Effect Of Thinning On Carbon Allocation Of Larix Principis-rupprechtii Plantation In Mt.Taiyue

This paper studied carbon allocation in Larix principis-rupprechtii plantation with thinning treatments in Mt.Taiyue of North China.The plot survey,nutrition analysis,hydrologic monitor,litter collection,decomposition experiment and soil respiration monitor were used.On the basis of computing the carbon density of different carbon stock in L.principis-rupprechtii plantation,the carbon dynamic change of carbon migration and emission along different carbon stock were investigated.Meanwhile,the relationship between carbon allocation and key factors of the plantation with thinning treatments.The main results of the research are as follows:(1)The canopy structure of the larch plantation was changed significantly by the thinning,and it generated the changes of rainfall redistribution,light environment,litter and soil characters.With the increase of treatment intensity,the spatial heterogeneity of canopy,rainfall and vegetation of understory were magnified in the larch forest.The light radiance of understory in three larch plantation with thinning treatment were higher 1.2-2.1 times than control(CK).The water holding capacity of litter was improved by thinning,but the characters of soil was inconspicuous.However,the microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)were improved by thinning,and the effect was decreasing along depth of soil.(2)The thinning was more obviously effect for carbon distribution of vegetation and soil than litter in the larch plantation.The biomass of tree decreased gradually with the increase of thinning intensity,but the accumulation of growth time can reduce the difference of tree biomass.The thinning was observably improved for the forest productivity and carbon sequestration ability.The change regulation of shrub and herb biomass were inverse to tree biomass.The biomass determined carbon density of vegetation.The carbon distribution pattern of litter was non-significant changed by the thinning.With the increase of soil depth,the carbon density of soil layer declined gradually.The soil carbon density of moderate thinned(MT)and heavy thinned(HT)stand were greater than low thinned(LT)and CK stand.The allocation proportion of soil carbon stock was largest,the second was tree carbon stock,the third was litter carbon stock and the least was undergrowth vegetation carbon stock.(3)The amount of carbon migration on producing of litter and decomposing of needle were magnified by the thinning in larch plantation.But the carbon migration on dead and decomposing of fine-root increased at first and then descended along the intensity of thinning.The total litter production of MT and HT stand greater than LT and CK stand.The amount of carbon migration on litter producing was proportional to litter production.The needle of litter decomposition rate was improved by the thinning,and the amount of carbon migration on decomposing of needle in LT,MT and HT stands were higher than CK stand.Fine-root biomass of LT stand was greater than the other treatment stands.The decomposition rate of fine-root was improved by the thinning,and the amount of carbon migration on dead and decomposing of fine-root were largest in LT stand.(4)The thinning treatments improved soil temperature and moisture,but had two coins for soil respiration(Rs).The Rs of MT and HT stands was higher than CK stand,but LT stand lower than CK stand due to the litter respiration rate(Rlitter)of Rs was restrained by LT thinning treatment.With the increase of thinning intensity,the root respiration rate(Rroot)of Rs decreased gradually,but mineral soil respiration rate(Rmineral soil)of Rs improved.The Rs was exponential correlation with soil temperature and R2 ranged from 0.51 to 0.65.The Q10 value of LT stand was higher than CK stand,but MT and HT stands was lower than CK stand.The correlation of Rs and soil moisture was low,and soil moisture was not limiting factor for Rs in the larch plantation.The proportion of carbon flux on R mineral soil was largest,the second was Rlitter,and the third was Rroot.The annual carbon flux of soil respiration of MT and HT stands were greater than CK and LT stands.(5)The thinning treatments can improve effectively productivity and carbon sequestration capacity of the larch plantation,and it was beneficial for carbon emission of soil and carbon migration between different carbon pool in ecosystem.The carbon surplus of Larix principis-rupprechtii plantation was incremental along the intensity of thinning.