Winter feeding ecology of cod (Gadus morhua) in a fjord of southern Norway

We investigated the winter feeding ecology of cod ( Gadus morhua ) in the Risørfjord and Flødevigen areas on the Skagerrak coast, southern Norway. Diets from the ice-covered Risørfjord were compared with diets from the more coastal Flødevigen area. In the Risørfjord area the diet featured numerically both decapods (56.0%) and fish (27.8%), but fish dominated by mass (75.1%). The most numerous dietary items from the Flødevigen area were decapods (48.1%) and isopods (30.6%), although fish still made up the bulk of the diet's mass (52.6%). Diets at Flødevigen shifted from winter to spring, as polychaetes became important numerically (67.8%) and also contributed substantially by weight (53.6%). Since cod feed opportunistically, differences between areas and seasons probably reflected differences in prey diversity and abundance. Prey size variability increased with increasing predator length, but maximum prey size relative to predator length was constant at about 9%. Prey fish increased in both length and numbers with the length of cod, particularly in the Risørfjord area, where fish were more important in the diet than at Flødevigen. However, the majority of fish consumed in both areas were small gobiids. Based on growth patterns observed in otoliths, with opaque zones (indicating faster growth) formed during winter, the quality and quantity of the winter diet may determine annual growth rates of cod on the Skagerrak coast. Fish and decapods constituted important, high energy food sources, and there was little indication that cod were food limited during winter in this area.     

Seed transmission of turnip yellow mosaic virus in winter turnip and winter oilseed rapes

This is the first record of seed transmission of turnip yellow mosaic virus (TYMV) in oilseed and turnip rapes. The seed transmission of TYMV in a naturally infected winter turnip rape (Brassica napus var. silvestris) cultivar Perko PVH was investigated. By ELISA 1.6%, 3.2% and 8.3% seed transmission of the virus was found in seed of plants from three localities. The proportion of infected seeds produced by artificially infected plants of winter oilseed rape (Brassica napus ssp. oleifera) and winter turnip rape cultivars was determined. The virus transmission rate, expressed as the proportion of virus-infected plants which germinated from the seed was for the oilseed rape cvs Jet Neuf 0.1%, Solida 0.4%, Silesia 0.8%, Darmor 1.2%, SL-507 0.2%, SL-509 0.0% and for the winter turnip rape cv. Perko 1.5%. ELISA cannot be used in direct tests on bulk seed lots to estimate proportion of infected seed, but must be used on germinated seedlings.     

Winter blooms of centric diatoms in the River Danube and in its side-arms near Budapest (Hungary)

Although the phytoplankton in large eutrophic rivers is often abundant, data on winter populations are scarce. Phytoplankton has been sampled since 1979 in the main arm of the River Danube at Göd (20 km north from Budapest), and also from two side-arms, upstream and downstream of Budapest. Analysis of winter samples has shown high population densities of phytoplankton blooms on several occasions. In general centric diatoms (20 taxa determined) were abundant and dominant during the blooms. The most abundant taxon in November was Stephanodiscus hantzschii f. tenuis, and in February S. minutulus. The most important factors in forming winter blooms of Centrales are rich nutrient supply, slow current speed and high transparency.Massive phytoplankton blooms occurred several times between November and March in the small side-arm at Göd. In the large side-arm downstream of Budapest (Soroksári-Dung) large blooms of centric diatoms were found in winter (often under ice, which was covered by snow in many cases). Here S. hantzschii f. tenuis and S. minutulus were the most abundant species.     

Habitat selection and space use overlap between feral horses,pronghorn, and greater sage-grouse in cold arid steppe

Populations of feral horses (Equus ferus caballus) in the western United States have increased during the past decade, consequently affecting co-occurring wildlife habitat. Feral horses may influence 2 native wildlife species, greater sage-grouse (Centrocercus urophasianus; sage-grouse) and pronghorn (Antilocapra americana) through mechanisms of habitat alteration and competition. Wyoming, USA, contains the largest populations of pronghorn and sage-grouse of any state and also has the highest degree of range overlap between feral horses and these species. Consequently, the effects that horses may have on pronghorn and sage-grouse populations in Wyoming have implications at local, state, and population-wide levels. Managers need information concerning habitat selection and space use overlap among these species to develop appropriate management strategies; yet this information is absent for most feral horse management areas. To address this knowledge need, we attached global positioning system (GPS) transmitters to horses, pronghorn, and sage-grouse within the greater Bureau of Land Management–Adobe Town Herd Management Area in southern Wyoming and northern Colorado, USA, between 2017 and 2021 to evaluate habitat selection and space use of all species during 3 biologically relevant seasons: spring (Apr–Jun; sage-grouse breeding, nesting, and early-brood rearing; pronghorn late gestation and early parturition), summer (Jul–Oct; sage-grouse summer and late-brood rearing; pronghorn late parturition and breeding), and winter (Nov–Mar; non-breeding season). Feral horses selected flatter slopes and shorter mean shrub height across all seasons and were closer to water in spring and summer. Pronghorn habitat selection was similar to horses, but they also avoided oil and gas well pads year-round. During spring, sage-grouse selected greater herbaceous cover, flatter slopes, and areas farther from well pads. In summer, sage-grouse selected greater mean shrub height, flatter slopes, and were closer to water. In winter, sage-grouse selected flatter slopes and areas with greater vegetation production during the preceding summer. Our results indicate strong year-round overlap in space use between horses and pronghorn, whereas overlap between horses and sage-grouse is greatest during the summer in this region. Consequently, managers should recognize the potential for horses to influence habitat quality of pronghorn and sage-grouse in the region.     

