The Research On Forest Ecosystem Health Envaluation And Early Warning In East Dongting Lake Area

Based on the second-class investigation of forest resource in Yueyang city, typical plot survey, forest resource management information system in Hunan province,TM remote sensing image and environment monitoring network system, the forest ecosystem health envaluation and early warning in East Dongting Lake area were taken as the main research objective in this paper. The quantitative evalution on the state of forest health in the studied area was carried out at small patch level,region level and landscape level. Then the paper carried out early warning of the state of forest ecosystem by BP neural system and the evaluation of forest eco-service in researched region was implement. At last,some existing problems that affected forest health were be analysed and corresponding countermeasures were be put forward in East Dongting River area.The forest ecosystem health evaluation of East Dongting Lake area from sublot,landscape and regional level respectively was carried out in the paper,a. The paper firstly carried out forest ecosystem health evaluation of East Dongting Lake area at sublot scale by selecting14index including diameter at breast,the height of tree,the stocking volume of unit area,natural update status,community structure, forest canopy density, near natural degree, thickness of soil, soil organic matter, soil content of N、P、K, forest fire, plant of diseases and insect pests through the second-class investigation of forest resource in Yueyang city, typical plot survey, forest geography information system in Hunan province. Then determined index weight based on the method of factors variance contribution rate.calculated the health score and carried the health classification in small patch.level. High quality in in small patchs was14,health76,sub-health221, insalubrity18.occuping respectively the total area proportion of7.33%,24.62%,61.34%,6.71%, holding the selected sample amount of4.25%,23.1%,67.17%,5.47%.Accoring to result of the study, the health state of forest ecosystem in East Dongting River area was not healthy, the situation is likely to be more serious unless good protection and powerful management.In order to improve the forest health state,high management level,powerful measures and effective omplement should be adopted. b. The paper launched forest ecosystem health evaluation of East Dongting Lake area at landscape scale.The two phase data of landsat TM remote sensing image which was shot in2006,2009covering East Dongting Laker area can be obtained.Based on the platform of ENVI4.9remote software,image enhancement,image cutting and geometric correction were all preprocessed.the land use type map of two phase can be get through ArcMap module of ArcGIS software which can implement space superimposed analysis.The rasterized images can calculate the14related forest landscape index with fragstas3.3software, then the paper got comprehensive analysis through landscape index in4aspects which covering the pattern of elements, shape characterstics,heterogeneity and, diversity and spatial ditribution.The mixed forest and coniferous forest was the region’s main advantage landscape types, further more better patch area、more complex distribution and better connection were the main characteristics. Scatter and low distribution and low patch shape were bamboo forest and grassland’s main characteristics, samller edge density and plaque density, higher broken degree were also their outstanding features.The result was from human factor to greate degree. Then bigger patch shape index、complexed boundary shape and higher integration of patches were mixed forest.coniferous forest and forest’s main characteristics. The index refeleted stronger self-adjustment ability and better maintainace in forest health.Higher shannon’s diversity index reflected the patches distribution’s diseequilibrium in regional landscape,much more not qualitative information and lower heterogeneity.And higher shannon’s evenness index explained the difference in proportion of landscape types, so there were advantagoues landscape,such as higher heterogeneity in mixed forest and relatively lower heterogeneity in bamboo forest.c. The paper performanceed forest ecosystem health evaluation of East Dongting Lake area at regional scale.Combining previous research results,the paper selected presentative18indicators from natural environment、forest structure、social factors and economic factors.The paper assessed the health of forest ecosystem in regional level through analytic hierarchy process which structures judgement matrix to determine the weight of indexes, divides the indexes into5grades,and changes the original data into different rank through the subordinate function.Then the membership level of forest health can be determined through the fuzzy comprehensive evaluation.The fuzzy comprehensive index of forest ecosystem health which can be calculated was3.133by5rank assignment in the study area.To certain content,the high quality condition was0.1632,the index of health state was0.18, the index of subhealth was0.3917and the index of sick state was0.125in some degree.The health state of East Dongting Laker belonged to Ⅲlevel,equivalent to sub-health state according to the maximum membership principle.the rank of forest ecosystem health was between Ⅱ level and Ⅲ level,serious partial to III level, and it was developing from health state to sub-health.The result was accurate because the overall evalution result was equal to experts’ opinion.(2)The paper established a early warning model of three-layer BP neural network based on selected index of forest health evalution,with which we could predict the forest health state in East Dongting Laker area.From the predicted result, the R value was0.99994and the MSE was9.83e-6,so it showed that the output value and expectation were tracking much better. According to the weight and threshold value of neural network input and output, the neural network early warning model of forest patch health evalution was established and it was used to the research of early warning in East Dongting Laker area.The prediction could overcome subjective factors on the evalution result of adverse effect based on BP neural network in forest ecosystem health state,thus it had great practical value.(3)The evalution of forest’s eocsystem service function mainly covered eight aspects including bimber production efficiency,water conservation, soil conservation,fixing carbon and releasing oxygen, accumulating nutrients,purifying atmospheric environment, forest protection and recreation value in East Dongting Laker area.The forest ecosystem’s service function value of East Dongting Laker area are mainly as follows:timber production benefit for653.7million yuan per year,water storage for14.973billion yuan per year,, soil conservation for1.8541billion yuan per year,, fixing carbon and releasing oxygen for6.969billion yuan per year,, accumulating nutrients for0.148billion yuan per year,, purifying atmospheric environment for2.0854billion yuan per year,, forest protection for1.2538billion yuan per year,, recreation value for1.181billion yuan per year,, so the total evalution was29.118billion yuan per year,.The actual service function evalution was bigger than the calculation if including organic pollutants purification to the environment.It showed that the maximum of service function value was pinus massoniana for8.9575million yuan per year,, secondly was fir for5.8052million yuan per year,,broad leaved tree for3.7186million yuan per year,, ecological service function value of three types firs was least,only for38.35million yuan per year. The senquencing of ecosystem services value from forest types was in turn:pinus massoniana,cunninghamia lanceolata,deciduous tree,foreign pine,bamboo,economic forest,poplar three chinese fir.From forest providing ecological service function in unit area,the largest was pinus massoniana, secondly was foreign pine,the least was economic forest,the numbe was6.033,6.017,3.083ten thousand yuan per arce per year.in proper sequence.The horizontal comparison of forest provided eco-service value was made in Jiangxi province,Henan province and East Dongting River area. Eco-service value from East Dongting River area was far lower than Jiangxi province which was in good health in water conservation, soil conservation,fixing carbon and releasing oxygen,accumulating nutrients and purifying atmospheric environment.Even it was lower than Henan province that was in general situation in fixing carbon and releasing oxygen, accumulating nutrients, forest protection and recreation value.Measuring forest health only in eco-service value,we believe that the forest in Dongting River area was not healthy.(4) Combining forest health evalution result in different scale level,the paper showed that the forest in studied area was in subhealth state. Then it analysised the facing problems that affected forest health as follows:unreasonable forest types structure,single species and poor ecological stability; uneven distribution of space,so it was difficult to play its ecological service function.that the contradictions between fast development of urbanization and reducing woodland area was serious,forest product processing enterprise development was out of control were some of the problems. Lower eco-services value and fragmented forest landscape were thecharacter in no health.Then the paper put forward countermeasure that made forest healthy including forest management technology,forestry policy,management system and operation mechanism.