桉树不同成熟度叶片营养元素内循环特征     

吉玉  田湘  张雨蒙  吴庆标 《森林与环境学报》2021,(3):242-247

揭示桉树人工林不同成熟度的叶片器官所需营养元素变化以及土壤肥力对其影响,对于桉树营林和科学施肥具有重要的生产指导意义。选取广西隆安县小林镇和田东县思林镇的桉树2代萌芽林作为研究对象,测定两个人工林嫩叶、成熟叶、黄叶的C、N、P、K、B、Ca、Mg以及土壤C、N、P、K、Ca、Mg元素含量,并进行相关分析。结果表明,植物叶片的N、P、K、Mg营养元素转移规律是黄叶向成熟叶和嫩叶转移,但C、Ca、B营养元素则是随着叶片的生长发育逐渐积累,黄叶中含量最高,说明施肥时应关注Ca、B元素的持续和有效供给。两片人工林都表现出类似的规律,说明土壤肥力的差异不影响桉树人工林叶片营养元素的内循环规律。桉树嫩叶营养元素含量及其生态化学计量比学特征具有与成熟叶和黄叶不同的表征,在营养物质研究中应予以足够重视。  相似文献   

Comparing the behavioural thermoregulation response to heat stress by Atlantic salmon parr (Salmo salar) in two rivers     

Emily Corey  Tommi Linnansaari  Stephen J. Dugdale  Normand Bergeron  Jean-François Gendron  Michel Lapointe  Richard A. Cunjak 《Ecology of Freshwater Fish》2020,29(1):50-62

Climate change is expected to increase the frequency and magnitude of extreme thermal events in rivers. The Little Southwest Miramichi River (LSWM) and the Ouelle River (OR) are two Atlantic salmon (Salmo salar) rivers located in eastern Canada, where in recent years, water temperatures have exceeded known thermal limits (~23°C). Once temperature surpasses this threshold, juvenile salmon exploit thermal heterogeneity to behaviourally thermoregulate, forming aggregations in coolwater refuges. This study aimed to determine whether the behavioural thermoregulation response is universal across rivers, arising from common thermal cues. We detailed the temperature and discharge patterns of two geographically distinct rivers from 2010 to 2012 and compared these with aggregation onset temperature. PIT telemetry and snorkelling were used to confirm the presence of aggregations. Mean daily maximum temperature in 2010 was significantly greater in the OR versus the LSWM (p = 0.005), but not in other years (p = 0.090–0.353). Aggregations occurred on 14 and 9 occasions in the OR and LSWM respectively. Temperature at onset of aggregation was significantly greater in the OR (T_onset = 28.3°C) than in the LSWM (T_onset = 27.3°C; p = 0.049). Logistic regression models varied by river and were able to predict the probability of aggregation based on the preceding number of hours >23°C (R² = 0.61 & 0.65; P₅₀ = 27.4°C & 28.9°C; in the OR and LSWM respectively). These results imply the preceding local thermal regime may influence behaviour and indicate a degree of phenotypic plasticity, illustrating a need for localised management strategies.  相似文献   

New ways and new hopes for IGR development     

Marek Jindra 《Journal of Pesticide Science》2021,46(1):3

Insect Growth Regulators (IGRs) represent advanced, bio-rational insecticides. This Special Issue reflects progress in IGR development that has been enabled by insight into the molecular principles of biosynthetic or hormone signaling pathways. The unifying principle is aiming at processes and molecular targets that are unique to arthropods and ideally to narrower insect taxa representing pests or disease vectors. While some strategies of obtaining the desired compounds for chemical intervention rely on rational, structure-based design or computational power, others exploit technologies allowing automated, high-throughput screening of large chemical libraries. All avenues leading to selective and environmentally safe pest control are valid as we face the imminent threat of the declining world insect population.  相似文献   

Cohort‐specific variation in juvenile coho salmon habitat use          下载免费PDF全文

Catherine Bradley  Suresh Andrew Sethi  Joshua Ashline  Jonathon Gerken 《Ecology of Freshwater Fish》2017,26(4):695-706

