Ascertaining Elk Impacts on Plant Communities     

Charles G. Johnson  Marty Vavra  Catherine G. Parks  Mitch Willis 《Herpetological Monographs》2013,35(3):11-15

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A microsporidian pathogen of the predatory beetle Rhizophagus grandis (Coleoptera: Rhizophagidae)     

Yaman M  Radek R  Weiser J  Aydin C 《Folia parasitologica》2010,57(3):233-236

A new Microsporidium sp. infects Rhizophagus grandis Gyllenhall, a beetle which preys on the bark beetle Dendroctonus micans Kugellan in Turkey. Mature spores are single, uninucleate, oval in shape (3.75 +/- 0.27 microm in length by 2.47 +/- 0.13 microm in width), with a subapically fixed polar filament. The polar filament is anisofilar, coiled in 7-8 normal and 3-4 reduced coils. Other characteristic features of the microsporidium are the four/five nuclear divisions to form 16/32 (commonly 16) spores, subpersistent sporophorous vesicles (pansporoblasts) remaining till formation of the endospore, and the vesicles dissolved with free mature spores. The polaroplast is divided into three zones: an amorphous zone, dense layers, and a lamellartubular area extending to the central part of the spore.  相似文献   

Changes in the air pollution load in the Jizera Mts.: effects on the health status and mineral nutrition of the young Norway spruce stands     

Bohumír Lomsky  Vít ?rámek  Radek Novotny 《European Journal of Forest Research》2012,131(3):757-771

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Biodiversity,exotic plant species,and herbivory: The good,the bad,and the ungulate     

Marty Vavra  Catherine G. ParksMichael J. Wisdom 《Forest Ecology and Management》2007

Invasion of natural ecosystems by exotic plant species is a major threat to biodiversity. Disturbance to native plant communities, whether natural or management induced, is a primary factor contributing to successful invasion by exotic plant species. Herbivory by both wild and domestic ungulates exerts considerable impact on structure and composition of native plant communities. Intensive herbivory by ungulates can enhance exotic plant invasion, establishment, and spread for three reasons: (1) many exotic plants are adapted to ground disturbances such as those caused by ungulate feeding, trampling, and movements; (2) many exotic plants are adapted for easy transport from one area to another by ungulates via endozoochory and epizoochory; (3) many exotic plants are not palatable or are of low palatability to ungulates, and consequently, their survival is favored as ungulates reduce or eliminate palatable, native plants. Ungulate herbivory is a chronic, landscape-scale disturbance capable of influencing plant communities as much as episodic events such as fire. Consequently, ungulate herbivory has the potential to facilitate the invasion and establishment of exotic plants in the interior Pacific Northwest where ungulates occupy nearly every ecosystem. Moreover, ungulate herbivory has intensified in many ecosystems, owing to the addition of domestic ungulates with that of existing, wild ungulates, coupled with the reduction or elimination of migratory movements and predators that previously regulated wild ungulate populations and influenced their distributions. Despite the observational evidence for ungulate herbivory as a strong facilitator of exotic plant invasion and establishment, current knowledge of cause–effect relations is severely limited by a lack of manipulative experiments. Most studies have been observational, unreplicated, and lack the experimental controls needed to eliminate or account for confounding sources of variation. Heightened attention to conservation of biodiversity will increase the importance of managing ungulates in balance with the plant communities that support them.  相似文献   

Zur Weiterentwicklung eines halbsynthetischen Nährmediums fürIps typographus L.     

J. Mattanovich  M. Ehrenhöfer  C. Vavra  E. Führer 《Journal of pest science》1999,72(2):49-51

The semiartificial diet for the bark beetleIps typographus L. ofSimsek andFührer (1993) andSimsek (1995) was further developed in its handling and composition of the vitamin solution. The biological availability of the vitamins of the vitamin b-group was investigated. The diet is useful as rearing medium for larvae, pupae and adult beetles. But it is not possible by now to grow reproducibly a whole generation cycle on this diet.  相似文献   

Topography and arterial supply of the thyroid and the parathyroid glands in selected species of Falconiformes     

