【作者】 颉鹏；

【导师】 蔺海明；

【作者基本信息】 甘肃农业大学 ， 作物栽培学与耕作学， 2009， 博士

【摘要】 随着全球温室效应的加剧,为探索降低大气温室气体浓度的对策,陆地生态系统碳循环及碳收支研究成为当前全球变化研究的热点问题。农田生态系统是重要的温室气体源和汇,一方面通过作物光合作用和人为途径吸收大量的碳;另一方面通过作物和土壤的呼吸作用以及各种途径的人工投入过程间接释放碳。另外,原始土地转化为耕地的过程也使土壤丧失了大量的有机碳。随着耕作强度的增加,农业领域面临着越来越多的碳释放。因此,如何采取措施实现农田土壤固碳增汇成为目前亟待解决的问题之一。本文结合碳源/汇模型,通过1949～2005年的统计资料,对河西4市县绿洲农田生态系统土壤固碳现状潜力、主要农作物的碳吸收、不同土地利用方式下的土壤碳汇以及农田生态系统碳汇功能的经济效益等方面进行分析,初步了解了大尺度上河西绿洲农田生态系统碳汇的特征及河西绿洲农田生态系统在减缓全球变暖中的贡献,提出了河西绿洲农田生态系统碳增汇/减排的战略措施。通过研究,得出以下几点结论:（1）河西绿洲农田生态系统土壤固碳潜力估算研究的结论是:通过对河西4市县绿洲农田生态系统土壤碳现状和固碳潜力的分析表明,①河西4市县绿洲农田土壤固碳现状和单位面积的平均固碳速率在不同耕作水平下是不同的。在施用化肥、有机肥、秸秆还田和少免耕等不同耕作条件下,土壤固碳现状和单位面积的平均固碳速率分别为6.65Tg·a-1和240.51kg·hm-2·a-1、5.97Tg·a-1和215.91kg·hm-2·a-1、3.27Tg·a-1和118.26kg·hm-2·a-1以及7.86Tg·a-1和284.27 kg·hm-2·a-1。相对而言,少免耕的耕作措施更适用于河西4市县。②在土地利用方式、耕作措施、施肥水平和气候条件不变的情况下,经过多年的农田管理措施后,土壤有机碳密度都将达到一个新的稳定状态。根据模拟计算,河西全区的土壤有机碳密度由1989年的10.33kg·m-2达到新稳定状态后的12.31kg·m-2。③河西土壤碳储量由1989年的620Tg达到新稳定状态时的740Tg,固碳潜力为120Tg。④从土壤有机碳密度及其储量上看,随着时间的推移,地区间碳密度和储量发生的变化不是很大。第二次土壤普查期间,河西土壤高碳密度区主要分布在张掖市,其次为永昌县、武威市和酒泉市;在2005年时,仍然是张掖市的碳密度最高,其次为永昌县、酒泉市和武威市。（2）河西绿洲农田生态系统土壤碳汇估算研究结论是:通过对河西4市县绿洲农田生态系统主要农作物的碳吸收的估算、不同农作物生态系统碳源汇变化以及农田管理土壤碳汇估算分析表明,①河西绿洲农田生态系统主要农作物碳吸收的贡献者是粮食作物和蔬菜,但是在具体的碳吸收上存在较大差异,这与农作物本身的特性和种植面积有关。②在作物——土壤系统CO2源汇关系的日变化中,CO2源汇关系存在不确定性,小麦生态系统是一个中等水平的碳汇;棉花生态系统是一个弱碳汇;玉米生态系统是一个强碳汇;在年变化中,小麦生态系统除8～9月份是弱碳源外,其余月份均属于碳汇,棉花生态系统在6～9月份为碳汇,其余月份为碳源,玉米生态系统6～9月份为碳汇,其余月份为碳源。③1949～2005年河西绿洲农田生态系统碳吸收呈阶段性增长趋势,碳吸收总量从1949年的24.39万t增加到2005年的298.37万t,净增273.98万t,增长了12.23倍。碳吸收的发展趋势基本呈现出三个发展阶段即:波动式增长阶段（1960年以前）、恢复性增长阶段（1960～2000年）和快速增长阶段（2000年以后）。④河西4市县绿洲农田生态系统的碳汇效应中,有机无机配施的作用较为明显,可使SOC增长0.81tCha^-1·a^-1,其次为免耕,SOC增长0.62tCha^-1·a^-1。秸秆还田和施有机肥的效果相当, SOC的年增加量分别为0.57和0.38 tCha^-1·a^-1。施单一氮、磷、钾肥几乎不能使SOC增加,甚至起负作用。配合施用氮、磷、钾肥也只能弥补土壤有机质的矿化损失,不能明显提高其含量。（3）不同土地利用方式对土壤碳汇的影响研究结论是:从土地利用及其变化的角度出发,对河西农田、草地和林地的土壤有机碳储量、生态系统碳汇功能等方面的影响进行分析表明,①灌木林、山杨林和青海云杉×祁连圆柏变成农田或草地后,土壤表层（0～50cm）的土壤有机碳含量下降;而在农田或草地中营造落叶松人工林后,土壤表层（0～40cm）的土壤有机碳含量将增加,在土壤剖面底层的有机碳含量受土地利用变化的影响较小。②灌木林、山杨林和青海云杉×祁连圆柏变成农田或草地后,土壤有机碳密度下降（35%和14%）;农田中营造落叶松人工林后,土壤有机碳密度将增加;在草地中营造落叶松人工林后,土壤有机碳密度未显著变化。另外,土地利用变化后,土壤有机碳密度的变化幅度比土壤有机碳含量的变化幅度小。③不同土地利用方式下土壤有机碳的积累不同。在0～45cm土层,草地的土壤有机碳均显著高于农田;在翻耕、少耕和免耕3种耕作方式下,土壤碳积累贡献的次序是:少耕>免耕>翻耕。④天然次生林生态系统通过土地利用变化变成农田或草地后,土壤碳贮量汇功能强度降低,稳定性和非稳定性汇减弱,保护和非保护性、活性碳汇的强度也都将减弱。而农田或草地生态系统通过造林变成人工林生态系统后,土壤碳贮量这些汇功能强度都将增加。⑤在植被生产力碳积累方面,天然次生林和人工林生态系统都具有较强的汇,而农田和草地生态系统则相对较弱。在土壤有机碳贮量变化方面,天然次生林生态系统是强汇,而农田和草地生态系统为源,人工林生态系统为弱汇。（4）河西绿洲农田生态系统土壤碳汇功能评价结论是:通过数学模型,对河西绿洲农田生态系统土壤碳汇功能的经济效益进行分析表明,①1949～2005年间,河西绿洲农田生态系统碳汇功能的经济效益变化趋势呈阶段性增长趋势,碳汇功能的经济效益从1949年的0.63亿元增加到2005年的7.76亿元,净增7.13亿元,增长了11.32倍。②河西绿洲农田生态系统碳汇功能的经济效益的发展趋势基本呈现出波动式增长（1960年以前）、恢复性增长（1960～2000年）和快速增长三个发展阶段。（5）通过以上分析,得出河西绿洲农田生态系统碳增汇/减排的战略措施:①调整耕作制度:免耕法是一种对土壤扰动最小的耕作方式,能非常有效的提高农田土壤有机碳。②改善施肥方式:长期施用有机肥能显著提高土壤活性有机碳的含量,有机无机配施,可提高作物产量,而使用化学肥料能增加土壤有机碳的稳定性。③秸秆还田:秸秆还田是减少农田碳排放、增加土壤有机质含量的重要途径,还可以将秸秆过腹还田,不仅能增加土壤有机质含量,而且还能发展养殖业,增加经济效益。④其他措施:如改良作物品种,有计划地抓紧培育具有对高温、干旱等极端气候及病虫害有抗性的品种,确保在新的生态环境中农牧产量不断提高,扩大碳的吸收存储。另外,也可以采取措施改变地表径流、改良土壤,扩大人工草地等来间接增加农田的碳汇功能。更多还原

【Abstract】 With the escalation of global warming, in order to explore the strategy of reducing atmospheric concentrations of greenhouse gases, the problem of terrestrial ecosystem carbon cycle and the research of carbon balance of payments has become a hot issue of current global change research. Farmland ecosystem is an important greenhouse gas sources and sinks. On the one hand, through photosynthesis of crops and man-made way to absorb a lot of carbon; on the other hand, crops and soil through respiration, as well as artificial ways indirectly the release of carbon into the process. In addition, the original cultivated land into the process so that the loss of a large number of soil organic carbon. With the increase in intensity farming, the agricultural sector is faced with an increasing number of carbon releases. Therefore, how to take measures to achieve carbon sequestration by agricultural soils sinks become one of the issues to be settled urgently.In this article, from 1949 to 2005 statistics, combined with carbon source / sink model, 4 cities and counties of the Hexi oasis Farmland ecosystem carbon sequestration of soil carbon sequestration potential of the status, the major agricultural crops, under different land use patterns of soil carbon sinks, as well as Farmland ecological carbon sink function of the system cost effectiveness analysis, a preliminary understanding on the large-scale farmland ecosystem in Hexi Oasis of the characteristics of carbon sinks and Hexi oasis farmland ecosystem in reducing the contribution to global warming. Finally, put forward in Hexi oasis farmland ecosystem increasing carbon sinks & emissions reduction strategies. Through research, received the following conclusions:（1） The conclusion of the estimate study Hexi oasis farmland ecosystem soil carbon sequestration potential is:Through the analysis the current situation and sequestration potential of oasis farmland ecosystem soil carbon of 4 cities and counties of Hexi showed that:①soil carbon sequestration per unit area status and the average rate of carbon sequestration in different levels of farming is different. In the application of chemical fertilizers, organic manure, straw and no tillage or minimum tillage and other farming conditions, the soil carbon sequestration per unit area status and the average carbon sequestration rates of 6.65Tg·a-1 and 240.51kg·hm^-2·a^-1, 5.97 Tg·a-1 and 215.91 kg·hm^-2·a^-1, 3.27 Tg·a-1 and 118.26 kg·hm^-2·a^-1 and 7.86 Tg·a-1 and 284.27 kg·hm^-2·a^-1, relatively speaking, less no-tillage farming measures applicable to Hexi.②in land use patterns, farming measures the level of fertilization and climatic conditions remain unchanged, after years of farm management practices, the soil organic carbon density will reach a new steady state. According to simulation, the region west of the soil organic carbon density in 1989 by the 10.33kg·m-2 to reach a new steady state after 12.31kg·m-2.③Hexi soil carbon reserves 620Tg by 1989 to reach a new steady state at the time of 740Tg, the potential for carbon sequestration 120Tg.④the density of organic carbon from the soil and its reserves, the carbon density and inter-regional changes in reserves is not very big.The second time during the soil survey, soil carbon density in Hexi District are mainly distributed in Zhangye, followed by Yongchang, Wuwei and Jiuquan; in 2005, Zhangye is still the highest density of carbon, followed by Yongchang, Jiuquan and Wuwei.