Community Characteristics Of Vegetation Regeneration After Fire In Permafrost Regions Of Cold Temperate Zone

Through the field investigation of post fire vegetation(wetland,forest and shrub)in high latitude Daxing'anling Forest Region,this study,for the first time,through numerical model simulation,long-term field quantitative observation,geophysical exploration,remote sensing and other means,adopted the method of "space for time",and adopted the method of combining internal and external investigation to investigate the grassland swamp moderation,shrub swamp wetland and grass Larix gmelina after fire The death status,regeneration type and regeneration rate of four different forest types of Rhododendron and Larix gmelina were studied under three conditions of non fire,moderate light fire and severe fire.The NDVI and vegetation coverage of the vegetation before and after the fire were monitored by remote sensing,and the regeneration and restoration situation and species composition dynamics of different forest types in different restoration stages were studied Change,and vegetation community diversity.The results are as follows:(1)The biomass of aboveground herbaceous layer in grassland wetland was higher than that in non burned grassland wetland after moderate fire.The results showed that after the fire,there were some plant species which had not been found before in the grass swamp wetland community.(2)Shrub swamp wetland The herbaceous species in the burned shrub wetland are quite different from those in the unburned shrub wetland.That is to say,the species in the burned shrub wetland,such as Cares callitrichos V.Krecz,Trollius chinensis,Saussurea japonica(Thunb.)DC.,Hedysarum alpihum I,Cicuta virosa Linn,etc.,prefer sunlight to those of the unburned shrub wetland,such as Risensata Thunb and Thalictrum aquilegiifolium var.sibiricum,and the number of shrub species in the burned shrub wetland is less than that in the unburned shrub wetland,This indicates that the species of burned shrub wetland is still in the process of evolution from the partial positive species after fire to more negative species.(3)Community characteristics of grass Larix gmelinii forest Because of the forest death caused by fire,the canopy density of forest has changed greatly.After the surface vegetation burned,the soil layer is exposed,the ground temperature rises,and the ecosystem structure changes.Especially,the heat balance of permafrost layer is broken,the frozen soil is reduced or melted,and the soil characteristics and water environment are affected.These factors directly lead to the forest shrub and grass vegetation The forest vegetation formed new communities in the process of regeneration.(4)The Rhododendron Larix gmelina forest is still in the process of evolution to the pre Fire State six years after the fire,especially the heavily burned Rhododendron larch forest.Moderate / mild fire could promote the optimization of tree layer composition of Rhododendron and Larix gmelina forest.The changes of forest canopy density and soil nutrients caused by forest death after fire are the main reasons for the differences in species composition and biomass of shrub layer and herb layer in unburned,moderately and severely burned plots.The forest regeneration was promoted by fire,especially in the severely burned area,but the tree species composition of the regeneration saplings was quite different from that before the fire.