Landscape Patterns Analysis And Stability Of Robinia Pseudoacacia Plantation In Dijiaogou Basin

Landscape pattern refers to the spatial distribution of landscape elements with different sizes and shapes.The essence of the stability of plantation community is the sustainability of plantation community.The analysis of landscape pattern and community stability of plantations plays an important guiding role in the construction of plantations.This study is conducted in the artificial forest of Dijiaogou Basin in Yongshou County.Based on remote sensing image and the spatial analysis function of Arc GIS,the information of plantation in Dijiaogou Basin is analyzed and extracted.The landscape pattern and landscape index of Robinia pseudoacacia plantation in different sites are analyzed by Fragstats4.2.The stability of 11 typical Robinia pseudoacacia plantations in the basin is evaluated by fuzzy membership function discrimination.Based on canopy density and leaf area index,a rapid evaluation method for stability of Robinia pseudoacacia plantation is established.And the stability of Robinia pseudoacacia plantation in Dijiaogou Basin is evaluated rapidly.The management strategy of Robinia pseudoacacia plantation is put forward according to the stability and landscape pattern characteristics of Robinia pseudoacacia plantation in the basin so as to provide scientific basis for the formulation of technical measures to maintain the stability of Robinia pseudoacacia plantation in Dijiaogou Basin.It also provides a reference for the management of Robinia pseudoacacia plantation in the gully area of the Loess Plateau.The main results are as followed:(1)There are 6 types of plantation landscape in the basin:Robinia pseudoacacia forest,Shrubby,mixed forest of Robinia pseudoacacia and Pinus tabulaeformis,Pinus tabulaeformis forest,mixed forest of Robinia pseudoacacia and Populus davidiana,Platycladus orientalis(ranked by area).The whole area is 2098.89hm~2,the total perimeter is147.81km and the average class area is 41.15hm~2.Among them,the number of patches of Robinia pseudoacacia forest is the highest,the area is the largest and the perimeter is the longest.It is the dominant landscape type of basin plantation landscape,which is mainly planted at an elevation of 1180-1330m.(2)With the increase of the altitude,the total area of Robinia pseudoacacia plantation of Dijiaogou Basin rises first and then descends,and the area of Robinia pseudoacacia plantation is the largest at an elevation of 1230-1280m.The area of Robinia pseudoacacia plantation increases first and then decreases with the increase of slope,with the largest area in slope of 15-25°.The order of Robinia pseudoacacia plantations’s area in diffetent slope is:semi-shady slope>semi-sunny slope>shady slope>sunny slope>flat slope.(3)The total canopy density and leaf area index of Robinia pseudoacacia plantation in Dijiaogou Basin are both low.The area with canopy density less than 0.7 is about1209.68hm~2,accounting for 70.54%of the total area of Robinia pseudoacacia plantation in the basin.The area with leaf area index less than 4.6 is about 1408.13hm~2,accounting for82.11%.(4)The regression equation is obtained by using the average value of membership function of sample plot and the estimated value of LAI.The regression equation is obtained as follows:LAI screening value=4.31*LAI estimated value*LAI estimated value-39.28*LAI estimated value+89.81.The evaluation results of the selected value regression equation for the stability of Robinia pseudoacacia plantations in the basin are basically consistent with the fuzzy membership function comprehensive discriminant method.The preliminary screening of Robinia pseudoacacia plantation in Dijiaogou Basin shows that the area of low stable Robinia pseudoacacia is about 534.12hm~2,accounting for 31.15%and the low stability stand is mainly distributed in the northeast of the basin.Based on the results of this study,it is suggested to strengthen the overall spatial control of plantation in the construction of plantation on the Loess Plateau,strengthen the integration of the resources of small and medium patches and improve the overall forest coverage and quality.In terms of plantation structure,the proposal is to determine reasonable plant spacing,appropriate intensity of tending and thinning,and adjust stand density according to local conditions.