Spatial patterns in fish biomass and relative trophic level abundance in a wastewater enriched river

Abstract –  It is generally accepted that nutrient enrichment of aquatic systems will lead to increased production at the top trophic level (fish). We found that in the wastewater enriched Bow River, Alberta rainbow trout ( Oncorhynchus mykiss ) biomass increased over 25-fold, and brown trout ( Salmo trutta ) biomass increased 5-fold, however total sportfish biomass did not increase below the nutrient input point source. This was due to a dramatic downstream decrease in mountain whitefish ( Prosopium williamsoni ) biomass to 2% of the average biomass upstream of the municipal effluent source. The spatial pattern over a 177-km river section encompassing the city of Calgary, showed that the increase in trout abundance approximately tracked the expected nutrient concentrations in the river, but with a downstream lag of 20–30 km. Mountain whitefish biomass over the 177 km was inversely related to the dominant trout species, rainbow trout. Invertebrate abundance, macrophyte biomass and phytoplankton biomass all increased below the wastewater treatment plant outfalls. However, periphyton data were highly variable and showed no response. We propose several hypotheses as regards the factors that may have led to the decrease in mountain whitefish, based on the data from all trophic levels and the spatial pattern for fish biomass. Proposed factors influencing the mountain whitefish decline were; altered competitive ability because of macrophyte abundance, ammonia toxicity and barriers to movement (weirs).     

33个香菇栽培菌株的拮抗性测定及鉴定中的应用

本文选用３３个香菇菌株进行了拮抗性测定，同时比较了菌株间菌丝生长速度和ＣＭＣ酶活性变化。结果显示：不同的生态环境和栽培条件造成菌种的遗传差异。根据栽培地区不同这些菌种可分三大类。不同类菌株间桔抗性强，同一类中有些菌株与其余菌株间形成很明显的拮抗线，如０８７，２４１—４，７４０２，农①等，而有些菌株间拮抗线却很弱，如Ｗ０８，Ｗ０９，Ｗ１０等。说明这些菌株间遗传差异较小，遗传同源性较强。     

Effects of air humidity and K/Ca ratio in the nutrient supply on growth and postharvest characteristics of cut roses

Single node cuttings with one mature leaf were taken from the rose cv. Baroness and rooted in water culture. The rooted plants were grown in nutrient solutions and subjected to two levels of relative air humidity (RH): high (90%) and moderate (70%), in combination with high (12/1), medium (1/1) and low (1/5) K/Ca ratios in the nutrient solution. High RH plants accumulated less Ca in leaves and flowers than moderate RH plants. Roses grown at moderate RH had a longer postharvest life than high RH roses, irrespective of the K/Ca ratio of the nutrient solution. In general, a high K/Ca ratio had a negative impact on postharvest life. When grown at a high K/Ca ratio the ornamental value declined rapidly, mainly due to the appearance of necrotic petals as well as chlorotic and necrotic areas on the leaves. Bent neck occurred only with high RH plants but changes in the K/Ca ratio had no differential effect. Dry spots and brittle leaves were observed on high RH roses, and the occurrence increased with increased K/Ca ratio in the nutrient solution. Stomatal conductance increased in parallel with increases in RH and K/Ca ratio when measured on intact roses placed in dry air (40% RH).     

棉纤维的微原纤螺旋角和纤维素微晶相对取向指数在植株中的分布

用Ｘ射线衍射法对棉纤维细胞壁的微原纤维旋角和纤维素微晶相对取向指数在植株中的分布规律进行了研究。结果是：微原纤螺旋角随果枝位和果节位的增加略有增加，相对取向指数随果枝位和果节位的增加略有减小。     

群落多样性的研究进展(英文)

自从Ｆｉｓｈｅｒ等人（１９４３）提出群落多样性指数的概念以来,群落多样性一直是群落生态学研究的主题之一。然而,生态学家们经常为一些含糊不清的词语、概念及方法问题而感到困惑。本文结合作者近年来的科研工作,综述了群落多样性的研究进展,旨在概述该项研究的基本方法,即物种丰富度的比较、种一多度的分析及多样性指数的测定,阐明各种研究方法的基本原理及不足之处。文中指出,当前群落多样性研究存在的主要问题是：（１）多数研究者只注意到一个群落的某些部分或单个营养层次的物种,忽略分布在不同营养层次物种之间的相互作用;（２）把物种作为一个基本的生态元来测定群落多样性是不够的,因为物种在生活史中的不同阶段及其生活方式经常具有各自的生态位并在群落中起不同的作用;（３）把“种间相遇机率”作为群落多样性指数是不科学的,因为物种在群落中相遇并不意味着种间相互作用。进一步研究和解决上述问题在理论和实践上都是极其重要的。     

