杨农间作光能利用的研究   总被引：3，自引：0，他引：3  

裴保华  袁玉欣  贾玉彬  王文全  Josef Eitzinger 《林业科学》2000,36(3):13-18

根据实测光强,利用作物和树木光－光合曲线中的最大光合速率和表观量子效率以及各物候期的叶面积系数、叶幕消光系数等参数,估算了杨农间作与单一农作物（对照）的光能利用率。结果表明,三种杨农间作模式的总光能利用率都高于对照,约可提高２７．５６％￣４８．６４％。间作田农作物的日累积光合量随日累积光量减少而降低,呈线性正相关。当相对光强〉６０％时,间作田农作物的光能利用率稍高于对照田农作物;相对光强〈５０％时  相似文献   

Seasonal and diurnal variation of downstream fish movement at four small-scale hydropower plants     

Josef Knott  Melanie Mueller  Joachim Pander  Juergen Geist 《Ecology of Freshwater Fish》2020,29(1):74-88

Hydropower structures hinder the movement and migration of fishes, impairing their life cycles. Additionally, downstream moving fish are often at risk of being injured during turbine passage. To improve hydropower production towards more fish-friendly techniques and management, knowledge on timing and extent of natural patterns of fish downstream movement is necessary. So far, migration behaviour of long-distance migrators such as eel or salmon has been well studied, but little is known about seasonal and diurnal movement patterns of nonmigratory species or medium-distance migrators. In this study, movement patterns of 39 fish species captured by stownets while transiting hydropower facilities in four impounded rivers were assessed and compared with the fish community composition directly upstream of the hydropower plants assessed by electrofishing. Strong differences between the fish community composition inhabiting the upstream sides of the dams and the fish detected in downstream passage were evident. In each study river, the downstream moving fish community composition differed significantly between spring and autumn. On average, significantly more fish were caught during the night (2.9 fish/hr) than during the day (1.3 fish/hr). Topmouth gudgeon, European grayling and pike-perch mostly moved downstream during the night, whereas roach, spirlin and bleak were the most frequent downstream moving fish during daytime. Downstream fish movement was positively related with turbidity, water temperature and discharge. The strong differences in seasonal and diurnal fish movement patterns suggest that fish damage can be strongly reduced by adaptive turbine and corridor management, for example by shutting down turbines at peak movements.  相似文献   

Discussion of common and new indicating properties for the strength grading of wooden boards     

Markus Lukacevic  Josef Füssl  Josef Eberhardsteiner 《Wood Science and Technology》2015,49(3):551-576

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Altered light conditions following thinning affect xylem structure and potential hydraulic conductivity of Norway spruce shoots     

Roman Gebauer  Daniel Volařík  Josef Urban  Isabella Børja  Nina Elisabeth Nagy  Toril Drabløs Eldhuset  Paal Krokene 《European Journal of Forest Research》2014,133(1):111-120

Trees must respond to many environmental factors during their development, and light is one of the main stimuli regulating tree growth. Thinning of forest stands by selective tree removal is a common tool in forest management that increases light intensity. However, morphological and anatomical adaptations of individual shoots to the new environmental conditions created by thinning are still poorly understood. In this study, we evaluated shoot morphology (shoot length, needle number, projected leaf area) and anatomy (tracheid lumen area, tracheid number, tracheid dimensions, xylem area, potential hydraulic conductivity) in three Norway spruce (Picea abies/L./Karst.) families exposed to different thinning regimes. We compared shoot characteristics of upper-canopy (i.e. sun-exposed) and lower-canopy (i.e. shaded) current-year shoots in a control plot and a plot thinned to 50 % stand density the previous year. One tree per family was chosen in each treatment, and five shoots were taken per canopy position. We found that upper-canopy shoots in both plots had higher values than lower-canopy shoots for all studied parameters, except lumen roundness and tracheid frequency (i.e. tracheid number per xylem area). Thinning had little effect on shoot morphology and anatomy 1 year after thinning, except for small but significant changes in tracheid dimensions. Needles were more sensitive to altered light conditions, as projected leaf area of shoot, needle number and leaf hydraulic conductivity changed after thinning. Differences between upper- and lower-canopy shoots did not seem to be influenced by thinning and were almost the same in both plots. Our results suggest that lower-canopy shoots require several years to modify their morphology and anatomy to new light conditions following thinning. The slow light adaptation of the lower canopy may be of practical importance in forest management: thinned stands may be predisposed to drought stress because newly exposed shoots experience increased illumination and transpiration after thinning.  相似文献   

Identity: key to children's understanding of belief     

Perner J  Mauer MC  Hildenbrand M 《Science (New York, N.Y.)》2011,333(6041):474-477

Is knowledge structured and acquired as independent facts and concepts, as parcels of independent domains, or as domains that share conceptual abilities? For an answer, we looked at the development of two concepts, belief and identity. These concepts are not part of the same domain, but the application of both depends on the common ability to separate sense from reference. We show that both capacities become functional between the ages of 3 and 5 years, which provides empirical support for the contention that deep conceptual structures play an important role in cognitive development.  相似文献   

