【作者】 吴会军；

【导师】 蔡典雄；

【作者基本信息】 中国农业科学院 ， 农业资源利用， 2010， 博士

【摘要】 农田耕种措施与土壤有机碳、团聚体及土壤呼吸关系紧密,农田耕种措施对土壤固碳潜力和碳循环影响机制格外受到人们重视。本研究利用长期(10年)不同保护性耕种措施定位试验为研究平台,选择少耕(RT),免耕(NT),两茬(TC),深松(SS)和传统耕作(CT)五种典型农田耕种措施,采用土壤呼吸隔离分组、干筛和湿筛及化学分组研究方法,研究了不同耕种管理对土壤呼吸速率变化规律和土壤团聚体性质影响,及其与有机碳分布的关系,分析了土壤中有机碳含量及组分变化,为农田土壤固碳减排提供相关数据与理论依据,研究取得的主要结果为：土壤呼吸分量呈现不同的昼夜和季节变化规律,研究发现：土壤总呼吸速率和5cm土壤温度变化一致,有明显的昼夜变化规律；CT和RT处理在小麦返青期总呼吸速率较高,后期下降较快,而NT和SS处理呼吸速率变化较平缓。旱作农田小麦生长后期,土壤水分含量是限制呼吸排放的一个重要因子。土壤呼吸速率与5cm土壤温度成指数方程关系,总呼吸速率Q10值在1.24-2.06之间,NT下Q10值较小,对温度升高敏感性相对较弱；在小麦返青期,NT处理下总呼吸速率比CT低30.9%,显著低于CT及RT处理；NT的异养呼吸速率也最低,但差异不显著,各个处理异养呼吸占到总呼吸的63%-77%。耕种措施对呼吸速率的直接影响时间较短,结果显示：RT、SS和CT处理下耕作后1小时土壤呼吸速率分别比耕作前提高了53%,32%,39%,但是在耕作40天后的呼吸速率则和耕作前差异不大：NT和SS下NPP固碳量分别比CT增加了5.1和5.2%,虽然TC在小麦生长季NPP较低,但夏季花生生长增加了碳固定量。长期不同耕种措施可以导致土壤团聚体性质发生变化,主要结果为：NT和SS处理有利于干筛大团聚体的形成,在干筛法中,在0-5cm土层,NT和SS团聚体稳定性AS值分别比传统高7.8%和9.3%；在5-20cm土层,免耕和深松的平均重量直径(MWD值)最高,分别为2.15和2.16mm,TC处理的MWD值最低；在30-40cm底层土壤,NT和CT处理MWD值相似,差异不显著,两茬MWD值显著低于其他处理；TC处理湿筛团聚体稳定性最高,说明夏季花生根系或根系分泌物对水稳团聚体的形成有良好作用。土壤团聚体机械稳定性和水稳稳定性机制不一致,结果显示：SOC和活性碳含量与干筛团聚体稳定性参数负相关,而和湿筛团聚体稳定性参数正相关；湿筛下SOC和MWD的相关系数为0.699,达到极显著。有机碳对水稳团聚体贡献较大。经10年不同耕种管理,土壤剖面碳氮含量发生变化。主要结果为：在0-5cm土层中,免耕下SOC含量分别比深松、两茬、传统和少耕高8%、9%、30.8%和32.4%,深松处理高活性碳含量最高,达到0.58g kg-1,比传统高18%；免耕和深松SOC含量在20cm以上土层高于传统耕作,而在20cm以下却低于传统耕作；两茬0-40cm平均SOC含量比传统高17.6%,而免耕和深松分别比传统低0.6%和1.3%；各个处理高活性碳、中活性碳和活性碳分别占总总碳库的幅度为4.9-7.3%,18.6-29.4%和18.6-41.1%；免耕CPMI最高达到146.54,比传统高了46.54%,深松比传统高了16.98%。长期连续不同耕种影响了土壤有机碳储量,研究得出：40cm等深度SOC密度两茬处理最高,比传统耕作处理高12%,而免耕和深松处理分别比传统低9%和60%；两茬处理等质量SOC密度比传统高16.3%,而免耕和深松分别比传统低8.1%和6.3%；和豆科作物进行轮作,有利增加土壤碳库。综上所述,耕种管理措施改变有机物输入,进而影响土壤水分等因素,改变土壤呼吸排放、团聚体分布和有机碳含量。所以,通过优化农田管理措施,调控土壤呼吸排放、团聚体分布和有机碳转化过程,是实现农田固碳减排的重要手段。更多还原