温度条件对麦田土壤溶液养分浓度的影响

本文用实测资料分析了温度对麦田土壤溶液养分浓度的影响。研究表明,在农田土壤水分不亏缺的条件下,温度与麦田土壤溶液浓度呈正相关关系。随着太阳辐射增强,温度升高,土壤溶液中NO_3-N浓度增大,到14:00—15:00时,出现极大值。土壤溶液中钾浓度的高峰期基本是在中午温度高的时刻,低峰期在夜晚和午前10:00—11:00左右。10:00—11:00时的低值,可能与根系的同化吸收有关。土壤溶液养分浓度日较差大,光合面积增长快,营养生长旺盛。     

Supercooling and cold-hardiness in eggs of western and northern corn rootworms

Oviposition by northern corn rootworms, Diabrotica barberi Smith and Lawrence, and western corn rootworms, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), key pests of corn in the Great Plains of the USA, occurs in the soil during late summer. Overwintering eggs are exposed to variable soil moisture and temperatures below ?5 °C. The winter mortality of eggs in the soil is a primary factor that determines the potential for larval injury to corn the following spring. Our studies aimed to determine the comparative supercooling capacities of northern and western corn rootworm eggs and to assess egg mortality following brief exposure to extreme low temperature, ranging from ?12.0 to ?21.5 °C, under three moisture regimes. Eggs of northern corn rootworm were supercooled to a temperature as low as ?27 °C, and survived supercooling to a greater extent than did western corn rootworm eggs. Moisture treatment prior to supercooling had little effect on northern corn rootworm eggs. Western corn rootworm eggs were more resistant than northern corn rootworm eggs to the effects of desiccation followed by supercooling. The survival of northern corn rootworm eggs was better than western corn rootworms under dry conditions, followed by exposure to temperatures of ?12.0 and ?17.5 °C, but was very low at ?21.5 °C, regardless of the moisture regime. The results suggest that moisture and temperature may interact in the soil environment to determine the overwintering survival of corn rootworms. It is evident from these studies that both rootworm species experience mortality at temperatures well above the supercooling points of the eggs, but that differences exist in the effects of substrate moisture treatments on the cold‐hardiness of eggs from the two species.     

土壤水分和氮磷营养对冬小麦根系生长及水分利用的调节

模拟试验研究结果表明：在土壤相对含水量为４０％￣７０％范围内,水分亏缺严重,根水势和蒸腾蒸发量显著降低,根系生长严重受阻,根长变短,根干重降低,随着土壤水分趋于良好,根水势和蒸腾蒸发量显著增加,根干重在土壤相对含水量为５５％￣６２％之间时最大,而土壤相对含水量在５５％上下时根长达最长;土壤水分趋于轻度干旱有利根系下扎,土壤水分趋于良好利于根量增长。氮磷营养对小麦根系生长具有明显的调节作用。磷营养可     

冬小麦根表面氧化还原活力的研究

证实了两个不同品种的冬小麦根系表面存在着氧化ＮＡＤＨ和还原Ｋ３Ｆｅ（ＣＮ）６的氧化的活力。还原铁氰化物活力在ＰＨ５．５到８．５范围内随着ＰＨ值升高而增大,温度在１５℃到４５℃范围内随温度升高还原活力增强,４５℃达最高值,５５℃时活力急剧下降。     

小麦返白系与不同基因型小麦品种杂交后代IPO表达的研究

以小麦返白系和对照矮变１号以及返白系与各不同生态类型的冬性、半冬性、春性小麦的杂交、回交Ｆ１、Ｆ２代为材料,研究这些不同基因型品种在返白期间过氧化物酶同工酶（ＩＰＯ）基因表达模式的动态变化特点。结果表明,在返白期间以返白系为母本的各杂交、回交品种的白化苗中,ＩＰＯ的个别酶分子表现了可逆的基因阻遏和去阻遏的表达现象。这种表达特点在正、反杂交后Ｆ１代中表现一致,从遗传模式上分别属于质－核互作型的分子遗     

Plankton ecology in an ice-covered bay of Lake Michigan: utilization of a winter phytoplankton bloom by reproducing copepods

Plankton ecology was examined during the 1986 winter in Grand Traverse Bay, a 190 m deep, fjordlike bay on Lake Michigan. Before ice cover, algal concentration was low and uniformly distributed with depth, as it is in open Lake Michigan. During ice cover (February and March), a bloom of a typical winter-spring phytoplankton community developed in the upper 40 m, resulting in a 4 to 7-fold increase in feeding rate of adult Diaptomus spp. High algal concentration and zooplankton feeding persisted after ice melt (April). During and after ice cover, lipid concentrations of Diaptomus dropped rapidly from 34% of dry weight to 17 % because of egg production. High incident photosynthetically active radiation (PAR), high (45–50%) PAR transmittance of the ice due to little snow on the ice, and water column stability were probably responsible for the bloom. High ice transparency may be a common feature of large lakes and bays, where strong winds blow snow cover off the ice, or at low latitudes where snowmelt due to occasional rains and warm temperature is common. Winter reproducing calanoid copepods use these blooms to increase their reproductive output.