金堂环溪河流域土壤氮素含量及其影响因素分析

采集耕层(0～20cm)土样108个,研究其氮素含量及其影响因素。结果表明,研究区土壤全氮和碱解氮均呈正态分布。其中土壤全氮平均含量为0.52g kg-1,碱解氮平均含量为68.1mg kg-1。地形条件、土地利用方式和轮作制度是影响土壤氮素含量的重要因素。统计分析表明,不同台位之间土壤全氮含量均未达到显著水平;不同台位之间土壤碱解氮含量差异显著,冲沟水田(77.1mg kg-1)、一台地(72.3mg kg-1)和二台地(71.0mg kg-1)均显著高于丘顶地(51.6mg kg-1)。四种土地利用方式之间全氮含量呈显著差异,林地(0.69g kg-1)和旱地(0.45g kg-1)、水田(0.48g kg-1)分别达到极显著差异和显著差异水平,非林地之间差异不显著;四种土地利用方式之间碱解氮含量呈极显著差异,林地(81.3mg kg-1)与旱地(56.1mg kg-1)达到极显著差异,而在非林地之间,旱地与果园(77.2mg kg-1)、水田(70.8mg kg-1)分别达到显著差异。轮作制度对土壤氮素含量和分布的影响程度不如台位和土地利用方式,四种轮作制度之间土壤全氮和碱解氮含量均未达到显著差异。     

Nutrient concentrations and NH4+‐N mineralization under different soil types and fallow forms in southern Cameroon

To evaluate the soil‐fertility sustainability of the fallow systems, nutrient concentrations and NH₄⁺‐N mineralization were determined in different soil and fallow types in the humid forest zone of southern Cameroon. Two experiments were conducted, the first comprised planted leguminous tree Calliandra calothyrsus, planted leguminous Pueraria phaseoloides, and regrowth mainly composed of Chromolaena odorata on the Typic Kandiudult. The second experiment made up of a fallow dominated by C. odorata, a fallow with C. odorata removed, and a P. phaseoloides fallow on the Rhodic Kandiudult, Typic Kandiudult, and Typic Kandiudox. In the first experiment, available P, Ca²⁺, K⁺ concentrations and effective CEC under C. calothyrsus were, respectively, 40%, 22%, 45%, and 15% lower when compared to P. phaseoloides but no differences were found between soils under P. phaseoloides and C. odorata. Mineralization of NH₄⁺‐N was higher under C. calothyrsus than under C. odorata‐ and P. phaseoloides‐fallow types, indicating the impoverishment of organic material under the former. In the second experiment, the beneficial effect of P. phaseoloides was found in the Rhodic Kandiudult in the 0–10 cm layer throughout its low NH₄⁺ release from mineralization. In the Typic Kandiudult, no differences in NH₄⁺‐N mineralization were found between C. odorata and P. phaseoloides fallows. In the Typic Kandiudox, there was no difference in NH₄⁺ mineralization between the three fallow types. According to the nutrient concentrations and NH₄⁺ mineralization, the fertility sustainability of the different fallow types may be ranked as follow: P. phaseoloides ≥ C. odorata > C. calothyrsus > fallow without C. odorata.     

Nutrient immobilization and release patterns during plant decomposition in a dry tropical bamboo savanna,India

Summary Decomposition and changes in nutrient content of six litter types (leaves, sheaths, roots, twigs, and wood of bamboo, and grass shoots) were studied in nylon net bags for 2 years. The annual weight loss was (% of initial) bamboo leaves 56.5, bamboo sheaths 79.5, bamboo roots 65.8, bamboo twigs 49.6, bamboo wood 31.2, and grass shoots 74.9. Elemental mobility followed the order K>Na>C>P>Ca>N in all components except wood. Generally, an initial increase was followed by a consistent decrease in the contents of N (leaves), P (leaves, roots, wood) and Ca (leaves, roots, grass), and Na (wood). Most of the nutrients were immobilized in the rainy season. C and K contents showed a constant decrease throughout the decomposition period. Materials with a greater C:N ratio (>50) tended to accumulate more nutrients and retain them for longer, except for the bamboo twigs. The critical C:N ratio (at which a net release of N occured) for the leaf material was 25. Litter components with more initial N (sheaths) showed greater weight loss than those with less N (leaves, twigs, and wood). Overall, N and P were lost at the slowest rates while C and K were lost at faster rates. Initial lignin, lignin: N, C:N and C concentrations had a better predictive value for annual weight loss and nutrient release in bivariate relationships. A combination of the initial lignin value and the C: N ratio explained 93% of the variation in annual weight loss. A significant relationship was also observed between the annual weight loss rate and the nutrient mineralization/release rate.     

Interactions between soil micro- and mesofauna and plants in an ecofarming system

Interactions between crops and soil micro- and mesofauna within the root zone were investigated under field conditions on sandy loam on a larger spatial scale and in columns in the laboratory on a smaller spatial scale. During the vegetation period of summer wheat from April to July 1999 soil samples were taken monthly directly from the root zone within plant rows and between plant rows hardly penetrated by roots. Abundances of Enchytraeidae, Collembola, soil flagellates, enzyme activities and contents of total carbon and nitrogen were determined. Additionally, a laboratory experiment was carried out with soil columns. Soil from the field was defaunated and inoculated with soil fauna (Enchytraeidae, Collembola, earthworms) in different combinations. Furthermore, summer wheat was sown. Enzyme activities, soil flagellate abundance and contents of total carbon and nitrogen were measured after 2, 6 and 14 weeks. Our field results revealed considerable interactions between plant roots, sampling date and soil layer affecting Enchytraeidae and Collembola. Within plant rows flagellate numbers correlated higher with N_t and C_t than between plant rows. In the laboratory close relationships between soil fauna as well as enzyme activities and nutrients contents were found within the root zone.     

