【作者】 彭佩钦；

【导师】 刘强； 吴金水；

【作者基本信息】 湖南农业大学 ， 植物学， 2006， 博士

【摘要】 氮在土壤中的形态、周转和损失等均是土壤学家、植物营养学家和环境学家多年来经久不衰的研究热点。目前湿地作为土壤活性养分库和环境保护的作用越来越受到重视。洞庭湖区是我国湖泊地区中面积最大的湿地类型和重要的农产品生产基地，同时也是氮素化肥施用量较大的区域之一。因此，研究洞庭湖区自然与人工湿地土壤的微生物生物量氮状况与分布特点，揭示土壤微生物对外源无机和有机氮的同化和转化过程，对于正确评价土壤供氮水平，提高氮素的利用率，减少环境污染都具有十分重要的意义。本论文以洞庭湖区湿地土壤为研究对象，采用野外调查、模拟培养试验、盆栽试验、定位试验与¹⁵N同位素示踪技术相结合的方法，研究了洞庭湖区土壤微生物生物量氮及其与外源氮素转化的关系。主要研究结果如下：（1）洞庭湖区不同类型湿地（湖草洲滩地、芦苇洲滩地、垦殖水田）表层土壤（0-10 cm）微生物生物量氮含量为57.90-259.47 mg／kg，土壤微生物生物量氮占全氮的比例为3.1-6.4％。不同类型湿地土壤碳、氮和微生物生物量碳（B_C）、氮（B_N）差异明显，而且均随深度的增加而降低。湖草滩地表层有机碳、全氮含量明显高于芦苇滩地和垦殖水田，B_C与垦殖水田接近，而远大于芦苇湿地，B_N高于芦苇滩地和垦殖水田。土壤表层B_C占有机碳的比例：垦殖水田高于湖草滩地，高于芦苇滩地。土壤B_C、全氮、B_N与有机碳之间存在极显著的线性相关关系；土壤容重与有机碳、全氮、B_C、B_N之间呈现极显著的指数负相关关系；＜0.001mm土壤粘粒与有机碳、全氮和B_C、B_N之间呈现极显著的指数或对数正相关关系。（2）洞庭湖区不同利用方式的农田土壤B_N平均含量为115.47 mg／kg，主要分布区间在70-160 mg／kg，B_N占全氮的比例为1.0-7.4％，平均3.8％。农田不同利用方式的土壤碳、氮和B_C、B_N存在差异，水田土壤碳、氮和B_C、B_N明显高于旱地（苎麻为主的旱地、油菜为主的旱地），双季稻高于一季稻。较高的碳、氮投入量是导致双季稻土壤碳、氮和B_C、B_N高于其它三种利用方式的主要原因。土壤B_C、B_N能够很好地反映洞庭湖区农田土壤碳、氮水平。（3）水稻土长期田间定位试验结果证明，有机无机肥料长期配合施用显著提高了土壤全氮和B_N水平，也提高了土壤B_N占全氮的比例，同时也显著增加酸解性氮含量。土壤有机氮以酸解性氮为主，酸解性氮中氨基酸态氦占优势，氨基糖态氮所占份额最低。土壤酸解性氮及其组分均与B_N存在极显著的正相关关系。氨基酸氮和酸解未知氮对B_N的影响最大。（4）淹水培养条件下，B_N先迅速上升到一定峰值后逐渐下降，最后趋于稳定。其峰值大小为：稻草硫铵配施＞硫铵＞对照。微生物同化的标记底物硫铵氮，红黄泥为0.15-20.6％，紫潮泥为2.9-15.9％。化肥和秸秆配合施用能增强微生物对无机氮的同化，而紫潮泥微生物对硫铵氮的同化和固持快于红黄泥。红黄泥粘土矿物固定的标记底物氮最高为10.6％，紫潮泥30.0％。微生物同化的氮和粘土矿物固定的氮在试验期间均随时间的延长而减少。有机无机配施处理提高了标记底物氮的有机氮形态残留率，降低了无机氮形态（固定态铵和矿质氮）残留率。（5）盆栽条件下，B_N在水稻不同生育期有明显变化。在水稻孕穗期出现较低值，到成熟期有所回升。红黄泥微生物同化的标记底物氮最高为8.3％，紫潮泥为19.2％，尿素和秸秆配合施用能增强微生物对无机氮的同化。红黄泥粘土矿物固定的标记底物氮最高为2.0％，紫潮泥为18.7％。有机无机配施提高了微生物对尿素氮的竞争能力，降低了粘土矿物的固氮能力。尿素氮和秸秆氮的残留以有机氮形态为主，红黄泥为80％以上，紫潮泥72％，酸解氮是尿素和秸秆氮残留主要有机氮形态。红黄泥尿素氮残留的主要无机形态是矿质氮，占总残留的15％，而紫潮泥为固定态铵，占总残留的20％。尿素配合施用秸秆提高了化肥的利用率和残留率，降低了尿素氮的无机氮形态残留。更多还原

【Abstract】 The wetland and paddy soil have been recognized for importance in the retention ofactive nutrition and the environment protection nowadays. Studies on the forms and theturnover of N and the loss of N added in soil have been permanent research topics by soil,plant nutrition, and environmental scientists since nitrogen is distinguished to be one ofthe essential macronutrients for plant growth. The Dongting Lake plain is one of thelargest areas of wetland in lake regions in China and it is the important output area offarm production. Meanwhile, it is one of the districts where the input of chemicalfertilizer N is more excessive and the environmental pollution is more serious. Therefore,it is significant to evaluate the capacity of soil N-supplying, increase the recovery of Nand reduce the environmental pollution through revealing the situation and distribution ofsoil microbial biomass N (B_N) in natural and the artificial wetland, reveal the relationshipbetween B_N transformation and soil organic nitrogen components as well as the effect oforganic and inorganic fertilizers on soil N transformation and so on.Based on field investigation, long-term field experiments, laboratory-floodedincubation and pot experiment, the content of soil organic carbon(T_C), total