| Forest ecosystem plays a positive role in regulating the global carbon balance and curbing global climate change,and has been widely recognized as the carbon sequestration function by the international community.The Grain for Green Programme(GGP),a major ecological restoration project in our country,has great carbon sequestration capacity and ecological efficacy.In this study,we focused on the GGP in Henan Province,through the methods of combining the historical data collection,field investigation and indoor analysis to study the planted forest carbon sequestration efficacy.The distribution patterns of carbon storage and carbon density for two kinds of typical artificial forest ecosystem were analysed in different ages and soil layers.We estimated the carbon storage,carbon sequestration rate and potential of GGP in Henan Province by the volume growth equations and soil carbon stock changes model.We also explored the dynamic of forest vegetation biomass carbon stocks from 1949 to 2008 in Henan Province.These proposed researches would have important reference value for the evaluation of carbon sequestration efficacy of GGP,and provide an important scientific basis for the ecological construction and sustainable development of the Central China.The main results are as follows:(1)Trees were planted under three types of vegetation restoration(abandoned croplands afforestation,barren lands afforestation and closed forest)since the implementation of the GGP in Henan province in 2000.The GGP had little effect on the change of cultivated land area.From 2000 to 2012,the GGP had planted approximately 251.13×103 hm2 converting abandoned croplands to forest,699.72×103hm2converting barren hills and wastelands to forest and 128.30×103 hm2 of closed forest,respectively.From 2000 to 2012,the annual afforestation area of GGP in Henan Province acounted for 4.39%,3.37%,3.22%,3.68%,4.93%,4.90%,3.89%,4.74%,4.08%,3.89%,3.61%,1.98%,2.33% of the annual afforestation area of GGP in China.The abandoned croplands afforestation area in Henan Province showed the increasing-decreasing-increasing-decreasing trend.The cultivated land area in Henan province was maintained about 7200.00×103hm2.The abandoned croplands afforestation had little effect on the change of cultivated land area.(2)The litter and tree biomass carbon storage had an increasing trend and the soil carbon storage in different soil layers showed the decreasing-increasing-decreasing trend with the growth of plantation trees.Soil organic carbon(SOC)mainly aggregated in the surface soil and had positive correlation with soil carbon content,nitrogen content and C/N.Both the biomass carbon storage and litter layer carbon storage of Quercus and Platycladus orientalis had an increasing trend with the forest age increasing.The carbon storage of Quercus under different age groups were ranked in the order: 60a(275.82 Mg hm-2)>45a(261.39 Mg hm-2)>26a(163.82 Mg hm-2)>15a(103.45 Mg hm-2)>3a(52.04 Mg hm-2).The carbon storage of Platycladus orientalis under different age groups followed the sequence: 60a(279.81 Mg hm-2)>40a(268.95 Mg hm-2)>20a(148.06 Mg hm-2)>8a(62.18 Mg hm-2).The carbon pool of two tree species in tree layer and soil layer played a major role in the contribution of the whole ecosystem carbon storage.The soil carbon storage mainly aggregated in the surface soil and was significantly higher than that in the deep soil.The soil carbon storage of Quercus and Platycladus orientalis had a decreasing trend in the first few years after implementation of the afforestation,and was lower than that of farmland.The carbon storage in the same soil layer gradually enhanced with the trees age increasing.(3)The spatial distribution of carbon storage in the five regions was varied due to differences in the planted area and tree species in every region under the GGP.The GGP in Henan province showed a great carbon sequestration potential.The total carbon sequestration under Henan Province's GGP was 21.20 Tg by 2012.The changes of carbon storage in the five regions were consistent with the whole province.The carbon sequestration in the early period(from 2000 to 2006)was lower than that in the later period(from 2007 to 2012).The tree biomass carbon sequestration potential of Henan Province in 2020,2030,2040,2050 and 2060 is projected to be 31.48,46.82,52.47,55.56 and 57.71 Tg,respectively,Henan Province's soil carbon sequestration potential in 2020,2030,2040,2050 and 2060 is expected to be 32.56,57.41,76.77,81.41 and 81.62 Tg,respectively,the carbon sequestration potential under the GGP ecosystem is projected to increase with time and is expected to be 54.04,104.23,129.23,136.97 and 139.35 Tg by the years 2020,2030,2040,2050 and 2060,respectively.(4)The GGP under cutting scene had a great carbon sequestration potential,indicating the planted trees moderately cutting can improve its carbon sequestration capacity.Under no cutting scene,the potential increment of carbon sink of the GGP in Songxianhad a gradually increasing trend and were calculated to reach 0.74,1.44,1.83,1.96 Tg by the year of 2020,2030,2040,and 2050,respectively.Under cutting scene,the potential increment of carbon sink of the GGP had a first increasing then decreasing trend and were calculated to reach 0.74,1.23,1.64,1.98 Tg by the year of 2020,2030,2040,and 2050,respectively.The potential increment of carbon sink under cutting scene would be higher than that under no cutting scene after 2048.The moderate forest harvesting for GGP could increase the ability of carbon sequestration with the growth of planted trees when the cutted forest was planted in time.(5)The carbon storage of forest vegetation in Henan Province significantly increased for 60 years,especially the carbon storage of artificial forest increased significantly after implementation of the GGP.Forest stand,especially the young and middle-aged forests was the main contributor to forest vegetation carbon sink.The forest vegetation in Henan Province would have great carbon sequestration potential in the future.The carbon density of forest vegetation increased from 14.90 Mg hm-2 in 1949 to 19.86 Mg hm-2in 2008,and carbon storage increased from 34.56 Tg in 1949 to 80.31 Tg in 2008,with the 132.38% increment.Forest stands accumulated carbon of 39.74 Tg from 1949 to2008 with an average carbon accumulation rate of 0.674 Tg yr-1,which accounted for 86.97%of total biomass carbon sink between 1949 and 2008.The carbon storage of artificial forest increased 33.70 Tg from 1998 to 2008,which accounted for 84.80% of forest stand carbon sink increment from 1949 to 2008.The carbon storage of broad-leaved forest was higher than that of coniferous forest.The carbon densities of the different age groups were ranked in the order: old-aged > middle-aged > young-aged in different period.The forest vegetation in Henan Province would have greast carbon sequestration potential in the future with the young and mid-aged forests growing.(6)The measures selecting the tree species with high carbon sequestration capacity and strengthening the management of artificial forest land could improve the carbon sequestration ability.The planted tree species under GGP should be considered according to the climate and soil condition,such as the high carbon sequestration ability under the rational design tree species.The management measures,appropriate irrigation and fertilization,proper forest harvesting,reduce and prevent the natural and human disturbance to forest,and strengthen the prediction and control of fire,pests and diseases would improve artificial forest quality and carbon storage. |
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