南亚热带米老排人工林碳贮量及其分配特征

米老排是我国南方速生用材树种,研究米老排(Mytilaria laosensis)人工林碳贮量与碳分配的规律,可为评价米老排人工林的固碳能力与发展人工林多目标经营提供科学依据。采用样地测定的方法,对南亚热带米老排人工林不同器官碳浓度、碳贮量及分配特征进行了研究。结果表明:不同器官碳浓度均值的变化范围为:51.73%—55.75%,各器官碳浓度大小为:新叶>新枝>老叶>树干>老枝>根桩>粗根>细根;凋落物碳浓度为未分解层>半分解层;0—100 cm土壤碳浓度随深度增加而降低,变化范围为0.62%—4.10%。20年生米老排人工林总碳贮量为331.61 t/hm2,乔木层,凋落物层和土壤层的碳贮量分别为154.07、2.74和174.80 t/hm2。年均总固碳量为14.77 t/hm2,折合CO2量为54.16 t,其中乔木层、凋落物层和土壤层所占比例分别为60.73%,6.16%和33.11%。

The research of carbon storage and distribution feature of the Mytilaria laosensis plantation in south sub-tropical area

Measurements of carbon stock and carbon distribution of Mytilaria laosensis plantation are useful for assessing its carbon sink capacity and developing appropriate multi-purpose forest management model in subtropical area. In this paper, the concentration, storage and allocation of carbon for the Mytilaria laosensis plantation were investigated through biomass harvesting. Two dominant,three intermediate and two suppressed trees were destructively sampled. Stems were cut at the soil surface. Total tree height(from ground to the terminal bud, H),length of live crown, diameter at breast height(DBH), diameter at the base of live crown were measured and recorded immediately. The live crown was marked as three sections (top, middle and bottom), and all new leaves, old leaves, new branches, old branches from each canopy position were cut and weighted separately. Stem were cut into 2 m sections and weighted. At the end of each stem section, a 5cm thick disk was cut, weighted and taken into lab for moisture content determination. The root system were divided into stump, coarse root and fine root(<5mm in diameter) and weighted at the field. From each component approximately 500-1000g of fresh mass were randomly sampled and placed in a labeled bag for moisture content determination. Three standard plots were sampled in the 20-year-old Mytilaria laosensis plantation and three 1 m×1 m subplots were sampled along the diagonal. The litter layer was divided into fresh layer and humus layer. The fresh mass of the litter layer in the three 1m×1m subplots were determined, and about 500-1000g were taken into lab for moisture and carbon content determination. Three soil sampling profiles were set in each standard plot. The soil profile were divided into six layers: 0-10cm,10-20cm,20-40cm,40-60cm,60-80cm and 80-100cm. Soil bulk density were measured and the soil samples(500-1000g) in each soil profile were sampled and mixed into one sample for soil moisture and carbon concentration determination for each plot. The results showed that carbon concentration in different organs of Mytilaria laosensis ranged from 51.73% to 55.75%, which in the order as follows: new foliage>new branch>old foliage>stem>older branch>stump>coarse root>fine root. The carbon concentration of the fresh litter layer was higher compared to the decomposing litter layer. Carbon concentration in the 0-100cm soil decreased with the increasing of soil depth from 4.10% to 0.62%. The total carbon storage in the 20-year-old Mytilaria laosensis plantation was 331.61 t/hm². The carbon stocks of tree, litter, and soil layer were 154.07, 2.74, and 174.80 t/hm², respectively. The annual net carbon storage of the Mytilaria laosensis plantation was 14.77 t/hm², which equals to a mitigation of 54.16t CO₂, where the tree, litter, and soil layer accounted for 60.73%, 6.16%, and 33.11%, respectively.