Associations of fish with various types of littoral habitats in reservoirs

Fish associations with different types of littoral habitats were studied in four canyon‐shaped reservoirs in the Czech Republic in years 2010 and 2011 by gillnets. Two to three habitats per reservoir–beaches (former meadows), stump fields (former forest) and rubble slopes–were defined and sampled along the longitudinal axis of reservoirs. Effects of reservoir, habitat and locality (position along longitudinal axis) on fish biomass, abundance and species structure were tested for juvenile and adult fish separately. Hierarchical analysis of variance revealed that habitats differed significantly in fish biomass and abundance. Redundancy analysis showed that analysed environmental variables had significant influence on fish community structure. Most variability in community structure was explained by reservoir and then by combination of habitat and slope steepness. Locality position had the smallest influence on community structure. For both adult and juvenile fish total abundance and biomass, the most inhabited habitat was beaches; rubble slopes were the least inhabited. Habitat associations differed among species. Among adults, bream Abramis brama, white bream Blicca bjoerkna and roach Rutilus rutilus were associated with beaches and stump fields, whereas perch Perca fluviatilis, ruffe Gymnocephalus cernuus, asp Aspius aspius and pike Esox lucius were associated with rubble slopes. Bream, white bream, bleak Alburnus alburnus, roach, ruffe and pikeperch Sander lucioperca were associated with beaches among juveniles, whereas the only juvenile associated with rubble slopes was perch. We showed that most common species are associated with distinct habitats and also that utilisation of various littoral habitats differs in general.     

Production of mutants with high cold tolerance in spring canola (<Emphasis Type="Italic">Brassica napus</Emphasis>)

A major factor affecting spring canola (Brassica napus) production in Canada is killing frosts during seedling development in the spring and seed maturation in the fall. The objective of this study was to explore the possibility of producing spring canola lines with mutations that have altered biochemical pathways that increase cold tolerance. The approach was to generate UV point mutations in cultured microspores followed by chemical in vitro selection of individual mutant microspores or embryos resulting in measurable alterations to various biochemical pathways with elevated levels of key defense signaling molecules such as, salicylic acid (SA), p-Fluoro-d,l-Phenyl Alanine (FPA), and jasmonic acid (JA). In addition, since proline (Pro) is known to protect plant tissues in the cold-induced osmotic stress pathway, mutants that overproduce Pro were selected in vitro by using three Pro analogues: hydroxyproline (HP), azetidine-2-carboxylate (A2C); and, 3,4-dehydro-d,l-proline (DP). Of the 329 in vitro selected mutant embryos produced, 74 were identified with significant cold tolerance compared to their donor parents through indoor freezer tests at −6°C, and 19 had better winter field survival than winter canola checks. All chemically selected mutant doubled haploids with increased cold tolerance compared well with parent lines for all seed quality and agronomic parameters. Development of increased frost tolerant cultivars should allow for spring canola to be produced in western Canada without compromising seed quality.     

Systemic View on Heading and Overwintering: Are They Always Opposed?

The study investigated the cultivars of non‐obligatorily requiring vernalization plant Festulolium braunii and assessed the influence of non‐hardy reproductive and hardy vegetative structures on overwintering effect. The study was conducted taking into account systemic relations between these types of structures. The results show the cultivars differ according to the percentage of headed and overwintered plants, when the cultivars with the most abundant heading – ‘Felopa’ and ‘Sulino’ – are also better at overwintering. The positive correlation between heading and overwintering characteristics was also observed, what seemed to be a rather new finding. It can be explained by systemic effect: non‐hardy later reproductive structures induce the post‐generative regrowth of vegetative shoots, which during shorter days halt development and become potentially hardy. More detailed interpretation is also provided including discussion of causal mechanisms of the detected phenomenon. The authors suppose that these mechanisms constitute a survival strategy for such perennial plants. The observed late heading which represents reproductive structures could be applied in plant breeding as a marker of winter‐hardiness among perennial grass plants which non‐obligatorily demand vernalization.     

Predicting non‐native fish dispersal under conditions of climate change: case study in England of dispersal and establishment of pumpkinseed Lepomis gibbosus in a floodplain pond

