Carbon Storage And Balance In Chinese Fir Plantation Ecosystem

Chinese fir (Cunninghamia lanceolata (Lamb) Hook) is a fast-growing native Chinese species with valuable timber attributes in subtropical area of southern China. The statistics from the 5th National Forest Resources Inventory showed that the total area and stocking volume of Chinese Fir plantation have reached 12.39 million hm2 and 473.57 million m~3 respectively, accounting for 26.55% and 46.89% of those of plantations in the whole nation. Chinese fir plantation is one of main forest types in southern forest zone and will contribute a great deal to alleviating the huge timber demand from rapid economic growth and assisting national forest conservation at the national level. Study on carbon cycling in Chinese fir plantation ecosystem could provide some correct and basic data for making a further thorough study on carbon cycling in forest ecosystems by region scale or nation scale, or even by globe scale, and provide some references for correctly estimating ecological benefits of forest. Based on the data collected from long-term located observation and from angle of energy transformation, the absorption, storage and release rates of carbon in Chinese fir plantation ecosystem were investigated in this dissertation. The main results of the research are as follows:Used permanent sampling plots data investigated the carbon content of a Chinese fir plantation ecosystem. The results showed that the average foliar carbon contents in the vertical canopy profile varied from 46.12% to 55.24%, decreasing from the top to the bottom of the canopy and the average carbon content of branches in the vertical canopy profile varied from 39.17% to 49.65% in the following order: middle canopy > upper > lower canopy, The carbon contents of branches and leaves of different ages varied with the season in the following order: winter>autumn>summer>spring. The average foliar carbon content was 50.44%, with a coefficient of variation of 2.08%. The average carbon content for branches was 44.79%, with a coefficient of variation of 2.25%. The carbon contents of different organs varied form 45.29% to 49.72% for the 10-year-old plantation, form 45.80% to 50.22% for the 11-year-old stands, and 45.80% to 50.93% for the 14-year-old plantation. The variation coefficient ranged form 1.68% to 8.44%. The carbon contents of different organs varied in the following order: leaves> bark> roots > stems >branches >cones. The arithmetic average carbon content of different organs was 47.56% for the 10 years old Chinese firs, 47.79% for the 11-year-old Chinese firs, and 48.07% for the 14 years old Chinese firs. No obvious trends were detected for the carbon content in different groups of under-storey of plants or the duff layer as the forest aged. The carbon content in the whole canopy profile of a stand varied in the following order: over-storey trees > shrubs > herbaceous species.The soil organic carbon content decreased as the depth increased in the 10-year-old and the14-year-old Chinese Fir plantation, but that in the 11-year-old Chinese Fir plantation was lower and that in 0~l 5cm soil layer only was 0.60%. The diversity of soil organic carbon content in different layers displayed as: the 0~15cm soil layer (2.06%)>the 15~30cm soil layer (1.71%)>the 30~45cm soil layer>(1.24%)the 45~60cm soil layer (0.98%)>the 60~75cm soil layer (0.82%) in the 14- year-old Chinese fir plantation. Average soil organic carbon contents with three kinds of land use patterns was in the order as: the closed Chinese Fir forest-lands (1.36%)>the cash-tree forest-lands (1.23%)>the fallow-lands after farming (1.10%). The Vertical distribution law of soil carbon contents had no difference in three kinds of forest types, and soil carbon content decreased as the soil depth increased. Soil organic carbon contents of different layers in Chinese fir plantation was positive linear correlation with the soil pH value (r≥0.4), and had a significant positive relationship with total nitrogen (r≥0.81) and C/N ratio(r≥ 0.87).Carbon storage of Chinese fir plantation ecosystem mainly consisted of three sections, that was