| Decline of vegetation coverage induced by fire disturbance always results in some environmental problems,like soil erosion.Vegetation recovery following fire had arised people's concems.A wild fire attacked Maoan forest farm in 2006 summer.It was necessary to recover vegetation in Maoan forest farm.Before the vegetation recovery,it was significant to know the characteric of vegetation and soil property in burned field.In this paper,survival tree characteristic,understory composition and soil physical and chemical property were studied,for supplying basis to vegetation recovery in Maoan forest farm.Characteric of vegetation in unburned field was studied.The results showed that:There were 407 species in 297genus belong to 119 families in Maoan forest farm;The dominant life form was phanerophytes,which amounted 58.97%of total.;In Maoan forest farm,there were four types of forest community,such as Cunninghamia lanceolata forest,Pinus massoniana forest,mixed broadleaved coniferous forest and evergreen broadleaved forest.Based on investigation of survival tree in four types of forest stands(including unburned stand and high severity bumed stand),the effects of high severity fire disturbance on main trees of each forest community were studied.Trees had different manners to survive after fire distubrance.P. massoniana survived with crown survival,while C.lanceolata,Neolitsea aurata var glauca, Camellia oleifera and Symplocos lancifolia survived with sprout.Sprouts produced by C.lanceolata individuals were significantly taller than that produced by the C.oleifera individuals and S. lancifolia individuals in the high severity burned stand.Tree denisities in each DBH were compared beween unburned stands and high severity burned stand of the same forest,the results showed that: Density of C.lanceolata seedlings(DBH＜2.5cm)decreased,while density of C.lanceolata individuals(DBH＞2.5cm)changed little in high severity burned stands of C.lanceolata forest;Few P.massoniana individuals whose DBH were larger than 27.5cm surivived in high severity burned stand of P.massoniana forest;Few P.massoniana individuals whose DBH were larger than 17.5 cm and no Gordonia acuminate individual surivived in high severity burned stand of mixed broadleaved coniferous forest;In high severity burned stands of evergreen broadleaved forest,densities of C. oleifera seedling(DBH＜2.5cm)and S.lancifolia seedling(DBH＜2.5cm)decreased mostly,while densities of C.oleifera individuals and S.lancifolia individuals changed little,and few Neolitsea aurata var glauca individuals survived.Densities of survived individuals among four types of forest followed the sequence as:C.lanceolata forest＞evergreen broadleaved forest＞P.massoniana forest and mixed broadleaved coniferous forest.It suggested that the number of survival trees was associated with tree species composition in community after a high severity fire disturbance.It had more survival individuals in the C.lanceolata forest which was mainly composed by mature trees that can sprout effectively.C.lanceolata forest had strong resilience after a high severity fire disturbance.Combined with vegetation investigation on unburned stand,low severity burned stand and high severity burned stand in mixed broadleaved coniferous forest,effects of different severity fire disturbance on understory composition were researched.High severity fire disturbance could improve tree seedling regeneration,especially heliophilousis species seedling regeneration.Both low severity and high severity fire disturbance would induce the coverage and species number of shrub to decrease.Rhododendron bachi and Maesa japonica which can sprout effectively dominanted in low severity burned stand,while Rubus corchorifolius which is heliophilousis specie dominanted in high severity burned stand.There were larger specie number of annual herb,larger specie number of herb and larger coverage of herb in high severity burned stand.Pteridium aquilinum dominanted in low severity burned stand,while P.aquilinum and Conyza Canadensi dominanted in high severity burned stand.The results showed that both low severity and high severity fire disturbance can lead to changes of understory vegetation composition,especically high severity fire disturbance.Characteristics of soil physical and chemical property were studied in unburned stand,low severity burned stand and high severity burned stand of mix broadleaved coniferous forest and IFI (integrated fertility index)was used to evaluate the integrated ability of soil physical and chemical property,results were found as follow:(1)Soil bulk density of the first layer(0～5cm)soil was higher in both low severity and high severity bumed stands than that in unburned stand.Soil bulk density in second layer(5～10cm)soil had no significantly difference among three types of stand.(2) Soil pH values were no significantly difference among three types of stands.(3)Soil organic carbon content,soil total nitrogen content and soil available nitrogen content among different stands followed the sequence as:unburned stand＞low severity burned stand＞high severity burned stand, although they were no significantly difference between low severity burned stand and high severity burned stand.(4)Soil available phosphorus content in high severity burned stand was higher than that in other stands.Soil total phosphorus contents were no significantly difference among three types of stands.(5)IFI of the first layer soil among three types of stand followed the sequence as: unburned stand(0.821)＞high severity burned stand(0.586)＞low severity burned stand(0.584).The discrepancy of IFI between highest value and lowest value was 0.237 in the first layer.IFI of the second layer soil among three types of stand followed the sequence as:unburned stand(0.258)＞low severity burned stand(0.212)＞high severity burned stand(0.111).The discrepancy of IFI between highest value and lowest value was 0.148 in the second layer.The results showed that:fire disturbance would increase bulk density and reduce content of organic carbon,total nitrogen and available nitrogen,which induced integrated ability of soil physical and chemical property to decline.
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