Studies On Man-Made Forest Configuration Under Multiple-Objective Condition

Global warming is the severest situation we are facing, and experts from all the world are devoting to the research of the fixed carbon and reducing carbon emissions.Based on plentiful researches, professionals found that forest is the largest carbon pool in the terrestrial ecosystem, so it is an efficient way to slow down global warming by enlarging the area of woods in order to increase the amount of the fixes carbon in terrestrial ecosystem. Artificial forests, the most important part of forests, play a significant role in ecological protection and economy development, however, the lack of theory instruction and effective and appropriate measures during the early period of artificial forest building fails to bring the ecological, economical and social effects. For this reason, optimized allocation aiming at artificial forest will be the important contents for forests development. Taking into account the current international climate situation,we should not only make great efforts to play the ecological function of artificial forest,but also improve its carbon sequestration capacity, so that it can play a more solid carbon function. So that the carbon fixation benefit as the target to update the artificial forest is an effective measure to exert great potential of the artificial forest. The trend of the world’s forest resources is a general decline, how to have the quality of the artificial forest configuration and play its function and potential is our urgent need to solve the problem.Being the first county to put artificial forests into practice, Aohan County, in Chifeng Inner Mongolia, enjoys a large area of artificial forests and a complete age sequence, which is why we select this place as our research are. On the basis of comprehensive investigations of different kinds of soil, age sequence and different trees,the research analyzes the carbon sequestration effect of main artificial forests in Aohan County, and especially discussed the trend of carbon sequestration against the tree ages.This essay, which was made according to the understory vegetation variety of artificial forests, analyzes the stability of different artificial forests grown on different kinds of soil by adopting the method of grey relational analysis. This essay also discusses the trend of soil volume weigh, porosity and nutrient with the trees age growing, and evaluates the soil improvement effect thoroughly by analyzing and calculating the physical and chemical nature of the understory vegetation. According to the above research result,updating the artificial forest satus of Aohan county, and determine the optimal structure of land use and the proportion of tree species. This paper provides scientific evidence for multi-aimed artificial forests optimized allocation research firstly through the trend surface analysis of carbon sequestration, stability of artificial forests and soil improvement effect, and this method makes the results more intuitive. The above three research contents as the target of the construction of artificial forest structure, updated plantation and obtained optimal land use structure and tree species proportion. The objective of this paper is to provide scientific instruction for the forestry construction in Aohan County, and scientific evidence for ecology construction in the middle-east Inner Mongolia.The following conclusions are drawn from research（1）Based on the analysis of carbon sequestration effect of different kinds of soil and trees, especially the trend of different trees ages carbon sequestration effect and the influence on carbon density of tree layers, the paper provide scientific evidence for artificial forests optimized allocation. Evidence shows that, the feature of these superior carbon pools form 7 major artificial forests: soil carbon pool>tree layer>bush layer>litter layer>herbaceous layer. Average carbon sequestration rate of tree layer from Pinus tabulaeformis, Ulmus pumila and Larix principis-rupprechtii are : immature forest >near-mature forest>young forest>mature forest; Average carbon sequestration rate of tree layer from simon poplar are: young forest>immature forest>near-mature forest>mature forest >over-mature forest. The carbon sequestration rate of prunus armeniaca forest bush layer increases then goes down,the carbon sequestration rate is the largestwhen the tree age is 14a;The carbon sequestration rate of Hippophae rhamnoides increase rapidly first, then slow down, the carbon sequestration rate is the largest when the tree age is 15a;The carbon sequestration rate of Buxus microphylla Lam also increase rapidly then slow down, the highest carbon sequestration rate of different kinds of soil appears in different ages, the peak rates in chestnut soil, cinnamon soil and sandy soil are:9a,11 a,and 6a accordingly.（2） Artificial forest coverage rate and the diversity of understory herb are used to analyze the stability of artificial forests, which is aimed to improve the benefits of ecology,carbon sequestration,economy and social benefits.By analyzing the diversity of artificial understory herb,the author found that the forest coverage rate of superior trees appears in descending order as bellow:Cinnamon soil>Chestnut soil>Brown earth>Meadow soil>Aeolian sandy soil.The stability of ecological system and the tree age are presented in negative correlation which exists in Pinus tabulaeformis forest,Populus simonii,Larix principis rupprechtii, Ulmus pumila stand, Prunus armeniaca stand and Hippophae rhamnoide forest grown in different kinds of soil.The ecological stability of Buxus microphylla forest stand from different kinds of soil tends to slow down after increase,and when tree age reach 20 a,the forest stand is in the highest crown density,while the understory vegetation tends to reduce owing to the limited sunshine and water fertilizer spatial.（3）From the comprehensive analysis of soil improvement effect of artificial forests,the relation between the physical nature（unit weight and porosity） of the earth and the chemical nature（organic matter, total nitrogen, total phosphorus, total potassium）and the tree ages, the author thinks that the soil improvement effect of Pinus tabulaeformis,Ulmus pumila,Prunus armeniaca, Hippophae rhamnoide forest and Buxus microphylla forest stand from different kinds of soil will gradually increase according to tree ages. The soil improvement effect of Populus simonii will be the largest when tree age is 15 a,generally speaking, before 15 a, the effect strengthens gradually,while after 15 a, it tends to slow down. The soil improvement effect of Larixprincipis-rupprechtii presents in a decreasing tendency which proves that the pure forest soil fertility tends to reduce.（4）The carbon sequestration effect of Pinus tabulaeformis forest,Ulmus pumila,Prunus armeniaca and the stability and soil improvement effect of artificial forests are relative.When the stability and soil improvement effect enlarge,so does the carbon sequestration effect;while the similar relation of Hippophae rhamnoides,Populus simonii and Buxus microphylla are not evident.（5）The paper made a through research on the optimized allocation based on multi-aimed conditions, some adjustments to area of the land using type, also carried out some optimized allocation to the area of forests kinds and tree kinds by AHP.Therefore,the essay got the reasonable percentage on forest land,cultivated land,grassland,construction land, water filed and unused land are50.98%,20.41%,10.02%,11.04%,3.74% and 3.81%.The percentage of pure forest stand area are :Pinus tabulaeformis forest13.76%,Populus simonii20.40%,Ulmus pumila20.35%,Prunus armeniaca8.09%,Hippophae rhamnoide forest9.18%,Buxus microphylla fores2.30%,mingled forest22.89%. After optimized allocation, the carbon sequestration effect,soil improvement effect and forests stability has been enlarged, with carbon storage 2.80×10¹⁰kg,increased by 0.87×10¹⁰kg,1.45 times as large as before.We should reduce the proportion of artificial pure forest, and increase the area of the mixed forest in Aohan County. Replant other species in the existing artificial pure forest gradually update or replace now woodland, to finally be able to play the ecological benefit and solid carbon benefits of stable system. Artificial forest configuration has a strong system and complexity, so it needs to be further studied.