0959-B3
Zhou Mei Zhang Qiuliang 1
There are a lot of environmental problems of forest in Daxinganling in the northeast of China. The negative effects of permafrost degradation, the original wetland decreasing and the neonatal wetland increasing, the freeze-thawing erosion and forest fire on forest are analyzed in this article. The local government and environmental scientists should pay attention to the problems.
Forest is one of the most important environments for human being and the existing of forest is depending on its environment. Daxinganling in the northeast of China is the largest virgin forest and the unique cool-temperate forest in China. The Daxinganling mountain range is composed of low mountains and hills and its orientation is from the northeast to the southwest. Daxinganling inhibits the cool wind from Siberia and Mongolia Plateau to the southeast, so it maintains the natural environment of Sunnen plain. The health of the Daxinganling forest ecosystem is the living base to the residents in the local area and in the northeast of China.
There is a popular thought that the trees is very dense and there is not much environmental problem. After the implementation of natural forest resource protection plan, people think that the environmental problems are derived from large-scale forest cutting and the environmental problem will be cured after a while. But the actual situation is not in this way. The environmental protection function of Daxinganling forest is degrading drastically and induces a series of grave forest environmental problem such as permafrost degradation, the original wetland decreasing and the neonatal increasing, the freezing-thaw erosion and increasing recycle of forest fire. The forest environmental problems such as such as permafrost soil degrading, freeze-thawing erosion and forest fire are some special attributes compared with the other forest regions. The decreasing of permafrost soil induces all these problems. If the specific regional problem can not be solved, it will affect the sustainable development of Daxinganling region and the northeast of China. By the way, the forest environment of Daxinganling is part of the natural resource to local people. It is related with the economic development and local environmental protection.
Accepted date: Revised Date:
Foundation project: National natural science foundation (398399370, 39960021); 15 important project of forest bureau of China.
Introducing of the author: Zhou mei (1960-), female,(Mongol) , born in jinzhou of Liaonin province, vice professor, Ph D. candidate. The main research areas are forest hydrology, soil and water protection.
Daxinganling, which is in the cool temporal, main land seasonal wind climate, has Clear Mountain climate attribute. The average temperature is -2 ~ -5 in the southeast and -5~-7 in the north. The lowest temperature is -52.3, which is the lowest recording temperature. The permafrost soil of high latitude in China is mainly distributed in this area and it is the south edge of permafrost soil of Euron-asian land. The average atmosphere temperature and soil temperature affects the origin and distribution of permafrost soil. With the differentiation of temperature, the height of permafrost and the connection extent, the permafrost soil in Daxinganling is divided into 3 types: the connected large area permafrost, island-thawing permafrost soil and island permafrost soil. The permafrost soil height of the first type can reach to 115 meters. During the 4 million years of ice age and internal ice age, the mountains of Daxinganling are eroded into round mountain topography. The permafrost in that area is affected mainly by climate condition. With the increasing of green house gas increasing, the temperature increasing will be the main weather-developing trend. The distributing area of permafrost is decreasing drastically. Compared with the prosperous time of last ice age, the south edge of permafrost soil in Daxinganling has withdrawn 100-150 km to the north. The research indicates, with 10% increasing of temperature and precipitation, the south edge of the forest in the northeast will move 3~5 latitude degree to the north. At that time, the forest will move out to China and the forest will be displaced by temperate grassland and coniferous and broadleaf forest.
The permafrost soil is in that area is affected not only by climate, but also by local human being activity. The permafrost soil in yakeshi, Jagedaqi and Dayangshu disappeared in 1950`s. The temperature increases 0.7~2.1 in the north of Daxinganling where the permafrost soil is preserved best up to now.
2.1.2 The affection of permafrost degrading to forest and environment
The exist of Forest and permafrost soil are depended with each other. With the permafrost soil, the roots of Larix Gmilinii are distributed in the shallow soil and the thawing of ice in permafrost soil provide fresh water for the growth of the trees. In the other hand, forest decreases the soil temperature and maintains the existing of permafrost. By drilling in Dayangshu, the permafrost soil still existed in 1960`s and it disappeared when it is drilled again in 1978. With the disappearing of permafrost soil, the virgin Larix Gmilinii was displaced by ????.
2.2.1 The attribute of freeze-thawing erosion
The topography in Daxinganling has the attributes of round top of the mountain and broad ditch and stream. Daxinganling is in the place of cold and wet topography developing area, the topography in this area is developed mainly by freeze-thawing erosion. The main forces of freeze-thawing erosion are frozen weathering, freeze-swell erosion and snow erosion. The typical freeze-thawing erosion topography is stone mountain, stone sea, stone river, peat mountain, ice mountain, ice-erosion concave land. There is no vegetation in these areas. For the dense vegetation in this area, the wind and water erosion to soil is very light.
