Moss Carpet Research Articles

Environmental factors influencing decomposition rates in two Antarctic moss communities

Rates of disappearance of dead material of Polytrichum alpestre and Chorisodontium aciphyllum from a moss turf community and of Drepanocladus uncinatus, Calliergon sarmentosum and Cephaloziella varians from a moss carpet community, measured using litter bags over 2 years, were 1.5% year-1. Decomposition potential, estimated using loss in tensile strength of cotton strips inserted into the different bryophytes on the two sites, was also low. Ranking the five plant species in order of decomposition potential, from highest to lowest, gave D. uncinatus, C. aciphyllum, C. sarmentosum, P. alpestre and C. varians. The time taken for the tensile strength of the cotton strips at depths of 1–3 and 4–6 cm beneath the surface to decline by 50% varied from 1–2 years under the first two species to 3–4 years beneath the last two species. The main causes of these slow rates were low temperatures, short active season and low pH. Differences in decomposition between species, sites and with depth were related to temperature, nutrient status, water content and anaerobic conditions. Variation in anaerobic conditions beneath D. uncinatus, C. sarmentosum and C. varians in the moss carpet resulted in wide variation of decomposition rate beneath these species and with depth beneath C. varians. The peat in the moss turf was aerobic and experienced higher temperatures, but the average decomposition rate was no higher than in the moss carpet, because the peat was of a poorer quality and had a lower pH.

Expansion récente du mélèze à la limite des forêts (Québec nordique)

The contact between tamarack stands and tundra sites, located at the forest limit and at the tree line (Leaf River, Northern Québec), represents colonization ecotones where tree populations react to climatic change. At the forest limit, the ecotones are about 20 m wide and are supporting most of the young tamarack populations established from nearby forest seed bearers. Tamarack seedlings and saplings established mostly on moss carpets between 1940 and 1970 during the recent climatic warming. At the altitudinal and the latitudinal tree lines, seedling establishment was rather unimportant, considering the very low tamarack density and the absence of black spruce seedlings. The recent climatic warming had probably influenced the consolidation of preexisting tree populations more than the position of the tree line.

The terrestrial arthropods of the grass sward of Lynch Island, a specially protected area in Antarctica

The terrestrial arthropods of the grass sward of Lynch Island, a specially protected area in Antarctica

Sphagnum Invasion beneath an Evergreen Forest Canopy in Southeastern Alaska

The first detailed observations of Sphagnum colonization on the floor of a coniferous forest are used to evaluate the process of forest paludification. The forest, which is dominated by Picea sitchensis, is situated on a Neoglacial terminal moraine near the mouth of Glacier Bay in southeastern Alaska. The observations span a period of 14 years and have shown that (a) Sphagnum girgensohnii is the first peat moss to colonize the thick moss carpet on the floor of this forest, (b) establishment occurs only where the moss carpet has been disturbed by tree falls, (c) the number of Sphagnum patches in this forest is increasing with time, and (d) the patches are enlarging in surface area about 2% per year. As these changes occur on the forest floor, S. mendocinum and S. squarrosum are invading wet depressions and ponds in this forest. These events seem to result from soil-formation processes that are causing the water table to rise. The rate of local paludification will be affected directly, through the rise in the water table, as a water-tight seal forms within the stratified drift, and indirectly, as Sphagnum growth is stimulated by proximity to water. Investigations in this forest, at other places in Glacier Bay National Park, and elsewhere in southeastern Alaska suggest that colonization by Sphagnum takes place from 175 to 600 or more years following the initiation ofprimary succession. The development of muskeg vegetation through autogenic processes may take from 800 to several thousand years, or possibly much less if allogenic factors contribute to the paludification process.

Biomass and Respiration of Nematode Populations in Two Moss Communities at Signy Island, Maritime Antarctic

1. The biomasses of free-living soil nematodes from a moss turf and a moss carpet, two contrasting bryophyte ecosystems in the maritime Antarctic, are analysed and compared with other tundra studies. 2. The mean annual live-weight biomass of nematodes from the moss turf ranged from 105 to 355 mg m-2, that from the moss carpet showed less variation being from 222 to 236 mg m 3. Seasonal variations from a low winter biomass to a high summer value are explained by seasonal fluctuations in soil temperature. 4. Total annual nematode population respiration at the two sites was very similar, being 1726.1 1? 02 m2 d-1 in the moss turf and 1761.0 il ?2 m-2 d-1 in the moss carpet. 5. Nematodes form an important part of the soil fauna and are responsible for 16% and 35% of the metazoan respiration in the moss turf and carpet respectively. 6. The short Antarctic summer and generally low temperatures limit nematode production to 0.95 and 1.12 kcal m2 yr-1 at the two sites.

