极端暴雨条件下黄土丘陵沟壑区土壤蓄水能力和入渗规律

黄土高原退耕还林还草工程实施后,下垫面环境条件的变化可能对流域水文过程、水文通量、水量平衡以及生态系统产生十分重要的影响。研究极端暴雨条件下剖面土壤蓄水能力和入渗规律,对于阐明流域产汇流过程和影响机制具有重要的科学价值。采用土壤墒情仪对陕北"7·26"特大暴雨事件下黄土丘陵沟壑区草地剖面土壤水分进行了实时动态监测,分析了极端暴雨条件下剖面土壤水分的动态变化和蓄水过程,利用Horton入渗模型模拟了剖面土壤水分湿润锋的运动过程,揭示了极端暴雨条件下剖面土壤水分的入渗规律。结果表明:(1)极端暴雨条件下,黄土丘陵沟壑区坡面草地不同深度层次土壤水分与降雨过程的响应不同,具有层次性和明显的滞后效应,其中,0～140 cm是影响该地区土壤水文过程的关键层次;(2)土壤水分再分配结束时,湿润锋最深深度达140 cm,土壤蓄水量达225.99 mm,较降雨前95.37 mm增加了1.37倍;(3)极端暴雨过程中湿润锋的运动随时间呈对数递减关系,其稳渗速率随容重增加而减小,呈指数函数递减;(4)极端降雨过程中该地区坡面草地的产流机制仍以超渗产流为主,对于揭示流域的产汇流机制和完善水文预报模型具有重要的科学意义。     

Responses of plant community to the linkages in plant-soil C:N:P stoichiometry during secondary succession of abandoned farmlands,China

Succession is one of the central themes of ecology;however,the relationship between aboveground plant communities and underground soils during secondary succession remains unclear.In this study,we investigated the composition of plant community,plant-soil C:N:P stoichiometry and their relationships during secondary succession after the abandonment of farmlands for 0,10,20,30,40 and 50 a in China,2016.Results showed that the composition of plant communities was most diverse in the farmlands after secondary succession for 20 and 50 a.Soil organic carbon and total nitrogen contents slightly decreased after secondary succession for 30 a,but both were significantly higher than those of control farmland(31.21%-139.10%and 24.24%-121.21%,respectively).Moreover,C:N ratios of soil and microbe greatly contributed to the changes in plant community composition during secondary succession of abandoned farmlands,explaining 35.70%of the total variation.Particularly,soil C:N ratio was significantly and positively related with the Shannon-Wiener index.This study provides the evidence of synchronous evolution between plant community and soil during secondary succession and C:N ratio is an important linkage between them.     

The Application of GIS in Small Watershed Classification in Loess Plateau

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超氧化物歧化酶

本文就超氧化物歧化酶的种类、分布、结构、活性部位、催化机理、纯化、活力测定、理化特性等方面作了介绍,并叙述了它的研究动向和发展前景。     

山区农业面源污染的防治途径及对策

结合重庆市地形地貌特点和山区农业面源污染发生的因子，提出山区农业面源污染的防治对策。一方面必需结合当地的自然环境条件和经济发展水平提出农业面源污染的防治规划；另一方面必需结合生态农业建设这一主线，使物质、能量在生态系统内良性循环。紧紧抓住产生农业面源污染源的因子——化肥、农药、农田秸杆、畜禽粪便、农村生活废物等，提出科学的防治和减少途径。     

Detection of Colletotrichum coccodes from soil and potato tubers by conventional and quantitative real-time PCR

