Does sand content in spawning substrate result in early larval emergence? Evidence from a lithophilic cyprinid fish     

Tea Ba&#x;i&#x;  J. Robert Britton  Stephen P. Rice  Andrew G. Pledger 《Ecology of Freshwater Fish》2019,28(1):110-122

The spawning success of lithophilic salmonids is strongly influenced by the fine sediment content (“fines”) of spawning substrates, yet knowledge on the impacts of fines on the spawning of non‐salmonid lithophiles remains limited, despite their ecological and socio‐economic importance in European rivers. Consequently, the aim here was to use an ex‐situ experiment to investigate the impact of sand content on egg survival and timing of larval emergence of the surface‐spawning cyprinid European barbel Barbus barbus. Thirty incubator boxes within a recirculating system were filled with one of five experimental sediment mixtures (0%–40% sand by mass) that each contained 300 fertilised eggs at a depth of 50 mm. Emerged, free‐swimming larvae were captured and counted daily to assess grain‐size effects on larval survival and emergence. Specifically, total proportion of emerged larvae, cumulative daily proportion of emerged larvae and time required to reach 50% emergence were measured during the study. Whilst the proportion of sand in the sediments did not have a significant impact on egg‐to‐emergence survival (mean survival per treatment 75%–79%), it significantly affected the timing of larval emergence to the water column; early emergence was detected in treatments with elevated sand content (on average, 50% emergence after 12–13 days versus 19 days in the control). Similar to findings from salmonid studies, these results suggest high sand content in spawning gravels can influence timing of larval emergence and potentially cyprinid lithophilic fish survival.  相似文献   

Impact of High Night‐Time and High Daytime Temperature Stress on Winter Wheat          下载免费PDF全文

S. Narayanan  P. V. V. Prasad  A. K. Fritz  D. L. Boyle  B. S. Gill 《Journal of Agronomy and Crop Science》2015,201(3):206-218

High temperature is a major environmental factor that limits wheat (Triticum aestivum L.) productivity. Climate models predict greater increases in night‐time temperature than in daytime temperature. The objective of this research was to compare the effects of high daytime and high night‐time temperatures during anthesis on physiological (chlorophyll fluorescence, chlorophyll concentration, leaf level photosynthesis, and membrane damage), biochemical (reactive oxygen species (ROS) concentration and antioxidant capacity in leaves), growth and yield traits of wheat genotypes. Winter wheat genotypes (Ventnor and Karl 92) were grown at optimum temperatures (25/15 °C, maximum/minimum) until the onset of anthesis. Thereafter, plants were exposed to high night‐time (HN, 25/24 °C), high daytime (HD, 35/15 °C), high daytime and night‐time (HDN, 35/24 °C) or optimum temperatures for 7 days. Compared with optimum temperature, HN, HD and HDN increased ROS concentration and membrane damage and decreased antioxidant capacity, photochemical efficiency, leaf level photosynthesis, seed set, grain number and grain yield per spike. Impact of HN and HD was similar on all traits. Greater impact on seed set, grain number and grain yield per spike was observed at HDN compared with HN and HD. These results suggest that HN and HD during anthesis cause damage of a similar magnitude to winter wheat.  相似文献   

Transcripts levels of Phytoene synthase 1 (Psy-1) are associated to semolina yellowness variation in durum wheat (Triticum turgidum L. ssp. durum)     

《Journal of Cereal Science》2016

  相似文献   

Ecological implications of motor oil pollution: Earthworm survival and soil health     

《Soil biology & biochemistry》2015

The nontarget effects of fresh and used motor oil were studied in a soil test system involving such criteria as earthworm survival, response of soil dehydrogenase and urease, and nitrification. When earthworms were exposed to motor oil-contaminated soil for 4 weeks, the observed median lethal concentrations (LC₅₀) were 40.33 and 3.88 g kg⁻¹ soil for fresh and used oil, respectively. Only fresh motor oil application increased earthworms' body weight even at the higher dose of 19 g kg⁻¹ soil. Gas chromatography/mass spectrometry revealed that used motor oil contained more of aromatic hydrocarbons and heavy metals than fresh oil. This disparity in the chemical composition might be the factor responsible for the significant toxicity of used motor oil towards earthworms. Activities of soil dehydrogenase and urease were significantly enhanced in presence of both the motor oils, while there was a significant inhibition in nitrification by the used motor oil even at a low concentration of 0.2 g kg⁻¹ soil. This study clearly demonstrated that earthworm survival and nitrification could serve as suitable indices to assess motor oil pollution in soil.  相似文献   

