Energy investment in leaves of red maple and co-occurring oaks within a forested watershed

Despite its recent expansion in eastern US forests, red maple (Acer rubrum L.) generally exhibits a low leaf photosynthetic rate, leaf mass per unit area (LMA) and leaf nitrogen concentration ([N]) relative to co-occurring oaks (Quercus spp.). To evaluate these differences from the perspective of leaf energy investment, we compared leaf construction cost (CC) and leaf maintenance cost (MC) with leaf photosynthetic rate at saturating photon flux density and ambient CO2 partial pressure (Amax) in red maple and co-occurring red oak (Quercus rubra L.) and chestnut oak (Quercus prinus L.). We also examined relationships among leaf physiological, biochemical and structural characteristics of upper-canopy leaves of these three species at lower (wetter) and upper (drier) elevation sites of a watershed in the Black Rock Forest, Cornwall, NY, USA. Although A(max), leaf [N], leaf carbon concentration ([C]) and LMA were significantly less in red maple than in either oak species at both sites, CC per unit leaf area of red maple was 28.2 and 35.4% less than that of red oak at the lower and upper site, respectively, and 38.8 and 32% less than that of chestnut oak at the lower and upper site, respectively. Leaf MC per unit leaf area, which was positively associated with leaf CC (r2 = 0.95), was also significantly lower in red maple than in either oak species at both sites. When expressed per unit leaf area, A(max) was positively correlated with both CC (r2 = 0.65) and MC (r2 = 0.59). The cost/benefit ratio of CC/Amax of red maple was significantly less than that of chestnut oak at the lower site, however, CC/A(max) did not exhibit any significant interspecific differences at the upper site. Expressed per unit leaf area, CC was correlated positively with LMA (r2 = 0.90), leaf [N] (r2 = 0.97), and leaf [C] (r2 = 0.89), and negatively correlated with leaf molar carbon to nitrogen ratio (r2 = 0.92). Combined with red maple's general success in many oak-dominated forests, our findings suggest that reduced leaf-level photosynthetic capacity and related leaf characteristics in red maple are partially balanced by lower energy and resource requirements for leaf biomass construction and maintenance, which could enhance the competitive success of this species.     

Effect of parathion on honey bee larvae rearedin vitro

First instar honey bee larvae (0.2–0.4 mg) from outdoor (summer season) and flight-room colonies (winter season) were reared in an incubator on a semisynthetic diet. Parathion was either dissolved in the diet (0.01–10.0 μg/ml) or topically applied (0–0.5 μg) to the 3rd instar larvae. Increasing doses of parathion caused a delay in larval development and prepupal mortality. The half lethal concentration (LC₅₀) of the insecticide, if applied in the diet, was 0.02 and 0.14 μg/larva, respectively, for summer and for winter larvae. The half lethal dose (LD₅₀) after topical application was 0.18 μg parathion/larva. The utility of rearing honey bee larvaein vitro for evaluation of pesticide toxicity is also discussed.     

Influence of the degree of substitution and pretreatments on the surface structure of cellulose nitrate fibres

Summary Cellulose nitrate fibres of three different degrees of substitution (DS) were prepared by heterogeneous reaction. The fibre surfaces were observed in the scanning electron microscope. Apart from the DS the influence of pretreatments such as prenitration and boiling of the fibres prior to nitration was studied. The results reveal an interaction between the cell wall layers and the esterification and swelling capacity of the nitration medium. In all cases the DS was determined by the composition of the nitration medium. A pretreatment influenced the fibre surfaces after nitration. The peculiar role of the primary wall during esterification is emphasized.Supported by the Federal Ministry for Research and Technology (BMFT)     

Interaction of root-knot nematode and mycorrhizal fungi on common beanPhaseolus vulgaris L.

The interactions of root-knot nematode and VAM fungus on common bean plants (Phaseolus vulgaris L.), and the sequence of nematode infection were studied in the greenhouse. The inoculation with VAM fungus caused a significant increase in plant height and fresh weight compared with non treated plants.Meloidogyne infection unsignificantly decreased plant height and dry weight. When fungus was inoculated at 15 and 30 days prior toM. incognita infection, a significant increase in fresh weight was observed. There were no significant differences in total nitrogen (mg/plant) between plants inoculated withM. incognita alone or those inoculated with bothM. incognita and VAM fungus at the same time or 15 days after the fungus inoculation. Plants preinoculated with VAM fungus 30 days prior to nematode infection had a significant increase in total nitrogen. The inoculation with VAM fungus caused a significant increase in phosphorus content. However, it was significantly decreased in plants inoculated with nematode alone and in plants inoculated with VAM fungus andM. incognita at the same time. Gall index and final nematode population were significantly increased when nematodes were treated at the same time with fungus, although there were significant decrease in nematode final population and gall index when the plants were treated with nematodes at 15 and 30 days after mycorrhizal infection. A decrease in percentage of fungal colonization was observed when nematodes were inoculated with fungus at the same time.     