Predictions of future climate change include shifts in patterns of precipitation, evapotranspiration and water run‐off, resulting in increased periods of drought as well as variability and intensity of rainfall events. In the United Kingdom, the non‐native North American sunfish, pumpkinseed Lepomis gibbosus (L.), is expected to benefit from these changes. We examine how hydrological variability induced by predicted changes in climate will affect the dispersal and spread of pumpkinseed in England by: (i) determining the relationship between discharge regime and pumpkinseed propagule pressure; (ii) examining a newly‐established pumpkinseed population following a flood event in 2007; and (iii) comparing the growth and life‐history traits of this new population with fish collected from the source population to demonstrate how the pumpkinseed's life‐history plasticity contributes to its success as a coloniser. Using Bayesian modelling, we determined that the number of pumpkinseed escapees is likely to increase with increasing discharge. The newly‐established pumpkinseed population showed fast juvenile growth, early age at maturity and small size at maturity. These traits differed significantly from the source population, specifically total length (TL) means at ages 1 and 2 were significantly greater in the new population, whereas TL at age 4 was significantly greater in the source population, and a significantly higher proportion of mature females were found at smaller size classes in the newly established pumpkinseed population. This study demonstrates the potential link between hydrological variability (current and future) and the dispersal of non‐native pumpkinseed, leading to the establishment of new populations.     

Stand structure of an uneven-aged fir–beech forest with an irregular diameter structure: modeling the development of the Belevine forest, Croatia

This study focuses on the problem of irregular diameter structure in a silver fir–beech selection (plenter) forest with a “surplus” of large diameter trees and a lack of natural regeneration and small diameter trees. We sampled 274 plots (900 m² each) in the Belevine research site (266.24 ha) in the mountain region Gorski Kotar (Croatia), where diameter (dbh) distribution, diameter increment, and natural regeneration were analyzed in detail. A low density of natural regeneration, weak annual recruitment of small (10 cm dbh) diameter trees (only five trees per hectare), delayed diameter growth of trees, and a low annual rate of trees reaching the next dbh class were attributed to the current irregular dbh structure. The stand development prediction for the next 50 years is based on a simulation model, which considers the current diameter structure, increment, recruitment, and future cutting regime. Intensive cutting in the first of five 10-year cutting cycles (intensity higher of 25%) is needed to initiate natural regeneration and to accelerate growth of young silver fir trees. In the next 50 years, the irregular diameter structure will be gradually improved.     

Stand biometry and leaf area distribution in an old olive grove at Andria, southern Italy

The objectives of this paper were (1) to provide general biometry data for an 80-year-old olive (Olea europea L., cv. Coratina) grove in Andria, southern Italy, and (2) to compare different methods for estimating leaf area distributions. Stand biometry was represented by a stocking density of 132 trees ha^?1, mean spacing of 8.7 m and mean social area (proportional to spacing and tree size) of about 76 m² per tree. Trunk total circumference averaged 110 cm and after subtraction of missing or dead parts of stems averaged 81 cm, projected area of crowns averaged 17.7 m² and the mean tree height was 4.9 m. Leaf distribution was evaluated using calibrated ground-based side photographs through image analysis and through using a simple canopy-layer model (considering hollow volume within tree crowns) and double-Gaussian curves. The mean leaf size was about 5 cm² (distributed in a log-normal manner over the range of 2 to 12 cm²). Considering whole tree crowns, the mean leaf density was about 2.6 m²m^?3; the maximum leaf area occurred in canopy layers between 1.5 to 3 m, tailing with a steeper slope to the crown base and a less steep slope to the tree-top. The foliated volume of olive crowns (mean 33.2 m³) contained on average 145 thousand leaves of the total area of 72.6 m². The corresponding leaf area index on the stand level (LAI _grove = 0.96), was rather low due to low stocking density. However when taking into account only the projected crown areas (and avoiding free space between trees), the mean LAI reached about 3.5 (range from 1–7). The radial pattern of leaf distribution derived from image analysis indicated peak LAI _rad values at a distance from the stem of about 60 to 70% of crown radius in trees of different size. The applicability of different approaches to the estimation of the necessary allometric parameters is discussed.     

Landscape effect for the Cervidaes Cervidae in human-dominated fragmented forests

We analyse the relationships between the main Cervidae [moose (Alces alces), red deer (Cervus elaphus) and roe deer (Capreolus capreolus)] species and a complex of environmental factors in an extensive fragmented landscape of Central Lithuania. The highest determining positive influence on moose density was the proportions of wet forest sites. In forest complexes with fewer proportions of wet sites, the most important factor was the total forest area. The proportion of shrub cover, upland and dense undergrowth area, and road density also has significant effect on moose density. The total area of forest complexes has the highest determining positive influence on red deer density. The highest density of red deer was calculated in large forest complexes (>2,745 ha) with a <17.6 % proportion of pine and <36.5 % of deciduous forests. Other significant factors were core area, road density and urbanization level. Forest edge density has the highest influence on the roe deer populations. The highest density of roe deer was recorded on forest areas with >51 m ha^?1 of edges in wet forest (>25.4 %) dominating areas. The proportion of deciduous, coniferous mixed and pine forest, also shrub and density of edges also had significant effect.     

N. I. Vavilov — Persönlichkeit und Mensch

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