淹水条件对水稻芽撒播成苗的影响

对水稻芽撒播在不同灌溉方式下的成苗情况进行了研究。结果表明,无水层带泥浆撒播处理,根系发育与茎叶生长比较协调,成苗率达90.7%,秧苗综合性状好于其它处理,是水稻芽抛秧的首选方式;淹水48h后落干处理,有利于发根和扎根立苗,成苗率达92.7%,秧苗综合性状较好,是水稻芽抛秧应采用的第二种方式。     

水稻根系泌氧对水稻土磷素化学行为的影响

通过模拟试验研究了水稻根系泌氧作用对水稻土磷素化学行为以及水稻吸磷的影响。淹水极显著地增加土壤对磷的吸附,降低磷的解吸。而模拟的水稻泌氧作用则可明显降低土壤对磷的吸附,增加根际土壤的磷解吸和离子交换树脂对磷的吸收量。因此,水稻根系的泌氧作用应该是水稻在淹水明显降低土壤磷有效性情况下能正常从土壤获取磷的重要机制之一。淹水导致土壤磷有效性降低与淹水引起土壤磷组分转化有关。淹水2周,经富磷预处理而增加的Al-P组分,几乎全被转化为Fe-P。     

蕾期涝渍胁迫对盆栽棉花生长和产量特性的影响

涝渍灾害是棉花生产中面临的重要自然灾害之一,长江流域棉花蕾期常遭遇多雨天气而产生涝渍灾害。在盆栽条件下,以华棉3109为试验材料,研究了不同涝害胁迫7 d(T1处理)和14 d(T2处理)对棉花生长和产量特性的影响,正常灌水管理作为对照(CK)。结果表明,在涝渍胁迫处理期间,棉花叶片SPAD值、株高、绿叶数、倒四叶功能叶叶面积、开花数、蕾数、结铃数、果枝数和果节数均表现为:CKT1处理T2处理。在处理结束之后(花铃期),受涝渍胁迫棉株株高、茎粗、蕾数、开花数、结铃数、果枝数和果节数等指标都相继出现快速补偿性生长现象。但是随着涝渍胁迫时间的增加,棉花蕾铃脱落率升高,成铃率下降,最终产量构成因素和单株籽棉产量呈下降趋势。     

The impact of a hydroelectric dam on Neotropical fish communities: A spatio-temporal analysis of the Trophic Upsurge Hypothesis

We employed the trophic upsurge hypothesis as an analytical framework to describe the response of Neotropical fish communities to terrestrial inundation associated with river damming. Data were collected for the impact assessment of the Peixe Angical Dam, Tocantins River, Brazil. Monthly surveys were conducted at nine sites (seven upstream, two downstream) from 15 months before to 20 months after dam closure and a follow-up survey 60–83 months after closure. Fish responses differed in timing and magnitude across sites. In the new reservoir, populations peaked 8–13 months after flooding, demonstrating increases in richness (84 ± 52%), biomass (329 ± 266%) and abundance (681 ± 348%) with the maxima for richness and abundance tending to precede biomass maxima. Populations of all families increased but were greatest for Engraulidae, Hemiodontidae, Serrasalmidae and Characidae, and lower for the benthic catfish: Sciaenidae, Dorididae, Pimelodidae. Downstream populations peaked 5–12 months after closure or showed consistent decline. Five years after dam-closure richness and abundance were lower compared to predam levels, with populations at all sites demonstrating an ongoing decline. Reservoir creation triggers reproductive recruitment and otherwise pools spatially disparate populations from across the flooded valley. If the rise in richness is largely explained by the increased catchability of species otherwise present prior to flooding, it may be more appropriate to estimate species loss with reference to upsurge data. As peak biomass coincides with declining richness, modelling fisheries production from annually aggregated data may risk overestimating the potential for sustainable harvests. Upsurge–response curves can help identify the timing of critical ecological thresholds for flood-managed fisheries.     

Waterlogging differentially affects yield and its components in wheat,barley, rapeseed and field pea depending on the timing of occurrence

Waterlogging on croplands is increasing in various areas of the world. This study evaluated the yield penalty by early and late waterlogging on wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), rapeseed (Brassica napus L.) and field pea (Pisum sativum L.). Plants cultivated outdoors were exposed to a 14-day waterlogging during vegetative (at 65 days after sowing (DAS)) or reproductive (at 85/87 DAS) stages, followed by drained conditions until maturity. Yield (seed weight per plant) and its components (number of spikes/siliques/pods per plant, number of grains per spike/silique/pod and 1,000 grain weight) were assessed at maturity, along with morphological (number of tillers/branches) and shoot and root dry weight responses after waterlogging and during recovery. Wheat was the most tolerant species achieving 86% and 71% of controls in yield with early and late waterlogging, related to fewer grains per spike. Barley and rapeseed tolerated early waterlogging (yields 85% and 79% of controls) as compared to late waterlogging (32% and 26% of controls), mainly due to fewer spikes per plant (barley) or reductions in seeds per silique (rapeseed). Field pea was greatly affected by waterlogging at both timings, attaining a yield of only 6% of controls on average due to much fewer pods and fewer seeds per pod. So, wheat could be an option for areas facing either winter or spring transient waterlogging (i.e. early or late stages); barley and rapeseed are recommended only with if water excess occurs in early stages and field pea is intolerant to waterlogging.     