Structure and Function of Two Antarctic Terrestrial Moss Communities

Two bryophyte—dominated communities in the maritime Antarctic are analyzed in terms of the transfer and standing crops of organic matter within them. A moss turf dominated by Polytrichum alpestre and Chorisodontium aciphyllum and a moss carpet composed of Calliergon sarmentosum, Calliergidium austro—stramineum, and Drepanocladus uncinatus with the liverwort Cephaloziella varians were investigated at Signy Island, South Orkney Islands. Biomass, respiration, and production data for the primary producers (mosses, lichens, liverworts, and algae), for the fauna (Protozoa, Rotifera, Tardigrada, Nematoda, Acari, and Collembola), and for the microflora were synthesized, and annual rates of consumption, egestion, assimilation, and production were derived. The two communities showed similar levels of productivity, trophic structure, and efficiencies of organic matter transfer, but different Collembola and Acari standing crops, turnover of mosses, and accumulation of dead organic matter. These features are discussed in relation to the role of biotic and abiotic variables in determining community structure and function.

Peat respiration and decomposition in Antarctic terrestrial moss communities

Oxygen uptake by the peat of two Antarctic bryophyte communities (a moss turf and a moss carpet) is converted to organic matter loss and used to derive the rate of decomposition. The decay rates obtained in this way are evaluated in two mathematical models which simulate the accumulation of dead organic matter (DOM) in the communities from the litter production and decomposition rate. Litter production, the extent of DOM accumulations at present on the sites and mean decomposition rates (i.e. fraction of standing crop lost per year) were 409 g m-2 year-1, 33.5 kg m-2 and 0.017 g g-1 year-1 in the moss turf and 392 g m-2 year-1, 29.6 kg m-2 and 0.010 g g-1 year-1 in the moss carpet respectively (all weights expressed as dry weight). Aerobic decomposition rate declined with depth in both communities. From the model's predictions it is suggested that the observed decay rate was too high in the moss turf and too low in the carpet. Possible reasons for this are discussed and suggestions made for future work.

Studies on the Chemistry of Lichens and Mosses. XVII. Mercury Content of Several Lichen and Moss Species Collected in Norway

Samples of lichen and moss species collected in Norway have been analyzed for total amount of mercury. On the average the Hg content of lichens and mosses was greater than that of other higher plants or plant prod- ucts. Division of the lichen thallus into three parts showed that the upper part was essentially richer in mercury than the middle or lower parts. The mercury content of the plant material was determined by neutron activation analysis and flameless atomic absorption spectrometry. Recent reports concerning the content of heavy metals in cryptogams, led us to investigate the values of the total mercury content in a number of lichen and moss species. As far as the authors are aware, no measurements of Hg in lichen material sampled in Norway have previously been reported. This paper gives the results of a systematic investigation of these plant groups during the years 1973-1976. It may be assumed that the Hg content of plants is collected through concentrations of the mercury in rainwater or supplied absorbed in dust particles. Since Hg is known to be absorbed by most surfaces, it might be expected that dust particles would carry mercury if it were present in the atmosphere. Through the action of rain or of organic acids, the constituents of dust are released and absorbed by the lichen and moss carpet. Elevated concentrations of Hg in living lichen or moss samples may not be a result of air pollution alone, but may differ according to the ability of genus and species to absorb Hg. From our study it is evident that these plants may tolerate high concentra- tions of Hg. Distinct from vascular plants, lichens and mosses have little or no ability to utilize minerals directly from the substrate. The Hg content of the most common herbaceous plants fluctuates in the range from about 0.1 to 5 pg per 100 g dried material, depending upon plant species, plant parts and the supply of Hg during growth (Odelien, 1974). Unpublished analyses at our laboratory have given the following Hg content values: straw 5, ryegrass 2, timothy 3, clover 5 and needles of evergreens (30 samples) 3-16 pg per 100 g. Level of Hg in soil, however, has been reported to be very low.

Lead and zinc contamination of vegetation in the southern Pennines

Three types of heavy metal tolerant vegetation occurring on the spoil heaps in the Pennines are described sociologically and ecologically and their distribution in the Peak District National Park mapped. Concentrations of lead and zinc extractable from soils by acetic acid are recorded, as are total values for these two heavy metals in the tissues of the main component phanerogams and cryptogams of the vegetation. The range of values for zinc in plant tissues are uniformly higher than those for lead. Concentrations of lead accumulated by these plants are higher than those reported for the accumulation of atmospheric lead. The differences in heavy metal absorption, retention and excretion between ectohydric and myxohydric mosses are shown to be quite distinct. The heavy metals are excreted in the former type and form a crust in periods of drought with up to 6% lead and 1·5% zinc content, whilst, in the latter, the metals tend to be located mainly in the older growth at the base of the moss carpets. The concentrations of the two metal ions in two Peak District rivers proved to be less than 1 ppm in all samples.