秸秆深还机具特点和作业效率分析   总被引：1，自引：0，他引：1  

杨鹏  王瑞丽  张启辉  窦森 《吉林农业大学学报》2016,(5):645-650

秸秆深埋还田(秸秆深还)作为一种新兴的秸秆还田模式,其机具有别于地表覆盖还田和铧式犁翻压还田。为了科学管理、合理运用秸秆深还机械,提高机组的作业效率,在调查测试秸秆深还作业的基础上,对机具的特点进行了分析,同时对测试机组分别进行了时间利用率和作业效率分析。结果表明:对于各个机具的作业时间利用率和总作业效率影响因素有所不同。作业速度、幅宽、故障维修和地头转向是影响机械作业效率的主要因素。根据调查和分析的结果,针对秸秆深还作业中存在的问题提出了机组的合理运行模式。  相似文献   

Estimation of Crown Temperature of Winter Wheat and the Effect on Simulation of Frost Tolerance          下载免费PDF全文

T. Persson  A. K. Bergjord Olsen  L. Nkurunziza  E. Sindhöj  H. Eckersten 《Journal of Agronomy and Crop Science》2017,203(2):161-176

Accurate estimation of winter wheat frost kill in cold‐temperate agricultural regions is limited by lack of data on soil temperature at wheat crown depth, which determines winter survival. We compared the ability of four models of differing complexity to predict observed soil temperature at 2 cm depth during two winter seasons (2013‐14 and 2014‐15) at Ultuna, Sweden, and at 1 cm depth at Ilseng and Ås, Norway. Predicted and observed soil temperature at 2 cm depth was then used in FROSTOL model simulations of the frost tolerance of winter wheat at Ultuna. Compared with the observed soil temperature at 2 cm depth, soil temperature was better predicted by detailed models than simpler models for both seasons at Ultuna. The LT50 (temperature at which 50 % of plants die) predictions from FROSTOL model simulations using input from the most detailed soil temperature model agreed better with LT50 FROSTOL outputs from observed soil temperature than what LT50 FROSTOL predictions using temperature from simpler models did. These results highlight the need for simpler temperature prediction tools to be further improved when used to evaluate winter wheat frost kill.  相似文献   

基于SPEI_PM指数的渭河流域气象干旱时空演变特征     

杨睿  耿广坡  周洪奎  王涛 《中国农业气象》2021,42(11):962

利用渭河流域25个气象站点1980−2018年月值气象数据集，基于Penman-Monteith蒸散模型计算多个时间尺度的标准化降水蒸散发指数（SPEI），分析渭河流域气象干旱的演变、趋势、影响范围、发生频率和持续时间等时空变化特征，以期为渭河流域防灾减灾管理提供科学依据。结果表明：（1）近39a来渭河流域有明显的干湿周期变化，但整体上呈变干的趋势，干旱时段主要集中在1995−2009年，其中以2000−2009年的干旱站次比最大，平均达到36%，且干旱持续时间最长，约3.6个月，1980−1989年干旱持续时间最短，约1.6个月；（2）渭河流域秋季总体呈湿润变化趋势，而春季和夏季干旱在不断加剧，是区域年际干旱的主要驱动力；（3）渭河流域干旱以危害性较小的轻中旱为主，但2000年前后出现严重及极端干旱的站次相对较多，其中1997年研究区内发生的干旱程度较高，影响范围较广；（4）不同时间尺度各等级干旱发生频率的变化规律表现一致，均呈现出干旱等级越高发生频率越低的态势，且极端干旱在年际尺度内发生次数较为频繁，从空间上看渭河流域东北部是干旱多发区。总之，近39a来渭河流域总体干旱较为严重的时段为2000−2009年，且研究区内干旱呈北重南轻特征，因此北部地区仍需加强防灾管理。  相似文献   

