ISSN:0008-4026    

DOI:10.1139/cjbcontents98

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

I quantified the distribution and abundance of major plant taxa on three distinct cliff systems in Minnesota and examined the effects of recreational rock climbing on that vegetation. The three cliff systems differed significantly in the amount and type of vegetation present in undisturbed plots. Frequencies of most taxa were lower in climbed areas, although the differences were generally not significant. Total plant cover was significantly lower in climbed plots at all three locations. Fragile forms, such as umbilicate and fruticose lichens, were especially sensitive to human disturbance. The microtopography of the rock substrate had a significant impact on both the amount of vegetation present and the use of a cliff area by climbers. Cracks in the rock were significantly more common in climbed areas while ledges were less common. Microtopography also varied with the technical difficulty of the climbing route. While human impact decreased vegetation frequency and cover on these cliffs, identification of causal links between human disturbance and vegetation structure must include a careful assessment of the geological and environmental factors that strongly influence both human use and vegetation dynamics.Key words: cliff, lichen, rock climbing, vegetation, Minnesota, human disturbance.

ISSN:0008-4026    

DOI:10.1139/b98-178

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Increased atmospheric CO2and global warming may affect overall tree growth, but impacts of these combined stresses are largely unknown in terms of multiple growing season impacts on specific flushes. Thus, the effects of ambient or elevated CO2(approximately 200 µmol·mol-1above ambient) and ambient or elevated temperature (approximately 4°C above ambient) were evaluated for both main and second (lammas) flushes of Douglas-fir (Pseudotsuga menziesii(Mirb.) Franco). Established seedlings were grown for three full growing seasons in outdoor, sunlit chambers, which maintained diel and seasonal variation in climate. A reconstructed forest soil was used with a seasonal wet and dry cycle and without added fertilizer. Compared with ambient CO2, elevated CO2had no impact on overall phenology and growth of terminal shoots, needles, or buds. In contrast, compared with ambient temperature, elevated temperature resulted in higher shoot and needle growth rates early in the season; reduced final terminal shoot length; and either reduced, increased, or unchanged final needle length, depending on season. Initiation of the lammas flush was delayed and (or) decreased at elevated temperature. Leading terminal bud break and growth occurred earlier; however, resting bud length was reduced, and bud width tended to increase with elevated temperature. Thus, at least during early seedling growth, elevated temperatures may reduce both main- and lammas-flush growth, thereby altering tree productivity, whereas elevated CO2may have little effect on main or lammas growth at either the current or elevated temperature.Key words: climate change, leaf nitrogen,Pseudotsuga menziesii, shoot growth, lammas growth

ISSN:0008-4026    

DOI:10.1139/b98-169

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Previous research to determine the impacts of harvesting and site preparation on microbial processes and decomposer fungi in mixedwood forests indicated that effects were minimal. As an extension to this research, the present study was conducted to evaluate if microbial processes and decomposer fungi were sensitive to manual or chemical vegetation management in addition to harvesting and site preparation. The impact of vegetation management on microbial processes and decomposer fungi was examined in organic and mineral soil from harvested sites in northwestern Ontario. Three vegetation management treatments were applied to three clear-cut and prepared sites 2 years prior to the initiation of the study. Four treatments were established within each site: (i) harvested (control), (ii) glyphosate herbicide (Vision®), (iii) triclopyr herbicide (Release®), and (iv) manually operated brushsaws. The objective of the study was to determine the response of basal respiration, microbial biomass C, metabolic quotients (qCO2), microbial carbon : soil organic carbon ratio (Cmic/Corg), nitrogen mineralization, and fungal community structure to vegetation management by chemical and manual means. Relative to the harvested control, vegetation management had no significant impact on fungal community structure as evidenced through rank abundance curves and indices of fungal community richness, diversity, evenness, or dominance. Although the abundances of the majority of fungal species were not impacted by vegetation management, herbicide and brushsaw use decreased the isolation frequencies ofMortierella vinacea(Dixon-Stewart) andPaecilomyces carneus(Duché and Heim) Brown and Smith, respectively. Occurrence ofPaecilomyces carneuswas significantly greater in the organic soil than in the mineral soil of the harvested control, but this difference was not detectable in the blocks that had undergone vegetation management. Two years after vegetation management was imposed there were no detectable effects on basal respiration, microbial biomass C,qCO2, Cmic/Corg, or nitrogen mineralization in either the organic or mineral soil layers as compared with measurements made in the harvested control plots.Key words: harvesting, herbicide, brushsaw, fungal community, microbial processes

