| Eucalyptus is the most widely distributed species in the world.At present,China is the second largest countries with Eucalyptus plantations in the world with 4 million 500 thousand hectares,which accounts for 19.94%of the total Eucalyptus plantation area in the world.As the largest carbon pool on land,the dynamic changes in the distribution of carbon stocks affect the global carbon cycle and carbon balance.The biomass of the forest community is an important indicator of the productivity of the forest ecosystem,the most direct expression of the structure and function of the forest ecosystem,and the comprehensive embodiment of the environmental quality of the forest ecosystem.Controlled burning is a kind of woodland cleaning method commonly used in plantations in southern China.Biochar can help to improve soil quality.Controlled burning and biochar addition have an important influence on the biomass and the distribution of carbon stocks in the ecosystem.In this study,four treatments were set up in Eucalyptus plantations,i.e.no burning and no biochar(NBNB),no burning with biochar addition(NBB),burning without biochar addition(BNB)and burning with biochar addition(BB)to study the effects of burning and biochar addition on the biomass,productivity and carbon stocks.The findings of this study can provide scientific references for making scientific managements for Eucalyptus plantations.The major results are as follows:(1)Burning and biochar addition can effectively improve the components and the total biomass of tree layer.The total biomass of the tree layer in burning with biochar addition was the highest,which was 93.94 ± 1.83 t/hm2,followed by not biochar addition(87.90 ± 2.16 t/hm2),and no burning and no biochar(81 ± 0.82 t/hm2),and the total biomass of the arbor layer was the lowest(77.20 ± 0.86 t/hm2)without the addition of biochar.When the forestland was cleaned by controlled burning,biochar addition can increase the biomass of all the components of the trees with the total biomass of the tree layer increased by 6.86%.While in plantations without controlled burning,biochar addition can also increase the biomass of all the components of the trees with the total biomass of the tree layer increased by 4.92%.(2)No burning and biochar is addition can increase biomass of shrub,herb and litter layer.The total biomass of shrub,herb and litter layer were NBB>BB>NBNB>BNB.In the two ways of forest land cleaning,biochar addition is beneficial to the accumulation of understory vegetation and litter biomass.The total biomass of shrub layer was 16.66 ± 0.78 t/hm2,the total biomass of herb layer was 10.30 ± 2.14 t/hm2,and the litter layer was 9.82 ± 1.02 t/hm2,which was significantly higher than that of no biochar addition treatment.(3)In accordance with the characteristics of biomass,the productivity of each organ in the arbor layer was significantly different between the treatment and showed the trend of BB>BNB>NBB>NBNB.This was due to the increasing growth of the eucalyptus under burning and biochar addition treatment.The productivity of shrub,herbaceous and litter layer was NBB>BB>NBNB>BNB,and biochar addition without burning was beneficial to the improvement of net primary productivity of understory and litter.(4)Biochar addition can increase biomass carbon storage.Controlled burning and biochar addition is beneficial to the improvement of the total biomass carbon stocks,while the biochar addition without burning is beneficial to the increase of the biomass carbon storage of the understory.The carbon storage of trunk,branch and leaf are BB>BNB>NBB>NBNB,and that of dark and root are BB>NBB>BNB>NBNB.The carbon storage of the arbor layer are BB(46.77 ± 17.78 t C/hm2)>BNB(41.92 ± 0.77 t C/hm2)>NBB(41.25 ± 0.95 t C/hm2)>NBNB(37.22 ± 0.76 t C/hm2).Carbon storage of shrub,herbaceous and litter layer was NBB>BB>NBNB>BNB.The total biomass carbon storage were BB(65.82 ± 4.55 t C/hm2)>NBB(62.83 ± 0.67t C/hm2)>BNB(57.45 ± 2.43 t C/hm2)>NBNB(55.10 ± 0.38 tC/hm2).(5)Biochar addition is beneficial to soil carbon sequestration.While controlled burning can decrease soil carbon storage.Controlled burning and biochar addition can increased soil carbon sequestration in top soil layer.The content of soil organic carbon concentration and carbon storage in 0?20cm soil layer are as follows:NBB>BB>NBNB>BNB,20-40cm and 40-60cm are NBB>NBNB>BB>BNB,and the soil organic carbon storage in 0?60cm soil layer is NBB(92.45± 0.51 tC/hm2)>NBNB(89.35± 0.82 tC/hm2)>BB(88.47± 3.04 t C/hm2)>BNB(82.39±3.81 tC/hm2).(6)The ecosystem carbon storage are as follows:NBB>BB>NBNB>BNB.Ecosystem carbon storage in NBB and BB treatment are 152.05 ± 1.38 t C/hrrm2 and 151.94 ± 5.57 t C/hm2 respectively.Compared with no biochar addition,biochar significantly increased ecosystem carbon storage(7.03%).In the burning condition,biochar addition can increase ecosystem carbon storage by 10.26%.Although it is beneficial to improve the biomass carbon storage of the arbor layer,it is not conducive to the understory and soil carbon storage,but the addition of biochar can effectively alleviate the adverse effects of controlled burning,improve the soil nutrient availability,promote the growth of the eucalyptus and understroy and the soil carbon fixation.Therefore,ecosystem carbon storage under BB treatment is significantly higher than that of NBNB. |
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