The Impact Of Forest Fire On Vegetation Properties Of Pinus Tabulaeformis Forest In Liaoheyuan

To study the influence of fire disturbance and environment factors on vegetation change of Pinus tabulaeformis forest,we took burned areas of artificial Pinus tabulaeformis forest in Liaoheyuan National Forest Park in Pingquan county of Hebei province as research object,and divided the burned forest into three levels of mild,moderate,severe according to different degree of burned.The non-burned forests were also set near the burned area as contrastive plots.Through investigation of vegetation and environment factors(Fire intensity factors,terrain factors,soil factors)in different degree of burned area and non-burned forest,redundancy analysis(RDA)was applied to research the influence of environmental factors on vegetation important value and the Grey Relational Analysis was applied to research the influence of environmental factors on species Diversity of vegetation.The result are as follows:(1)The distribution of burned trees with different burned degree was significant different.The blackened height of trees in mildly burned concentrated below 3m,accounting for 76.1%of all trees in the plot;The blackened height of the trees in moderately burned concentrated in 2-6m,accounting for 74.5%,and the distribution is relatively uniform;There are 93.8%of trees with blackened height higher than 6m in the severely burned plot,and the trees higher than 10m accounted for 50.8%,most of the 10m above were all Burned trees.(2)The surviving conditions of trees after fire is related to the fire intensity and tree diameter.With the fire intensity increasing,the survival rate of trees decreases.The survival rate of trees in mild burned accounted for 92.86%,but it accounted for 16.76%in the severe burned.The survival rate of trees in three kinds of fire-disturbed increased with the tree diameter,that is,the larger individuals were more likely to survive in the fire.(3)The number of all the plant species increased after fire,and the importance factor of the herb and shrub showed different degrees of changes.The species in severely burned area had the sharpest increase,and the number of herbaceous species increased from 15 to 26,and the number of shrub species increased from 3 to 6.With the increase of fire intensity,the understory plant richness index(R)and the diversity index(H)showed a trend of increase(P<0.05),while evenness index(J)decreased(P>0.05).(4)The physical and chemical properties in the fired area changed significantly.The effects of different burning intensity(not burned,mildly burned,moderately burned,severely burned)on the physical properties of soil at burned Pinus tabulaeformis forest sites was significant different.The soil moisture content after fire was lower than unburned area(P<0.05),while the soil bulk density decreased(P>0.05),indicating that soil moisture missed after fire and the soil became more tight.The soil chemical properties with different fire intensity also changed.The pH of the soil increased(P>0.05).The organic carbon increased significantly in moderately burned area,but decreased in severely burned area.The total nitrogen content increased after mild and moderate fire,and decreased in severely burned area,but the difference was not significant(P>0.05).Soil total phosphorus increased significantly in moderately burned area(P<0.05),while different not significantly in the other two degree of the burned area.The soil available phosphorus content increased significantly with the increase of fire intensity(P<0.05),and reached the maximum value in the severely burned area.The total phosphorus content was not significantly different.Potassium content increased after the fire.(5)The growth of vegetation after fire was affected largely by tree mortality rate(DR),the ratio of tree blackened height to tree height(SH),soil bulk density(BUL),soil available phosphorus(AP),meanwhile,the total nitrogen(TN),organic carbon(SOM)and aspect(AS)had some effects on vegetation,but the effect of soil pH,soil total potassium(TK)and slope(SP)and slope position(SI)have little effect on species.Grey Relational Analysis indicates that the species richness index(R)and diversity index(H)were significantly correlated with tree mortality rate(DR),the ratio of tree blackened height to tree height(SH),soil available phosphorus(AP),while the slope position(SI)?soil pH and the total nitrogen(TN)showed low correlation with the two index.The factors which are highly correlated with the evenness index(J)are soil potassium(TK)and aspect(As).