In this study, we examined summer and fall freshwater rearing habitat use by juvenile coho salmon (Oncorhynchus kisutch) in the quickly urbanising Big Lake drainage in south‐central Alaska. Habitat use was assessed by regressing fish count data against habitat survey information across thirty study sites using generalised linear mixed models. Habitat associations were examined by age‐0 and age‐1+ cohorts separately, providing an opportunity to compare habitat use across different juvenile coho salmon life stages during freshwater rearing. Regression results indicated that the age‐0 cohorts were strongly associated with shallow, wide stream reaches with in‐stream vegetation, whereas age‐1+ cohorts were associated with deeper stream reaches. Furthermore, associations between fork length and habitat characteristics suggest cohort‐specific habitat use patterns are distinct from those attributable to fish size. Habitat use information generated from this study is being used to guide optimal fish passage restoration planning in the Big Lake drainage. Evidence for habitat use partitioning by age cohort during freshwater juvenile rearing indicates that pooling age cohorts into a single “juvenile” stage for the purposes of watershed management may mask important habitat use dynamics.  相似文献   

Seasonal growth and diet of juvenile chinook salmon (Oncorhynchus tshawytscha) in demonstration channels and the main channel of the Waitaki River, New Zealand, 1982–1983     

G. Power 《Ecology of Freshwater Fish》1992,1(1):12-25

Abstract– Juvenile chinook salmon in the Waitaki River, New Zealand and demonstration channels, living at about 16°C, increased in length by 0.32 mm day⁻¹ between 4 November and 4 March. They gained weight quickly, accumulated large visceral fat deposits and had high conditions factors. At 1600 h, stomachs averaged half full. The number of prey tended to decline as the fish grew and consumed larger items. Initially the diet was based mainly on chironomid larvae, but by December it included a diversity of prey in more equal proportions. These included Deleatidium in the Waitaki; amphipods in the demonstration channels; various trichopterans, hemipterans, elmid beetles, zooplankton. terrestrial dipterans and a variety of other prey. There were significant differences between sites in numbers of prey consumed and these probably reflected differences in the benthos. Diets in the Waitaki differ from those in the Rakaia River and the food of juvenile salmon appears closely linked to the availability of a diverse range of possible prey.  相似文献   

Effects of predator-induced visual and olfactory cues on 0+ perch (Perca fluviatilis L.) foraging behaviour     

V. N. Mikheev  J. Wanzenböck  A. F. Pasternak 《Ecology of Freshwater Fish》2006,15(2):111-117

Abstract –  Foraging juvenile fish with relatively high food demands are usually vulnerable to various aquatic and avian predators. To compromise between foraging and antipredator activity, they need exact and reliable information about current predation risk. Among direct predator-induced cues, visual and olfactory signals are considered to be most important. Food intake rates and prey-size selectivity of laboratory-reared, naive young-of-the-year (YOY) perch, Perca fluviatilis , were studied in experiments with Daphnia magna of two size classes: 2.8 and 1.3 mm as prey and northern pike, Esox lucius , as predator. Neither total intake rate nor prey-size selectivity was modified by predator kairomones alone (water from an aquarium with a pike was pumped into the test aquaria) under daylight conditions. Visual presentation of pike reduced total food intake by perch. This effect was significantly more pronounced (synergistic) when visual and olfactory cues were presented simultaneously to foraging perch. Moreover, the combination of cues caused a significant shift in prey-size selection, expressed as a reduced proportion of large prey in the diet. Our observations demonstrate that predator-induced olfactory cues alone are less important modifiers of the feeding behaviour of naive YOY perch than visual cues under daylight conditions. However, pike odour acts as a modulatory stimulus enhancing the effects of visual cues, which trigger an innate response in perch.  相似文献   

Decreased transport of orally administered protein into the blood circulation of developing juveniles of Japanese eel Anguilla japonica     

Osamu Nakamura  Yuzuru Suzuki  Katsumi Aida  Hajime Hatta 《Fisheries Science》2001,67(5):863-869