ISSN:0008-4026    

DOI:10.1139/b98-186

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Triuris hyalinaMiers, an unusual achlorophyllous plant, was investigated for subterranean morphology, root anatomy, and mycotrophy. Stems with scale leaves extend subterraneously to a depth of 15 cm. Pairs of adventitious roots develop at the scale leaves and clumps of apparently radiating roots, formed by accumulations of side shoot and scale leaf developments, occur. Roots consist of epidermis, short cell exodermis, three distinct layers of cortex parenchyma, endodermis, and an extremely reduced central cylinder with one or two central tracheidal xylem elements. The fungus associated withT. hyalinaroots exhibits thick-walled, 6-9 µm thick, aseptate external hyphae. It penetrates the epidermis by developing appressoria and enters the cortex solely through the short cells of the exodermis. In the cortex cells, the aseptate hyphae start to coil. In the outer cortex layer, hyphae are thin, frequently branched, and most densely coiled. In the middle cortex layer they are thicker and less densely coiled, and mostly appear degenerated to clumps of amorphous fungal material. The inner cortex layer rarely becomes colonized. Vesicles occur in the outer and the middle cortex layers. This mycorrhizal pattern is interpreted as an adaption to attain a sustainable use from the endophyte. It is suggested that the mycorrhiza inTriurishyalinabe interpreted as a type of arbuscular mycorrhiza (AM). Implications for systematics and ecology are discussed.Key words:Triuris, Triuridaceae, root structure, anatomy, arbuscular mycorrhiza, myco-heterotrophy.

ISSN:0008-4026    

DOI:10.1139/b98-168

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A re-assessment of members of the family Saxifragaceae in the Canadian Arctic Archipelago is presented as a traditional key and annotated checklist that recognizes 17 taxa. The information on which this paper is based is recorded in a developing DELTA database that aims to collect the following data: place of valid publication; synonymy, usually limited to names that have been associated with the Canadian Arctic; common name(s), if applicable; vegetative and floral morphological characters; data on the distribution, including information about the northernmost record of the taxon; habitat preferences of each species; notes on the species as an environmental indicator; indigenous knowledge; and expanded notes conveying additional information. The database also contains maps, illustrations of characters useful for identification, and colour photographs and line drawings of the taxa. Appendices list characters recorded in the database, brief taxonomic notes, and a sample species description. The data are available on the Internet at http://biodiversity.uno.edu/delta/ as natural-language descriptions and as an INTKEY interactive identification and information-retrieval package for Windows.Key words: Arctic, Canada, DELTA, Internet, Saxifragaceae, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b98-179

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Diarimella laurentidae, a new species occurring on dead bark and decorticated twigs of American beech (Fagus grandifoliaEhrh.), is reported from the Muir's Wood ecological reserve, located in the centre of the Haut-Saint-Laurent region in the province of Quebec.Diarimella laurentidaeis characterized by stromatic, pulvinate, black, setose fructifications composed of a basal stroma of textura angularis, a brown peripheral wall of textura porrecta, conidiomatal setae of two types, and unicellular multisetulate conidia. Its relationships with describedDiarimellaspecies is discussed. This is the first report of a species ofDiarimellafrom North America.Key words:Diarimella laurentidae, new fungus species, coelomycete,Fagus grandifolia.