【Abstract】 Soil organic carbon(SOC) is a key matter for soil nutrient supply and atmospheric carbon dioxide sequestration. There is a need to better understand soil carbon dynamics and management-induced carbon pool difference. A field experiment was carried out in a non-irrigated winter wheat (Triticum aestivum L.) field with the aim of evaluating the effects of different management practices on soil respiration, soil aggregate stability and soil organic carbon. The five treatments which selected in this study were reduced tillage(RT), No tillage(NT), two crop per year(TC), sub-soiling(SS), and conventional tillage(CT). trenching method was used for soil reparation(Rs) fractionation to study Rs diurnal and seasonal dynamics; dry and wet sieving were used to study soil aggregate stability and relationship to SOC; chemical fractionation methods were used for SOC dynamic study. Such understanding will provide information on how management practices influence SOC dynamics, and therefore, their role to mitigate, or contribute to, the greenhouse effect. fertility. The following results were obtained in this study:Total soil respiration(Rt) varied diurnally with the soil temperature changing. CT and RT had higher Rt at the turning green period of winter wheat growth, and went down rapidly, however the changes of Rt in NT and SS were much moderate. soil water content is a important factor which affects the variation of heterotrophic respiration(Rh)and autotrophic respiration (Ra) in dryland field.An exponential function provided the best fit for describing the relationship between Rs and 5 cm temperature. The Q10 is between 1.24-2.06. The NT treatment had smaller Q10 value, which mean that it is less sensitive to temperature. The NT had lowest Rt and significantly lower than CT to 30.9%, and had the lowest Rh, but the difference is not significant to other treatment. The Rh of NT、TC、SS、CT account to 64%、73%、77%和63% of Rt respectively.Tillage affection to Rt was in short-term, the Rt of RT SS and CT after 1 hour of tillage increased 53%,32%,39% compare to the Rt of before tillage respectively. The differences of Rt disappeared after 40 days of tillage compare to the Rt of before tillage. The NPP of NT and SS increased 5.1和5.2% compare to CT. even the NPP of CT is low during winter wheat growing season, it got extra harvest during summer time compare other treatments.Long term soil management practices affected soil aggregate stability. NT and SS increased the formation of big dry sieving aggregate. at 0-5cm layer, aggregate stability(AS) of NT and SS increase 7.8%和9.3% compare to CT. at 5-20cm, NT and SS had the higher mean weight diameter(MWD) value which are 2.15 and 2.16mm, and TC had the lowest MWD. At the 30-40cm depth, the MWD of NT and CT were similar. For the wet sieving, NT increased the aggregate stability at surface layer (0-5cm)only. TC had higher water sieving aggregate stability even it had lower dry sieving stability compare to other soil management practices. The soybean root or root secretion maybe are useful for the water stable aggregate formation.The mechanisms of dry and wet sieving aggregate stability are not the same. The contents of soil organic carbon (SOC) were negative correlate to dry sieving aggregate stability and positive correlate to wet sieving aggregate stability. For wet sieving, the correlation coefficient is significantly to 0.699.Soil management practices affected soil SOC and total nitrogen content after 10years treatment. For at 0-5cm layer, the SOC of NT is 8%、9%、30.8% and 32.4% higher than SS, CT, CT and RT respectively. The SOC content of NT and SS were higher than CT and RT at soil layer up to 20cm, however the order was reverse when soil depth lower than 20cm.0-40cm soil average SOC content,TC is 17.6% higher than CT, however NT and SS is 0.6%和1.3% lower than CT respectively. At 0-5cm layer, the high active carbon content of SS is highest to 0.58g kg-1. High active, medium active and active carbon account to 4.9-7.3%,18.6-29.4% and 18.6-41.1% of SOC respectively.After 10 years of different Soil management practices, TC had the highest equal depth carbon density and was 12% higher than CT, however, NT and SS were 9% and 6% lower than CT. for the equal mass carbon density, TC was 16.3% higher than CT, NT and SS were 8.1% and 6.3% lower than CT. NT was just change the distribution soil carbon content in soil profile, but did not increase the carbon pool, soybean planting during summer time increased the carbon pool.更多还原