The Freeze-thawing erosion in Daxinganling is influenced by latitude, altitude and low temperature climate. It is also influenced by permafrost soil. Freeze-thawing erosion is mainly distributed in medium and low mountains in the north reach of Daxinganling mountain, especially distributed in connective large-area permafrost soil region and island permafrost soil region. The freeze-thawing erosion is more drastically compared with water and wind erosion. To an area of 3060 m2, the total erosion quantity is 2142m3 for 3 years. From it, the erosion intensity is 26.67*104 t/km2.a
2.2.2 The erosion of freeze-thawing influences forest environment.
The forest vegetation furnishes a insulator surface for heat quantity of atmosphere input to soil. The existing of forest prevent the occurring of freeze-thawing erosion. When forest is cut, the heat balance will be destroyed, the freeze-thawing erosion will develop very quickly. From many years' study, when the forest is cut, the freeze-thawing erosion will occur in that area. The freeze-thawing erosion cannot be recovered, and the erosion quantity is very large to one specific erosion. The soil erosion has much more effect than that in Yellow Soil Plateau. With the extent increasing, the soil structure is changed, soil decreases down. With the soil structure change, the support function of soil to forest will lose and the trees will fall down. From our study, the area enlargement of soil decrease induced by freeze thawing reaches to 30 meters. Freeze-thawing erosion is one of the most important destroying forces to forest in Daxinganling.
2.3.1 The wet land of permafrost soil
The wet land area is the largest in all of the forest region of China. The special attribute of the wetland in Daxinganling is the existing of wetland depended on permafrost soil. Permafrost soil inhibits water permeate downward and forms wetland. This type of wetland is formed by nature and is affected less by human beings than the other types.
With the climate becomes warmer and human activity increasing and decreasing of water consuming of forest vegetation, permafrost soil thawing height is increasing, the potential water quantity is increased and more water is accumulated in the concave area. This is the reason of the neonatal wetland increasing. In some area, this type of wetland can be formed 3~5 years later when forest is cut. The trees cannot be cultivated in his type land and even though the seedling is alive, it can not live normally. The existing condition and the origin of water need to be studied.
2.3.2 The affection of wetland to forest environment
The wetland of Daxinganling is the fresh water source of local water resources and maintains the permafrost soil environment. The existing of some forest vegetation depends on permafrost soil. ?? Larix Gmilinni forests` vegetation, -----------------reside on connective large-area permafrost soil or island permafrost soil. The degradation of permafrost soil induces shrinking of wetland, the wetland on the permafrost destroyed also induces the enlargement of the thawing area of permafrost soil and thinning of the height of the permafrost soil. By the experience of change the wetland in the origin of the three rivers into cropland, the wetland of Daxinganling started to plant trees in the wetland by getting rid of water. This method disturbs the wetland environment and results in the enlargement of the thawing area of permafrost soil. The thawing of permafrost soil results in the water accumulation in the wetland again. At this time, when the water in the wetland is got rid of, the local area will be short of water resource. The wells became dry, after planting in the wetland for 10 years in Genhe which are in the north side of Daxinganling. The activity of changing wetland into forest is still going on in Daxinganling.
From the other side, the area enlargement of the neonatal wetland increasing results in the forestland to become wetland. While human being changes the wetland into forest, some of the 10s or 100 years` forests are becoming wetland. The shrinking of the original wetland and extending of the neonatal wetland will destroy the stability of the ecosystem and reduce the productivity of the forest
Daxinganling is one of the most grievous forest fire occurring places and is the t main lighting forest fire occurring place. Spring is the most frequent fire occurring season. Although the forest fire owns some positive effects to environment, the uncontrolled fire has disaster destroy to forest. The forest fires had taken place totally 1674 times, the forest area of fired is 82*104hm2 which equals to 12 times of the forest planted by human beings from 1962~1985 in Daxinganling. The average fired wood is 58*104m3 every year. The largest forest fire after 1949, which was taken place in 1987 and sustained 27 days, fired 133*104hm2 forest land which is 1% of the forest land of China, consumed 85*104m3 wood.
2.4.2 The influence of forest fire to forest environment
Besides large economic loss, the influence of fire to environment is concerned also. Most of the forest fires in Daxinganling are surface fire which clear the brushes, litters and grass in the land and ameliorate, change the stucture of the forest, decrease the density of the forest, increase the light intensity and ground temperature in forest, thaw the permafrost soil. Soil erosion takes place in some of the fire site, because the thinness of the vegetation. Some of the fire sites are resided by grass temporally and some of the lands depress and become neonatal wetland.
Another negative effect of forest fire is it disturbed the natural succession procedure. The natural reproductivity is very good for normal cutting and light fire. But the intense forest fires will result in destroy the seed pool of trees and some of the coniferous will become birch forest. From our study, the fire site of 1987 which normally should be reproduced in 10 years had not been reproduced until 1997.
The permafrost in Daxinganlin is the south edge of the permafrost of Europe-Asia continent, the thickness of the permafrost is very thin and is very sensitive to ascending of atmosphere temperature and the disturbance of land surface. So, the dynamics of the permafrost in Daxinganlin should be monitored as a long project. The specific location of it is the a special monitor area for forest site research in China.
3.2 The natural forest protection project should be connected with protecting permaforst, for forest of Daxinganlin is affected drastically by the climate change.
3.3 The strategy of encourage the local residents immigrate to the other region and decreasing the activity of the human being to land is the basic method to decrease the effect of hot island.
3.4 Managing forest based on different forest functions should be realized with fast speed. This strategy is the the foundation to realize socially and economically sustainable development in Daxinganling region.
3.5 Enforce the study to the mountain disaster of Daxinganling.
The fragile ecosystem of daxinganlin mountain needs to be protected drastically. It is not possible to inverse the unfavorable situation that is produced by the wrong decision of the past. The foundation of protecting forest and realize sustainable development is scientific decision. The forest environmental problem should be studied deeply.
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1 Forest department of Inner Mongolia Agriculture University 010010
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