Impacts Of Logging Residue Management On C And N Pools Of A15-year-old Chinese Fir (Cunninghamia Lanceolata) Plantation Forest

Forest ecosystem is one of the most important ecosystem, forest plantationmanagement practices would influence the C and N stocks. The area of planted forestin China stands first in the world, which is approximately one third of this nation'stotal forest area, therefore, reasonable management can make it be an important Cstocks.Chinese Fir(Cunninghamia lanceolata (Lamb.) Hook) is the current plantationspecie in South China,and Chinese fir plantation is a potentially huge C pools. Thisthesis studied the hot issues which are about the C and N stocks of15-year-oldplantation influenced by management practices, in long term fixed locationobservation plots which was established under the guidance from the Centre forInternational Forestry Research (CIFOR), analysed the different logging residuetreatment(including Stem Only and Burning, Double Residue, Floor Removed, StemOnly and Whole Tree Harvest) effects on plant layer C stocks, total mineral soil C andN stocks, soil soluble C and N concentrations, Soil microbial biomass C and Nconcentrations, the δ13C values of soil light/heavy fraction. The research conclusionsare in the following:(1) Effects of logging residue treatments on15-year-old Chinese Fir tree layerand undergrowth layer and litterfall layer C storage had no significant difference(P=0.05). The SB treatment on C stocks of the tree layer and litterfall layer showed anegative effect, which was not conducive to the maintenance of forest C pools, but itshowed some positive effects on the undergrowth layer.(2) According to the estimate of different treatment stand soil C and N stocks, theresult showed that DR(double logging reside) treatment on soil C pool had astimulative effect, but the FR(forest floor removal) treatment was not conducive to themaintenance of soil C pool, the impact of SB(stem only and burning)on stand N poolis negative, and the C and N stocks of different treatment in the same soil layer didn'thad significant difference (P>0.05).(3) By measuring of soil LF(light fraction) content, the results showed thatSB(stem only and burning) was the most detrimental to the soil light fraction organicmatter storage, secondly FR(forest floor removal)treatment showed negativeeffect,too. DR(double logging reside) treatment had a higher value in LFcontent,which is more conducive to maintain forest productivity.(4) By the δ13C value determination of LF and HF in different treatment stand,the results showed that HF-δ13C values are all higher than the LF, and both increasedwith the soil layer deepening, and the LF was more significant, although there weren'tsignificant difference among the different treatments(P>0.05).(5) Via measuring the concentations of soil soluble C and N in differentextraction method, no consistent regularity was showed in different treatment stand.But SB and FR treatment had significant difference(P>0.05) in some soil layer. FR treatment showed higher level in DKClN and DWN concentations,and DR treatmenthad higher DHWOC and DWOC concentations.(6) By measuring of soil mineral nitrogen content, the results showed that SO(stem only) had the highest value in NH4+-N concentration, SB treatment standshowed less concentration. DR and FR treatment both had approximate NO3--Nconcentration, and was about1.7-2.4times of other treatments.(7) By measuring of soil microbial biomass C and N in every soil layer,theresults showed that, in FR treatment stand, MBC and MBN both have the highestconcentrations in upper layer(0-5cm), middle level in5-10cm layer,and the theywere the lowest in10-20cm layer；DR and SO treatment showed the highestconcentrations in5-10cm layer, while SB treatment was the lowest. The C and Nratio of treatments except DR increased by soil layer from the upper to bottle.(8) According to the estimate of fine root biomass in3treatments(DR,FR,SB)stand, the result showed that the vertical spatial distribution regularity of fine root wasobvious,which was reduced by soil deepening, and the difference among differenttreatment didn't reach significance level(P>0.05). The SB treatment effect on fine rootbiomass was negative.