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Overview of Ailao Mountain Primary Forest

Penny FENG

1 Forest ecosystems:

Influenced by heat and moisture, the Earth’s surface exhibits spatial differentiation of vegetation, broadly classified into three major natural zones: forests, grasslands, and deserts. In China, grasslands predominate in the northern regions, particularly in Inner Mongolia, while deserts are primarily found in the northwestern areas, and forests dominate the northeastern and southwestern regions. Forests represent one of the most pivotal ecosystems on our planet, fostering the sustenance of numerous wildlife species and plants. Under conditions of adequate moisture, forests exhibit distribution patterns corresponding to varying latitudinal heat levels. Consequently, the forest natural belt, spanning from the equator to the poles, is categorized into several types, including the tropical rainforest belt, subtropical evergreen broad-leaved forest belt, temperate deciduous broad-leaved forest belt, and subfreezing coniferous forest belt and so on.

Forest ecosystems host the highest total biomass of living organisms on land, providing a vital environment and abundant natural resources for human habitation. They assume a crucial role within the global natural ecosystem and serve as a vital component of China’s ecological civilization construction.

2 Primary forest:

Within the distribution of forests, there exists a category of primary forests that remain untouched by human influence and display unique ecological characteristics. Termed as primary forests, or virgin forests, these ecosystems have not undergone significant disturbances by human activities. They tend to be situated in remote and less frequented areas, preserving the original state of the ecosystem. Primary forests boast a distinctive ecological structure and serve as habitats for numerous rare and endangered wildlife species and plant varieties, which are difficult to recover once destroyed. Nowadays, the virgin forests in China are basically classified as forest parks or nature reserves, and are well protected.

The Map of Forest Distribution in China

3 Ailao Mountains:

3.1 History and human:

The Ailao Mountains derive their name from the ancient Ailao Country, a primitive tribe that inhabited the region between the Nu River and Lancang River during the fifth century BC. In the first century BC, Emperor Wu of the Han Dynasty expanded his territorial dominion, annexing the Yunnan Plateau and designating it as the Ailao Country. The present Ailao Mountains once served as the eastern boundary of the ancient Ailao Country, thus attributing its name. Despite its geographical isolation, the mountain boasts a rich historical legacy. Notably, in the 1950s, archeological findings revealed the existence of the Kuchang people, the last primitive tribe in China still in the Stone Age, with a population numbering tens of thousands.

3.2 Geographic Location:

The Ailao Mountains are located in central Yunnan Province and belong to the remnants of the Yunling Mountains. Stretching from Chuxiong City in Chuxiong Prefecture to Luchun County in Honghe Prefecture, the mountain range runs in a general northwest to southeast direction, spanning a total length of approximately 450 kilometers. This region has been the ancestral domain of various ethnic minorities such as the Miao, Hani, Yi, Zhuang, Yao, and others for generations. The Ailao Mountains stand tall and majestic, generally rising above 2,000 meters above sea level, with over 20 peaks exceeding 3,000 meters. The highest summit, bearing the same name, reaches an elevation of 3,165.9 meters above sea level. Positioned at the convergence of three natural geographic regions-the Yunnan-Guizhou Plateau, the Hengduan Mountains, and the Tibetan Plateau-the Ailao Mountains hold a distinctive position within the low-latitude plateau mountains of southwestern China. Moreover, this area showcases remarkable biodiversity and a diverse range of flora species.

3.3 Climate characteristics:

3.3.1 Climate:

The Ailao Mountains experience a nearly perpendicular intersection with the southwest monsoon, resulting in year-round influence by this monsoonal system. This imparts clear vertical climatic zones along the mountain’s elevation gradient, characterized by successive transitions from southern subtropical, subtropical, northern subtropical, warm temperate, to temperate climates. In contrast to the eastern regions of China, the Ailao Mountains exhibit plateau mountain characteristics with “warm winters and cool summers.” Positioned on the edge of East Asia’s tropics, the Ailao Mountains serve as the transitional zone from tropical to subtropical development within Yunnan province. As a tall and extensive north-to-south range, the Ailao Mountains significantly impact the overall climate of Yunnan. The western and southern regions experience considerably higher precipitation compared to the eastern and northern areas, accompanied by higher temperatures at the same latitude and altitude. Additionally, the frequency of winter cold wave invasions is notably lower in the west.

3.3.2 River System:

In terms of the river system, the Ailao Mountains act as the watershed between the Yuan river and Amo river, which are part of the Red River system.

3.3.3 Geology and Soil:

The Ailao Mountains are characterized by fault-block formations that rise prominently along the deep and extensive fracture zone of the Red River. The core bedrock of the mountains primarily consists of deep metamorphic rocks, gneisses, and mélange rocks from the Yuanxian period, with ultramafic rocks from the Yanshan period and acidic granite bodies intruding into them. In the middle and lower sections of the mountain, exposures of Paleozoic and Mesozoic sand and shale mudstones are prevalent. The vertical zonation of soil types within the mountains exhibits distinct patterns, reflecting variations in geological and environmental factors along the elevation gradient.

