The Change Of Wetland Distribution And The Simulated Response To Climatic Change In The Great Xing' An Mountains

Wetlands in the mid-and high-latitudes account for about 64%of the total natural wetland area in the world and they have important ecological functions,such as water conservation,climate regulation,and biodiversity maintenance.They are important in maintaining regional ecological balance and security.Wetlands in the mid-and high-latitudes are terrestrial ecosystems that are sensitive and vulnerable to global climate change.They have experienced degrees of degradation affected by climate change and human activites in recent decades.Especially,wetlands degradation in the Great Xing'an Mountains exceeded other types of ecosystems in the region.Wetlands in the Great Xing'an Mountains have the characteristics of typical cold-temperate mountain forest wetlands.This study investigated wetlands in the Great Xing'an Mountains,(1)explores the variation characteristics of climate change in recent 50-60 years in the region,(2)analyzes the dynamics of wetlands landscape,(3)develops the wetland landscape distribution model and quantifies the relative importance of environmental factors affecting different types of wetland distribution,and(4)simulates the response of different wetland types area,distribution,and spatial pattern to different climate change scenarios.This study provided the theoretical basis for wetland conservation and wetland adaptive management under climate change.The main results are as follows:(1)Climate change in the Great Xing'an MountainsAnnual mean temperature showed a significant increasing trend with an inclination rate of 0.4°C/10a in the Great Xing'an Mountains in recent 56 years(1961-2016),reaching a significant level of 0.01.Annual mean temperature had 3-5and 15-18 years scale oscillation periods.The mutation year was 1984 and the mutation point was between±1.96 representing a 0.05 significance level.Annual precipitation showed an increasing trend slightly with an inclination rate of 11.92mm/10a,reaching a significant level of 0.01.The oscillation periods of annual precipitation were 3-5,8,and 28 years.The mutation yeas were 1978 and 2005-2007and the mutation points were between±1.96 representing a 0.05 significance level.Annual mean temperature under RCP2.6,RCP4.5,and RCP8.5 climate scenarios increased by 1.27-4.2?than the benchmark climate scenario,showing a gradual decrease from southwest to northeast spatially.Additionally,the warming under RCPs climate scenarios in 2070 was more significant than that in 2050.Annual precipitation increased by 18-65 mm under RCPs climate scenarios in 2050 and 2070.Generally,annual precipitation was higher in the midwest and was lower in the north of the study area.(2)Dynamic changes of wetland landscape in the Great Xing'an MountainsWetlands area showed a decreasing trend in recent 77 years(1940-2016)with a total decrease of 4541km~2 in the Great Xing'an Mountains.Spatial distribution with high aggregation gradually shifted from the central to the northwest and the southeast of the study area.In terms of different types of wetlands,arbor wetland and water body area changed slightly,shrub wetland increased by 136km~2 and herbaceous wetland decreased by 450km~2 from 1990 to 2016.Arbor wetland was mainly distributed in the north,shrub wetland was mainly distributed in the central and north,and herbaceous wetland was mostly distributed in the central and south of the Great Xing'an Mountains.Water bodies scattered throughout the whole study area.Wetlands landscape changed slightly from 1990 to 2016,but the spatial variation of different types of wetlands landscape was significant in the Great Xing'an Mountains.PLAND of arbor wetland was relatively high in the northern edge,PLAND of shrub wetland in the middle was higher than around of the study area,PLAND of herbaceous weland in the south central was higher than other regions,and the higher area of water body PLAND was concentrated in the northeast.PD of arbor wetland was relatively high in the north and east,PD of shrub wetland had a high value area in the east,PD of herbaceous weland was higher in the northeast than other areas,and PD of water body in the north was higher than that in the south averagely.Patch shape of arbor wetland was more complex in the north,patch shape of shrub wetland was more complex in the central and northwest,patch shape of herbaceous wetland was relatively complex in the midwest and southeast,patch shape of water body was more complex in the northwest and east.AI of arbor wetland was higher in the northeast,AI of shrub wetland was relatively high in the north,AI of herbaceous wetland was higher in the south than other regions,and AI of water body was higher in the north of the study area.