| Under the context of globale warming, forest as the most important terrestrial ecosystem, its function as a carbon reservoir is increasingly recognized. Well manag ed plantation is not only a reservoir, but also a carbon sink. Studies on the biomas s and carbon stock of a plantation will be useful both for carbon sequestration pote ntial assessment and for caybon offsetting oriented silviculture technology developme nt. Betula alnoides is one of the most important species widely used for afforestatio n in Yunnan. To reduce uncertainty on biomass carbon estimation and generate tech nical tools for carbon accounting and monitoring for the plantation, a biomass surve y was conducted in two prefectures withing its central distribution areas in Yunnan, using harvesting method and allometric equations jointly. Based on data gathered fr om the survey, biomass density, carbon density and carbon accounting parameters fo r the plantation were calculated and their spatial distribution patterns and dynamics were analyzed respectively. Then technical issues regarding carbon accounting and m onitoring for Simao pine plantation were disscussed with feference to the foundings from this study. The results showed that:During the periods of young and middle age, with the increase on stand age, biomass of the plantation accumulated rapidly, ratios of different layers over the wh ole stand both for biomass and productivity varied significantly.Biomass density for t he plantation of Betula alnoides with ages of3-20a was in a range of10.44-224.63t.hm-2. Of which, arbor layer was determined as3.47-208.13t.hm-2, shrub layer determined as0.26-10.16t.hm-2, and grass layer determined as0.65-3.88t.hm-2. Significant linear correlations were found between the biomass density and the stand age for the arbor layer and shrub layer, and biomass density of grass layer was ne gatively related to its age. Logistic models developed by this study to relate biomas s density with age (variable)gave satisfied estimates for the stand, arbor layer and above-groud layer. Productivities of the plantations aged3-20for the stand, arbor layer, shrub layer and grass layer were7.57±2.30t.hm-2.a-1,7.06±2.30t.hm-2.a-10.27±0.27t.hm-2.a-1and0.23±0.21t.hm-2.a-1respectively. With the increase on age, productivity for the arbor layer increased remarkably following a logistic model, w hile the productivity for shrub layer changed following an S curve function and gra ss layer declined exponentially.Significent differences were found among biomass conversion and expansion fa ctor (BCEF), biomass expansion factor (BEF), and root-shoot ratio (R) compaired wi th the IPCC defaut values.Mean BCEF for Betula alnoides plantation was0.5018M g m-3(n=13,95%confidence interval=0.3419-0.6617), lower than the IPCC default value. BCEF for Betula alnoides plantation was negatively related to mean stand height (H), mean diameter at breast level (D),stand growing stock (V) and st and age(A)(P<0.05). And BCEF for the plantation was positatively related to st and density (N)(P<0.01). Regression equations developed for relating BCEF wit h stand factors gave satisfied estimates. Mean BEF for Betula alnoides plantation w as1.3562(n=13,95%confidence interval=0.1159～0.1857), lower than the IP CC default value. BEF was negatively related to D、H、V and A (P<0.01) and could be simulated successfully. Mean R for Pinus kesiya var. langbianensis plant ation was0.1508(n=13,95%confidence interval=0.1159～0.1857), lower tha n the IPCC default value. R was negatively related to D,H,V,A (P<0.01) and N (P<0.05)..Carbon content for Betula alnoides was lower than the commonly used default value (50%).Carbon content increased with the increase on stand age. Significent di fferences were found among different organs of the plant. The mean whole tree car bon content of Pinus Kesiya Var. langbianensis was calculated.as48.33%based on the dry biomass percentages of different organs and their respective carbon contents. The carbon content of main stem was48.08%,a little bit lower than that of bar k(49.70%, leaf (49.47%), roots (48.50) and branch(48.27%).The mean basic wood density of Betula alnoides was0.341-0.651g/cm3. It i ncreased outward from the heart to bark and reached its maximum at the age of11years. It was positively related to the age, and the basic wood density was logarith mically increased with the age of growth ring. The whole tree basic density of1year old Betula alnoides was0.391g/cm3, then increased logarithmically with age a nd reached0.567g/cm3at the13th year.Young and middled aged planation of simao pine had relatively high carbon d ensity, showing very strong carbon sequestration capacity.Biomass carbon density for the plantations of age3-5a,6-8a,9-11a,12-14a and17-20a were (11.92±10.28)、(21.07±7.29)、(35.72±7.76)、(51.75±5.64) and (90.89±23.78) t.hm-2respectiv ely. With the increase on stand age, carbon densities for arbor,shrub and stand layer were increased significantly, while that for grass layers decreased slightly. Relation s between carbon density and stand age for stand, arbor and shrub layer could be f itted by a curve of second order..Annual rate of carbon sequestration for the pla ntations of3～5a,6～8a,9～11a,12～14a and17～20a were (2.69±1.61),(3.04±1.07),(3.58±0.78),(3.97±0.13) and (4.87±0.73) t.hm-2.a-1respectively. T he rates for whole stand and arbor layer were both positively related to stand age (P<0.01) and that for grass layer was negatively related to stand age (P>0.05). The rate for shrub layer was negatively related to age but not statistically significant. M oreover, there was a typical power function relation between annual rate and age fo r whole stand.Results from this study could be used for carbon accounting and monitoring f or Betula alnoides plantation carbon offseting projects. Since the definitions and res earch procedures of this study were in line with relevant guidelines by IPCC and th e State Forestry Administration, results gained could be used directly for carbon acc ounting and monitoring for local carbon mitigating projects. However, site condition, stand age and management practice need to be fully taken into consideration when applied.To generalize, carbon accounting parameters gained from the study were speci es, forest type and site specific, thus the use of these parameters would be helpful i n reducing the uncertainty of carbon stock estimation. Secondly, methodologies for c arbon stock accounting and monitoring for the plantation of Betula alnoides was pro posed based on the results from the study. At last, the production, accumulation and allocation of biomass and carbon stock were studied, the results would be helpful for gaining a deep understanding on the dynamics of biomass and carbon stock acc umulation of Betula alnoides plantaion.The study could also provide valuable referen ce for carbon oriented silviculture technology development. |
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