Effects Of Prescribed Burning On Fine Root Biomass And Soil Organic Carbon Of Three Artificial Forests In Northeast China

Plant fine roots,as an important functional organ,provide a necessary pathway for the transfer of plant carbon and energy to the soil,and play an important role in the carbon and nutrient cycling of terrestrial ecosystems.Prescribed burning,as one of the important and effective means of forest management,is increasingly receiving attention from domestic and foreign managers and researchers.Therefore,the research on fine roots of forest ecosystem under prescribed burning will help to understand the composition of plant community and the underground competition of ecosystem,and is of great significance to explore the carbon input and output process of forest ecosystem.This study focuses on three typical artificial forests,Pinus koraiensis,Larix gmelinii,and Quercus mongolica,at Hongqi Forest Farm in Hegang City,Heilongjiang Province.The fine root biomass and soil were monitored during the early growth season(June 2019),mid growth season(August 2019),and nongrowth season(October2019)of the first year after prescribed burning,to explore the dynamic changes between them And the proportion of fine root biomass in living fine roots of different life forms and functional types,based on which,the nutrient content and soil physicochemical properties of fine roots are measured to elucidate the impact of different functional types of fine root nutrients on underground soil organic carbon.To provide theoretical support for conducting research on forest fire management and reasonably implementing prescribed burning artificial forest management methods.The main research findings are as follows:(1)There are significant differences in the biomass of live and dead fine roots among the three forest types on prescribed burning.Specifically,the fine roots of the Pinus koraiensis forest respond to the interference of prescribed burning by reducing the biomass of live fine roots and increasing the biomass of dead fine roots.The response of live fine root biomass to fire in the Larix gmelinii forest first increases and then decreases,while the biomass of dead fine roots,in contrast to live fine root biomass,decreases first and then increases.Fine roots in Quercus mongolica forests respond to prescribed burning disturbances by increasing the biomass of live fine roots and reducing the biomass of dead fine roots.The fine root biomass of different levels of plant vegetation exhibits different adaptive survival modes under the action of fire.The prescribed burning significantly reduced the fine root biomass of three forest types of trees by 9.5-14.3%(p<0.05),and significantly increased the fine root biomass of shrubs and herbs by 6.27-14.4%(p<0.05).In addition,prescribed burning significantly increased the proportion of absorbed root biomass in total fine root biomass,and the biomass of absorbed/transported roots in the three forest types significantly increased by 4.2-12.9%(p<0.05).Under favorable nutrient conditions,vegetation changes the biomass allocation of fine roots to different functional organs in order to obtain as much soil resources as possible.Prescribed burning significantly inhibited the organic carbon content of fine roots in the three forest types,and the organic carbon content of dead fine roots also generally decreased.In terms of total nitrogen content in fine roots,it will stimulate the accumulation of total nitrogen content in fine roots.(2)The impact of prescribed burning on soil physical and chemical properties will vary according to different forest types,soil layers.Specifically,after the prescribed burning,the soil temperature of the Pinus koraiensis is more sensitive to changes in the external environment and fluctuates greatly.Overall,the soil temperature of the larch forest has been reduced.It has a positive promoting effect on the soil temperature of Quercus mongolica.The prescribed burning suppressed the soil moisture content of three forest types.After the fire,the soil p H of larch forest and Mongolian oak forest significantly increased.The prescribed burning significantly increased the soil organic carbon content of the Pinus koraiensis,and inhibited the soil organic carbon content of the deciduous pine forest and the Quercus mongolica forest.The prescribed burning significantly reduced the total nitrogen content of Larix gmelinii soil.(3)Prescribed burning has changed the correlation between fine roots and soil,and the structural equation indicates that after fire,the ability to return nutrients is increased by reducing the carbon nitrogen ratio of absorbed and dead fine roots,thereby enhancing the positive role of absorbed and dead fine roots in the soil carbon pool.That is,prescribed burning promotes the exchange process of input and output of soil organic carbon between absorbed and dead fine roots.