Coupling Research On Restoration Of The Degraded Grassland Ecosystem And Carbon Budget In Western Jilin Province

According to the fourth Assessment Report of IPCC, global CO₂ emissions of fossil fuels and cement production process that is led by man-made causes is 26.4Pg/a(1Pg=10⁹t)during 2000 to 2005. CO₂ net absorption of terrestrial ecosystems is 3.3Pg/a, which is equivalent to offsetting 12.5% of CO₂ emissions. For a long period, human beings can not achieve zero emissions of CO₂, the trend of concentration increase of atmospheric CO₂ can not be reversed. In this background, how to improve biosphere's ability of the fixation of atmospheric CO₂ is an important issue of climate change mitigation.Grasslands of western Jilin located in most eastern part of Eurasia is meadow steppe. The area is a closed flow area. Unique terrain and climate result in high salinity of groundwater and the full development of saline-alkali soil. Salinization of large areas affects the production and distribution of grasslands in the region. Since the Quaternary, the area has experienced a number of positive and reverse evolutions of desertification and deterioration caused by salinization, forming large areas of saline-alkali soil deposition in plain, becoming one of the world's three famous saline soil. Grasslands in western Jilin belongs to the Northeast China Transect which is one of International Geosphere - Biosphere Programme transects. Therefore, grasslands in western Jilin discussed in this article is a sensitive and typical area, where the study of degraded grassland restoration and carbon balance is very representative.The paper supported by the National Natural Science Foundation of China (Grant No. 40871088) and Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090061110057) , through establishing the database of degradation area of grasslands in western Jilin and transformation of degradation space-time of the past 20 years and identifying the impact of LUCC on net primary productivity of terrestrial ecosystems and soil organic carbon in temporal and spatial distribution, reveals the driving mechanism of natural and man-made factors on grassland ecosystem carbon stock changes.For the environmental problems caused by grassland degradation in the study area, using state transition model to simulate the community succession, carbon sequestration capacity of various succession stages and distribution of vegetation - soil system of carbon of photosynthesis in the process of degradation and recovery can be achieved. In the context of constructing ecological province, the paper implements ecological restoration of degraded grasslands in western Jilin, demonstrates the feasibility of three kinds of ecological restoration models of soil carbon converge, calculates the potential of carbon sequestration of three kinds of ecological restoration models, and predicts the prospect of carbon converge grass industry under Clean Development Mechanism in western Jilin. The coupling study carried out by this paper on the carbon balance of grassland and the restoration of degraded grassland has theoretical significance and social value on the objective understanding of carbon source / sink effect of grassland ecosystems in western Jilin under the influence of LUCC and response to the fixation of CO₂ in atmosphere of global biosphere, and the establishment of the policy on carbon increasing converge and ecological compensation of grassland.According to the study, the following conclusions can be drawn:Grassland area of the study area shows a tendency of decline after increase. Specifically the area has continued to decrease from 1989 to 2000, and increase from 2000 to 2008. The rate of increase from 2000 to 2004 is minor, while that is major in 2008 because of the improvement of ecological environment. The continuous decrease of high grass area indicates that though the grassland ecosystem has recovered to some extent, the overall quality is still showing a downward trend.This paper selects TM image data in September of 1989, 2004 and 2008, and the spatial resolution of which is 30m×30m. Using CASA model, the NPP value of 1989, 2004 and 2008 can be achieved. Extracting the NPP values of various land by Arcgis software, analysing the impact of LUCC on carbon storage in vegetation, From 1989 to 2008, total carbon stock of vegetation in the study area has shown a decreasing trend, a net decrease of vegetation carbon storage of the study area is 230.02Tg C. The carbon stock of vegetation of grassland has increased by 53.97 Tg C for 1989 to 2008.From the Second Soil Survey to 2009, SOC content has always declined.The reverse and forward successions of Jiangjiadian pasture constitute a state transition model which contains State 1, state 2, state 3, state 4 and state 5. As succession progresses, moisture content and total N index of the soil gradually decrease. At the same time, pH and volume weight gradually increase, organic matter increases at first and then decreases. Organic carbon is positively correlated with moisture content and total N, while it is negatively correlated with pH and volume weight. By calculating the density of soil organic carbon, SOCD of soil in the depth of 0 to 100cm rises from state 1 to state 2. then reduces to state 5. That shows a moderate grassland degradation can increase carbon storage.Grassland degradation caused by excessive grazing will result in the loss of soil organic carbon. By setting three types of tests, the conclusion that fencing and artificial grass can increase soil organic carbon storage in a straight line can be drawn. The process of returning farmland to pasture, the storage of soil organic carbon shows a tendency of decreasing after increasing. Furthermore, by calculating carbon sequestration rates and carbon sequestration potential of the three methods, the conclusion shows that carbon sequestration rate of artificial grass which is the largest . Besides, the effect of fencing is also very good, in conclusion,it is suggested that the western Jilin implements fencing to increase carbon sequestration of grassland. If the policy of fencing is implemented to restore degraded grassland in western Jilin, the carbon converge potential for fencing for 5 years is 4.08×106t/a, and for 10 years is 1.3×107t/a.Status of the study area for the degraded grassland, grassland in ginger store set to select a different kind of pasture, fencing and artificial grass and three test, set against the background carbon pools and carbon pool. Obtained by experiment, fencing and artificial grass can increase soil organic carbon storage line, and the process of returning farmland to pasture, soil organic carbon showed an increasing trend after the first reduction. And by calculating the rate of carbon sequestration potential of artificial grass obtained the maximum rate of carbon sequestration. Comprehensive view, fencing is the best ecological recovery mode, if the implementation of the fencing policy to restore degraded grassland in western Jilin, fence carbon sequestration potential of five years was about 4.08×106t / a, fence 10 years of carbon sequestration potential to 1.3×107t / a.If the western Jilin Province in 2008 in accordance with the degradation of the grassland area estimates of carbon sequestration of different measures to reach 1.47 13.27×108tC, of which CDM current trading price of 6.3€/ tC prices, and 1€=8.5038 yuan in now,then the total value of carbon sequestration will be able to reach 7.7×10⁹ to 71.4×10⁹ yuan, degraded grassland carbon sequestration value of 140.3 4021.4 yuan ? hm-2 ? a-1. The implementation of the standard reference in Qinghai Province, the total value of carbon sequestration to the development of carbon trading 30% of annual available 2.3×10⁹ 21.4×10⁹ yuan of funds can be used to speed up the construction of artificial turf and natural grass conservation. Therefore, the strengthening of the recovery of degraded grassland in western Jilin, can not only improve the quality of the ecological environment of the study area, but also can improve the degraded grassland in western Jilin carbon trading market in carbon emission reduction credits to win more.