nitrogen (T_N),microbial biomass carbon (B_C), B_N, mineral N, mineralizable N, amino acid N (AAN),ammonium N (AN), amino sugar N (ASN), hydrolysable unidentified N (HUN), totalhydrolysable N (THN), nonhydrolysable N(NHN) and fixed ammonium were measured.The main results were as following:(1) There are eight profiles of three types of wetland, including Carexspp-dominated,Phragmites-dominated and paddy soil, for field investigation in Dongting floodplainwetland. Results showed that content of B_N in the top layer (0-10 cm) is 57.90-259.47mg/kg, the proportion of microbial biomass nitrogen in soil total nitrogen in DongtingLake is 3.1-6.4%. Vertical distribution of soil C, N, B_C and B_N were very similar in soil profiles (0～100 cm) of the three types, and decreasing gradually with the increase indepth. The soil organic C, N and B_N in the Carexspp-dominated floodplain were higherthan those of paddy soil and the Phragmites-dominated floodplain at 0～10 cm; The B_C inCarexspp-dominated floodplain and paddy soil were higher than that ofPhragmites-dominated floodplain at 0～10 cm. There were significant logarithmcorrelations between organic carbon, soil N, B_C, B_N, and soil clay granules(＜0.001mm) inour studied three type of soil (p＜0.01). There was also significant power correlationbetween organic carbon, soil N, B_C, B_N, and bulk density in our studied soil (p＜0.01).(2) Field investigation on the farming soil derived from wetlands (purple alluvial soil)were conducted in a selected landscape unit (112°16′- 112°56′E, 28°42′- 29°11′N) in theDongting lake region of Hunan province. The results showed that the content of B_Nranges from 70 to 160 mg/kg (average of 115.47 mg/kg) in different land-use types andcropping systems, and approximately, the percent of B_N in soil total nitrogen in DongtingLake was 3.1-6.4%. The amount of soil C, N were significant different in variousland-use types and cropping systems, such as paddy soil (double rice, single rice), upland(rape, ramie). The T_C and T_N in the double rice paddy soil were higher than those ofsingle rice, rape, and ramie, the same as the content of B_C and B_N in double rice paddysoil. The percentages of soil B_C, B_N in organic C, total nitrogen in farmland of DongtingLake region were 0.6～7.2% (average of 3.00%), 1.0～7.4% (3.8%), respectively. Theratios of T_C to T_N and B_C to B_N were 3.87-17.31 (9.15), 4.06～9.29 (7.26), respectively.There were significant correlations between T_C, T_N and B_C, B_N(p＜0.01). And B_C, B_Ncould responses to the changes of T_C, T_N in farmland of Dongting Lake region.