the trees, the litter and the soil at Huitong, Hunan, and the order of whose carbon storage could be ranked as follow: the soil > the trees > the litter. Carbon storage of the 10-year-old Chinese fir plantation, the 11-year-old Chinese fir plantation and the 14-year-old Chinese Fir plantation was 120.52, 90.48 and 171.40 t/hm2, respectively, with characteristics of age stage and zone. Superiority of carbon storage in the trees gradually strengthen with the forest stands age growth, carbon storage of the trees had gone up from 30.38 t/hm2 in the 10-year-old to 61.24 t/hm2 in the 14-year-old, carbon storage of the trees in the ten-year-old, the 11-year-old and the 14-year-old occupied 25.21%, 38.44% and 38.50% of total carbon storage in the whole ecosystem, respectively, carbon storage of different organs was basically direct proportion with its biomass, for example, biomass of the trunk occupied greatest proportion of stands biomass, its carbon storage accounted for greatest proportion of the trees carbon storage, up to 47.17%, and increased with the forest stands age growth, carbon storage in branches, leaves, bark and roots occupied more than 48.11% of that in the trees, and carbon storage of aboveground accounting for more than 84.73% of that in the trees.Carbon storage in forestlands soil layer (0~60cm) was a considerable figure, soil carbon storage in the 10-year-old, the 11-year-old and the 14-year-old Chinese fir forestlands was up to 88.21, 54.03 and 108.20 t/hm2, respectively, accounting for more than 59.59% of carbon storage in the whole ecosystem. In the soil layer, carbon storage of the surface soil (0~15cm) layer in the 10-year-old, the 11-year-old and the 14-year-old Chinese fir forestlands held 36.57%, 18.53% and 34.26% of that in the soil layer (0~ 60cm) respectively, and that of the soil layer (0~30cm) in the 10-year-old, the 11-year-old and the 14-year-old Chinese fir forestlands took up 63.44%, 55.62% and 61.05% of that in the soil layer (0~60cm), respectively. The ratio of carbon storage of aboveground to that of underground in the 10-year-old, the 11-year-old and the 14-year-old Chinese fir plantation ecosystem was 1 : 3.53, 1 : 2.05 and 1 : 2.22, respectively, and deceased as the Chinese fir forest age growth. Extant carbon storage, potential carbon storage and potentiality of carbon sequestration of Chinese fir forest vegetation in Hunan Province was 0.1916×10~8t, 1.4710×10~8t and 1.2794×10~8t, respectively, extant carbon storage was only accounting for 13.03% of potential carbon storage, was less than the whole national level 26.46%. The annual net primary production of the 10-year-old, the 11-year-old and the 14-year-old Chinese fir plantation was respectively 11.624, 12.807 and 19.459 t/hm2 · a, while their annual carbon amount was up to 5.488, 6.059 and 9.285 t/hm2 · a, respectively, the annual carbon amount in the litter-fall was respectively 0.305, 1.141 and 0.550 t/hm2 · a.Before deforestation, carbon storage of forestlands soil (0~60 cm) amounted to 160.38 t/hm~2 in the 22-year-old Chinese Fir plantation, that one year after 100% of clear cut, carbon storage in the deforested-land soil (0-60 an) lost 35.00%, two years, 44.65%, and three years, 43.93%, compared with the control standing forest, three years after 50% thinning and 100% of clear cut, carbon storage in the deforested-land soil (0~60 cm) lost 16.14%and 45.15%, respectively, and carbon storage in the deforested-land soil (0~60 cm) indicated evidently the diversity with different land use patterns. Carbon storage in the deforested-land soil (0~60 cm) with three kinds of land use patterns was ranked in the order as: the closed Chinese Fir forest-lands (108.20t/hm2)>the economic forest-lands (98.64 t/hm2)>the fallow-lands after farming (94.21t/hm2). In contrast to the closed Chinese Fir forest-lands, carbon storage in the fallow-lands after farming soil (0~ 15 cm) layer lost 12.70%, soil (0~30 cm) layer 21.33%, soil (0~ 60 cm) layer 51.78%. Carbon storage in the fired land soil (0~45 cm) lost 22.60% within 40 days after fired, the loss in soil (0~45 cm) attained 12.52 t/hm2, accounting for 75.51 % of the total