| Soil respiration is one of the crucial sources of carbon dioxide(CO2)in the atmosphere and a virtual joint in the terrestrial carbon cycle.It has a direct impact on greenhouse gas emissions and occupies a significant position in the global carbon balance.Forest soil respiration is an imperative and complex chemical process,which is dominated by many factors.Fire is a decisive disturbing circumstance in the forest ecosystem.It will fluctuate the succession process of forests and the interaction within plants,even affect forest biomass and biogeochemical circles.In recent years,there have been merely a few studies on the release of CO2 from the soil via forest fires and burned sites management practices.The potential consequence of firewood logging and regeneration management on fire sites is still controversial.This paper takes the grass-Larix gmelinii in the burned area as the research object,within different firewood management methods and other regeneration methods in the early stage of forest reforestation after fire disturbance.With the soil respiration positioning-observation technology,combined sampling experiments and indoor analysis to study soil respiration and its influencing factors,revealing the early stage of forest restoration of soil respiration and release pathways in frozen soil areas under diverse management methods in burned sites after forest fire interference,exploring proper implement strategies for the restoration burned places.The principal findings are as follows:1.Fire interference after forest restoration early-stage burned area,different firewood management burned area and different post-fire regeneration burned area of soil respiration,the maximum value of the monthly average performance appears in the peak growing season(June-August),the minimum amount occurs during the frozen soil thawing period(4-5 months)or the freezing period(October).2.The study of soil respiration in early stages of forest restoration after fire interference found that:(1)When compared with the unburned site,the soil respiration increased by 13.14%in the burned area,and the soil heterotrophic respiration increased significantly by 38.38%,while soil autotrophic respiration curtailed by 34.09%,in the first three years of restoration(P<0.05);the contribution rate of soil autotrophic respiration weakened in the burned area,but the contribution rate of soil autotrophic respiration recorded an upward trend as the recovery interval transferred.(2)After forest fire interference,soil temperature(T5,T10)and soil moisture(W10)both increased,soil pH and microbial biomass carbon to nitrogen ratio shrink,while soil organic carbon,available phosphorus,available potassium,soil microbial biomass carbon and nitrogen content and soil invertase and catalase activities increased;the number of soil fungi,actinomycetes and bacteria decreased significantly at the initial stage of restoration of burned sites.After two months of the rehabilitation of soil fungi and actinomycetes,the figure has risen sharply and exceeded the unfired plot.(3)The increment in soil temperature and humidity in the initial stage of restoration of burned sites is the chief determinant affecting the soil respiration and its components.Changes in other soil properties will modify the soil respiration and its components but move relatively small.Diversity in forest vegetation and sufficient root biomass will make an impressive contribution to soil autotrophic respiration.3.Research on soil respiration under different burnt wood management methods.Select burned sites with 13 years of fire occurrence and 12 years of burnt wood management for experiments.The results found that:(1)Compared with the unburned site,the soil respiration and soil heterotrophic respiration had little fluctuation in the burned area.The soil autotrophic respiration and contribution rate increased by 54.76%and 49.98%respectively(P<0.05);The selective cutting of burning wood increased the respiration rate and heterotrophic respiration rate,but decreased the autotrophic respiration rate;the soil respiration rate and its components were decreased by clear cutting of burning wood.The firewood felling the contribution rate of soil autotrophic respiration reduced,and the greater the cutting intensity,the smaller the contribution rate of soil autotrophic respiration;(2)The soil temperature(T5,T10)and soil moisture(W10)of the burned area are still higher than those in the unburned area;the contents of organic carbon,total potassium and urease in the burned area were significantly lower than those in the unburned area(P<0.05).Selective cutting of firewood has a notable decrease in the soil organic carbon,available phosphorus and potassium in the burned area.It has a vital inhibitory outcome on catalase activity and an enhancement effect on urease activity(P<0.05).The clear-cutting of firewood has a significant decrease on the content of soil organic carbon,total nitrogen and available phosphorus in the burned area,and inhibits invertase and catalase(P<0.05).(3)Soil temperature increases after fire interference,thereby promoting soil heterotrophic respiration and soil autotrophic respiration,which in turn increases soil respiration.The fine root biomass has a direct and significant effect on the soil autotrophic respiration,and the fine root biomass of the fire wood logging plot decreases,which has a more substantial impact on the soil autotrophic respiration.The higher humidity of the burned area,the lower soil pH and higher quantity of actinomycetes may be the key to the increase of soil autotrophic respiration in this area.4.The study of soil respiration under different regeneration methods burned area,where selected ten years after regenerated.The results showed that:(1)The maximum soil respiration of the natural regeneration plot was 3.37 ?mol·m-2·s-1.The minimum soil respiration of the artificially promoted natural regeneration plot was 2.23 ?mol·m·-2·s-1.(2)There is no significant difference in soil temperature(T5,T10)and soil moisture(W10)of the four types of regeneration plots.T10 and W10 are different under different regeneration methods,which have other effects on soil respiration.(3)Natural regeneration plot the soil urease activity is the highest in the field,which promotes the soil respiration.The soil catalase activity of the realistic non-arbour regeneration plot has the highest soil respiration and inhibits the soil respiration;the artificial regeneration plot has the most correlation between the soil respiration and fine root biomass,the correlation between soil respiration and fine root biomass of artificially promoted natural regeneration plot is the smallest.To sum up,fire interference can enhance soil respiration in frozen soil areas,and the increase in soil respiration in the initial stage of restoration of the burned area is mainly due to the rise in soil heterotrophic respiration.The increase in soil respiration in not cut of fire wood plot is primarily due to the increase of soil autotrophic respiration.The burned area management has effect on the soil respiration and driving factors.Selective cutting of fire wood has an enhanced effect on the soil respiration of the burned area,mainly due to the increase in soil heterotrophic respiration after selective logging.After cleaned cutting of fire wood the soil respiration and its components has a reduced effect in the burned area.The number of trees in the natural regeneration plot was the highest,and the soil respiration was the highest.In the process of restoration of burned areas,due to mechanical and human interference,vegetation restoration and soil structure in frozen soil areas will change,and soil respiration will adjust accordingly.Therefore,it is appealed to reduce fire wood logging after forest fires.If logging has taken place,human disturbance should be minimized,to avoid the influence of human disturbance on vegetation succession and soil carbon cycle again.Studying the effects of fire interference and management of burned area on soil respiration is of great significance in the ecological restoration of burned area and the carbon cycle of forest ecosystems. |
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