Study On The Effect Of Fire On The Community Structure Of Nematode-Trapping Fungi

Objective:To understand the effect of fire on soil microbial community structure,and take nematode-trapping fungi as the research object to explore the effect of fire on soil microbial community structure.Methods:1.Sampling design: The burned area of Yunlong County was selected as the study sample area.According to the different ways of restoration(artificial restoration and natural restoration)after burning and the distance(near and far)from the burned area,the study sample area was divided into four different sample areas,namely,the fire area(artificial restoration area),the fire area(natural restoration area),the control(near-end area)and the control(far-end area).2.Sample acquisition: Remove the surface defoliation,collect about 100 g of soil for each sample,put it in a disposable aseptic self-sealing bag,record the sample information in detail,take the sample back to the laboratory,and dispose of all samples within a week.3.Sample Quantity: 320 soil samples were collected,of which the altitude of fire site(artificial restoration area)and control(remote area)ranged from 2800 to 2950 m,30 samples were collected from each area,two samples were collected from each sample point,60 samples were collected from each sample point;the altitude of fire site(natural restoration area)and control(near-end area)ranged from 2800 to 3000 m,and 50 samples were collected from each area.Two samples were collected and 100 soil samples were collected.4.Sample treatment: Nematode-trapping fungi were isolated and purified by soil dispersion method and monospore separation method.5.Identification of strains: Species are identified mainly according to the morphological characteristics of strains,which are difficult to identify by morphological identification and molecular biological methods.6.Data processing: According to species richness,detection rate,diversity index(Shannon index)and other indicators,the data were analyzed and processed.Results:A total of 569 nematode-trapping fungi were isolated from 320 samples.They were identified as 3 genera and 23 species.Among them,19 species belonged toArthrobotrys,395 species belonged to Dactylellina,155 species belonged to Drechslerella,and the diversity index was 2.04.Dactylellina drechsleri and Drechslerella aphrobrocha were dominant species.The number and detection rate of strains were 197 strains and 115 strains,41.25% and 25.31% respectively.From the fire field(natural restoration area)and the control(proximal area),191 strains of 3 genera,16 species and 172 strains of 14 species of 3 genera predatory nematode fungi were obtained,and the diversity index was 2.05 and 1.62,respectively.The total number and diversity index of bacteria in fire field(natural restoration area)were higher than those in control(proximal area).191 nematode-trapping fungi belonging to 20 species and 3 genera were isolated and identified from the fire site(natural restoration area)and the control(proximal area).In the control(proximal region),the species richness of nematode-trapping fungi decreased with elevation,which accorded with the decreasing pattern;in the fire(natural restoration area),the species richness of nematode-trapping fungi increased with elevation at first,then decreased with elevation,and the peak species richness tended to lower elevation,showing a frontal pattern.The regional diversity indices of fire site(natural restoration area),control(proximal area)and control(distal area)at altitudes of 2800-2900 m were 2.07,1.78 and 2.03,respectively.In addition,the number of strains nematode-trapping fungi was correlated with the distance from the fire field,and the number of strains of Arthrobotrys and Dactylellina was positively correlated with the distance from the fire field.The farther the distance was,the more the number of strains was(r = 0.40,P <0.05;r = 0.43,P < 0.05);while the number of strains of Drechslerella was negatively correlated with the distance from the fire field,and the number of strains increased with the distance.It decreased gradually(r=-0.53,P< 0.05).Statistical analysis showed that there were 46 strains of Dactylellina and 35 strains of Drechslerella in 7 species and 35 strains of Drechslerella in fire field(artificial restoration area),fire field(natural restoration area)and control(remote area)at the same altitude(2800-2900m).The number of strains and species of Arthrobotrys,Dactylellina and Drechslerella in the fire field(natural restoration area)were 3,8,68 and 4,56 respectively.The number of strains and species of Arthrobotrys,Dactylellina and Drechslerella in the control(distal region)were 14 in4 species,93 in 7 species and 12 in 4 species,respectively.The community structure of the fire site(natural restoration area)was closer to that of the control(remote area).Conclusions:1.Fire can significantly change the community structure of nematode-trapping fungi and increase the diversity index of nematode-trapping fungi.2.Burning can change the vertical distribution pattern of nematode-trapping fungi.3.Distance from the fire field will have different effects on the number of strains of different genera of nematode-trapping fungi.4.The community structure of nematode-trapping fungi will be affected by different restoration methods after burning.