人工淡水湿地的水文过程模拟:综合系统法(摘要)

人工淡水湿地的水文过程模拟:综合系统法(摘要)(英文)@张立$Olentangy River Wetland Research Park,The Ohio State University,352 W.Dodridge Street,Columbus,OH 43210,USA @威廉.杰.米奇$Olentangy River Wetland Research Park,The Ohio State University,352 W.Dodri     

Inferred longevity of Amazonian rainforest trees based on a long-term demographic study

We used data from a long-term (14–18 years) demographic study to infer the maximum longevity for populations of 93 relatively abundant tree species in central Amazonia. We also assessed the influence of several life-history features (wood density, growth form, mortality rate, recruitment rate, stem diameter, growth increment, population density) on tree longevity. Data on 3159 individual trees were collected in 24 permanent, 1 ha plots in undisturbed forest arrayed across a large (ca. 1000 km²) study area. For each species, three estimates of longevity were generated (by dividing the stem diameter of the largest tree by the median, upper quartile, and upper decile of observed diameter-growth rates), and the mean of these three values was used as a longevity estimate. Longevity values ranged from 48 years in the pioneer Pourouma bicolor (Cecropiaceae) to 981 years for the canopy tree Pouteria manaosensis (Sapotaceae), with an overall mean of 336±196 years. These growth-based estimates of maximum tree age were concordant with those derived from analyses of mean mortality rates. Tree longevity was positively correlated with wood density, maximum stem diameter, and population density, and negatively correlated with annual mortality, recruitment, and growth rates. On average, pioneer species had much lower longevity than did non-pioneers, whereas among old-growth trees, emergent species had greater longevity than did canopy species. Our results are consistent with radiocarbon-based studies that suggest that Amazonian trees can occasionally exceed 1000 years of age.     

Field tests on the efficacy of baits based onBacillus thuringiensis and chemical insecticides against the greasy cutwormAgrotis ypsilon Rdf. in Egypt

Field tests were conducted to determine the effectiveness of wheat-brain baits based onBacillus thuringiensis var.kurstaki HD-1 (dipel 2x) compared to the organophosphorous insecticide Hostathion against the greasy cutwormAgrotis ypsilon infestations on horse bean (Vicia fabae) cultivations. Significant larval reductions were observed in all treated plots after one application with a significant increase in the yield (1.45–1.60 folds) compared to the control plots. The yield was not obviously affected by varying the dose of dipel in the bait between 150–250 g/feddan. The addition of the adjuvant potassium carbonate to the dipel bait caused a significant larval reduction, 10 days after application and showed to be as efficient as baits based on Hostathion.     

Comparison of two sampling methods for leafhoppers (Homoptera, Cicadellidae) associated with sesame in the east Mediterranean region of Turkey

Yellow sticky-traps and a modified Johnson-Taylor suction-trap were used to index the relative population dynamic of leafhoppers associated with sesame in the east Mediterranean region of Turkey. Comparison of the obtained results signified important differences between both traps. 32 leafhoppers species were caught in the suction-trap while only 18 species were determined on yellow sticky-traps. For most of the leafhopper species, relatively more males were determined on the yellow-traps than in the suction-trap, indicating a higher activity of male leafhoppers during daytime hours. A close relationship between the seasonal flight pattern as indexed by sticky-traps and by suction-trap was only observed forAsymmetrasca decedens (Paoli) andEmpoasca decipiens Paoli. For most other leafhopper species no or only a very poor correlation for the relative population dynamic was determined between both traps. Important leafhopper vector species, e.g.,Circulifer haematoceps (Mulsant et Rey) andOrosius orientalis (Matsumura) were better represented in yellow sticky-trap catches than they were in the suction trap.

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Zusammenfassung Die relative Populationsdynamik der mit Sesam assozüerten Zwergzikaden wurde mit beleimten Gelbtafeln und einer stationären Johnson-Taylor-Saugfalle an der südöstlichen Mittelmeerküste der Türkei untersucht. Beim Vergleich beider Methoden zeigten sich deutliche Unterschiede zwischen den Fallentypen. In der Saugfalle konnten 32 Zwergzikadenarten erfaßt werden, während dies auf den Gelbtafeln nur 18 Arten waren. Die meisten Zwergzikadenarten zeigten auf den Gelbtafeln ein stark in Richtung der Männchen verschobenes Geschlechterverhältnis, was eine erhöhte Flugaktivität der Männchen während des Tageslichts vermuten läßt. Auch der Verlauf der saisonalen Flugaktivität war für die meisten Zwergzikadenarten zwischen den beiden Fallentypen sehr unterschiedlich, und es konnten zwischen Saug- und Gelbfalle keine deutlichen Korrelationen hergestellt werden. Nur für die beiden zusammen erfaßten ArtenAsymmetrasca decedens (Paoli) undEmpoasca decipiens Paoli wurde ein enger Zusammenhang zwischen der mit der Saugfalle und den gelben Leimtafeln erfaßten relativen Populationsdynamik festgestellt. Wichtige Vektorenarten unter den Zwergzikaden, z. B.Circulifer haematoceps (Mulsant et Rey) undOrosius orientalis (Matsumura) waren auf den Gelbtafeln besser repräsentiert als in der Saugfalle.