摘要:

The forested shoreline of the Saint Lawrence River upper estuary is frequently damaged by spring ice, currents, and waves during episodes of high water levels. A dendroecological analysis of the significant river floods, as recorded by ring-width patterns of uprooted woody plants, population growth and decay structures, and scars caused by ice on trees within the shore environment, provides direct evidence of a landward migrating shoreline. Regressive succession of vegetation is associated with a general rise in year-to-year flood levels. Plant community dynamics and shore sediment migration were investigated in a particularly exposed site between Grondines and Sainte-Anne-de-la-Pérade. Most of the oldest sublittoral trees are undergoing slow degradation and hydrophilous shrubby stands show extensive expansion within the shoreline habitat, which is associated with an important landward displacement of sediments. These ecological and geomorphological results concur with the general rising trend of flood levels of the Saint Lawrence during the last 30 years.

ISSN:0008-4026    

DOI:10.1139/b88-261

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Ontario members ofCrataegusseriesRotundifoliaedisplay breeding behavior that is characteristic of apomictic taxa. Based on a series of analyses, including histological studies of ovule development, chromosome counts, pollen stainability and pollination studies, and phenological analyses, it appears that most of the OntarioRotundifoliaeare tetraploid (2n = 2x = 68), self-fertile, pseudogamous, facultative apomicts. Some triploid (2n = 3x = 51) apomicts are also present inC.dodgeivar.flavida(Sarg.) Smith & Phipps. The results presented are congruent with previous studies ofCrataeguscytogenetics. Moreover, these results have assisted the taxonomic analysis of the series by permitting the identification of predominantly apomictic microspecies as well as possible hybrid taxa.

ISSN:0008-4026    

DOI:10.1139/b88-262

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

During the summer of 1986, plants were collected from University of British Columbia Research Farm at Oyster River, Vancouver Island, and their mycorrhizal status was determined. Of the 60 plant species examined, 44 were always vesicular–arbuscular mycorrhizal, 13 were always nonmycorrhizal, and three varied. Nonmycorrhizal plants were found in species belonging to the following families: Araceae, Caryophyllaceae, Compositae, Cruciferae, Gramineae, Onagraceae, Polygonaceae, and Portulacaceae. The mycorrhizal status of 15 plant species is reported here for the first time. Of these, the nonmycorrhizal species includedLysichitum americanum(Araceae),Stellaria simcoei,Stellaria calycantha(Caryophyllaceae), andEpilobium minutum(Onagraceae), and the mycorrhizal species includedAdenocaulon bicolor,Eriophyllum lanatumvar.achillaeoides,Grindelia squarrosavar.serrulata(Compositae),Poa gracillima(Gramineae),Brodiaea coronaria,Disporum hookerii(Lilaceae),Polypodium glycyrrhiza(Polypodiaceae),Ranunculus uncinatus(Ranunculaceae),Rosa nutkanavar.nutkana(Rosaceae),Collinsia parviflora(Scrophulariaceae), andViola glabella(Violaceae).

ISSN:0008-4026    

DOI:10.1139/b88-263

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The Eremomycetaceae is shown to contain three species:Eremomyces bilateralisMalloch & Cain,Rhexothecium globosumSamson & Mouchacca, andPithoascus langeroniivon Arx, which is treated as a new combination inEremomyces. The family is characterized by members having pseudoparenchymatous ascomatal initials, cleistothecia, clavate to ovoid evanescent asci, and one-celled hyaline to pale brown ascospores. Two of the three species haveArthrographis-like orTrichosporiella-like anamorphs. The pseudoparenchymatous ascomatal initials characteristic of this family strongly suggest that it should be included in the class Loculoascomycetes.

ISSN:0008-4026    

DOI:10.1139/b88-264

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Microcosms, simplified analogues of natural ecosystems, are a useful tool for studies of litter decomposition. A literature review shows that if microcosms are carefully constructed to mimic nature accurately, they allow researchers to control and independently vary normally covarying environmental factors (temperature, moisture, soil animals) that influence decomposition rates, while maintaining a sufficiently natural situation so that results of laboratory tests may be extrapolated to the field situation with confidence. A simple, inexpensive system of laboratory microcosms for decomposition studies is described and evaluated in this paper. The microcosm, housed within an airtight PVC chamber, consists of a litter layer overlying a core of forest floor strata collected with a minimum of disturbance to physical structure and populations of soil organisms. The microcosms have been tested with soil and litter from an aspen woodland and a pine forest, at temperatures ranging from −6 to +26 °C, and have been maintained in the laboratory for up to 6 months without significant deterioration. The microcosm system provided decomposition estimates that were precise, replicable, and rapidly obtained by measuring either mass loss or CO2efflux from litter samples. Problems with the method include rapid increases in populations of some soil animals, difficulty in controlling relative humidity, and acceleration of decay rates compared with those in litter in the field.