Colletotrichum coccodes is the causal agent of the potato blemish disease black dot. Two PCR primer sets were designed to sequences of the ribosomal internal transcribed spacer (ITS1 and ITS2) regions for use in a nested PCR. The genus-specific outer primers (Cc1F1/Cc2R1) were designed to regions common to Colletotrichum spp., and the species-specific nested primers (Cc1NF1/Cc2NR1) were designed to sequences unique to C . coccodes . The primer sets amplified single products of 447 bp (Cc1F1/Cc2R1) and 349 bp (Cc1NF1/Cc2NR1) with DNA extracted from 33 European and North American isolates of C. coccodes. The specificity of primers Cc1NF1/Cc2NR1 was confirmed by the absence of amplified product with DNA of other species representing the six phylogenetic groups of the genus Colletotrichum and 46 other eukaryotic and prokaryotic plant pathogenic species. A rapid procedure for the direct extraction of DNA from soil and potato tubers was used to verify the PCR assay for detecting C. coccodes in environmental samples. The limit of sensitivity of PCR for the specific detection of C. coccodes when inoculum was added to soils was 3·0 spores per g, or the equivalent of 0·06 microsclerotia per g soil, the lowest level of inoculum tested. Colletotrichum coccodes was also detected by PCR in naturally infested soil and from both potato peel and peel extract from infected and apparently healthy tubers. Specific primers and a TaqMan fluorogenic probe were designed to perform quantitative real-time (TaqMan) PCR to obtain the same levels of sensitivity for detection of C. coccodes in soil and tubers during a first-round PCR as with conventional nested PCR and gel electrophoresis. This rapid and quantitative PCR diagnostic assay allows an accurate estimation of tuber and soil contamination by C. coccodes .     

旱地(土娄)土长期定位施肥土壤剖面硝态氮分布与累积研究

通过12a大田长期定位试验研究了在自然降水条件、冬小麦—大豆轮作(或休闲)种植制度下,0～400cm土娄土剖面硝态氮分布与积累的特点。结果表明,长期单施氮肥,氮的表观利用率特别低,仅0.51%,氮肥配施钾、磷肥,氮的表观利用率为25%～35%,氮磷钾平衡施肥及配施有机肥,氮的表观利用率达到50%;施N肥方式显著影响土壤硝态氮积累和淋移,旱地土娄土长期单施化学氮肥或氮钾、氮磷、氮磷钾肥使土壤NO-3-N大量积累和淋移;氮磷钾与有机肥的配合施用能有效地缓解土壤对硝态氮的积累,提高氮肥利用率。     

西南边疆地区粮食安全问题研究

在介绍粮食安全概念的基础上,分析了西南边疆粮食安全的重要性和制约西南边疆粮食安全的因素,提出了保障西南边疆粮食安全的路径。     

鄂西南民族地区养殖业与旅游业互动发展研究

为了研究鄂西南民族地区养殖业、旅游业的互动发展,文章在文献分析的基础上,结合实地调研掌握的资料和收集的数据,分析了鄂西南少数民族地区养殖业与旅游业互动发展的意义、基础条件和存在的主要障碍。结果表明,鄂西南民族地区具备开展养殖旅游的基础条件,但在发展观念、目标、层次以及人力资源等方面仍存在一些障碍。因此,文章从发展观念转变、发展规划制定、发展层次提升、人才培养和政策支持等方面提出了促进该地区养殖业、旅游业互动发展的对策建议。     

根区滴灌对干旱山地苹果树生长发育和结实的影响

根区滴灌是将雨水促渗管与传统滴灌相结合而组装集成的一项节水灌溉新技术。为了探讨根区滴灌在山地果园的应用效果,为山地果园的栽培管理提供依据,本文以陕北米脂县6 a生山地红富士苹果树为研究对象,以世界公认的最佳苹果优生区洛川县的降雨量和土壤贮水量为灌水依据,分析了不同灌溉方式对苹果树萌芽、坐果、枝叶生长、果实发育和水分利用效率的影响,以及山地果园土壤水分达到优生区标准后与优生区苹果树生长结果的差异。结果表明,采用根区滴灌能有效提高苹果树的萌芽率和坐果率,萌芽率比传统滴灌提高了2.14%~2.76%,坐果率比传统滴灌提高了0.80%~1.42%;能有效促进苹果树新稍和叶片的生长,新稍长度比传统滴灌提高了1.44%~4.94%,百叶鲜质量比传统滴灌提高了2.13%~4.16%;能显著促进苹果树果实的生长,单果重比传统滴灌增大了7.05~14.99 g,优果率比传统滴灌提高了9.4%~14.7%;能显著提高水分利用效率,灌水量比传统滴灌节约了8.09%,水分利用效率比传统滴灌提高了10.62%~15.30%。可见,根区滴灌技术在陕北黄土丘陵区山地苹果生产中具有广阔的应用效果,但是,单纯依靠人为限量补水,山地苹果还不能达到优生区的生产水平。