(3)Developing wetland landscape distribution model and quantifying the relative importance for wetland distributionThe research used the wetlands distribution and environmental factors to develop the wetland landscape distribution model according Random Forest method.Wetlands included arbor wetland,shrub wetland,herbaceous wetland,and water body.Environmental factors mainly included 10 climatic variables and 10 geographical landscape variables.We verified and evaluated the accuracy for the wetland landscape distribution model and its AUC value was 0.8874,which proved that the model had good simulation ability for wetland distribution.Simultaneously,the relative importance of environmental factors affecting the wetland distribution of different types in this area was also obtained.For arbor wetland:HII>ROA>RA>TS>SL>ISO>ROA>SOI>MAT>ASP,for shrub wetland:SL>ASP>HII>RIV>ISO>ROA>SR>RA>SOI>MAT,for herbaceous wetland:SL>ASP>HII>RA>SR>RIV>ROA>SOI>ISO>AI,for water body:GEO>SOI>HII>ISO>TS>MAT>RIV>AP>RA>PWQ.(4)Simulation of potential wetland distribution in response to climate change in the Great Xing'an MountainsGenerally,climate change led to large areas of degradation on potential arbor wetland and shrub wetland in the north of the Great Xing'an Mountains.Degradation of potential herbaceous wetland was in the south and new potential herbaceous wetland was found in the north.Potential water bodies decreased in the whole study area and degraded to the eastern edge.Specifically,potential arbor wetland and shrub wetland were seriously affected by climate change and only a small amount of sporadic distribution remained in the north under RCP2.6 climate scenario.In 2050,potential herbaceous wetland mainly showed a large decrease in the south,a large increase in the northwest,and some unchanged areas in the middle of the study area.Additionally,with the enhancement of climate scenarios in 2050,the increased areas of potential herbaceous wetland gradually decreased,while the decreased areas increased to some extent.In 2070,with the enhancement of climate scenarios,the potential decreased herbaceous wetland in the south and middle gradually increased,while the increased area in the northwest gradually decreased.As a result of climate change,potential water bodies across the whole study area decreased significantly and the increased areas were mainly distributed in the eastern edge.The loss in 2050 was higher than that in 2070 averagely.Response of landscape pattern of different wetlands to climate change varied.PLAND of potential arbor wetland and shrub wetland decreased obviously and PLAND of potential herbaceous wetland increased generally.In 2050,PLAND of potential water body increased continuously but it increased first and then decreased in 2070.PD of both potential arbor wetland and shrub wetland decreased.PD of potential herbaceous wetland decreased in 2050 but it increased in 2070.PD of potential water body decreased significantly in 2050 and increased in 2070 with the enhancement of climate scenario.Climate change had relatively small effect on the PARA_MN of different types of wetlands.Under RCP2.6 climate scenario,AI of potential arbor wetland increased slightly in 2050 and decreased in 2070.AI of potential shrub wetland was significantly decreased under RCP2.6 climate scenario.AI of potential herbaceous wetland increased averagely but it decreased with the enhancement of climate scenarios.AI of potential water body increased gradually with the enhancement of climate scenarios in 2050 but it decreased gradually in 2070.According to the changes of wetland distribution and the simulated response to climatic change in the Great Xing'an Mountains,the adaptative countermeasures of wetland under the background of climate change were formulated.On the one hand,the wetland habitat protection needed to be strengthened;on the other hand,the degraded wetlands needed to be restored to give priority to the adaptation to climatic change.Wetland policy system,wetland nature reserve system,and wetland protection monitoring system based on climate change should be improved and wetland should be continuously protected to improve its ability to adapt to climate change in the Great Xing'an Mountains.