西南喀斯特地区土壤侵蚀特征研究现状与展望

受地质背景的强烈制约,西南喀斯特地区土壤侵蚀与其他类型区显著不同,叠加了化学溶蚀、重力侵蚀和流水侵蚀的耦合作用,呈现地面流失和地下漏失的混合侵蚀机制。从土壤地表侵蚀产沙、土壤地下漏失、土壤侵蚀强度与分级标准、土壤侵蚀过程模拟等几个方面简要综述了该区土壤侵蚀特征,并对未来研究方向进行了展望。今后应该加强西南喀斯特地区水土流失途径与土壤流失/漏失定位监测技术研究,进一步发展水土二元流失模拟模型,为该区土地利用变化的水土保持功能定量评估提供科技支撑,服务石漠化综合治理和后续规划制订。     

Evaluating the genetic biodiversity of Bambara groundnut accessions from Nigeria using SDS-polyacrylamide gel electrophoresis

Biochemical characterization of Bambara groundnut accessions collected across Nigeria has been performed. Percent (%) fat content varied from 1.42 to 8.16, while mg/ml protein values varied from 42 to 142. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed considerable heterogeneity in the different storage protein fractions. Polypeptide subunits of high molecular weights (above 200 kd), as yet, not reported in other Vigna species were observed in the profile of the protein fractions. The accessions also exhibited significant similarity in their polypeptide profile. However, the presence or absence of the 34 kd subunit band allowed the classification of the accessions into two. The 34 kd band was absent or not detected in six of the accessions (acc. 2, 5, 10, 11, 14 and 17). The results are discussed in the light of the controversy surrounding the taxonomy of Bambara groundnuts.     

A note on the Nigerian vegetable cowpea

Summary The Nigerian vegetable cowpea belongs to Vigna unguiculata (L.) Walp. ssp. unguiculata. It was found to be high yielding, day neutral, adequately adapted to the region south of 10°N latitude and consisten phenotypically. The morphological features include the climbing and decumbent growth habits, the coiled, curved and straight pendant pods; the lanceolate and rhomboid leaf forms and the presence or absence of the soluble compound, anthocyanin on the shoot, pods and seeds.When planted with the early rains, the climbing type yields higher with an average fresh pod and dry grain yield of 13.lt/ha and 1.66t/ha, respectively as against the fresh pod and dry grain yield of 11.4t/ha and 1.35t/ha of the decumbent type. The plant ensures an uninterrupted protein supply throughout the year either as fresh immature pods or as dry grains.     

西南岩溶山区生态系统基本特征及其调控措施研究——以贵州省为例

西南岩溶山区生态环境脆弱．是我国实施西部大开发战略中生态建设的重点地区。通过对生态系统多样性和易损性、容量、生物生产力与生物量、敏感性和承灾能力等5个因素的分析,阐述了西南岩溶山区生态系统的基本特征,探讨了西南岩溶山区生态系统建设的原则。根据西部大开发中对生态建设的要求,提出了西南岩溶山区生态建设与调控的对策措施。     

西南地区1902—2018年干旱时空演变特征分析

鉴于西南地区干旱的危害程度及其严峻形势,定量刻画干旱时空特征、揭示干旱发展规律,已成为抗旱防灾、保障农业健康发展的迫切要求。基于1902—2018年标准化降水蒸散指数(SPEI)数据,统计了西南地区不同等级干旱发生频率及干旱强度,并采用Sen趋势分析、Mann-Kendall检验法和经验正交函数(EOF)分析方法研究了西南地区干旱的时空演变特征,以期为西南地区干旱变化及生态维护提供科学依据。结果表明:(1)1902—2018年西南地区SPEI12整体呈下降趋势,下降速率为0.025/10 a,其中1954—1974年呈干旱—湿润的频繁交替,发生多次不显著突变;(2)西南地区干旱强度均呈增强趋势,其中中旱和重旱强度增强趋势显著;(3)西南地区干旱发生频率存在空间分布差异,其中轻旱发生频率最高,极端干旱最低;(4)西南地区干旱变化趋势以不显著下降为主,占研究区面积的68.22%,表明西南地区百年来呈干旱化趋势;(5)干旱时空模态分析中,3种模态分别反映了研究区干旱全区相同、南北相反、东西相反的分布特征。综上所述,揭示了西南地区干旱的时空变化基本特征。     

Effects of nutrients omission on maize growth and nutrient uptake in three dominant soil types of southwestern Nigeria