Collembola succession on deposits from a chemical factory     

Josef Rusek 《Pedobiologia》2004,48(5-6):519-525

Primary succession of collembolan communities was studied on deposits of a former factory producing nitric, sulphuric, and muratic acids and soda at Petrovice u Karviné, NE Moravia, Czech Republic, in 1978–1979. Chemically loaded deposits were 15, 25 and 60 years old in 1979 and a primary succession without plant re-cultivation took place there. The succession was delayed on small humps and slopes where the deposited substrate was covered by terrestrial algae, lichens and mosses. A total of 4871 specimens of Collembola containing 78 species from 23 sampling sites were evaluated. The quantitative species data were analysed using TWINSPAN and CANOCO programs. Coenotic similarity was determined with a polythetic classification produced by two-way indicator species analysis performed for log (n+1) transformed quantitative data. Collembolan communities were composed of 3–23 species in densities from 1300 to 80,700 ind·m². Lower species number (3–9) in low densities and low diversity occurred on sites with the initial stages of succession covered with algae, lichens and mosses. Collembolan species typical of early succession included Mesaphorura atlantica, Hypogastrura assimilis, Schoettella ununguiculata and Doutnacia xerophila. The succession on two different deposit substrates converged in more advanced stages to a collembolan community including Mesaphorura hylophila, Parisotoma notabilis, Lepidocyrtus lanuginosus, Folsomia quadrioculata and F. lawrencei as typical species. Species such as Isotomiella minor, Megalothorax minimus and Friesea mirabilis entered the succession only in the most advanced stage of the 60 years old deposit. The absence of F. mirabilis was probably connected with the missing aquatic soil microfauna (Nematoda, Tardigrada, Rotatoria) in the chemically unfavourable substrates of the less advanced succession stages.  相似文献   

Effect of inoculation with soil yeasts on mycorrhizal symbiosis of maize     

Manfred Josef Gollner  David Püschel  Miroslav Vosátka 《Pedobiologia》2006,50(4):341-345

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Comparison of RAPD, STS, ISSR and AFLP molecular methods used for assessment of genetic diversity in hop (Humulus lupulus L.)   总被引：1，自引：0，他引：1  

Josef Patzak 《Euphytica》2001,121(1):9-18

CoxI genomic and cDNA sequences from gymnosperms and angiosperms were used to study the effects of RNA editing on gene evolution and phylogenyre construction. In six gymnosperms harboring edited coxI gene the number of nucleotide substitutions at 1^st, 2^nd and 3^rd codon positions was similar. In contrast, in angiosperms, the number of nucleotide substitutions at 1^st and 2^nd codon positions was much lower than at the 3^rd. The coxI gene in long-lived gymnosperms evolved much faster than in annual angiosperms. This accelerated rate of nucleotide substitution in gymnosperms is due to accumulation of T-C substitutions at edited sites that can randomly appear at all three codon positions. Editing predominantly occurred at 1^st and 2^nd codon positions as a result of selection against non synonymous T-C substitutions and other types of mutations. The tree topologies for the investigated species based on genomic DNA data were in concordance with their taxonomic positions. The trees based on polymorphic edited sites agreed with trees derived from complete sequence information. This indicates that edited sites are reliable sources of phylogenetic information especially for species that contain many edited sites. However, the fast evolution rate of coxI gene in gymnosperms has caused the long branches in the phylogenetic trees. The inclusion of the species with a processed paralog i.e., edited form of the coxI gene, affected the topology of phylogenetic trees, especially when the taxon with a processed paralog was closely related to the other species analyzed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Production potential,biodiversity and soil properties of forest reclamations: Opportunities or risk of introduced coniferous tree species under climate change?     

Vacek  Zdeněk  Cukor  Jan  Vacek  Stanislav  Linda  Rostislav  Prokůpková  Anna  Podrázský  Vilém  Gallo  Josef  Vacek  Oldřich  Šimůnek  Václav  Drábek  Ondřej  Hájek  Vojtěch  Spasić  Marko  Brichta  Jakub 《European Journal of Forest Research》2021,140(5):1243-1266

European Journal of Forest Research - In the time of ongoing climate change and the increasing area of post-mining landscape, the successful afforestation of reclamation sites by suitable adaptive...  相似文献   

Molecular typing of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma mali’ and epidemic history tracing by a combined T-RFLP/VNTR analysis approach     

Sanja Baric  Jennifer Berger  Christian Cainelli  Christine Kerschbamer  Josef Dalla Via 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(4):573-584

Apple proliferation caused by ‘Candidatus Phytoplasma mali’ is a disease of apple trees gaining increasing importance in Europe. The present study describes a high-throughput method for simultaneous typing of ‘Ca. P. mali’ at two genetic loci. This novel approach combines terminal restriction fragment length polymorphism (T-RFLP) analysis of a putative rhodanese-like protein gene and the analysis of the variable number of tandem repeats (VNTR) of the ribosomal protein L22 gene. The typing approach was applied to analyse a collection of DNA isolates from 310 apple trees tested positive for ‘Ca. P. mali’. Samples were taken between 2002 and 2010 in South Tyrol (Northern Italy). In addition, 15 samples of Cacopsylla melanoneura and 19 of C. picta were typed. Seven combined genetic profiles were found in the samples of infected apple trees: AT-2/rpX-A (81.0%), AT-1/rpX-D (8.4%), AT-1/rpX-E (4.2%), AT-1/rpX-A (3.2%), AT-1/rpX-B (1.6%), AT-1/rpX-C (1.0%) and AP/rpX-A (0.3%), and one mixed infection AP + AT-1/rpX-A + rpX-D (0.3%). Subtype rpX-E was discovered for the first time. In C. melanoneura samples the most frequent subtype was AT-1/rpX-E, followed by AT-1/rpX-D and AT-1/rpX-C. All C. picta samples displayed subtype AT-2/rpX-A. Analysis of the temporal distribution of subtype frequencies in apple trees revealed that exclusively subtype AT-1 in combination with four rpX subtypes was present in South Tyrol in the period from 2002 to 2004. From 2006 onwards subtype AT-2/rpX-A became dominant with an average frequency of 90%. The data obtained suggest that there may be a co-adaptation of particular ‘Ca. P. mali’ subtypes with different insect vector species.  相似文献