreen monsoon forest, with high plant density, and most of them are shade-tolerant trees. There are few trees in deciduous or semi-deciduous monsoon forest. The height of shrub layer is 0.5 ~1m. The herbaceous layer is sparse, and the coverage is only about 5%. Tropical monsoon forest in China can be divided into deciduous monsoon forest, semi-evergreen monsoon forest and limestone monsoon forest according to habitat conditions, appearance structure and species composition.

Tropical monsoon forest contains a variety of plant resources, especially tropical precious hardwood and economic plants such as oil, medicinal materials, fibers and dyes, as well as a wide variety of rare birds and animals. However, after a large number of development and utilization, the number of species has dropped sharply, and there are not many remaining virgin forests. On the basis of strengthening protection, we should actively develop and introduce precious and excellent tropical trees.

philology

China Vegetation Editorial Committee: China Vegetation, Science Press, 1983.

Guangdong Institute of Botany, Guangdong Vegetation and Science Press, 1976.