loss. In the same forest zone, carbon storage of the soil (0~75 cm) in Chinese fir forest-land, Masson Pine forestland and the second broadleaf forestlands was respectively 123.45, 89.95 and 134.41 t/hm2, the order of which could be ranked as follow: Masson Pine forestland> Chinese fir forest-land > the second broadleaf forestlands, and mainly distrusted in the soil (0~30cm) layer.The average annual litter-fall was 1201.24 kg/hm2 (dry weight) in the 14~ 16-year-old Chinese fir plantation, of which needle accounted for 69.84%, twig, 24.54%, fallen fruit and other fragments, 5.63%, carbon contents of which had some difference, varied with the components of litter-fall, carbon storage in different components was in the order as follow: needle>fallen fruit>other fragments>twig. The annual return of carbon amount gradually increased with the forest stands age growth. Variation of carbon content in litter-fall possessed different not only in time but also in components, carbon contents in needle or intwig decreased but their release ratios increased with the passage of time in the decomposition course, carbon release ratios of needle was higher than that of twig, there were some difference between carbon release law of litter-fall and decomposition speed of total dry matter. The annual release amount of carbon was about 149.25 kg/hm2 · a through one year decomposition, occupying 27.22% of carbon amount in the falling, of which carbon release amount of needle was up to 120.12 kg/hm2 · a, accounting for 81.03%, twig, fallen fruit and other fragments, 29.13 kg/hm2 · a, accounting for 18.97%.The soil CO2 release from three kinds of forestlands of Chinese fir plantation was in the range of 0.1005~0.8865 g/m2 · h at Huitong, Hunan, the average value of which was in the order as: the afforested land > the deforested land > the closed woodland, there was significant difference of average soil CO2 release between the afforested land, the deforested land and the closed woodland. The soil CO2 release from forestland had a certain seasonal change; the highest value of soil CO2 release appeared in summer and the lowest in winter. The soil CO2 release circadian change with a regular rhythm, the soil CO2 release on day was higher than that at night. The soil CO2 release from the deforested lands with different treatments was evident difference in a certain time lapse. The average value of soil CO2 flux from the afforested lands was 127.776 kg/hm2 · d, from the closed woodland, 86.352 kg/hm2 · d, and form the deforested lands, 120.00 kg/hm2 · d.The soil CO2 release was positive liner correlation with the soil temperature and soil moisture at a certain range, and also with the soil C/N ratio, was parabola correlation with air temperature in stands. The relationship between the soil CO2 release and environment factors was more complicated, and different with the difference of forestlands type. The order of correlation coefficients between soil CO2 release and environment factors in the afforested land ranked as: soil temperature at 10cm depth > soil temperature at 5cm depth>ground temperature>soil temperature at 15cm depth>soil temperature at 20cm depth>C/N ratio in soil (0~45cm)>air temperature in stands>soil moisture at 10cm depth>C/N ratio in soil (0~15cm)>soil moisture at 20cm depth>ground moisture, in the closed woodland, as: air temperature in stands >ground temperature > soil temperature at 10cm depth>soil temperature at 5cm depth > soil temperature at 15cm depth > soil temperature at 20cm depth > ground moisture > C/N ratio in soil (0~15cm)>C/N ratio in soil (0~45cm)>soil moisture at 10cm depth>soil moisture at 20cm depth, in the deforested lands, as: soil temperature at 10cm depth>soil temperature at 5cm depth>C/N ratio in soil (0~45cm)>soil temperature at 15cm depth>soil temperature at 20cm depth>ground temperature >soil moisture at 10cm depth>C/N ratio in soil (0~15cm)>ground moisture>soil moisture at 20cm depth. P value of t-test showed that the soil CO2 release in Chinese fir forestlands was the result of comprehensive effects by manifold environment factors. The soil CO2 release from the afforested lands...