【作者】 郑宪清；

【导师】 胡锋； 孙波；

【作者基本信息】 南京农业大学 ， 生态学， 2008， 硕士

【摘要】 氮素是植物的重要营养元素之一,植物生长的主要限制因子,但多以植物难以利用的有机态存在土壤中。土壤微生物是氮素转化（如氨化过程、硝化过程）的主要驱动力。水热条件和土壤性质是影响土壤微生物数量和活性的重要因素。全球变暖已是一个不争的事实,预计未来几十年内全球平均气温将每10年升高0.2℃,我国平均气温将增加0.45℃,降水增加3%。全球变化通过影响温度、降雨和养分形态转化等影响着土壤生态过程,最终影响生态系统的生产力及其稳定性。本文选择我国东部地区三种主要农田土壤（黑土、潮土、红壤）,通过在温带的黑龙江海伦,暖温带的河南封丘和中亚热带的江西鹰潭三个野外生态实验站设置野外土壤置换（每种土壤各取三份,原地留一份,运抵其余两站各一份）试验,模拟研究不同气候带水热条件下各土壤氮素氨化和硝化阶段土壤微生物数量和作用强度的变化。两年的试验结果表明:受水热条件的影响同种土壤在不同气候带上,氨化细菌的数量差值平均为15.19×10⁶个/克干土,其中黑土、潮土、红壤的平均差值分别为15.60×10⁶个/克干土、17.96×10⁶个/克干土、12.00×10⁶个/克干土;硝化细菌的数量差值平均为4.77×10²个/克干土,其中黑土、潮土、红壤的平均差值分别为2.82×10²个/克干土、9.22×10²个/克干土、2.28×10²个/克干土。不同生长期,氨化细菌在玉米生长旺盛期高于玉米种植前和玉米成熟期;而硝化细菌在玉米生长旺盛期低于种植前和成熟期。同一生长期的不同气候带,氨化、硝化细菌数量在海伦和封丘高于在鹰潭。相关性分析表明在不同气候带上,氨化细菌数量与温度和降水量基本呈负相关关系(r_温度=-0.295,r_降水量=-0.267,P＜0.01)。硝化细菌在三个时期没有与月均温和降水量呈现出显著的相关性。不同土壤间,氨化细菌、硝化细菌数量黑土和潮土高于红壤。回归分析显示:硝态氮、土壤pH成为了氨化细菌数量的影响因子,综合解释能力达40.5%。土壤氨化强度在玉米不同生长季节的差异不显著。受水热条件的影响同种土壤在不同气候带上,氨化强度差值平均为4.65 NH₄^--Nmg/100ml,其中黑土、潮土、红壤的平均差值分别为4.30NH₄^--Nmg/100ml、4.71NH₄^--Nmg/100ml、4.95NH₄^--Nmg/100ml。不同土壤间,黑土和潮土中氨化强度（30～40 NH₄^--Nmg/100ml）高于红壤（20～30NH₄^--Nmg/100ml）。施肥处理与不施肥处理差异不显著。相关分析表明:氨化强度与土壤pH达到了极显著相关（r=0.700,P＜0.01）。回归分析表明,在玉米种植前,土壤pH和有机质含量是决定土壤氨化强度的关键因素。玉米生长旺盛期,土壤pH、有机质含量和土壤硝态氮含量是决定土壤氨化强度的关键因素。在玉米成熟期鲜土含水量、有机质含量、氨态氮含量和速效钾是决定土壤氨化强度的关键因素。经通径分析:种植前和旺盛期的土壤pH（1.414,0.321）及成熟期的速效钾（-0.587）与氨化强度的直接通径系数最大。在玉米的整个生长季水热-土壤,水热-土壤-施肥,水热-施肥等对氨化强度有着明显的交互影响作用,达到了显著甚至极显著程度。而土壤-施肥之间对土壤硝化强度的交互作用不显著。硝化作用强度受水热条件的影响同种土壤在不同气候带上,硝化作用强度差值平均为36.20%,其中黑土、潮土、红壤的平均差值分别为44.91%、45.30%、8.53%。且差异性显著。在玉米种植前和成熟期不同气候带之间,硝化强度:海伦＞封丘＞鹰潭,且差异显著;不同土壤之间,潮土＞黑土＞红壤,潮土中微生物的硝化强度高达90%以上,而红壤却不到20%;施肥处理高于不施肥处理。相关分析显示:硝化强度与土壤pH达到了极显著相关（r=0.800,P＜0.01）。回归分析知:不同气候带水热条件下,玉米种植前,温度、降水量、土壤pH和土壤全磷含量是决定土壤硝化强度的关键因素;旺盛期,温度、土壤pH、NO₃-N、NH₄-N以及速效钾是决定土壤硝化强度的关键因素;成熟期,降水量、鲜土含水量和全钾是决定土壤硝化强度的关键因素。而经交互性分析可知:土壤-施肥,土壤-水热,水热-施肥等对硝化强度有着明显的交互影响作用,达到了显著甚至极显著程度。而水热-土壤-施肥对土壤硝化强度的交互作用不显著。通径分析可知:土壤pH和全钾对硝化强度的直接影响力最强,直接通径系数为0.652和0.606。特别在玉米生长旺盛期,三种土壤均随着温度和降水量在不同气候带上的增加而下降。从海伦到鹰潭,2006年月平均温度由22.53℃上升到28.31℃,月降水量由119.2mm增加到265.0mm,2007年月平均温度由22.14℃上升到25.19℃,月降水量由82.38mm增加到134.2mm。由北向南,从海伦到鹰潭,三种土壤的硝化强度总体上呈下降趋势,海伦＞封丘＞鹰潭,而且差异显著,土壤硝化强度与温度和降水量均呈极显著负相关(r_温度=-0.354,r_降水量=-0.290,P＜0.01)。更多还原