A method for observing and manipulating roots and root associated fungi on plants growing in nonsterile substrates

Standard 14‐cm plastic‐petri dishes were used as root substrate chambers allowing controlled inoculation, regular inspection under the dissecting microscope, and manipulation of root infections with pathogens and mycorrhizal fungi under nonsterile conditions. Roots of young pine seedlings were placed on the root substrate and, especially those growing on the substrate surface under the lid, were very easy to manipulate. Mycorrhizal species and inoculation methods were compared and the infection process followed continuously under various conditions. The air pockets formed between the lid and the substrate favoured mycorrhiza formation. Brief, periodic flooding prevented formation of mycorrhizas in two mycorrhizal species having hydrophobic hyphae but did not prevent it in less hydrophobic species. IAA treatment of roots led to heavy production of mycorrhizas. Fruiting body formation in Lacearia laccata was induced and followed in the dish cultures. Pure mycorrhizal stock cultures were able to be revitalized in the dish cultures and reisolated in pure culture. The infection strategy of a weak root pathogen, Cylindrocarpon destructans, was studied with the same technique, which was also used for investigating treatments predisposing seedlings to pathogen infection.     

基于GIS技术的石佛寺水库三维淹没模拟分析

根据石佛寺水库高效移民管理的要求,在GIS技术、遥感技术与虚拟地理环境的基础上,以石佛寺水库1∶2 000地形图为基础,从中提取数字高程模型（DEM）等数据信息,然后与土地分类遥感数据、行政区划、遥感图片等相互叠加分析,基于FLTK和OpenGL,利用C++构建了三维淹没模拟分析系统。该系统具备三维库区漫游、三维剖面分析、土地淹没分析查询、洪水淹没分析演示等功能,界面友好、方便,易于操作和维护。该系统在石佛寺水库得到应用,系统的实现为水库的移民土地补偿提供决策支持,从而实现水库高效移民管理。     

水肥交互作用对稻田氮素利用率和氮素平衡的影响

采用蒸渗仪方法和同位素示踪技术研究了稻田常规灌溉和节水灌溉条件下不同施肥水平和施肥方式的氮素利用率和氮素平衡,结果表明:稻谷氮素累积量占植株氮素累积量一半左右,间歇灌溉模式和传统淹灌模式氮素累积量的差异反应在茎和绿叶和实粒,而在黄叶和秕粒中差别不大;差值法测得氮肥利用率比同位素法偏高,但二者均表现为间歇灌溉氮肥利用率高于淹灌模式,且间歇灌溉模式下低氮水平氮肥利用率高于高氮处理;根据同位素示踪法计算氮素平衡,氮素在稻田系统中的分配为氨挥发和反硝化占37.4%~51.7%,土壤残留占20.4%~37.7%,作物吸收占9.2%~36.4%,淋失占0.3%~16.4%。     

水稻“少灌多蓄”节水灌溉新技术研究与推广

厦门同安地区群众习惯采用淹灌法灌溉水稻,耗水量大,有效利用雨量少。同安灌溉试验站从１９９４～１９９６连续３年研究“少灌多蓄”节水灌溉新技术,即充分利用自然降雨使田间水层保持为０～３０ｍｍ,一般水层至０时再隔一天灌水至上限（３０ｍｍ）,降水时使水层上限保持在７０ｍｍ。这样在产量不减少情况下减少了灌水量与灌溉次数达三分之一,省水省工,此法已在当地推广近４６７ｈｍ２,平均增产３１８ｋｇ／ｈｍ２,节水３０％。     

清代关中渭河流域洪涝灾害研究

通过对历史文献资料的搜集、整理、分析,对清代关中渭河流域洪涝灾害的时间、空间特征、灾害的等级序列和灾害成因进行了研究.结果表明:清代渭河流域关中段洪涝灾害共发生130次,平均每2.06年发生1次.清代中后期,洪涝灾害发生频率显著增加.该流域洪涝灾害的发生主要集中在渭河中下游的大荔、华县、华阴、渭南、潼关5县市.根据涝灾的等级序列可以得出,清代该流域2级涝灾发生次数最多,其次为1级偏涝灾,3级大涝和4级特大洪涝灾害发生次数较少.清代该流域洪涝灾害多发的主要原因是由气候波动和流域自身的地形、降水特征等因素决定的,人为因素加剧了灾害的发生频率和强度.