Evaluation And System Realization For Regional Forest Change And Water Conservation Function

Forest ecosystem and its ecological functions play an irreplaceable role in the survival and development for human beings.In addition,the changes of forest vegetation(e.g.,disturbance and recovery)will have important influences on forest ecological functions.Under the context of water resource shortage and aquatic ecosystem deterioration,the water conservation function of forest ecosystem is particularly significant.Scientific assessment of regional forest change and its impact on water conservation functions can provide an important theoretical basis for forest ecological engineering.This study quantitatively estimate forest changes based on the ERA(Equivalent Recovery Area)index and forest succession,and evaluate forest water conservation according to comprehensive water storage capacity method.Moreover,based on ENVI/IDL and ArcGIS Engine/C#.NET secondary development platform,this study designed and developed the evaluation system of regional forest change and water conservation function.The system mainly consist of modules including data management,data processing,simulation and prediction of forest change,evaluation of water conservation function and visualization.Not only do the system support the evaluation of forest water conservation,it can also simulate and predict the change of forest,and predict spatio-temporal changes of forest water conservation in different forest change scenarios.In addition,the system also provides functions including statistical analysis,charting,thematicmapping and spatio-temporal dynamic rendering.These will benefite for sector of forestry and water resources management to assess changes of forest and its water conservation capacity quickly and accurately.In order to verify the availability of the system,this paper used the upstream watershed of minjiang Zagunao Valley as an application case to evaluate the forest change and its water conservation function,and the main conclusions are as follows:(1)From 1996 to 2030,under the“natural restoration”and“natural restoration+artificial restoration”scenarios,the proportion of forest equivalent recovery area both showed an increasing trend.The percentage of equivalent recovery area of“natural restoration”was about 22%in 1996 and 34%in 2030,respectively.In addition,its annual average recovery rate was about 0.35%.By contrast,the proportion of equivalent recovery area of“natural restoration+artificial recovery”was 22%in 1996 and 32%in2030,whose annual average recovery rate was close to 0.29%.In general,the rate and effect of forest hydrological recovery under the“natural recovery”scenario is better.(2)In 1996,the total forest water conservation in the study area was approximately9.45×10~7m~3.The contribution rate of canopy interception,water holding capacity of litter layer and water storage capacity of soil layer is about 2.57%,5.40%and 92.03%,respectively.The soil water storage capacity is the main body of forest water conservation.Besides,the contribution rate of forest water conservation at the altitude of 3000-4000m is the highest(nearly 84.3%).Natural coniferous forest ranks first in the contribution rate of total water conservation,artificial coniferous forest ranked second,followed by shrub and broad-leaved forest.Furthermore,natural coniferous forest ranks first in the water conservation capacity per unit area,followed by artificial coniferous forest ranked,broad-leaved forest and shrub.Besides,overripe natural coniferous forest ranks first in the water conservation capacity per unit area in different age groups,mature natural coniferous forest ranked second,followed by middle-aged artificial coniferous forest,mature artificial coniferous forest,overripe artificial coniferous forest,near-mature natural coniferous forest,middle-aged natural coniferous forest,young natural coniferous forest and young artificial coniferous forest.(3)From 1996 to 2030,the regional water conservation gradually increased because of regeneration and restoration of forest.Moreover,the interception of forest canopy fluctuated greatly and frequently because of rainfall,which led to the fluctuation of total water conservation and water conservation capacity of different forest types.During1996-2030,the rate and capacity of water conservation contribution for coniferous forest was always the highest.Compared with the historical rainfall scenario(1996-2017 year),the water conservation capacity per unit area of different coniferous forest age groups in the future rainfall scenarios(2018-2030 year)were weaker(about 100t/hm~2 difference),which was mainly affected by the reduction of rainfall in future scenarios.(4)In general,the water conservation and water conservation capacity of natural coniferous forest was better than artificial coniferous forest in the study area.Especially,compared with the same age group of artificial coniferous forest,the water conservation capacity of young,mature and overripe natural coniferous forests was stronger,while the water conservation capacity of middle-aged and near-mature natural coniferous forests was worse.From 1996 to 2030,in terms of total water conservation,“natural restoration"was less effective than“natural restoration+artificial restoration",while the difference decreased over time.In the short term,the total water conservation of artificial coniferous forest was better.However,over the long term,as forest growmaturely,the total water conservation of natural coniferous forest will exceed that of artificial coniferous forest.