（2） The conclusion of the estimate study Hexi oasis farmland ecosystem soil carbon sinks is that: Through the analysis oasis farmland ecosystem carbon sequestration, the main crop estimates, different crop changes in ecosystem carbon sinks, as well as agricultural management soil of carbon sinks of 4 cities and counties of Hexi showed that:①farmland ecosystem in Hexi Oasis major contribution to carbon sequestration crop it is corn crops and vegetables, but on specific carbon sequestration, there is a big difference, which is in itself the characteristics of crops and planting of the area.②in crop-soil system of sources and sinks of CO2 on the relationship between changes, CO2 sources and sinks of the relationship between uncertainty, wheat ecological system is a medium level of carbon sinks; cotton ecosystem is a weak carbon sink; corn ecosystem is a strong carbon sinks; changes in the year, wheat ecosystem in addition to August to September is a weak carbon source, the rest of the month are carbon sinks;cotton, ecosystem in the June to September for carbon sinks, and the rest of the month as carbon source.③1949²005 years in Hexi oasis farmland ecosystem carbon sequestration was phased growth trends, the total carbon sequestration from 243,900 tons in 1949 to 2,983,700 tons in 2005, a net increase of 2,739,800 tons, an increase of 12.23 times. Carbon sequestration, the basic trend of development shows that the three stages of development: growth of fluctuations in phase （before 1960）, the resumption of growth stage （1960 2000） and the rapid growth phase （after 2000）.④In 4 cities and counties of the farmland ecosystem effects of carbon sinks, organic and inorganic fertilizers in which the role of a more obvious increase in SOC will enable the 0.81tCha^-1·a^-1, followed by no-tillage, SOC annual growth of 0.62 tCha^-1·a^-1. The effects of straw and organic fertilizer rather, soil organic carbon, respectively, the annual increase of 0.57 and 0.38 tCha^-1·a^-1. With single N,P,K, SOC increased almost can not even play a negative role. Combined application of nitrogen, phosphorus and potassium can only compensate for the loss of soil organic matter mineralization, can not significantly improve its content.（3） The conclusion of the patterns of different land utilization effect on soil carbon sinks is that: From changes in land use and its point of view, on the west of farmland, grassland and woodland reserves of soil organic carbon, ecosystem carbon sink functions of the impact analysis showed that,①bush, Populus davidiana and （Picea crassifolia×Sabina przewalskii） to cropland or grassland, the soil surface （0 50cm） of soil organic carbon content decreased; and in the grass in the fields or to create a larch plantation, the soil surface （0 40cm） of soil organic will increase the carbon content in the soil profile of organic carbon content of the underlying land-use changes by less affected.②bush, Populus davidiana and （Sabina przewalskii×Picea crassifolia） or grassland into farmland, the decline in soil organic carbon density （35% and 14%）; farmland Create a post in the larch plantation, soil organic carbon density will be increased; in the grass to create a larch plantation, the soil organic carbon density is not changed significantly. In addition, after the land-use change, soil organic carbon density than soil organic carbon content of the small magnitude of changes.