【Abstract】 Nitrogen is the most important nutrient element for higher plants.It is the main limiting factor during the growth period of plant,for most of it in the form of organic matter and poor absorption by plant.Soil microorganism plays key roles in the processes of ammonification and nitrification.Climate conditions,soil properties and management practices influence the numbers and activity of soil microorganisms and affect the cycling and balance of nitrogen in agro-ecosystems.Some scholars studied that the average temperature of global increased 0.2℃each decades,and average temperature increased 0.45℃,while,rainfall increased 3%in China in future multi-decades.Global change may alter soil ecological process and eventually influence productivity stability of ecosystem through temperature,rainfall and transformation morphology of nutrient. The interaction of temperature,rainfall,soil type and fertilization on soil nitrification and ammonification process was studied by the soil transplantation experiment installed in 3 experiment stations of Chinese Ecological Research Network,i.e.Hailun,Fenqiu and Yintan Agricultural Ecological Station,which represents middle temperature,warm temperature and middle subtropical zone,respectively.Three types of cropland soils were selected,i.e.neutral black soil（Phaeozem）,alkaline Chao soil（Cambisol） and acidic red soil（Acrisol）.Then one-meter depth of soil profiles for each soil were transplanted in 3 stations to build the field experiment.The results of two-year,2006 and 2007,experiment showed:the number of ammonifying and nitrifying bacteria change range of 0.08×10⁶～74×10⁶（/g·dry soil） and 0.001×10⁴～25.86×10⁴（/g·dry soil）.The number of ammonifying bacteria in period of blooming higher than before growing and harvesting of maize,Meanwhile,nitrifying bacteria in period of blooming lower than before growing and harvesting of maize.Both of them in Hailun Station higher than in Fengqiu and in Yingtan Station.Analyse of correlation showed:the correlation between ammonifying bacteria and temperature （r=-0.295,P＜0.01） and rainfall（r=-0.267,P＜0.01） is negative correlation,but nitrifying bacteria is not,among different climatic zones.Among different types soils,the number of ammonifying and nitrifying bacteria in Phaeozem and Cambisol higher than Acrisol. Regression analysis showed:the main effect factors to the number of bacteria are NO_3-N, Available P,Available K,pH,Water content and Temperature.There are no significant differences of soil ammonification intensity（SMI） during the different growth period of maize.But it is higher at Hailun Station than at Fengqiu and Yingtan among different climate zones,and is higher in Phaeozem and Cambisol （30～40 NH₄^--Nmg/100ml） than in Acrisol（20～30NH₄^--Nmg/100ml） among different types soil.Analyse of correlation showed:it reaches very obvious correlation between SMI and pH（r=0.700,P＜0.01）.Regression analysis showed:the main effect factors to SMI are pH and SOM before maize planted,but pH,NO_3-N and SOM in blooming,and water content,SOM,NH₄^--N,and Available K in harvested times of maize.Path analysis showed:the most large path coefficient of effect factors to SMI will be change in different periods of maize,for example,pH is the biggest one in the period of before planting and blooming,but Available K is the biggest one in the mature stage.In generally,climate condition（temperature and rainfall）,soil type and fertilization exert an integrated impact on soil ammonification process,and there was a significant interaction of climate-soil type,climate-fertilization,and climate-soil type-fertilization. But soil type-fertilization with no significant interaction impact on soil ammonification.Soil nitrification intensity（SNI） changed with the temperature and rainfall during the maize stage.Because temperature changed in different climate zones in the period of before planting and mature stage,SNI in Hailun was higher than Fengqiu and Yingtan, and there is a significant impact.The intensity of soil nitrification was affected by soil types,which was in a sequence of Cambisol＞Phaeozem＞Acrisol.It reached 90%in Cambisol,but no more than 20%in Acrisol.Analyse of correlation showed:it reaches very obvious correlation between SNI and pH（r=0.800,P＜0.01）.Regression analysis showed:the main effect factors to SNI are temperature,rainfall,soil pH and total P before maize planted,but temperature,soil pH,NO_3-N,NH_4-N and Available K in blooming,and rainfall,water content and total K in harvested times of maize.Also,climate condition（temperature and rainfall）,soil type and fertilization exert an integrated impact on soil nitrification process,and there was a significant interaction of climate-soil type,climate-fertilization,soil type-fertilization. But climate-soil type-fertilization with no significant interaction impact on soil ammonification.Path analysis showed:the most large path coefficient of effect factors to SNI is pH and Total K,direct path coefficient is 0.652 and 0.606,correlation coefficient is（r=0.739,P＜0.01） and（r=0.585,P＜0.01）.Specially,From Hailun to Yingtan,with an increase of monthly average temperature from 22.3℃to 26.8℃and the monthly rainfall from 100.8 mm to 199.6mm, SNI decreased by 64.2%—67.2%for black soil,52.1%—52.5%for Chao soil,and 41.7%—75.2%for red soil,respectively.There was a significant negative correlation between SNI and temperature and rainfall,with a correlation coefficients of r=—0.354 （p＜0.01） and r=—0.290（p＜0.01）,respectively.The total number of soil nitrobacteria and the intensity of soil nitrification was affected by soil types,which was in a sequence of Chao soil＞black soil＞red soil.更多还原