Abstract

A pot experiment was conducted to determine most limiting nutrients for maize performance using nutrient omission treatments in three soil types of southwestern Nigeria. There were six treatments; full nutrient [120?kg nitrogen (N)/ha, 40?kg phosphorus (P)/ha, 80?kg potassium (K)/ha, 10?kg molybdenum (Mo)/ha, and 5?kg zinc (Zn)/ha]; full nutrient minus N, P, K, Mo, and Zn including control was replicated thrice. Treatments were arranged as split plot in a complete randomized design. Data were collected on growth parameters, shoot, root dry weights, and NPK uptakes. Data were subjected to analysis of variance and means separated using LSD_0.05. Majeroku and Egbeda soils and full nutrient supported better maize growth and NPK uptakes. Shoot weight was higher in Egbeda while root weight was higher in Itagunmodi soil. Phosphorus was the most limiting in Egbeda and Itagunmodi soils, and nitrogen in Majeroku soil. In conclusion, maize growth, nutrient uptake and most limiting nutrient varied with soil types.     

Termite mounds in relation to the surrounding soils in the forest and derived savanna zones of southeastern Nigeria

Some physical and chemical properties of the two common termite mounds in southeastern Nigeria, Macrotermes (MM) and Cubitermes (CM) mounds, were compared and their relationships with the surrounding top and subsoils investigated. Percentage sand, silt, pH, calcium, magnesium, potassium, sodium, iron, and organic carbon were higher and clay and penetrometer resistance lower in the CM than the MM. Sand, silt, organic carbon, and calcium decreased and clay increased from the forest to the derived savanna in the CM, but no clear trend was shown with the other properties in both the CM and the MM. Most of the nutrients were higher in the CM than in the adjacent top or subsoil but the reverse was the case with the MM. More nutrients are associated with the inorganic fractions of the soil than with the organic carbon in the mounds and the soils surrounding them. The Ca:Mg ratio in the mounds and the top and subsoils adjacent to them was low for most crops but the K:Mg ratio was mostly adequate. Because of these differences in properties and sizes of the mounds, different management strategies are recommended for them and the soils around them.     

Amelioration of a degraded Oxic Paleustalf by leguminous and natural fallows

Abstract. The restorative ability of herbaceous ( Psophocarpus palustris, Pueraria phaseoloides ) and woody ( Leucaena leucocephala, Senna siamea, Acacia leptocarpa, Acacia auriculiformis ) legume species and of natural regrowth was studied on an eroded and compacted Oxic Paleustalf in southwestern Nigeria. Compared to the control treatment that was continuously cropped for 15 years, four years of fallowing significantly improved test crop yields. However, fallowing with the above species did not substantially improve soil properties, particularly soil bulk density. A longer fallow period may be needed to amend soil physical conditions of this degraded Alfisol. Soil chemical properties were greatly improved following land clearing and plant biomass burning in 1993. However, the residual effect of burning on soil fertility was insignificant in the second cropping year. Among the fallow species, P. palustris and natural fallow showed the best residual effect on test crop performance. Despite the high biomass and nutrient yields of S. siamea and A. auriculiformis , test crop yields on these plots were low due to the border effects from the uncleared and fallowed subplots.     

连续两年丹东地区春季暴雪过程对比分析

利用常规高空和地面形势场资料对2012和2013年的2次春季暴雪过程进行对比分析,结果表明,中高纬脊前冷空气不断补充,促使浅槽加深东移,低空西南急流建立,均为丹东地区暴雪提供有利环流背景和动力、水汽条件;地面倒槽顶部暖切变以及蒙古低压槽前切变是暴雪直接影响系统;中低层温度的分析是春季降雪预报的关键点,前期冷空气波动以及各层温度的垂直变化,尤其是低层逆温层的分析,均可以为判断降雪相态预报提供依据。     

成都金沙遗址沉积物微量元素特征及环境意义

采用电感耦合等离子体质谱仪(Q-ICP-MS)测试了成都金沙遗址河流相沉积物微量元素质量分数,并通过对微量元素质量分数和比值特征及其与粘粒、铁游离度和有机质等的相关性分析,探讨了微量元素特征对环境变化的指示意义.结果表明:Ba,Cr,Zr,Sr质量分数和Ba/Nb,Rb/Sr,Ba/Sr比值可用于指示沉积物源区环境的变化;龙门山及成都平原地区近3 400年以来的气候变化趋势为温暖湿润—温暖潮湿—温和偏干.沉积物微量元素特征分析与前人利用矿物、磁化率和孢粉分析手段的研究结果一致,揭示了古气候和古环境演变历史.