Study Of Soil Respiration,Its Components And Organic Carbon Mineralization In Early Stage Of Different Regeneration Of Broad-leaved Evergreen Forests

The carbon emission of forest soil account for 60%-70%of the carbon emission of global soil,as a result,a little change in forest soil respiration,would have affect the global carbon cycle,especially have a significant impact on the concentration of CO2 in atmosphere.How would soil respiration and its components and soil organic carbon mineralization response to different forest regeneration in early stage,would have a profound significance in calculation of forest ecosystem carbon balance and forest carbon sink.We studied a 36-year-old secondary Castanopsis carlesii forest with different regenerations(silvicultural plantation and artificial regeneration)after clear-cutting and prescribed burning in Sanming city,Fujian province for one year.We studied soil respiration and its components in early stage of different regenerations;whilst studied the soil carbon mineralization in early stage of different regenerations,emphatically discusses the response and mechanism of soil respiration,its components and soil carbon mineralization to different regenerations in early stage.Our results showed that:(1)soil respiration and heterotrophic respiration rates showed significant seasonal changes with the maximum value appearing between June and July,in the form of a single-peaked curve;while autotrophic respiration rate was lower during the first four months,the rates soil respiration and its components were both characterized by control>artificial regeneration>silvicultural plantation;(2)Soil respiration and its components showed significant correlations with soil temperature at 5 cm depth in early stage of different regeneration,while there were no significant relationship between soil respiration and soil water content at 0-12 depth,soil temperature explained 39.7%-75.2%of the monthly variations in soil respiration.The results of using soil temperature and water content of two-factor fitting model and temperature for single factor exponential fitting models showed no difference.The soil respiration Q10 values of silvicultural plantation and artificial regeneration were both 1.67,which lower than that of control,this phenomenon means that different regeneration made the temperature sensitivity of soil respiration became lower;(3)The annual estimates of heterotrophic respiration in silvicultural plantation and artificial regeneration account for 74.4%and 76.6%of soil respiration,apparently higher than the proportion of autotrophic respiration.The annual estimates of soil respiration and its components were both characterized by control>artificial regeneration>silvicultural plantation;(4)After 6 and 18 months clear-cutting,the organic carbon content at 0?10cm depth of silvicultural plantation had declined by 6.0%and 1.9%,comparing to control.While,the organic carbon content at 0-10cm depth of artificial regeneration had increased by 25.0%and 15.6%.After two incubation test,the cumulative mineralized amount of each soil layer in silvicultural plantation were significantly lower than control and artificial regeneration treatment;after 6 months clear-cutting,the cumulative mineralized amount of each soil layer in artificial regeneration treatment were significantly lower than control,but 18 months later,the cumulative mineralized amount at soil depths of 10-20cm and 20-40cm became significantly higher than the those of control.The cumulative mineralized amount of each soil layer in artificial regeneration treatment were significantly higher than those of one year before,increased by 57.0%,112.0%and 49.9%,respectively,while the cumulative mineralized amount of each soil layer in silvicultural plantation and control treatment between the first and second incubation test didn't show obvious regularity.The cumulative mineralized amount showed significantly liner relationship with the initial content of organic carbon,microbial biomass and dissolved organic carbon(p<0.05).