3.4 Biological resources:

The Ailao Mountains region lies precisely on the north-south transition zone between the Pan-Arctic and Paleotropical zones, boasting an abundance of plant and animal resources. Due to the expansive breadth of the mountain range, the region exhibits more distinct changes in biological distribution, both horizontally and vertically. This vertical distribution across the tropics and subtropics establishes a corridor for north-south animal migration and serves as a biological species gene pool.

The primary vertically distributed forest types include warm and cool coniferous forests (hemlock forests, Huashan pine forests, etc.), warm coniferous forests (dominated by Yunnan pines), warm and hot coniferous forests (dominated by Simao pines), evergreen moist-leaved forests (comprising woolly-leaved cycad forests, gravels, mossy dwarf forests, and rhododendrons, among others), and deciduous broad-leaved forests (encompassing birch forests, mountain poplar forests, etc.), with shrub meadow vegetation found at the summits. Notably, the residual surface of the ancient plateau centered around Xujiaba houses nearly 6,000 hectares of dense, continuous, and intact forest cover, boasting a complex structure and extensive area, all carefully preserved and exhibiting minimal anthropogenic interference. Within this area, the dominant vegetation consists of subtropical montane moist evergreen broad-leaved forests, populated with various Yunnan endemic plant species.

The region showcases remarkable biodiversity, standing as the most comprehensive area globally in terms of biodiversity preservation and plant community conservation at the same latitude. In the northern-central portion of the Ailao Mountains alone, an impressive 207 families, 720 genera, and a total of 1,482 species of vascular plants (excluding mosses and lichens, etc.) have been documented, signifying the richness of local species. Furthermore, the Ailao Mountains Protected Area preserves numerous endemics, rare, and endangered national protected plants. Beyond plant diversity, the forest ecosystem of the Ailao Mountains hosts an extensive array of wildlife species, including several precious and rare varieties, and even newly identified animal species. Notably, recent discoveries include several new amphibian species like the Ailao Toad. The northern section of the Ailao Mountains currently records 26 amphibian species, 38 reptile species, 384 bird species, and 86 mammal species.

The Map of Forest Land Resources in China (2015)

4 Ailao Mountain National Nature Reserve:

The Ailao Mountain National Nature Reserve is situated on the northern and central ridge of the Ailao Mountains, precisely located in Xinping Yi Dai Autonomous County, Yuxi City, Yunnan Province, approximately 240 kilometers from the provincial capital, Kunming. It earned its designation as a provincial-level nature reserve in 1986 and was subsequently upgraded to a national-level nature reserve in 1988. Covering an area of about 546.67 square kilometers, the reserve spans 5 kilometers in width and 102 kilometers in length, making it the largest expanse of pristine montane moist evergreen broad-leaved forests in China.

The Ailao Mountain National Nature Reserve serves as a forest ecosystem-type reserve, primarily safeguarding the original forests and a diverse array of rare and endangered flora and fauna. It is exemplified by the montane moist evergreen broad-leaved forest and semi-humid evergreen broadleaf forest, both of which represent the dominant vegetation unique to the Yunnan Plateau. Within the same latitude zone of the Earth, this reserve boasts the most well-preserved and primitive area of montane moist evergreen broad-leaved forest. Furthermore, it stands as one of the world’s eight major migratory bird corridors and a significant gene pool of biological species. The reserve also holds the distinction of being the world distribution center of the nationally protected western black-crowned gibbon and has earned recognition as the “Man and Biosphere” forest ecosystem positioning observatory by the United Nations.

The subtropical evergreen broad-leaved forests within the Ailao Mountain reserve are all natural and meticulously protected, exhibiting impressive water storage and soil conservation capabilities, robust climate regulation capacities, and resilience against natural disasters. Additionally, these forests host a rich genetic gene pool of species, making the reserve a prime site for scientific research, teaching internships, and science and technology education initiatives. The Ailao Mountain National Nature Reserve’s importance extends beyond the urgent preservation of subtropical broad-leaved evergreen forests in the eastern and central regions of China. It also stands as an irreplaceable and ideal research area for studying ecological sample zones along the eastern edge of the Qinghai-Tibet Plateau. The monitoring, research, and protection of primary forests in this reserve hold immense significance for addressing cutting-edge scientific issues in ecology, such as global change, biodiversity conservation, and sustainable development. Furthermore, these efforts provide a crucial scientific basis for the rational development of natural resources in subtropical mountainous regions.


Tang AQ, 2021. Analysis on the characteristics of soil physical and chemical properties and soil quality along the altitude gradient in the East and West slopes of Ailao Mountains National Nature Reserve[D].

Web-1:Geographical distribution of forests in China– The Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences

Web-2:Encyclopedia of China Publishing House — Ailao Mountain, Zhongshan wet evergreen broad-leaved forest landscape, Ailao Mountain National Nature Reserve Etc.

Geographical Information Monitoring Cloud Platform (Map download)

Chen H, Gong HD, LU ZY, et al. Temporal and Spatial Variations of Soil Nutrients in the Montane Moist Evergreen Broad-leaved Forest in Ailao Mountains[J]. Journal of West China Forestry Science, 2022, 51(02):74-79.

Song L, Yang B, Liu LL, Mo YX, Liu WJ, Meng XJ, et al. Spatial-temporal differentiations in water use of coexisting trees from a subtropical evergreen broadleaved forest in Southwest China. Agricultural and Forest Meteorology 2022; 316: 108862.