ISSN:0008-4026    

DOI:10.1139/b98-234

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The threeMoniliniaspp., known as the brown rot fungi of fruit crops, are usually distinguished from each other on the basis of (qualitative) colony characteristics. We linked these qualitative features to unambiguously defined, quantitative colony and germ tube characteristics. A wide collection of isolates ofMonilinia fructicola(Winter) Honey,Monilinia laxa(Aderhold & Ruhland) Honey, andMonilinia fructigena(Aderhold & Ruhland) Honey was used to determine growth rate and sporulation intensity on potato dextrose agar (PDA) at 22°C under two light regimes (darkness, 12 h light : 12 h dark). The following germ tube characteristics were determined on water agar after incubation for 18 h at 22°C in darkness: length of the (leading) germ tube, distance to the first branch, and the number of germ tubes per conidium. Increase in colony diameter from day 3 to day 5 and sporulation intensity measured after 14 days was the highest inM. fructicola, whilstM. laxaandM. fructigenashowed considerable overlap in these features. The length of the germ tube after 18 h incubation was shortest inM. laxa, ranging from 161 to 466 µm. InM. fructicolaandM. fructigenathese ranges were 465-851 and 307-806 µm, respectively. The occurrence of more than one germ tube per conidium was most prominent inM. fructigena. Discriminant analysis on the basis of different combinations of the quantitative characteristics measured, showed that the combination of growth rate on PDA and length of the germ tube was sufficient to delineate the three brown rot fungi. One of 11M. fructicolaisolates was misclassified, the same held forM. fructigena(one misclassification of nine isolates). No misclassifications occurred inM. laxa.Key words: brown rot fungi, growth characteristics,Moniliniaspp., taxon

ISSN:0008-4026    

DOI:10.1139/b98-183

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

During a study on the live crown characteristics of Pinus laricio (Pinus nigraArn. ssp.laricio(Poir.) Maire), the observation of branch cross-sections allowed us to work on the problem of the discontinuance of cambial activity. This work points out the existence of missing rings with a histologic point of view and establishes the generality of the phenomenon for this species. In addition to the observations at the base of living branches, the cross-sections in all the successive growth units of the branch were observed to establish the distribution of the annual wood layers along the branch and to ascertain the dissymmetry between the upper side and the lower side of the branch. The occurrence of this phenomenon in the upper part of the crown raises the problem of the contribution of these branches to tree development and its implication in forest management.Key words: growth rings,Pinus nigraArn. ssp.laricio(Poir.) Maire, missing rings, anatomy, branch growth, crown.

ISSN:0008-4026    

DOI:10.1139/b98-194

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

PetasitesMill. (Asteraceae: Senecioneae) is a taxonomically difficult genus of polygamodioecious, perennial herbs with a widespread distribution across North America. As many as 10 species and as few as two species (Petasites sagittatus(Banks ex Pursh) A. Gray andPetasites frigidus(L.) Fries with three varieties), with one hybrid taxon, have been recognized previously. Considerable taxonomic controversy has surrounded the genus as a result of a conservative floral morphology and a high degree of polymorphism in leaf morphology. Additionally, a number of intergrading leaf forms among those with rather consistent taxonomic characteristics across various treatments have contributed to the taxonomic ambivalence surroundingPetasites. Our taxonomic revision of North AmericanPetasitesis based on results obtained from recent multivariate morphometric and isozyme analyses. These data have indicated that taxa ofPetasitesare not sufficiently differentiated, morphologically or isozymically, from one another to warrant the recognition of separate species. Therefore,Petasitesis circumscribed as a single species containing three varietal taxa and one hybrid taxon between two of the varieties. Although our circumscription ofP. sagittatusis in accordance with most previous circumscriptions, we have removed it from the rank of species to varietal status underP. frigidus. The new combinationPetasites frigidusvar.sagittatus(Banks ex Pursh) Cherniawsky is proposed. Subsequent to the new status of one of its parental taxa (P. frigidusvar.sagittatus), the new combination forPetasites×vitifolius(Greene) Bogle is proposed:Petasites frigidusvar. ×vitifolius(Greene) Cherniawsky. The three entities of thefrigiduscomplex are united under one polymorphic taxon,P. frigidusvar.frigidusand the circumscription and name ofPetasites frigidusvar.palmatus(Ait.) Cronq. is in accordance with previous authors. A complete list of synonymy and a key to the taxa ofPetasitesis presented together with distribution maps.Key words:Petasites, Asteraceae, Senecioneae, North America, taxonomic revisio

ISSN:0008-4026    

DOI:10.1139/b98-222

出版商:NRC Research Press    

年代:1998

数据来源: NRC