| Connectivity of forest landscape is a measurement index of forest landscape ecological processes and functions,which has an important impact on the exchange process of some key substances or energy in the forest ecosystem.Scientifically evaluating the connectivity of forest landscape and determining the forest landscape components that play a key role in the connection provide important technical support for multifunctional forest management at the landscape scale.The connectivity index based on the ecological network model is an important method for evaluating landscape connectivity.Determining the nodes and the threshold of the connection distance of edges in the forest landscape network model,and evaluating the importance of forest landscape connectivity under temporal and spatial changes are currently key technical problems to be solved urgently.Taking Hupingshan Nature Reserve,Houhe Nature Reserve and the three adjacent counties as the study area,and integrating the habitat suitability model(HSM)and morphological spatial patterns analysis(MSPA)as well as the network model,this paper attempted to consider the influence of different interference intensities and seasonal changes on the nodes and edges in the forest landscape network model,and in the meantime studied the importance of the forest landscape connectivity.The main contents and conclusions are as follows:(1)This paper has constructed a forest landscape spatial suitability index model.Six evaluation factors,namely,landscape cover,altitude,slope,distance to water source,distance to forest edge,and distance to disturbance were selected,and the impact of three different disturbance intensities,that is,high,medium,and low,and seasonal changes on the suitability of forest landscapes were considered.Based on these,this paper has evaluated the suitability of forest landscapes in six scenarios,determined the suitable forest landscape area and distribution,and compared the suitable forest landscape area with the forest land area in the land use data.The results show that the suitable forest landscape area is about 6044 to 10211 square kilometers.The suitable forest landscape areas in the summer high-and middle-assessment scenarios and the winter high-assessment scenarios are larger than that of the forest land,which are 108.5%,107.5%,and 101.0%of the forest land area respectively.The suitable forest landscape areas in the summer low-assessment scenarios and winter mid-and low-assessment scenarios are smaller than that of the forest land,which are 72.5%,94.4%,and 63.4%of the forest area respectively.The results indicate that the forest landscape suitability index model that takes into account the impact of vegetation types and spatial locations on habitat suitability can assess the suitability of forest landscapes more accurately than using a single factor of land type.(2)This paper has constructed forest landscape network models.Based on the results of forest landscape suitability assessment,this paper has selected suitable forest landscape patches as nodes by combining morphological spatial pattern analysis and area method,and then compared them with the nodes determined solely by morphological spatial pattern method or area method.What's more,this paper has determined the appropriate forest landscape connection distance threshold by applying the correlation analysis between the overall probability of connectivity(PC)of the landscape and the edge connection distance threshold,and applying the community analysis to determine the appropriate forest landscape connection distance threshold,and then it is compared with the forest landscape network built with the initial connection distance threshold.The results show that there are 94-110 nodes in the six scenarios,which is 22-195 fewer compared with area method and 85-276 fewer compared with morphological spatial pattern method.The suitable connection distance of the forest landscape is 530-550.The edge connection distance threshold used in this paper is 550,and the corresponding maximum community area is 91.5-93.9%of the total area of the study area.The results also shows that the overall possible connectivity index of the landscape is almost the same through comparing the edge connection distance threshold of 550 with the forest landscape network model with the initial connection distance threshold of 2000.However,the number of edges differs by 34-59 respectively.In addition,the results show that the combination of habitat suitability index model,morphological spatial pattern analysis and area method can determine nodes with better ecological functions from the four dimensions of vegetation cover,spatial location,morphology and area,which,therefore,can reduce the number of nodes in the forest landscape network and lower the difficulty of building forest landscape network model.Last but not least,the forest landscape connection distance threshold is determined through the correlation between the overall possible connectivity index of the forest landscape and the connection distance threshold,as well as the community analysis.As a result,it is possible to determine a more suitable landscape connection distance threshold which can ensure the overall landscape connection,reduce unnecessary connections,and avoid the adverse effects of excessive connections.Especially when the scale of the forest landscape network is large and the number of edges is huge,this method can greatly reduce the complexity of network construction and connection evaluation.(3)This paper has determined the evaluation of the importance of forest landscape connectivity based on multi-scenario integration.The overall importance of forest landscape connectivity is obtained by evaluating the importance of the connectivity of nodes(patches)and edges(corridors)in the six scenarios,dividing the degree of the importance of connectivity,and merging the importance of connectivity of nodes(patches)and edges(corridors).The results show that there are 2-3 and 3-5 nodes and edges that play a key role in the six scenarios respectively,which are 2.2%-5.5%and 2.0%-5.8%of the total network scale.The total patch area is about 317-3216 square kilometers corresponding to the key nodes,which is 3.1-51.3%of the total patch area.The results indicate that the number of nodes and edges in the forest landscape network is not much different,but the numbers or positions of nodes and edges that play a key role are significantly different.What's more,the nodes and edges only account for a very small part of the forest landscape network model,but they are areas that need crucial management,protection or restoration in forest management.Since different disturbance intensities and seasonal changes have an important impact on the evaluation of the connectivity of nodes and edges in the forest landscape network,the method of evaluation of the importance of forest landscape connectivity based on multi-scenario integration can evaluate the importance of forest landscape connectivity more accurately and objectively and determine the part(location)of the forest landscape that plays a key role in connection.(4)The method of integrating suitability index model,morphological spatial pattern analysis and network model can more accurately determine the connection distance threshold of nodes and the distance of edges in the forest landscape network model.By considering the impact of forest landscape connectivity of different interference intensities and seasonal changes,the method of evaluation of the importance of forest landscape connectivity based on multi-scenario integration can evaluate the importance of forest landscape connectivity more accurately and objectively. |
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