Radek T  Piasecki T 《Anatomia, histologia, embryologia》2007,36(4):241-249

Birds of two suborders, Accipitres and Falcones were the subjects of the study. The thyroids were always located asymmetrically. In Accipitridae the larger left gland was usually situated significantly more cranially than the right one. In common kestrel, the size of bilateral thyroids was similar while their mutual relationships were individually variable. The location of the parathyroid glands in common kestrel was relatively constant. Seven topographical patterns of the location of the parathyroid gland were noted in Accipitridae. In birds of both the suborders, the thyroid might be supplied by three (groups of) arteries: the cranial thyroid, the caudal thyroid and the middle thyroid arteries. The aforementioned vessels were derived from the common carotid and the oesophagotracheobronchial artery. In common kestrel, the thyroid vessels might also branch from the ascending oesophageal artery, which passes along the thyroid, while in common buzzard and other Accipitridae - from the common trunk of the comes nervi vagi and the ascending oesophageal artery. The parathyroid glands were supplied by one to three parathyroid arteries. The vessels for the cranial parathyroid gland mostly originated from the caudal thyroid artery, while for the caudal one - from the oesophagotracheobronchial artery. The average number of thyroid and parathyroid arteries in common buzzard was significantly higher than those in common kestrel.  相似文献   

Natural development and regeneration of a Central European montane spruce forest     

Miroslav Svoboda  Shawn Fraver  Pavel Janda  Radek Bače  Jitka Zenáhlíková 《Forest Ecology and Management》2010

Montane Norway spruce forests of Central Europe have a very long tradition of use for timber production; however, recently there has been increasing concern for their role in maintaining biological diversity. This concern, coupled with recent severe windstorms that led to wide-spread bark beetle outbreaks, has brought the management of montane spruce forests to the forefront of public policy discussions in Central Europe. In order to shed light on the natural development and current structure of mature montane spruce forests, we established four 0.25 ha research plots in a semi-natural montane spruce forest in the Šumava Mountains (The Bohemian Forest), Czech Republic. We mapped all trees, extracted increment cores for age and growth-pattern analyses, and inventoried all current tree regeneration, including the substrates on which it was found. Stands were characterized by uni-modal tree diameter distributions and high basal areas (56.6 m² ha⁻¹ on average), indicating a natural transition from the stem exclusion phase towards the understory reinitiation phase. The stands showed largely single-cohort recruitment age structures, however, with recruitment spanning seven decades. Our analyses suggest that this cohort existed as advance regeneration prior to major disturbances in the late 1800s, which included post-bark beetle salvage logging. Spatial pattern analyses of living and dead stems combined, showed an increase in uniformity of living trees, pointing to the role of natural density-dependent mortality. However, past growth patterns and historical documentation suggest that low intensity canopy disturbances (wind and snow) also caused mortality and diversified canopy structure. Because the stands developed naturally over the past 120+ years and thus escaped thinning operations, high volumes of coarse woody debris (94 m³ ha⁻¹) and snag densities (546 stems ha⁻¹) have accrued. Advance spruce regeneration was quite abundant and existed primarily on deadwood substrates, even though these occupied only a small percent of stand area. Because of salvage logging in the late 1880s, these stands do not qualify, according to the traditional paradigm, as natural spruce forests. As a result, they are recently subject to active management practices including salvage logging that remove dead and dying trees. Given the importance of deadwood for forest regeneration and recovery from disturbance, as demonstrated in this study, we argue that dead wood removal may limit future natural regeneration in these stands. Thus, the purported benefits of removing dead and dying trees from semi-natural forests must be carefully weighed against the potential detrimental impacts on natural spruce forest regeneration and biodiversity.  相似文献   

Symptomless infection by strawberry virus 1 (StrV-1) leads to losses in strawberry yields     

Lucie Valentova  Martina Rejlova  Jana Franova  Radek Cmejla 《Plant pathology》2022,71(5):1220-1228

