Qunatitative Assessment Of Matching Trees To Sites Based On Both Distribution Suitability And Potential Site Productivity

Matching tree species to sites is a basic principle in forest management,and it is also a classic issue of forestry.The traditional research on site-tree species matching was focused on native tree species,based on expert experience and qualitative evaluation,usually used in plantations.The distribution of tree species and growth of natural forests provide an important reference for tree suitability to different sites.However,previous studies were mainly aiming at a certain tree species and lack of information on the distribution of forest types,especially for mixed forests.Therefore,it is necessary to systematically evaluate the suitability of the geographical distribution of natural tree species and forest types,to determine the dominant environmental factors affecting the distribution of forest type's suitability;and combined with the potential site production,answered quantitative and suitable of trees in geographical area and landscape level.Basing on the data of national forest inventory,the data of forest mangement planning survey for Wangqing Forest Bureau and environmental factors of in Jilin Province,focusing on the problem of the lack of quantitative evaluation of the distribution of forest types and growth,this study evaluated the suitability of natural tree species and forest types systematically,and dominant environmental factors and the potential site productivity of the sites.The results will provide reference for natural forest restoration and structural adjustment in the region.The main research and results were described as follows.?1?Simulation of distribution suitability of tree species and forest types in natural forests.Species Distribution Models?SDMs?were used to investigate the response of tree species to site suitability.Base on the data of the 8^thh Chinese national forest inventory in Jilin Province,16 tree species and 11 forest types from the natural forest?as its real distribution point?were classified.In addition,the study selected 55 variables,including 19 bioclimatic,33 soil variables and 3 terrain environmental-related variables which potential affect tree growth.Different SDMs were developed for 16 major tree species and 11 forest types.The accuracy of each developed SDMs was evaluated by AUC?area under the receiver operating characteristics curves?using maximum entropy modelling.The maximum entropy models were successful at discriminating on training set and test set for all 16 tree species they were from 0.7496 to0.9557,for all 11 forest types,the AUC values were from 0.6872 to 0.9469.The Jackknife method was used to evalutate the importance of different variables which determined dominant variables affecting the distribution of tree species and forest types.The study investigated the dominant environmental factors affecting the distribution of tree and types suitability and their thresholds.The dominant environmental factors were ranked as max temperature of the warmest month,mean temperature of the warmest month,elevation,annual mean temperature,and mean temperature of the coldest month.Temperature and elevation were important to the distribution of the specific tree species and forest types.Therefore,Maximum entropy models are used for predicting to the distribution of the specific tree species and forest types.The study also generated the distribution suitability maps of 16 major tree species and 11 forest types with five levels in Jilin province.?2?Site quality evaluation of natural mixed forestBased on the 5^th,6^th,7^th,8^th national forest inventory data of Jilin Province,models were developed of realized and potential site productivity by stand volume.The study selected within Jilin Changbai Mountain?site partition for 7B?region to build models.The study explored the site quality evaluation methods and techniques,which including 10 site classifications and 6 growth process types classifications.Models of volume potential site productivity for six growth process types were developed,and the maximum of the annual growth were obtained by the optimization solution.With Wangqing Forest Bureau as a case of application,potential productivity at subcompartment level was realized.Using machine learning algorithm,based on forest site quality evaluation method,the forest and non forest land evaluation system that mentioned above was implemented.The results on current site's quality assessment showed that,there were still space to narrow the gap between the realized and potential site productivity in the Wangqing Forest Bureau.?3?Qunatitative assessment of matching trees to sitesA comprehensive index of qunatitative assessment of matching trees to sites for the main tree species?forest types?were constructed,which combined the distribution suitability with potential site productivity.Based on the species distribution model,the distribution suitability grades of 6 forest types were obtained in Wangqing Forest Bureau.Based on the stand volume potential growth method,the growth suitability of different site grades were obtained.The comprehensive index of the suitability of tree species based on the distribution and growth of tree species were synthesized.The quantitative distribution and growth of the combination of suitable forest types estimation,completed the Wangqing Forest Bureau of adaptation level mapping,that implemented the site quality evaluation of forest management units and suitable forest types application.The results showed that in the Wangqing Forest Bureau,the largest areas of highest level of suitable forest type was broadleaf mixed forest-??Tilia mongolica and other hard broadleaf and soft broadleaf species?,followed by broadleaf mixed forest-??Tilia mongolica,pure forest-other broadleaf?,broadleaf mixed forest-??Populus ussuriensis,Salix koreensis,Betula platyphylla?,mixed conifer-broadleaf forest and mixed coniferous forest,and the suitable of broadleaf mixed forest-??Fraxinus mandshurica,Ulmus pumila,Betula costata,Juglans mandshurica,Phellodendron amurense,etc.?was the lowest level.To conclude this paper,the distribution suitability of natural tree species and forest types were simulated basing on the species distribution model,which answered the question of their distribution suitabity;the site quality evaluation of natural mixed forests were realized by using the potential site productivity evaluation technique,which answered the question of their growth suitability.Finally,a quantitative evaluation technique was developed to answer the questions of both growth and distribution suitability.This study provides a noval method for qunatitative assessment of matching trees to sites.