ABSTRACT: To clarify the quantitative changes in the transport of orally intubated protein into the blood circulation as macromolecules in development, immunoglobulin Y (IgY) extracted from chicken eggs was administered orally to juvenile Japanese eel, Anguilla japonica . For the first experiment, which was performed before the commencement of artificial feeding, the oral delivery of 2.0 μg/0.1 g bodyweight of IgY resulted in a rapid increase in plasma IgY to a maximum of 2.30 μg/mL. However, the transport of IgY into the blood decreased significantly in the experiments that followed, which were performed after 12, 25 and 42 days. During this period, bodyweight increased approximately by a factor of eight, and rapid growth of the stomach was observed histologically. Possible contributions for the development of the alimentary canal to the diminishment of intestinal protein assimilation are discussed.  相似文献   

Importance of the River Teviot to Atlantic salmon, Salmo salar, rod catches in the River Tweed, Scotland     

M. HEDDELL-COWIE 《Fisheries Management and Ecology》2005,12(2):137-142

Abstract  The body mass distributions and variations in abundance of the spring and autumn catches of Atlantic salmon, Salmo salar L., were compared between fisheries above and below the confluence of the rivers Tweed and Teviot, Scotland. Significant differences between the distributions were found over three periods, one in spring and two in autumn, when salmon catches were high. Correlations were found between abundance trends for periods when distributions were similar or dissimilar. Abundance of salmon returning to the River Teviot was proportional to the main river. However, its population structure differed when abundances were high, suggesting different survival strategies. It appears that changes in the numbers returning to the river were resultant of changes in the marine rather than freshwater environment.  相似文献   

Dilated Cardiomyopathy in Juvenile Doberman Pinschers     

Andrea Vollmar DVM  Dipl. ECVIM-CA  Philip R. Fox DVM  MSc  Dipl. ACVIM  ECVIM-CA  Dipl. ACVECC  Kathryn M. Meurs DVM  PhD  Dipl. ACVIM  Si-Kwang Liu DVM  PhD  Dipl. ACVIM 《Journal of Veterinary Cardiology》2003,5(1):637

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Resistance to Leveillula taurica in the genus Capsicum   总被引：1，自引：0，他引：1  

V. L. de Souza  A. C. Café-Filho† 《Plant pathology》2003,52(5):613-619

One hundred and sixty-two Capsicum genotypes were evaluated for powdery mildew (Leveillula taurica) resistance, following inoculations with a suspension of 5 × 10⁴ conidia mL⁻¹ on 10-leaved to 12-leaved plants. Genotypes were graded into five resistance classes, based on the areas under the disease progress curves calculated from disease incidence (percentage infected leaves per plant) and severity (total number of colonies per plant). Results revealed a continuum from resistance to susceptibility, with the majority (70%) of C. annuum materials being classified as moderately to highly susceptible to L. taurica. Conversely, C. baccatum, C. chinense and C. frutescens were most often resistant, indicating that resistance to L. taurica among Capsicum species is found mainly outside the C. annuum taxon. Nevertheless, some resistant C. annuum material was identified that may be useful for resistance breeding. Eight genotypes were identified as immune to the pathogen: H-V-12 and 4638 (previously reported), and CNPH 36, 38, 50, 52, 279 and 288. Only H-V-12 and 4638 are C. annuum, while all others belong to the C. baccatum taxon. Latent period of disease on a set of commercial sweet pepper genotypes varied, indicating diverse levels of polygenic resistance. The latent period progressively reduced with plant maturity, from 14·3 days in plants at the mid-vegetative stage to 8·6 days in plants at the fruiting stage. Young plants of all commercial genotypes tested at the early vegetative stage were immune, irrespective of the reaction of the genotype at later stages, demonstrating widespread juvenile resistance to L. taurica in the Capsicum germplasm. Inoculation of plants of different botanical taxa with a local isolate indicated a wide host range. Some hosts, including tomato (Lycopersicon esculentum), artichoke (Cynara scolymus) and poinsettia (Euphorbia pulcherrima), produced large amounts of secondary inoculum. Other hosts included okra (Abelmoschus esculentus), eggplant (Solanum melongena), cucumber (Cucumis sativus), Solanum gilo, Chenopodium ambrosioides and Nicandra physaloides.  相似文献