Introduced northern pike predation on salmonids in southcentral Alaska

Northern pike (Esox lucius) are opportunistic predators that can switch to alternative prey species after preferred prey have declined. This trophic adaptability allows invasive pike to have negative effects on aquatic food webs. In Southcentral Alaska, invasive pike are a substantial concern because they have spread to important spawning and rearing habitat for salmonids and are hypothesised to be responsible for recent salmonid declines. We described the relative importance of salmonids and other prey species to pike diets in the Deshka River and Alexander Creek in Southcentral Alaska. Salmonids were once abundant in both rivers, but they are now rare in Alexander Creek. In the Deshka River, we found that juvenile Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch) dominated pike diets and that small pike consumed more of these salmonids than large pike. In Alexander Creek, pike diets reflected the distribution of spawning salmonids, which decrease with distance upstream. Although salmonids dominated pike diets in the lowest reach of the stream, Arctic lamprey (Lampetra camtschatica) and slimy sculpin (Cottus cognatus) dominated pike diets in the middle and upper reaches. In both rivers, pike density did not influence diet and pike consumed smaller prey items than predicted by their gape‐width. Our data suggest that (1) juvenile salmonids are a dominant prey item for pike, (2) small pike are the primary consumers of juvenile salmonids and (3) pike consume other native fish species when juvenile salmonids are less abundant. Implications of this trophic adaptability are that invasive pike can continue to increase while driving multiple species to low abundance.     

5种有机酸对华山松木蠹象的拒食作用

为了寻找华山松木蠹象(Pissodes punctatus Langor et Zhang)环境友好的防治方法,研究了亚油酸、庚二酸、辛二酸、壬二酸、壬酸的酒精溶液、乙酸乙酯溶液和水溶液对华山松木蠹象成虫的拒食作用,采用了完全拒食虫率与相对拒食率来评价有机酸的拒食效果.结果表明,壬酸的3种溶液都具有很好的拒食作用,特别是水溶液其完全拒食虫率和选择性相对拒食率都高达100%.其它4种酸的不同溶液、不同试验方法的结果不尽相同.壬二酸的相对拒食率有的较高,有的表现为促进取食的作用,其乙酸乙酯溶液的完全拒食虫率高达100%.亚油酸、庚二酸、辛二酸主要表现为促进取食的作用.     

Release from root competition promotes tree seedling survival and growth following transplantation into human-induced grasslands in Sri Lanka

The density of colonising tree seedlings is often very low in degraded human-induced tropical grasslands. To investigate the mechanisms that constrain seedling establishment in grasslands on former tea plantations in Sri Lanka we planted seedlings of the native tree species Dimocarpus longan Lour., Macaranga indica Wight, Symplocos cochinchinensis (Lour.) S. Moore and Syzygium spathulatum Thw. and examined effects of vertebrate herbivory, and above- and below-ground competition exerted by the grass sward on seedling growth and survival over 28 months. Seedlings of the same species were also planted in remnant patches of lower montane rain forest to determine the effects of habitat on seedling growth and survival. Less than 40% of seedlings survived to 28 months post-transplantation. The highest survival was recorded for Symplocos cochinchinensis in both grassland and forest, while Macaranga indica seedlings had the highest relative growth rate of height (RGRh) in both habitats. Root competition reduced survival of Macaranga indica and the RGR_h of Macaranga indica, Symplocos cochinchinensis and Syzygium spathulatum in the grassland, while above-ground competition and exclusion of vertebrate herbivores had no effects on seedling establishment. These results suggest that Symplocos cochinchinensis would be suitable for re-establishing forest cover on degraded grasslands, although Macaranga indica would be more likely to catalyse succession because it possesses animal-dispersed fruit. Measures that overcome or restrict the effects of root competition from grasses would enhance tree seedling growth and survival more than manipulation of the light environment or protection from vertebrate herbivores.