(3) Soil samples were collected from two long-term field fertilizer experiments sites,which had been for 18 years. One soil derived from wetlands lacustrine sediment and theother derived from alluvial sediment in the Dongting lake region. Data suggested that T_C,T_N, organic N components and B_N has changed significantly after the long-term combinedapplication of organic and chemical fertilizers (NPKM). NPKM increased the content ofT_N, B_N, total hydrolysable N (THN) and the ratio of B_N to T_N. The majority of organic Ncomponents in soil were total hydrolysable N (THN). In THN components, thepercentage of ammonia acid N (AAN) was the highest, followed by ammonium N (AN),then hydrolysable undefined N (HUN), and ammonia sugar N (ASN) was the lowest. B_Nhad significant positive correlation with THN and all THN components (p＜0.01). Theavailability of AAN and HUN for B_N were the highest in THN components.(4)The laboratory-flooded incubation experiment, using the paddy soil developed from Quaternary red soil (reddish clayey soil) and derived from wetlands (purple alluvialsoil), showed that the majority of B_N was native, and the percentage of labelled substrateB_N in reddish clayey soil and purple alluvial soil were 0.30～6.7% and 1.0～3.5%,respectively. The combined application of rice straw and chemical fertilizer improved theimmobilization of inorganic N by microbes. In addition, the maximum of labeledsubstrate N assimilated by microbe in reddish clayey soil and purple alluvial soil were20.6% and 15.9%, respectively. The assimilation of labeled substrate N in NPKMtreatments was higher than those in chemical fertilizer treatment. The maximum oflabeled substrate N immobilized by clay in reddish clayey soil and purple alluvial soilwere 10.6% and 30.0%, respectively. B_N and fixed ammonium decreased with theincubation time. NPKM increased the remained percentage of organic N and decreasedthe remained percentage of mineral N and fixed ammonium.(5) For pot experiments, there was dynamic change for B_N during the period of ricegrowth. B_N was the lowest at booting stage, and then re-increased at matured stage. Thenative B_N was the majority part, and the percentage of labeled substrate B_N in reddishclayey soil and purple alluvial soil were 1.6～24.3% and 1.15～17.6%. The capability ofmicrobe assimilating inorganic nitrogen increased in the combined application of urea andrice straw treatments. The maximum of immobilization of labeled substrate N by microbein reddish clayey soil and purple alluvial soil were 8.3% and 19.2%, respectively. Theassimilation of labeled substrate N by microbe in NPKM treatments was higher thanthose in chemical fertilizer treatment. The contents of fixed ammonium in fertilizerstreatments in the two soils were lowest at tillering stage. The-maximum of immobilizationof labeled substrate N in clay in the studied soils were 2.03% and 18.69%, respectively.The immobilization of labeled substrate N by clay in NPKM treatments was lower thanthose in chemical fertilizer treatment. The remained majority status of labeled substrate N(urea and straw) were organic N, and the percentage accounted for 80% in reddish clayeysoil and 72% in purple alluvial soil, respectively. The status of labeled substrate N inremained inorganic N (urea) was mineral N (12%) in reddish clayey soil and fixed-N(20%) in purple alluvial soil.更多还原