| Xiaolongshan forest area is an important nature reserve,which is one of the most complete preservations of the existing natural forest in Gansu province because of its ecological value.And it is important for water and soil,water conservation and biodiversity protection in the area.Baoji-Tianshui Expressway in Gansu province is located in the southeast part of the Tianshui Beidao District and most of the engineering construction passes through the Xiaolongshan forest.The highway project has passed through the Xiaolongshan Dangchuan,Maiji,Dongcha and Baihua Forest.The opening of the highway brings convenience to the local traffic,but also many negative ecological effects on the growth and distribution of road forest.In view of this,we set sampling surveys and counted the structure of forest community in the high-speed road ecosystem section and Xiaolongshan nature reserve by the variance/mean ratio(C),negative two parameters(k),clumping index(I)and Green index(GI),Cassie index,patchiness index(PAI)and diffusion index(I delta)distribution pattern and aggregation intensity index,respectively.We choosed Pinus armandii,Pinus tabuliformis and Quercus alienavar population as the research object and mainly focused on the distributing pattern of expressway forest population space and population dynamic changes at different age classes.At the same time,we compared the distributing pattern of expressway forest population and natural reserve deeply in order to study their spatial pattern differences.The results showed that:(1)The expressway forest population had 27 species and a variety of important population value showed that the dominant species include Larix kaempferi,Pinus armandii,Pinus tabuliformis,Larix principis-rupprechtii,Ulmus davidiana,Quercus alienavar and Cerasus polytricha,Acer maximowiczii.The study expressed that the distribution pattern of 8 dominant species showed aggregated distribution,but the aggregation intensity of different populations are different.Cerasus polytricha population aggregation intensity is maximum,Ulmus davidiana population aggregation intensity is minimum and the other population aggregation intensity from high to low are Acer maximowiczii,Larix kaempferi,Pinus tabuliformis,Larix principis-rupprechtii,Quercus alienavar,Pinus armandii by the negative two parameters(K)and(PAI)block of poly judgment index.(2)The type of Road area of Larix principis-rupprechtii population distribution pattern change in the growth process of specific cluster-uniform-gathered-uniform rules;Larix kaempferi population in the growth process in the tree only in the stage performance of uniform distribution,the other phases are clumped;Acer maximowiczii population stage of seedling and sapling clustered distribution,in the later stage showed a tree as a state of uniform distribution;Cerasus polytricha in the growth process,the pattern of dynamic variation of aggregation-uniform.In addition to the old stage Ulmus davidiana population aggregation distribution,the other phases were uniformly distributed.(3)By comparing the spatial distribution pattern of Pinus armandii,Quercus alienavar and Pinus tabuliformis in the Baotian expressway forest population and Xiaolongshan nature reserve,we found that there were some differences in the distribution pattern of two different geographical populations,which was mainly related with the biological characteristics of the population itself.But on the whole,the status of the aggregation degree of Pinus armandii,Quercus alienavar and Pinus tabuliformis the Xiaolongshan nature reserve was significantly higher than that of Baotian expressway forest population,and the nature reserve forest population growth was relatively stable and unable to appear the spread tendency.With respect to the nature reserve,Baotian expressway forest population in the growing process was more prone to diffuse.Meantime,it showed uniform distribution in young stage,and was easy to turn into recession in advance. |
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