贡嘎山暗针叶林枯落物截留特征研究

 采用现场模拟法和浸泡法观测贡嘎山不同演替阶段的暗针叶林群落枯落物截留、枯枝落叶层的最大持水量和林内枯落物的截留特征。结果表明:不同林型的枯落物截留量与林外降雨量有不同程度的线性相关关系,而与林内降雨量存在幂函数关系。同林型内,由于枯落物数量、组成成分与分解程度等不同,其持水能力也存在着较大的差异。过熟林中枯落物吸水饱和时间最短,最大持水率最低,枯落物与林下苔藓层混杂在一起,截留水分的能力相对较弱;幼龄林中枯落物饱和需要时间最长,最大持水率也最高,对林下降雨的再分配作用也相应最大。同时,枯落物层的截留作用及截留量的大小,除与枯枝落叶层的数量和质量相关外,也与枯落物的湿润程度相关。     

根-土界面区域磷酸盐的分布和移动: Ⅲ. 动力学

The depletion rate of phosphate in the soil-root interface zone increased along with growth and phosphate uptske of wheat or maize,which indicated that the phosphate distribution in soil near the root surface agreed well with the phosphate movement in rhizosphere and phosphate uptake by plant,The relative accumulation zone of phosphate within 0.5mm apart from the root surface developed at the 15th day or so after cultivating wheat or maize since the root phosphate secretion increased gradually in this stage.The phosphate distribution in the soil-root interface zone against the growing time(t)and the distance from the root plane(x) could be described by the non-linear regression equation with the third powers of x and t.     

三峡水库消落区土壤胶体对Cd在土壤中迁移的影响

选取三峡水库消落区典型土壤,即紫色土、黄壤、紫色潮土和灰棕潮土为研究对象,以相应土壤胶体、蒙脱石矿物的10 mg/L Cd(NO3)2淋洗液分别淋洗土柱,研究了水分散态胶体对镉在土柱中迁移的影响.添加上述胶体的镉淋洗液,在紫色土、黄壤、紫色潮土和灰棕潮土土柱中镉迁移量分别是对照的1.18～4.96,1.05～2.37,1.10～4.33,1.03～3.33倍.结果表明胶体能够促进镉离子在土层中的迁移,其迁移能力遵循紫色土胶体≥紫色潮土胶体＞灰棕潮土胶体＞蒙脱石胶体＞黄壤胶体的规律.由此得出,胶体吸附态镉的迁移能力取决于胶体类型和土柱性质.     

祁连山不同森林植被类型对土壤微生物影响的研究

通过研究不同植被类型下土壤微生物区系、土壤酶活性和土壤生化作用强度,分析了祁连山不同森林植被类型土壤微生物的数量变化、垂直分布、土壤呼吸强度和纤维素分解能力等的变化规律和特征。     

致灾农业昆虫捕集滑板表面结构仿生构建与性能验证

致灾农业昆虫光电诱导滑移捕集技术中,致使昆虫产生良好滑移行为的捕集滑板是获取该技术高效应用的关键。红瓶猪笼草(Nepenthes alata)叶笼滑移区依靠特殊形貌对昆虫附着系统表现出显著滑移功能,为致灾农业昆虫捕集滑板的研制提供了仿生原型。采用扫描电子显微镜(scanning electron microscope,SEM)与三维白光形貌干涉仪(scanning white light interferometer,SWLI)对滑移区表面微形貌进行观测分析并获取三维结构参数,据此构建了致灾农业昆虫捕集滑板表面结构的仿生模型;采用激光微纳加工技术和高压静电吸附技术实现捕集滑板的仿生制备。为验证仿生制备致灾农业昆虫捕集滑板功效,测试了蝗虫(Locusta migratoria manilensis)在捕集滑板和仿生原型的附着力,结果分别为(402.9±26.1)m N和(361.9±25.5)m N,相近的附着力预示研制的致灾农业昆虫捕集滑板具有与仿生原型类似的性能。     

气候对旱地紫色土微生物功能多样性的长期影响

研究了暖温带和中亚热带气候对紫色土的理化性质、微生物活性及其多样性的长期影响.将安徽休宁的紫色土分别放置在暖温带的封丘和中亚热带的鹰潭,18年的旱作定位试验结果表明,中亚热带紫色土的pH、全N含量、NO3--N含量和有效P含量显著低于暖温带紫色土;中亚热带气候条件下紫色土微生物整体活性高于暖温带;中亚热带气候条件下紫色土微生物对羧酸和糖类利用较多,而在暖温带气候条件下紫色土微生物对氨基酸和胺类的利用能力较高.说明中亚热带气候条件促进了紫色土微生物对含C化合物的利用,而暖温带气候条件促进了紫色土微生物对含N化合物的利用.