③under different land use patterns of soil organic carbon accumulation is different in the 0 45cm soil, grassland soil organic carbon were significantly higher than that of soil organic carbon; in tillage, less tillage and three kinds of no-tillage farming methods, the contribution to soil carbon accumulation of the order is: Reduced tillage> no tillage> tillage.④natural secondary forest ecosystems through land-use change to cropland or grassland ecosystem, the soil carbon storage sinks lower functional strength, stability, and reduced non-stability of exchange, protection and non-protective, the strength of activated carbon sinks will also be weakened. And farmland or grassland ecosystem through reforestation plantation into the ecosystem, the soil carbon storage function of the strength of these sinks will increase.⑤Carbon accumulation in vegetation productivity, the natural secondary forest and plantation ecosystems have a strong sink, and farmland and grassland ecosystem is relatively small. Reserves in the soil organic carbon change, natural secondary forest ecosystem health is strong, and farmland and grassland ecosystem as the source, plantation ecosystem health for the weak.（4） The conclusion of the assessment the function of soil carbon sinks of Hexi is that: By the mathematical model of Hexi oasis farmland ecosystem functions of soil carbon sinks analysis showed that the economic benefits,①1949 2005 years in Hexi oasis farmland ecosystem carbon sink function of changes in the trend of economic growth was phased, carbon sink function of the economic benefits from 63 million yuan in 1949 to 776 million yuan in 2005, a net increase of 713 million yuan, an increase of 11.32 times.②Hexi oasis farmland ecosystem carbon sink function of the basic economic trends showing a growth of fluctuations （before 1960）, the resumption of growth （1960 to 2000） and the rapid growth of the three stages of development（since 2000）.（5） Through the above analysis, the strategies of oasis farmland ecosystem carbon by sinks & emissions reduction of Hexi are that:①The adaptation of farming systems: no-tillage is the least disturbance of soil tillage which can be very effective to improve soil organic carbon.②Fertilization to improve the way: long-term application of organic manure could significantly increase the activity of soil organic carbon content, inorganic fertilizer organic fertilizer can increase crop yield, and the use of Chemical fertilizers to increase the stability of soil organic carbon.③Straw: straw is to reduce the carbon emissions of farmland, increasing soil organic matter content in an important way, it can be treated straw as cattle feed, sheep, and then stool after ripening fields, not only can increase the soil organic matter content, but also the development of aquaculture, increase cost effectiveness.④Other measures: such as improved crop varieties, there are plans to have to pay close attention to nurturing high temperature, drought and other extreme weather and pest resistant varieties, to ensure that the ecological environment in the new production of farmers and continuously improve and expand the absorption of carbon storage. Alternatively, you can take measures to change the surface runoff, soil improvement, expansion of artificial turf fields, such as to indirectly increase the carbon sink function.更多还原