东沙窝沙漠区不同造林技术效果分析     

陈玉桂  赵之旭  李梅英  张伟 《防护林科技》2013,(5):23-24,27

通过对东沙窝沙漠区采取提前整地、压沙等方式,选用良种壮苗、蘸泥浆、覆沙、平茬复壮、纯林改混交林等综合技术进行造林试验,结果表明,试验区造林成活率、保存率普遍提高,小气候环境明显改善:植被区风速比旷野区降低了25.8%～32.6%;灌木固沙林在夏季降低气温10℃左右,降低地温6～10℃,冬季地面最高温度提高2～4℃。  相似文献   

不同埋藏方式及杀菌剂处理对黄土高原3种植物种子存活的影响     

侯金伟  陈焘  南志标 《草业学报》2021,30(3):129-136

为了探讨黄土高原典型草原植物病原真菌如何影响土壤种子存活,采用“种子袋埋藏与取回”的方法,对该地区3种常见植物胡枝子、长芒草和狗尾草种子进行杀菌剂处理、并且以不同方式（单种或者不同种混合）装入尼龙网袋后埋入土壤中,在田间分别埋藏1和3个月后取回种子袋,统计每袋种子的存活情况,并且进行萌发试验,检测种子生活力状况。结果表明：1）长芒草种子的田间发芽率最高,平均约为51.9%,显著高于胡枝子（14.6%）和狗尾草（26.1%）（P<0.05）;随着埋藏时间的增加,3种植物种子发芽率显著增加;然而杀菌剂处理以及不同埋藏方式对种子发芽率没有显著影响。2）胡枝子种子的田间死亡率最低,平均约为1%,长芒草和狗尾草种子的田间死亡率分别为5.1%和4.4%;埋藏1个月后,杀菌剂未处理和单种埋藏条件下长芒草和狗尾草种子的田间死亡率分别为12.5%和11.0%,显著高于其他处理组合下两种植物种子的死亡率（P<0.05）;胡枝子种子在埋藏1和3个月时,其种子死亡率在不同处理组合之间均无显著差异。3）长芒草种子的室内萌发率最高,平均约为64.3%,显著高于胡枝子（5.9%）和狗尾草（29.2%）（P<0.05）。随着埋藏时间的增加,胡枝子和狗尾草种子的室内萌发率显著下降,而长芒草种子的室内萌发率却显著增加。结果表明,病原真菌对土壤种子存活的影响因植物种而异;较单种埋藏相比,混合埋藏降低了种子的死亡率,可能是由于混合埋藏稀释了病原真菌的效应所致。  相似文献   

补播羊草和黄花苜蓿对退化草甸植物群落特征的影响     

孙伟  刘玉玲  王德平  赵敏  杨合龙  宋倩  肖红  王开丽  曹婧  戎郁萍 《草地学报》2021,29(8):1809-1817

呼伦贝尔草原区是我国北方重要的生态屏障,近年来不合理的利用方式导致该地区退化草地面积不断扩大,为了探究牧草补播时间及补播比例对呼伦贝尔退化草甸草原植物群落特征的影响,为该地区退化草地修复提供依据。本研究以羊草（Leymus chinensis（Trin.） Tzvel.）和黄花苜蓿（Medicago falcata L.）为试验材料,采用双因素随机区组试验设计,通过测定幼苗数、高度、生物量等群落指标,并综合评价补播效果,结果表明：夏播羊草和黄花苜蓿幼苗数量显著高于春播和秋播（P<0.05）,夏播和秋播植物群落总生物量呈增加趋势,春播则呈减少趋势;补播措施提高了退化草地植物群落Shannon-Weiner指数、Simpson指数和Pielou指数,豆科和禾本科植物重要值呈增加趋势,其他科植物呈下降趋势。呼伦贝尔地区夏季补播羊草和黄花苜蓿以1∶3补播效果较好,而春播由于恢复时间短,需进一步观察。  相似文献