The Effect Of Patch Pattern Of Sophora Alopecuroides On The Damage Rate Of Seed Past And Community Structure Of Its Natural Enemies

Sophora alopecuroides is one of the main plants for windbreak and sand fixation in desert and semi-desert regions in western China and also is one of the essential sources of honey,forage,and medicinal plants.Its roots are well developed,and typical patching patterns appear in the growing regions of the natural environment.Studies have found that Etiella zinckenella is the main pest of seeds of Sophora alopecuroides and these peats also have some parasitic natural enemies.Habitat fragmentation impact on biological diversity,in terms of impact on the ecosystem community structure as so is one of the hot topics in the field of ecology.This study selected Ningdong Township,Lingwu City,Ningxia,which is close to the central and northern regions of Lingwu Baijitan,National Nature Reserve in Ningxia.A total of 27 patches as experimental plots,includes Yujia Lake(YJH,6 patches),Yangchang Bay(YCW,7 patches),Liujiazhai(LJZA,8 patches;LJZB,6 patches).During the period from June to September in 2016-2017,we investigated and collected the pest of seed in Sophora alopecuroides and its parasitic natural enemies in 27 patches by using a five-point sampling method.Indoor strip check and artificial feeding experiments has been conducted with pods of Sophora alopecuroides L picked in labs.During the experiment,some index can be counted,such as pods harmed by Etiella zinckenella,seed condition,the number and species of parasitic natural enemies.Using biostatistical methods,patch characteristics index,landscape fragmentation index,etc.to analyze the effects of the patch pattern of Sophora alopecuroides over the damage rate of seed pests,the community structure of the parasitic natural enemies of the seed pests,and the edge effects.The main findings and conclusions are as follows:(1)The average patch area in the four experimental plots is YJH(2629.08m2)>LJZA(1457.79m2)>YCW(1010.34 m2)>LJZB(949.87m2).The number of Etiella zinckenella in plots shows the relation that YJH(0.1681 per pods)>LJZA(0.1423 per pods)>YCW(0.1248 per pods)>LJZB(0.1072 per pods).The correlation analysis between the patches area of 27 patches and per pods numbers of Etiella zinckenella in each patch,pod damage rate,damage rate of bean shows that there is no significant positive correlation(r=0.0470)between the number of Etiella zinckenella and the area of patches and there is no significant negative correlation between the number of Etiella zinckenella and the damage rate of pods(r=-0.3713),the damage rate of seed(r=-0.3073).Although the patch connectivity index shows no significant positive correlation with the number of Etiella zinckenella(P=0.6421>0.05,r=-0.093688),the damage rate of pods(P=0.1018>0.05,r=-0.321698)and the damage rate of seed(P=0.0643>0.05,r=-0.361049),however,there is an insignificant negative correlation.The area and partterns of have a certain correlation with the number of seed pests and harm rate,but they are not significant.These indexes,namely,patch density index(FD),landscape patch fragmentation index(FN)and internal landscape fragmentation index plot area(FI1,FI2)is LJZB>YCW>LJZA>YJH.The landscape patch shape fragmentation index(FS1,FS2)sorted from small to large all is YJH>LJZA>YCW>LJZB.The results show that degree of landscape fragmentation in the four plots is LJZB>YCW>LJZA>YJH.Taking FD(X1)ⅢFN(X2),FS1(X3),FS2(X4),FI1(X5),FI2(X6)as independent variables,The per pods numbers of Etiella zinckenella(Y1),the damage rate of pods(Y2),and the rate of damage to seeds(Y3)were used as the dependent variables,using the method of multiple stepwise regression to study the effect of landscape fragmentation on the number of Etiella zinckenella,the hazard rate of pods,and the hazard rate of the seeds and get the positive correlation among the internal landscape fragmentation index(FI2)plot area,the landscape patch shape fragmentation index and the per pods numbers of Etiella zinckenella(R2=0.999998,P=0.0014<0.05),the damage rate of pods(R2=0.996128,P=0.0622>0.05),and the rate of damage to seeds(R2= 0.976497,P＝0.1533).Fragmentation of landscapes will increase pest damages to pods and seeds to some extent.(2)Field investigations and artificial rearing experiments towards parasitic natural enemies of Etiella zinckenella which sampled from three sample plaques of YCW,LJZA and LJZB were carried out to study the effect of landscape fragmentation on the community structure of parasitic natural enemies of the seeds of Sophora alopecuroides L pests.The results showed that the number of Parasitoid wasp in YCW sample was the largest(537),followed by LJZA sample(141),and the least was LJZB sample(66);there were three families,eight genera and ten species of parasitic natural enemies of the seeds of Sophora alopecuroides L pests.Among them,Elasmus hyblaeae,Phanerotoma flava、Braccon nigrorufum,Iconella sp.,Elasmus hyblaeae was the dominant species,and the Braccon nigrorufum was common species.FD(X1),FN(X2),FS1(X3),FS2(X4),FI1(X5),and FI2(X6)were treated as independent variables,the species richness index(Y1),community diversity index(Y2),and evenness index(Y3)of the Parasitoid wasp were treated as dependent variables.Multiple stepwise regression analysis showed that there was no significant negative correlation between landscape shape fragmentation index(FS2)and species richness index of parasitic enemies((R2=0.709030,P>0.05));There was no significant positive correlation between the fragmentation index of interior sample area in landscapes(FI1)and the diversity and evenness of natural enemies(R2=0.775865,P>0.05);(R2 =0.7758621,P>0.05)).The fragmentation of landscape plaques lowers the species diversity of the parasitic natural enemies of Sophora alopecuroides to a certain extent.(3)Selecting a cycle patch with the area of 2964.23m2 in Yujiahu and take the center of patch as the origin,taking 5m,10m,15m,20m,25m as radius,a total of 40 samples point were set in 8 different orientations to pick the pods from Sophora alopecuroides.And whether there is an edge effect between the number of seeds pest and rate of damage to pods and seeds were studied.There is no significant difference in 40 plots of the growth of Sophora alopecuroides pods(F0.05(4.35)=0.7500<2.64,P=0.5647),and the number of seeds per pods showed no significant difference.The total damage rate of seeds gradually increased from 29.4769%to 53.2946%from the center of the patch to the edge and the difference was significant(F0.05(4.35)=3.3558>2.64,P<0.05).The total damage rate of seeds also showed a gradual falling trend from the center of the patch to the edge,increased from 16.9414%to 36.3383%,and the difference was significant(F0.05(4.35)=3.2183>2.64,P<0.05).The number of Etiella zinclkenella per pod gradually increased from 0.4323 per pod at 5 m in the center to 0.7328 per pod at 25 m,which demonstrates that the damage rate over the number of Etiella zinckenella per pod to pods and bean seeds shows a significant marginal positive effect.The damage orientation presents strip distribution of southeast and northwest mainly.