ISSN:0008-4026    

DOI:10.1139/b88-265

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Freshly fallen leaf litter was collected from a stand of trembling aspen (Populus tremuloidesMichx.) in the Rocky Mountains of Alberta each autumn from 1981 through 1984. Leaves from 1981 and 1982 were yellow, waxy, and strong. Leaves from 1983 were pale brown and very brittle, and almost 1% of them suffered symmetrical deformities. Leaves from 1984 were composed of 80% yellow leaves and 20% green leaves, which apparently abscissed before senescence. Green and yellow 1984 leaves were distinctly different with respect to total (3 days) leaching loss, leachate conductivity, and proportions of ash, cellulose, and labile material. Green 1984 leaves contained twice as much nitrogen as yellow ones (13.1 vs. 6.5 mg∙g−1) and significantly more phosphorus (1.6 vs. 1.3 mg∙g−1). Leaves of different years varied widely with respect to leaf mass, water absorption rate, mass and conductivity of leachate, and proportions of cellulose, labiles, lignin, and ash, but there was no consistent ordering among years; leaves of different colouration (especially 1981 and 1983) were often physicochemically similar, while leaves identical in appearance were often chemically different. Small but significant differences in N and P concentrations among years were removed by 2 h leaching. Leaves of 1981 decomposing in laboratory microcosms at 26 °C lost less mass than either 1982 or 1983 leaves after 1 month, but not after 2 months. Ability of the cuticle to resist water absorption was probably responsible for the difference in initial decomposition r

ISSN:0008-4026    

DOI:10.1139/b88-266

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Respiration rates and mass losses of decomposing pine (Pinus contortaLoud. ×P.banksianaLamb.) and aspen (Populus tremuloidesMichx.) leaf litter were compared in laboratory microcosms for a range of temperature and moisture levels. For both litter types, a pair of high-temperature treatments (18, 26 °C) and a pair of low-temperature treatments (2, 10 °C) were distinguishable on the basis of respiration rate, mass loss, shape of the respiration curve, and (for pine) estimated microbial efficiency. Respiration rates in high-temperature treatments showed an initial increase to a wide peak (wider and later at 18 than at 26 °C), followed by a sharp decline; respiration of low-temperature treatments was nearly constant through time or declined slowly. Moisture level (15, 30, or 60 mL∙week−1watering rate) was less important than temperature in determination of mass losses or respiration rates. Aspen respiration at 18 and 26 °C peaked sooner and declined more rapidly at higher moisture levels than at lower ones; at 2 and 10 °C, higher moisture levels inhibited respiration owing to saturation. Mass loss of pine needles after 153 days decay was a linear function of temperature (R2 = 0.92). The best regression describing mass loss of aspen litter after 130 days decay was a linear function of both temperature and moisture, without interaction (R2 = 0.82). Moisture level became more influential as temperature increased. Researchers are cautioned about the limitations of cumulative respiration curves, and alternatives, such asANOVA, correlation, and the runs test, are suggeste

ISSN:0008-4026    

DOI:10.1139/b88-267

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Leaf litter of trembling aspen (Populus tremuloidesMichx.) and lodgepole–jack pine (Pinus contortaLoud, ×P.banksianaLamb.) was decomposed in laboratory microcosms at 2, 10, 18, or 26 °C and three watering rates (15, 30, or 60 mL∙week−1) for 16 weeks. Aspen litter lost 5.0–37.3% of original mass, and pine litter lost 7.8–14.9%. Decay curves fit a sample linear model equally as well as the negative exponential model regardless of temperature or moisture conditions or species of litter. A general explanation of circumstances promoting apparently linear mass loss from decaying plant litter is derived from these data, a survey of the literature, and the assumption that all decay curves are ultimately curvilinear. Mass loss rates are expected to appear linear from slowly decaying substrates such as bole wood or when decay of rapidly decomposing substrates is not followed past the inflection point of the curve. Climatic variables that favour decomposer activity are hypothesized to increase the concavity of decay curves, while adverse conditions do the opposit

ISSN:0008-4026    

DOI:10.1139/b88-268

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

To explore the relative influences of substrate type, temperature, and moisture on litter decomposition rates, leaf litter of aspen (Populus tremuloidesMichx.) and pine (Pinus contortaLoud, ×P.banksianaLamb.) was decomposed in laboratory microcosms for 16 weeks at 2, 10, 18, and 26 °C and 15, 30, or 60 mL∙week−1watering rate. Multiple regressions on mass remaining indicated temperature was a more important influence than watering rate for both species, but the degree and nature of response were different for pine compared with aspen. Decay rates of aspen were strongly affected by temperature and less so by watering rate, but pine decomposition was quite insensitive to both. For aspen, watering rate was a more important influence on decay rates at low temperatures (2 and 10 °C), while for pine it was more important at high temperatures (18 and 26 °C). There was a very strong interaction of time with temperature in the determination of aspen decomposition rate, but none for pine. All these differences are attributable to the disparate chemical and physical natures of the two litter types. The time × watering rate interaction was weak for both species, and there was no temperature × watering rate interaction at all. As a consequence of these differences in response to climatic variables, aspen leaves decomposed faster than pine needles under most conditions, but under cold, dry conditions pine decomposed faster than aspe

ISSN:0008-4026    

DOI:10.1139/b88-269

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The acarianEriophyes cladophthirusNal. causes necrosis of the vegetative shoots of tomato andNicandraand an inhibition and a modification of their apical growth, which are often accompanied by fasciation phenomena, the development of supernumerary buds and the proliferation of various shapes on the leaves. The foliar proliferations are warts, simple outgrowths, radially or dorsiventrally symmetrical appendices looking like small leaves and neoformed buds. In both species, intermediate forms of the various categories are found. The radially or dorsiventrally symmetrical appendices are simple or branched, vascularized or not, irregularly grouped or laid out in a more or less obvious phyllotaxy. They may appear directly on the leaf or may be the result of the activity of a neoformed apex. In this great diversity of shapes, many morphological continua, based on a number of criteria (symmetry, vascularization, etc.), have been identified. Some of them are common to both species, others only pertain to one or the other. [Journal translation]

ISSN:0008-4026    

DOI:10.1139/b88-270

出版商:NRC Research Press    

年代:1988

数据来源: NRC