Adaptation Mechanism Of Nematode-trapping Fungi Under Fire Disturbance

Objective: Taking Nematode-Trapping Fungi(NTF)as the research object,to explore the adaptation mechanisms of microorganisms to fire from individuals to communities.To provide innovative ideas for the systematic understanding of environmental adaptation mechanisms of microorganisms from individuals to communities,and to provide data support for the construction and practice of fire restoration ecology theory.Methods: 1)Distribution of NTF in 0-10 cm and 10-20 cm soils in natural fireground: 2 fire-placed sample areas and 1 unfired control sample area were set up in Yunlong County,Dali Prefecture,Yunnan Province.Fifteen sampling points were set up in each sample area,and soil samples were collected from 0-10 cm and 10-20 cm soil layers at each point using the five-point sampling method NTF separation,purification,and identification,and measured the soil’s physical and chemical indexes such as soil water content,p H,organic matter,total nitrogen,and total phosphorus.2)Migration adaptation of NTF: NTF vertically distributed communities were constructed in nine 40 cm × 25 cm × 25 cm concrete pots using sterile soil as substrate,i.e.,Arthrobotrys oligospora in the 0-5 cm soil layer,sterile soil in the 5-10 cm soil layer,Dactylellina ellipspspora and Drechslerella dactyloides in the 10-20 cm soil layer(Group A),and Dac.ellipspspora,Dre.dactyloides,and A.oligospora(Group B),and Groups A and B received surface heating treatment for 1.5 h on the10 th day after species addition.In Group C,species were added in the same way as in Group A,but without heat treatment.Groups A,B,and C were isolated from exotic species and monitored the distribution of NTF species in each soil layer of the pots once a week.Meanwhile,sterile soils were placed in three 25 cm × 25 cm × 25 cm cement pots with no one as the additive species(Group D),which were placed in an open area of the practice teaching base of Dali University,and their topsoil was scraped for NTF isolation,purification,and identification once a week.3)Phenotypic adaptation of NTF after fire: three species of Arthrobotrys,Dactylellina,and Drechslerella NTF were selected in both fire and non-fire habitats,as follows: Arthrobotrys: A.oligospora,A.musiformis,and A.conoides.Dactylellina:Dac.drechsleri,Dac.ellipspspora,Dac.gephyropage.Drechslerella: Dre.dactyloides,Dre.aphrobrohum,Dre.coelobrochum,three strains of each species.Determined the individual conidial morphological size,growth rate,and predation efficiency of each NTF separately.Results: 1)In the nature fireground,the detection rate,and species diversity of NTF were higher in the fire site than in the control area(P > 0.05),while the soil physicochemical properties were the opposite.The detection rate of each genus of NTF in the topsoil of the fire area was in the order of Drechslerella > Dactylellina >Arthrobotrys,and the control area,Arthrobotrys > Dactylellina > Drechslerella.The detection rate of each genus of NTF in the subsoil of both the burned and control area was in the order of Dactylellina > Drechslerella > Arthrobotrys.Soil p H and moisture content are the main environmental factors affecting the distribution of NTF.2)NTF detected in each soil layer before the fire were artificially added species.In Group C,A.oligospora was detected in 5-10 cm at 14 d after the stabilization period and in 10-20 cm at 35 d but did not achieve long-term stable detection in this soil layer.In contrast,Dac.ellipspspora and Dre.dactyloides were stably detected at all time points in the 10-20 cm,and Dre.dactyloides was only detected fluctuatingly in 5-10 cm.After the fire,all A.oligospora in 0-5 cm was removed.In Group A,Dac.ellipspspora and Dre.dactyloides,originally located in 10-20 cm,were detected in 5-10 cm at 7 d and 21 d post-fire,respectively,and were subsequently monitored in 0-5cm at 49 d and 35 d post-fire,respectively.In Group B,Dac.ellipspspora and Dre.dactyloides were detected at 14 d and 21 d post-fire in 5-10 cm,respectively,and then at 56 d and 35 d post-fire in 0-5 cm,respectively,and A.oligospora added to the 10-20 cm was detected at this layer fluctuating.In Group D,NTF started to migrate into the sterile soil one after another from 21 d.A total of 2 genera and 9 species of NTF were isolated from Group D throughout the monitoring cycle,among which A.oligospora was the dominant species of air migration.3)There were some differences in the growth characteristics of NTF in fire and non-fire habitats,specifically: after the fire,Measurements of conidial length,width,separation width,and distance from separation to the base were smaller than in nonfire habitats of Arthrobotrys,and the differences were significant(P < 0.05).There were no significant changes in the growth rate of A.oligospora,a significant decrease in the growth rate of A.musiformis(P < 0.001),a significant increase in the growth rate of A.conoides(P < 0.001),predation efficiency of fungi of Arthrobotrys was significantly higher(P < 0.001).The conidia were smaller than those in non-fire habitats of Dactylellina and Drechslerella,and all measures of conidia in fire and non-fire habitats were significantly different(P < 0.05),and they had significantly higher growth rates and predatory abilities after the fire(P < 0.001).Conclusions: Fire adaptation mechanisms of migration and phenotypic plasticity exist in NTF.At the population level,fire shapes higher NTF diversity,Dac.ellipspspora and Dre.dactyloides have the ability to migrate vertically from lower to upper soil layers after the fire,and there are interspecific differences in this migration ability,and A.oligospora,Dac.ellipspspora and Dre.dactyloides have the ability to migrate vertically from lower to upper soil layers after the fire.The competition among three species,A.oligospora,Dac.ellipspspora and Dre.dactyloides,affect the migration rate of NTF,and the vertical migration of NTF promotes the community recovery of NTF in the soil surface layer after fire.Air contains a large amount of NTF germplasm resources,and the migration of airborne NTF is also important for the recovery of soil NTF communities during the recovery process of post-fire soil microorganisms.At the individual level,NTF adapts to post-fire habitats by reducing cell size and enhancing saprophytic and predatory abilities.