High-throughput sequencing has opened up possibilities of detecting new plant pathogens, especially viruses, with relative ease. However, information about biological characteristics and relevance to plant production is usually lacking. Recently, a new strawberry cytorhabdovirus named strawberry virus 1 (StrV-1) was described and characterized at a molecular level. The virus can be transmitted by aphids and is commonly found in commercial plantations. Here, we studied the impact of a sole StrV-1 infection on production in two strawberry cultivars—Darselect and Karmen. All plants infected with StrV-1 remained symptomless during the experiment. In general, Darselect was more resilient to StrV-1 infection, and the average yield per plant was nonsignificantly lowered by 11.7% over the 2-year experiment. In contrast, StrV-1 infection in cultivar Karmen led to a significant yield loss of 31.8%, indicating that the genetic background plays a role. While the average fruit weight and diameter were relatively unaffected, lower yields in infected plants stemmed from a significantly reduced number of inflorescences, by 23.6% and 29.6% in Darselect and Karmen, respectively, which resulted in a reduction in the average number of flowers per plant (decreased by 16.5% and 27.3%, respectively), and hence the number of fruits per plant (by 14.5% and 27.6%, respectively). The StrV-1 load was higher in spring than in autumn, and generally higher in the second year after infection, which corresponded to higher losses in the second harvest, especially in cultivar Karmen.  相似文献   

Morphology and development of the veins of the uterus in cattle during the fetal and neonatal periods     

P Wyrost  O Molenda  J Radek  T Radek 《Anatomia, histologia, embryologia》1990,19(1):1-15

A total of 101 specimens were used; they came from 89 fetuses (4th to 40th week of gestation) and 12 neonates (1 to 14 days old). The age of the fetuses was determined according to the method of Kantorova (1960). The uterine veins were filled with latex using an automatic injection apparatus of our own construction. The study showed that blood left the uterus of the examined animals through constantly present veins (Ramus uterinus venae ovaricae, V. uterina and Ramus uterinus venae vaginalis) as well as through a number of inconstant veins to which belonged the Vv. vaginales accessoriae craniales et caudales. The constant uterine veins and their branches differed from their adult counterparts by being morphologically more differentiated, especially by having more branches of which some disappeared with time. The uterine veins developed toward the end of the fetal period. They arose either from the most caudal Vv. mesonephridicae lumbales (V. ovarica and its branches), or from the segmental, visceral veins of the pelvis (V. uterina and Vv. vaginales).  相似文献   

Effect of combined nitrogen and sulphur fertilization on yield and qualitative parameters of Camelina sativa [L.] Crtz. (false flax)     

Tomas Lošák  Jaroslav Hlusek  Jiri Martinec  Johann Vollmann  Jiri Peterka  Radek Filipcik 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(4):313-321

Abstract

Camelina (Camelina sativa (L.) Crtz., false flax) is described as a species requiring fewer inputs than other oilseed crops thus making it an interesting alternative in sustainable cropping systems. As information on the combined effects of nitrogen and sulphur on camelina yield and quality parameters is meagre, a pot fertilization experiment was carried out with nitrogen applied as NH₄NO₃ at three increasing rates equivalent to a range from 63 up to 127 kg ha^?1. These treatments were combined with sulphur additions applied as (NH₄)₂SO₄ to achieve a soil sulphate content of 25 or 45 mg kg^?1, respectively (equivalent to 75 and 135 kg S ha^?1). The medium and high nitrogen rates combined with the low sulphur fertilization level increased the number of branches per plant compared with the lowest nitrogen fertilization at the same sulphur rate. Camelina seed yield increased with increasing nitrogen doses at the same low sulphur level, whereas straw yield increased only at the highest rate of nitrogen. Thousand-seed mass increased at the highest nitrogen dose and with the low sulphur application rate. In addition, the increase in nitrogen fertilization reduced seed oil content from 39.8% to 37.1%. A highly negative correlation was observed between oil and protein content of seeds. Nitrogen fertilization increased total oil yield and total protein yield. Differences in crop parameters between the sulphur treatments were not significant statistically, although the higher sulphur treatment tended to increase seed yield as well as oil and protein content compared with the low sulphur treatment. Thus, the combined application of N and S as mineral fertilizers is only recommended when growing camelina on sulphur-deficient soils if the aim is to achieve both high oil and protein production.  相似文献