摘要:

In this paper reference will be made to three widely recurrent types of functional specialization. These correspond to (1) strategies* apparent in the established (adult) phase of the life history, (2) strategies of the regenerative (juvenile) phase and (3) strategies of growth response to seasonal variation in temperature and moisture supply. In each case a comparison will be drawn between the range of strategies displayed by bryophytes and that already described for vascular plants. Reference will be made also to some of the implications of these strategy theories for the role of bryophytes in the structure and dynamics of plant communities.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02217.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Classical niche theory, particularly in terms of competitive exclusion, does not appear to apply as well to bryophytes as to other organisms. Bryophyte communities, as well as those of other plants and of animals, can be thought of in terms of individual species each utilizing particular portions of various resource or habitat continua. Quantitative studies carried out since 1981, particularly those involving niche breadth and overlap, are reviewed. Special attention is given to niche diversification inSphagnum, Splachnaceae, bryophyte communities in streams, and to ephemeral bryophyte communities. Some bryophyte communities appear to have equilibrium characteristics and to contain species with relatively narrow niche breadths and with no or only partial niche overlap. In many habitats, however, bryophyte communites have non‐equilibrium characteristics and diversification of species in microhabitats is opportunistic. Do any bryophyte communities persist long enough for complete saturation by species which have realized niches determined by competitive interactions? Recent studies indicate that this is the case for at least someSphagnumcommunities, but that it is the exception not the rule for bryophyte

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02218.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The main reasons for extremely limited information about liverwort genetics, particularly population genetics, are: (a) the continuing practice of phenetic species definition, which initiates a chain of confusion, and (b) a concentration on observational studies rather than experimentation. Useful genetical and cytological markers are known, and ways of harnessing them to obtain a detailed and precise insight into the genetic structure of liverwort species are discussed.Once the genetical bases for enzyme polymorphisms in liverworts have been identified, isoenzymes can be expected to assume the major role in population genetics. Certain chromosome markers, especially Giemsa C‐bands, however, hold similar promise. Detailed information concerning each of the following should now be forthcoming: (a) the relationship between inter‐ and intra‐populational genetic variation; (b) the genetic structure of populations; (c) the extent of gene flow; (d) the degree of self‐fertilization; (e) the degree of outcrossing; (f) the possibility of unidirectional gene flow between haploids and diploids, and (g) the possibility of hybrid

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02219.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The literature on heavy metals in bryophytes is reviewed, including mechanisms of metal uptake, retention, toxicity and tolerance. Interspecies differences in particular are discussed, including the development of extreme tolerance encountered in certain taxa. The use of bryophytes in monitoring heavy metal deposition is considered and comparisons are made with direct deposition measurements.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02220.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The responses ofSphagnumspecies to atmospheric pollution by sulphur and nitrogen oxides are reviewed. An explanation of the tolerance of sulphur dioxide inSphagnum cuspidatumis provided. This involves an exclusion mechanism by the oxidation of bisulphite ions to less toxic sulphate ions catalysed by the presence of iron and possibly other metals on the cell wall cation‐exchange sites. Tolerance is influenced by changing the iron content of the plants. A similar mechanism may account for sulphur dioxide tolerance inSphagnum recurvum.Evidence for a close coupling of nitrate assimilation with the atmospheric nitrogen supply in ombrotrophicSphagnumspecies in unpolluted regions is reviewed, and this coupling is shown to be lost in polluted environments with high atmospheric nitrogen supply. The potential effects of a supra‐optimal atmospheric nitrogen supply toSphagnumspecies on the ecology of mires is discussed.The effects of nitrogen and sulphur pollutants onSphagnumspecies are used to make broad generalizations as to how other bryophyte species might respond to these pollutants and to explain known effects of atmospheric pollution on bryophyte communit

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02221.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The widespread distribution of bryophytes and the tolerance of many species to certain contaminants has led to their use for monitoring purposes. Early this century, changes in the distribution of mosses in urban habitats indicated deteriorating air quality; alterations in species composition in rivers has reflected changing water quality. The main focus in the past 10 to 20 years has been on measuring levels of contaminants in both terrestrial and aquatic bryophytes. Concentrations of metals, organic chemicals, radionuclides and derivatives of acidic gases have been widely reported in species from contaminated and background areas. More rarely, physiological and biochemical parameters are monitored. This paper describes the approaches which have been used and results obtained from monitoring bryophytes in urban and industrial habitats. Data are reviewed from a range of countries illustrating the increasing interest in low cost methods for monitoring contamination.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02222.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Water relations of bryophytes must be understood along at least four dimensions: hydration/dehydration frequency; hydration duration; dehydration duration; degree of water loss. All these are biomass‐dependent functions such that large colonies of bryophytes may maintain hydration longer than smaller colonies. The spread of a bryophyte colony allows lateral movement of capillary water; contiguous clones will thus allow lateral conduction of that water. In contrast, separated tufts or cushions may store water but will contribute very little to its transfer over the surface of the phorophyte.Many of the tropical rainforests of New Guinea have a larger mass of epiphytic bryophytes than any temperate forest. The primary effect of disturbance in these forests is a reduction in bryomass, presumably due to desiccation because of increased insolation and wind movement. The reduction of bryomass will decrease water and mineral retention in the bryophyte clones; and the reduction in the size of those clones will reduce their contiguity and thus interfere with bryophyte‐mediatcd water and mineral transfer. Disturbance may alter bryophyte species frequency but, under present agricultural and forestry practices in New Guinea, I have seen no evidence of significant loss of bryophyte spec

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02223.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1990.tb02207a.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY