The Characteristics Of Growth And Carbon Sequestration And Water Consumption In The Small Watershed Of Xiangshuihe, Liupan Mountains

In order to evaluate the carbon sequestration function of vegetation accurately, on the base of quantitate understand of the relationship of vegetation growth and carbon sequestration with its water consumption. and to provide the theoretic basis and the technical support for accurate assessment and prediction carbon storage of Liupan mountains and similar area, and to guide the vegetation recovery and management, Base on the survey of vegetation and soil and tree ring analysis, and measure of tree transpiration and radial growth based on the sap flow and dendrometer, the studeies were carried out in 2009 growth season in small watershed of Xiangshuihe, Liupan Mountains of Ningxia.1.Biomass of typical vegetation typesThe regression relationships between each organ biomass with DBH and H of Larix principis-rupprechtii and Betula spp. were established. The relationships of shrub organ biomass and basal diameter were builded.The order of mean biomass of each vegetaiton type is as Pinus armandii forest (102.70)> Betula forest (84.42)> Populus davidiana forest (79.97)> Larix principis-rupprechtii plantation (58.37)>open forest(44.91). The biomass proportion of tree and shrub and herb layer is 90.04, 8.09 and 0.87%. The order of organ biomass ratio (%) of tree layer is as thunk(54.06)>branch(21.04)>root(16.92)>bark(5.34)>leaf(2.65), and for the shrub layer, it is followed branch and thrunk (62.68)>root(30.55)>leaf (6.77), and is above-groud (58.82)>root (41.18).Average litter biomass of varios forest is 12.56 t/hm².Its order is as Larix principis-rupprechtii plantation (18.21)> Pinus armandii forest(102.70)> Betula forest (10.90)>. Populus davidiana forest (7.67)>open forest (7.06), and higher than litter biomass of shrub (3.13),meadows (0.82) and grass land(0.49).2. Vegetation carbon content The whole plant mean carbon content is 52.22%. The order of carbon content of each tree species is as Pinus armandii (55.51%) > Larix principis-rupprechtii (53.60%) > Betula platyphlla (51.13%) > Populus davidiana (50.30%) > Betula albosinensis (49.92%). The carbon content of tree organ is leaf (53.89%) > trunk≈branch (52.6%) > bark(52.1%) > root (50.7%), the root is minimum (50.7%). The shrub whole plant carbon content is 47.81%. The order of carbon content of each shrub species is as L.rupicola var.(48.30%) > Rosa meiensis (48.24%) > Prunus salicina (48.23%) > Cotongaster acutifolius (46.65%). Different organ carbon content (%) decreased in the order of trunk andbranch (50.34)>root≈leaf (47.1). The average carbon content of herbaceous plant is 36.92%, which of stem and leaf (44.22%) is higher than which of root (29.63%).3. Vegetation carbon content and carbon sequestration of typical forest vegetation standThe average vegetation carbon density is 37.65 t/hm². which is 33.42 and 3.97 and 0.26 t/hm² of tree and shrub and herb layers. The order of carbon density of each vegetation type is Pinus armandii forest (56.69) > Populus davidiana forest (43.43) > Betula forest (42.99) > Larix principis-rupprechtii plantation 30.37) > open forest (22.67), all of which is larger than its of shrub land (10.16). The order of the carbon storage proportion of tree layer is Pinus armandii (98.85%) > Larix principis-rupprechtii plantation (92.40%)> Betula spp. forestation (89.36) > Populus davidiana (87.61%) > sparse secondary forest (65.44%).4. The soil organic carbon storage of typical vegetation typesThe average litter carbon content of different vegetation types was 38.15%. which of undecomposed and half-decomposed and decomposed were 44.87 and 35.69 and 30.07% respectivly. The average litter carbon density of different vegetation types decreased in the order of Larix principis-rupprechtii plantation(4.06) > Pinus armandii (2.03) > > Betula utilis (1.52)> Populus davidiana (0.82)>Betula platyphlla (0.65) > Tilia paucicostata (0.35).5. The respond of soil carbon pool for plant year and disturb degreeIn every slope aspect, the SOC presented a trend of firstly decreasing after tree-planting and then recovering with tree age; The sensitivity of SOC response to the tree-panting disturbance declined with increasing soil depth. The difference of stand condition and recoved years of soil organic desity recover to the level of before afforestation indicated that: young plantation (96.33) in sunny and semi-sunny slope < shrub land (122.12) < middle-aged plantation (189.27); for the shady and semi-shady slopes, the order of SOC density is as young plantation (192.37) < middle-aged plantation (222.03) < secondary forestation (256.64), showing that the SOC have been recovered after forestation for 20 years. The soil carbon orgnic carbon density of shady slope is higher than which in sunny slope at all stand age, suggested that the forest soil carbon pool of shady slope has strong ability for carbon sequestration than sunny slope.Based on the statistical analysis of the investigated data, the SOC content will decrease to its lowest point after 8 years forestation on the sunny/semi-sunny slopes, with a decrease of 3.72 g/kg compared to the control of shrub land (32.13g/kg) on sunny slope, and the fully recovering of SOC to the pre-forestation level will appear after 16 years of forestation. On the shady/semi-shady slopes, the SOC content will decrease to its lowest point after 16 years forestation, with a decrease of 22.77 g/kg compared to the control of secondary forests (66.30g/kg), and the fully recovering of SOC to the pre-forestation level will appear after 32 years forestation.The absolute values of SOC pool on the shady slopes were always higher than that on the sunny slopes at any forest age, suggesting that the capacity of carbon sequestration of shady slopes is bigger than that of sunny slopes. 5)The types of planting disturbance can affect the variation of SOC pool. The mean SOC content of the 0-45 cm soil layer on sunny/semi-sunny slope was 31.05 g/kg after 10 years plantation if the trees were planted with sparse spacing, still lower than that of the control of shrub land (35.55 g/kg), but higher than that if planted with the normal density (23.17g/kg). This indicated that looking for the rational techniques in tree planting and forest management is an effective approach to reduce the SOC loss for young or middle-aged plantation to enhance their carbon sequestration function. In summary, the influence of plantation age, site condition and tree-planting disturbance on SOC should be considered for a more precise evaluation and prediction of the carbon sequestration of plantation.6. The characteristics of growth and carbon sequestration of dominent tree of main tree species All of annual carbon sequestration increment and cumulative carbon sequestration have quadratic correlation, with r2 higher than 0.99. The order of annual carbon sequestration between 10-20 tree age is as Larix principis-rupprechtii (4.06) > Pinus armandii forest (5.35) > Betula utili. (4.29) > Populus davidiana (3.17) > spares secondary forest (2.59)> shrubbery (1.03)> meadow (0.28)> grass land (0.17). And 75% and 73.7% of that were accumulated in June to July.Mean annual carbon sequestration of single tree decreased in the order of Betula platyphlla (3.74)>Larix principis-rupprechtii (3.28) > Pinus armandii (1.80) > Betula albosinensis (0.86). the annual carbon sequestration increment of stand woods of Larix principis-rupprechtii plantation and Pinus armandii-Betula forestation were 2.1 and 1.05 t/hm² respectivly, andThe average of vegetation carbon storage of several forest types is 37.65t/hm², in order Pinus armandii forest (56.69) > Populus davidiana forest (43.43) > Betula forest (42.99) > Larix principis-rupprechtii plantation 30.37) > open forest (22.67), all of which is larger than shrub land (10.16) The carbon content of mineral soil is 2.32-7.32%. the average is 4.42%. The mineral soil carbon content and its fluctuation between different stand is decreased with increase of soil depth. Mineral soil organic carbon density is 94.10-335.09 t/hm². The average is 186.91. The order of soil carbon density of different vegetation types is as Larix principis-rupprechtii plantation (197.66)>natural forest (191.74t > meadow (163.11)>grass land (160.74)>shrubbery (140.06).7.Forest water consumption and water use efficeient on carbon sequestrationTotal water consumption in growth season of Larix principis-rupprechtii stand wood is 972.9kg.The transpiration of stand wood of secondary forestation were 2272.9 kg of Betula albosinensis2279.and 1860.4 kg of Pinus armandii. The total water consumption of growth season of Larix principis-rupprechtii plantation was 426.4mm, and 343.0 mm of Pinus armandii-Betula spp. secondary forestation. those were 97% and 78% of precipitation respectively.The order of water use efficiency (t C/ 104 t H₂O) for carbon sequestration of single plant was Larix principis-rupprechtii (47) > Betula platyphlla (16) > Pinus armandii (11). The water use efficiency on carbon sequestration of plantation and secondary forest were 4.9 and 3.0 (t C/ 104 t H₂O). The water use efficiency for holding of carbon pool of ecologysystem were 947 and 1851 (t C/ 104 t H₂O). corresponding water consumption cost of carbon storage increment were 10.6 and 5.4 t H₂O/ t C. which of plantation is 1.95 times to that of secondary forestation. 8. ConclusionOverall, biomass, vegetation carbon reserves of Larix principis-rupprechtii plantation was higher than secondary forestation, and has good productivity and growth of carbon sequestration functions. With water-consumption approached preciptation, wter consumption of plantation would lead to the decrease of water-yield of watershed. Artificial afforestation measure would lead to the decrease of soil carbon storage. and restore cycle is long, which need 20-30 years to reach the level of soil carbon stock before afforestation. Most importantly, the cost of water consumption of plantations carbon sequestration of soil and vegetation is as much as 1.95 times to secondary forest. When the whole basin from while simultaneously maintaining solid carbon function andwater production function to consider the stage, based on this research results, can think, want to reduce excessive interference of existing forests, do not carry all after thinning afforestation, don't, but large soil preparation afforestation trees natural regeneration ability reasonable utilization of realizing forest area maintenance and growth, be reasonable limit consumption more Larix principis-rupprechtii plantation were, the near natural operation way gradually transformed into the forest of local growth, can not only maintain and enhance the watershed forest fixing carbon and function, and can guarantee the watershed water production function.