Dynamics Of Biomass And Carbon Stock For Young And Middle Aged Plantation Of Simao Pine (Pinus Kesiya Var. Langbianensis)

Under the background of global change, forest's function as a carbon sink is increasingly recognized. So far, "afforestation and reforestation" is the most important CDM project of forestry sector. Studies on the dynamics of biomass and carbon stock of a plantation will be useful both for carbon sequestration potential assessment of the plantation and for carbon offsetting oriented silviculture technology development. Simao pine(Pinus kesiya var. langbianensis) is one of the most important species widely used for afforestation in Yunnan. To reduce uncertainty on biomass carbon estimation and generate technical tools for carbon accounting and monitoring, a biomass survey for the plantation was conducted in its central distribution areas in southern Yunnan using harvesting method. Based on data gathered from the survey, allometric equations for Simao pine were developed, biomass density, carbon density and carbon accounting parameters for the plantation were calculated, and their spatial distribution patterns and dynamics were analyzed respectively. At last, technical issues regarding carbon accounting and monitoring for Simao pine plantation were discussed with reference to the results from this study. The results of the study showed that:(1) With the increase on stand age, biomass of the plantation accumulated rapidly, ratios of different layers over the whole stand both for biomass and productivity varied significantly. Biomass density for Simao pine plantation with ages of 3-26 was in a range of 22.39-308.96 t·hm-2. Of which, arbor layer was determined as 7.07-295.74 t·hm-2, shrub layer determined as 1.73-52.46 t·hm-2.grass layer determined as 0.78-16.40 t·hm-2, and liter-fall determined as 0.90-11.00 t·hm-2. Significant linear correlations were found between the biomass density and the stand age for the arbor layer, the stand and the litter-fall layer. Biomass density of the shrub layer and grass layer were negatively related to their ages but not statistically significant. Logistic models developed by this study to relate biomass density with age (variable)gave satisfied estimates for the stand, arbor layer and litter-fall. Productivities of the plantations aged 3-26 for the stand, arbor layer, shrub layer and grass layer were 9.52±1.31 t·hm-2·a-1, 6.29±1.19t·hm-2·a-1,2.52±0.83 t·hm-2·a-1 and 0.71±0.31 t·hm-2·a-1 respectively. With the increase on age, productivity for the arbor layer increased remarkably following a logistic model while the productivity for shrub layer and grass layer declined exponentially.(2) Remarkable differences were found among biomass conversion and expansion factor(BCEF) and biomass expansion factor (BEF) compaired with the IPCC defaut values while root-shoot ratio (R) was in line with the IPCC defaut value. All three parameters varied with stand age. Mean BCEE for Pinus kesiya var. langbianensis plantation was 0.5483 Mg·m-3 (n=30,95% confidence interval= 0.5357～0.5609), lower than the IPCC default value. BCEF for Pinus kesiya var. langbianensis plantation was negatively related to stand form height (FH), mean stand height (H), stand growing stock (V) and stand age(A) (P< 0.05). Regression equations developed for relating BCEF with stand factors did not give satisfied estimates. Mean BEF for Pinus kesiya var. langbianensis plantation was 1.78378 (n=30,95% confidence interval=1.71714～1.85043), higher than the IPCC default value. BEF was negatively related to D,H,FH,V and A (P<0.01). Mean R for Pinus kesiya var. langbianensis plantation was 0.2400 (n=30,95% confidence interval=0.2194～0.2606), very close to the IPCC default value.R was negatively related to D,H,FH,V and A (P< 0.01).(3) Carbon content for the whole tree from simao pine plantation was lower than the commonly used default value (50%).Carbon content increased with the increase on stand age. Significent differences were found among different organs of the plant. The mean whole tree carbon content of Pinus Kesiya Var. langbianensis was calculated as 47.91% based on the dry biomass percentages of different organs and their respective carbon contents. The carbon content of main stem was the highest as 48.48% and tended to decrease from the base to the shoot upward. Carbon contents followed were 48.13%,47.49%,47.27%,47.02%46.80% in branch, bark from main stem,needle leaf,cone and root respectively.(4) Young and middle aged plantation of simao pine had relatively high carbon density, showing very strong carbon sequestration capacity. Biomass carbon density for the plantations of age 3-5,6-10,11-20 and 26 years were (20.15±3.09),(27.24±2.25),(94.89±9.90) and 147.58 t·hm-2 respectively. With the increase on stand age, carbon densities for stand, arbor and litter layer were increased significantly, while that for shrub and grass layers decreased slightly. Relations between carbon density and stand age for stand, arbor and litter layer could be performed well by a logistic model. Mean annual rate of carbon sequestration for the plantations of age 3-5,6-10,11-20 and 26 a were (4.92±0.63),(3.52±0.25),(6.44±0.30) and 5.68 t·hm-2·a-1 respectively. The rates for arbor layer and the whole stand were positively related to stand age and the rates for shrub and grass layers were negatively related to stand age. The relations between the rates and the stand age could be performed well by a logistic model for the arbor and grass layer, and by a Gauss model for the shrub layer.(5) Results from this study could be used for carbon accounting and monitoring for Simao Pine carbon offsetting projects. Since the definitions and research procedures of this study were in line with relevant guidelines by IPCC and the State Forestry Administration, results gained could be used directly for carbon accounting and monitoring for local carbon mitigating projects. However, site condition, stand age and management practice need to be fully taken into consideration when the results applied.To sum up, carbon accounting parameters gained from the study were species, forest type and site specific, thus the use of these parameters would be helpful in reducing the uncertainty of carbon stock estimation. Secondly, methodologies for carbon stock accounting and monitoring for the plantation of simao pine was proposed 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 accumulation of the Simao pine plantaion.The study could also provide valuable reference for carbon oriented silviculture technology development.