Carbon Storage Of Cunninghamia Lanceolata Mature Plantation In Shaowu, Fujian Province

Optimal biomass models were used to estimate biomass of Cunninghamia lanceolata mature plantation ecosystems (28-year old) in Shaowu, Fujian Province, with the measured data of trees' biomass. Carbon storage of mature plantation ecosystems was estimated with stand survey data and organic carbon contents of tree layer(including leaf, branch, peeled stem, bark, root head and root),shrub layer,herbaceous layer, litter and soil of the mature forest ecosystems. Carbon storage of mature plantation ecosystems and its spatial distribution was studied, as well the relationship between it and planting density-site index class. The main results were as follows:1. Selection of biomass estimate models for Chinese fir plantationIn this paper, 11 kinds of biomass models were used to estimate the single-tree biomasses in a young (7-year old), middle-aged (16-year old), mature Chinese fir plantation (28-year old) and the mixed-age Chinese fir stand, respectively. There were 308 biomass models fitted totally. The results showed that: (1) The power function models( W1 = aDb,( )bW = a D H) present the best fitting results followed by exponential models( ( )W 8 = a expbD,W 9 = a exp(b D2),( )W1 0 = a expbDH,( )W1 1 = a expbD H) and the polynomial models ( W 4= a + bD + cD2,W 5= a + bD 2 + cD4,( )W 6= a + bDH + c DH,2 22W 7= a + bD H + c D H)with the least effective fitting results. 21 optimal biomass models for individual organ of tree and total single-tree in young, middle-aged and mature Chinese fir plantation were chosen, including 18 for organ and 3 for total single-tree. 7 optimal biomass models of individual tree regardless of ages were chosen, which contained 6 for organ and 1 for total single-tree. All of the optimal biomass models were in the form of power function ones; (2) The optimal biomass models of single-tree with different ages had poor generality, but the ones regardless of ages had a certain generality with high accuracy, which can be used for estimating the biomasses of single-tree with different ages; (3) To predict single-tree biomass of mature Chinese fir plantation (28-year old) in Jiangxi Province, optimal biomass models of single-tree in Shaowu, Fujian Province, which was based on a large sample of forest biomass, showed relatively high accuracy and can be applied in a large range. The regional model with small sample is limited to small application area.2. Soil organic carbon storage and vertical distribution of mature Chinese fir plantation with different planting density and site indexThere were 5 planting densities and 6 site index classes in mature Chinese fir plantation. Based on 75 soil profiles (0～100 cm), the storage and distribution of soil organic carbon for the plantation was studies. The results were as follow: (1) Soil organic carbon contents in different planting density-site index class levels were significantly different among stands (P<0.05). The average soil organic carbon content of the whole soil section (0～100 cm) for the stands was 0.9126%～1.3886%. The average soil organic carbon content was the highest in the stand with planting density 6667 hm-2 and Site Class 20 m, and the lowest with planting density 10000 hm-2 and Site Class 14 m. Soil organic carbon contents generally decreased with depth, but decreasing amplitude was different for the stands, and decreasing amplitude of the stand with planting density 5000 hm-2 and Site Class 16 m, is highest (84.22 %). (2) Soil organic carbon densities in different planting density-site index class levels were significantly different among stands (P<0.01). The average soil carbon density in every soil layer of the stands changed greatly, with a range of 4.9591～35.7399 Mg·hm-2. Soil carbon density decreased generally with the depth, too. For the whole soil section (0～100 cm), the average soil carbon density in the stands varied from 114.2279～187.2361 Mg·hm-2, their total mean values were 150.3215 Mg·hm-2. (3) The soil organic carbon assembled obviously in surface layer soils. The carbon storage contribution rate of the soil layer 0～30 cm was up to 57.08%. Carbon density of soil surface 0～10 cm and site index showed significant positive correlation (P<0.05). The conclusion played an important role in the evaluation of woodland quality and soil management. (4) Planting density and site quality were the main factors, which effected on soil carbon sink levels. If the management purpose was to have large carbon sink capacity of the plantations, the suitable planting density should be chosen with site quality. Low site index classes (SI≤14 m) of woodland should be combined with high planting density (≥6667 hm-2), medium and high classes (SI≥16 m) with low density (≤6667 hm-2).3. Characteristics of carbon storage and the spatial distribution in Chinese fir plantation ecosystemCarbon content and storage of different organs and components of ecosystem were studied in 15 plots of a 28-year old Chinese fir plantation in Shaowu, Fujian. The results showed that: (1) Organic carbon densities in different organs of Chinese fir were significantly different (P<0.01). The average organic carbon contents in different organs were in the range of 49.1829%~ 53.4352%, the descending order: leaf (53.4352%)> peeled stem (53.2206%)> root head (51.6617%)> branch (51.1115%)> bark (50.9420%)> root (49.1829%). Organic carbon content of various organs may be related to differences in the growth pattern of the fir. Therefore, the response to measure organic carbon content of each organ, was in order to estimate accurately carbon storage of mature Chinese fir plantation. Peeled stem in vertical distribution of organic carbon content was no significant difference, which could be regarded as uniformly distributed vertically. The organic carbon contents in different layers of the forest floor were in the order as: litter layer (47.6355%~52.8923%, an average of 50.6268%)>shrub layer (39.8711%~ 46.5126%, an average of 44.0429%)>herb layer (35.9797%~43.9649%, an average of 40.5909%).(2) The means and distribution sequence of the carbon storage in each organ of plantation ecosystem with different initial planting densities and site index classes was that peeled stem (78.8943 Mg·hm-2, 58.0832%~64.6194%)>underground parts (22.8704 Mg·hm-2, 16.0528%~20.9624)>bark (13.1020 Mg·hm-2, 9.3927%~ 10.7423%)>branch (7.0874 Mg·hm-2, 4.0841%~7.5481%)>leaf (5.5873 Mg·hm-2, 3.0739%~5.6319%). With the same planting density and stand densities difference little among the plantations, the higher the site index class of the plantation, the greater carbon storage of different organs in the one. 79.0376%~83.9472% of carbon stored in aboveground organs; differences of carbon storage in mature fir plantations with the same planting density and site index class were mainly caused by the stand density. Carbon storage of Chinese fir plantation in different organs was the result of the interaction of individual growth and plant stand density.(3) The means and distribution sequence of the carbon storage in each component of plantation ecosystem with different initial planting densities and site index classes was that soil (150.3215 Mg·hm-2, 45.4608%~63.7434%)>tree layer(127.5417 Mg·hm-2, 33.4074%～52.0212%)>litter layer (4.8947 Mg·hm-2, 1.0893%～2.2838) >herb layer (0.7065 Mg·hm-2, 0.0797%～0.4246%)>shrub layer (0.2103 Mg·hm-2, 0.0070%～0.2685%). The carbon storage in tree layer was larger than one in the soil of plantation ecosystem, which was high site index class with high biomass of individual tree. Such stand were studied in this paper, including site index class of 20 m with the initial planting density of 1667 hm-2, site index class of 20 m with the initial planting density of 6667 hm-2, site index class of 22 m with the initial planting density of 1667 hm-2 and site index class of 22 m with the initial planting density of 5000 hm-2. With the same planting density and stand densities difference little among the plantations, the higher the site index class of the plantation, the greater carbon storage of tree layer and total layers in the one.