Effect Of Landscape Structure On Leaf Blight Of Dalbergia Odorifera

Dalbergia odorifera(DalbergiaodoriferaT.Chen.),alias rosewood,scentedros wood and dalbergia,belongs to Dalbergia of Papilionaceaeof Leguminosae,which is an evergreen semi-deciduous tree and a rare plant under secondary protection in China.The tree has beautiful shape which can be used as ornamental plants in gardens and landscapes,and also be used as high-grade furniture and handicraft materials.It has very high economic value.Leaf blight is one of the serious diseases that hinder growth of Dalbergia odorifera.The purpose of this paper is to research The relationship between landscape stand structure factors,landscape spatial structure factors and leaf blight of Dalbergia odorifera plantation from perspective of landscape pathology,and to screen out the key factors affecting the occurrence of leaf blight,and put forward the corresponding forest management measures.The results are as follows:(1)Effects of landscape stand structure factors on leaf blight in Dalbergia odorifera plantation.Selection of nine landscape stand structural factors:Average tree height(Hy),Average height under branches(Hb),Average DBH(D),Average crown width(Cw),Average positive crown width(Cs),Crown diameter ratio(PCD),Stand density(SD),Ratio of height to height under branches(Ph),Canopy density(CD).According to the principle of principal component analysis,nine landscape stand structural factors were synthesized into three main factors.The relationship between three main factors and the occurrence of leaf blight was analyzed,which were stand biomass factor(Ht?Hb?D),stand crown factor(C?CSA?PCD?CD)and stand vertical distribution factor(SD?Ph?),respectively.The results showed that the order of correlation between comprehensive factors and disease index was canopy structure factor>vertical spatial factor>biomass factor.The order of correlation between forest comprehensive factors and morbidity was canopy structure factor>biomass factor>vertical spatial factor.Disease index and incidence were negatively correlated with canopy structure factors(P<0.05,R=-0.112;P<0.05,R=-0.310).Disease index and incidence were negatively correlated with biomass factors(P<0.05,R=-0.062;P<0.05,R=-0.120),but positively correlated with vertical spatial factors(P<0.05,R=0.090;P<0.05,R=0.107).(2)Effects of landscape spatial structure of Dalbergia odorifera plantation on leaf blight.Hegyi competition index,mixing degree,size ratio,angle scale and aggregation index were selected as landscape spatial structure indicators.The results showed that the competition index of Hegyi ranged from 0.2 to 0.5,and the main distribution frequency ranged from 0.3 to 0.5,which indicated that the stand competition of plantation sample land was weak.The proportion of zero,weak and medium mixed forests accounted for more than 49%,while that of strong mixed forests and super strong mixed forests was lower,accounting for less than 4%,indicating that the mixed degree of plantation sample forests was not high.The average size ratio ranged from 0.4 to 0.5,indicating that the diameter differentiation of tree species in plantation plots was not obvious,and the growth dominance was relatively balanced.The average stand angle scale ranges from 0.43 to 0.48,which indicates that the stand distribution of plantation sample land is more uniform.The average aggregation index was more than 1.0,which indicated that the stand of each plantation sample was evenly distributed on the whole.The regression model for predicting the incidence of leaf blight of Dalbergia odorifera was established by the stepwise regression method of SPSS software.Y(incidence)= 0.213-x1*0.32 + x2*0.15-x3*0.07-x5*0.06 can be used as a reference for adjusting the structural factors of landscape forest.(3)The influence of key landscape structural factors on the occurrence of leaf blight.After grouping the canopy structure factors(Cw?PCD?CSA?CD)and disease index,multiple comparisons showed that the incidence and disease index of grade I leaf blight were significantly higher than those of grade ?,? and ?,and there were significant differences between grade ?,? and ?(P<0.05).The incidence and disease index of grade ? leaf blight on canopy surface area were higher than those of grade ?,? and ?.There was no significant difference between grade ? and ?,but there was significant difference between grade ? and grade ? and grade ?(P<0.05).The incidence and disease index of canopy diameter ratio grade ? leaf blight were significantly higher than those of grade ?,? and ?,and there were significant differences between grade ?,? and ?(P<0.05).The incidence and disease index of canopy density grade ? leaf blight were lower than those of grade ? and ?,and there was significant difference between grade ? and grade ? canopy density(P<0.05).The incidence and disease index of uniform angle index grade ? leaf blight were lower than those of grade ? and ?,and there was significant difference between grade ? and grade ? uniform angle index(P<0.05).uniform angle index canopy density.Thus,the incidence of leaf blight decreased with the increase of average crown width,leaf area index and crown diameter ratio.When the average crown width was between 3.01 and 4.00,the incidence of leaf blight was the weakest.When the leaf area index is between 22.01 and 30.00,the crown health is better and the disease resistance is stronger.The occurrence of leaf blight decreased with the increase of canopy density.The control of leaf blight in Dalbergia odorifera plantation is dominated by the regulation of landscape stand structure.The corresponding forest management measures such as reasonable thinning,rational dense planting,pruning and shaping of tree types,and rational matching of tree species are adopted to control the occurrence of leaf blight.