Forest Health Assessment For Mountainous Area Of Beijing

Based on theories of systemic science and landscape ecology and in terms of data consisting of standard plots investigation, forest resources inventory and collected charts else, evaluation index system of forest health is built by exploring the conception and essence of forest health. A forest health evaluation study for Beijing mountain area is conducted, based on forest landscape zoning in this research. The evaluation indices of forest health is assigned by adopting the method of normal regression analysis and the way of equidistant dividing, the index weight is determined by applying the method of AHP, and membership degree is determined by the method of multilevel fuzzy comprehensive evaluation. Five forest health degrees, namely, Robust (Perfect), Healthy, Sub-healthy, Unhealthy and Disease are assigned, forest health status of Mountainous Beijing is evaluated at compartment, landscape and Region level respectively, in order to provide theoretical base for Beijing's sustainable forest management. Main outputs of the paper conclude:(1) Eighteen forest landscape divisions in total are found in Beijing from this study, by using land tape, forest type, forest origin and dominant tree species as the main indices to analyze forest in Beijing mountainous area. Based on the forest management inventory data and remote sensing image classification, the classification accuracy is above 83%.(2) On the scale of sub-compartment, based on the theory of modern system science, this paper conducts 14 preliminary forest health indices by considering integrality, stability and sustainability of forest ecosystem, 8 forest health indices are selected after screening. On the scale of forest landscape division, based on the theory of landscape ecology, 6 preliminary forest health indices are conducted by considering the relationship of ecosystem structure and distribution pattern and relationship between ecosystem function and process, 4 forest health indices are selected after screening.(3) Regression analysis models are established to measure the indices that cannot obtain directly. On the scale of sub-compartment, to calculate the total biomass of each unit area, 18 volume-biomass regression models of stand layer, 18 height-biomass regression models of shrub layer and 18 height-biomass regression models of grass layer are established; Eighteen tree height, DBH and leaf area index models are established, to calculate leaf area index,.On the scale of forest landscape division, 18 indices are calculated, such as fractal dimension, landscape diversity, landscape dominance, evenness; based on the investigation data of forest pests and disaster grades collected from each landscape sample plot, 18 indices of forest pest and disease are calculated by calculating the relative position of fuzzy membership degree.(4). On the scale of sub-compartment, the healthy indices are categorized into 3 classes, namely, qualitative index, unrestricted comparable quantitative index, and semi-restricted comparable quantitative index. The standards of each unrestricted comparable quantitative index and semi-restricted comparable quantitative index are divided into 5 classes respectively. On the scale of forest landscape division, the standard of fractal dimension and landscape diversity is divided into 5 classes respectively.(5) Applying the method of AHP to confirm the index weight, index weight vectors are calculated as follow:The forest health index weight vector of sub-compartment scale is:A_P =(0-0211 0.0646 0.2476 0.0333 0.3000 0.0861 0.2123 0.0349);The index weight vector of landscape scale is:A_L =(0.1250 0.3750 0.4375 0.0625);The index weight vector of total Beijing mountain area forest health is:A_T =(0.0719 0.0602 0.0632 0.0618 0.0495 0.0670 0.0414 0.0476 0.0640 0.0523 0.0493 0.0496 0.0536 0.0477 0.0451 0.0668 0.0677 0.0411),(6) The evaluation results show that, in the scale of sub-compartment, 11265 sub-compartments are classified as in sub-healthy category, which accounts for 42.21% of the total Beijing Mountainous area, while sub-compartments are classified as in either robust or disease occupy 10% of the total area respectively. On the scale of forest landscape, there are 4 kinds that are classified as robust, 12 kinds as sub-healthy and 2 kinds as unhealthy among the total 18 forest landscape types. Neither high-quality nor diseased forest landscape types is found in Beijing mountainous area in this study. On the scale of whole Beijing mountain region, the healthy condition of Beijing mountainous forest is classified as sub health.The above conclusions shows that it is both urgent and necessary carry on forest health management, so as to improve forest health grade in Mountainous Beijing.