Bryology in arctic and boreal North America and Greenland

Bryological research in boreal and arctic North America is in very preliminary stages. Although the flora is moderately well documented, details are lacking in much of the region. Greenland, Alaska, and Ellesmere Island are better understood than the rest of the area. Much of the information has been accumulated as casual collections and observations and incidental to other research. Bryophyte cover in arctic regions is less than that of vascular plants; in boreal regions wetlands are often dominated by bryophytes and open forests have extensive moss carpets. Turfs dominate the growth forms in the arctic while in boreal regions whorled-branched turfs, wefts, and compact mats become the predominant growth forms. Bryophytes are important in plant community structure and dynamics of both boreal and arctic regions, but detailed studies are few. Cytology of arctic and boreal bryophytes in North America rests on a single paper, thus any generalizations are hazardous. Physiology of bryophytes in northern North America has been inadequately documented. The sexuality, reproductive cycles, growth rates, and metabolic activities of bryophytes are areas that could yield intriguing results. Reproduction in bryophytes in northern regions appears not to be greatly different from that of more southern regions. In spite of the shorter growing season and the terrain and climate favoring wind dispersal, this had not led to an increase in the incidence of asexual reproduction in spite of the fact that more than 60% of the bryophytes are dioicous. Bryogeographic patterns are similar to those of the vascular flora but the presence of western North American taxa in the easternmost arctic and their absence in intervening areas is highly suggestive of eastern refugia. Glacial refugia are supported by the bryophyte distributions; their presence in unglaciated Alaska–Yukon, Ellesmere Island, and parts of Greenland seems best documented. Thirty-six maps are given showing bryophyte distribution patterns in the region under discussion.

Hibernation and the production of glycerol in the Ichneumonidae.

THE Ichneumonidae (Hymenoptera) are a family of parasitic wasps (15,000 species in the world1) which deposit their eggs in larvae or pupae of other insects. Twelve genera can overwinter as free adults, and individuals of these genera may be found hibernating in rotten forest logs, between rocks and under moss carpets. It seems likely that species that survive the winter possess some physiological mechanism absent in non-hibernating species. Glycerol and sorbitol accumulate in a limited number of unrelated diapausing and non-diapausing insects subjected to temperatures resembling overwintering conditions2. This study was undertaken to see if (a) the overwintering ability of a group of closely related species is manifested by a common observable phenomenon, namely polyol accumulation, and (b) this phenomenon is restricted to those species which hibernate.

Sorption and Retention of Heavy Metals in the Woodland Moss Hylocomium splendens (Hedw.) Br. et Sch.

The capacity of Hylocomium splendens to sorb heavy metal ions from dilute solutions was studied. The sorption and retention generally followed the order: Cu, Pb > Ni > Co > Zn, Mn. This order proved valid within a wide range of concentrations and independently whether the ions were supplied in pure or mixed solutions. The capacity of the moss tissues to sorb traces of Cu and Pb in the presence of comparatively large amounts of Ca, K, Mg, and Na was found to be very great. This makes it probable that these ions, supplied with the precipitation, are almost quantitatively sorbed by the moss carpets. A large share of Ni when present in precipitation, will also possibly be sorbed. A natural carpet of Hylocomium splendens showed a continuous uptake of Mn, Fe, and Ca from young to old tissues, whereas the increase in the concentrations of minor heavy metals was balanced by the dry matter decrease through decomposition. The developing and mature mor layer below the moss carpet had not enriched heavy metals above the concentrations of the old moss tissues.

Moss-Arthropod Associations

Moss-Arthropod Associations

Seasonal vartadoosln the nutrtent content of carpets ofAcrocladium cuspidatum(Hedw.)Lindb.

Abstract1. Seasonal variations in the percentaae of potassium, sodium, calcium and phosphorus in the current season's growth segment of Acrocladium cuspidatum at three different habitats are presented.2. The results show that the nutrient content of the moss carpet varies with time of year and also between habitats. For this reason comparisons between the nutrient content of moss carpets from different habitats are unlikely to be valid unless made at the same time of year or during comparable stages in the annual growth cycle of the species concerned.3. In conditions where the moss becomes inundated by natural waters having a high concentration of calcium ions, the moss accumulates calcium to abnormally high levels.4. Comparison of the nutrient content of the moss on open downland and under scrub shows a greater accumulation of potassium in the moss carpet of the scrub habitat. The monthly differences between the potassium contents from the two sites are positively correlated with the monthly rainfall as ...

Growth and Plant Nutrient Concentration in Hylocomium Proliferum (L.) Lindb. in Relation to Tree Canopy

This paper describes, part of an investigation in which an attempt has been made to elucidate the relationships between the growth of plants in a community and environmental factors. Here we shall deal only with the total annual growth of a plant community, and with the average concentrations of nutrients in the members of the community, within certain areas. Variations in size, in rate of growth and in nutritional status among individual plants have also been investigated, and in a further publication some relationships will be discussed between environmental factors and these variations, which are closely connected with the structure of the plant community. On account of their relatively simple structure the moss carpets often found in spruce forests were chosen for study. It was already known that these moss carpets present interesting ecological problems since STALFELT (1937 a) had observed that they obtain very little of their water requirements from the substratum. ROMELL (1939) has suggested that they obtain supplies of plant nutrients from the rain water Teachings of forest litter (needles and blueberry leaves). The material was collected from a spruce forest situated in eastern Uppland near the Baltic coast (590 52' lat. N.). The forest also contained a few pine and birch trees. Samples were taken towards the end of May and again towards the end of July from the closed community of the carpet of mosses. All samples were taken from patches where Hylocomium proliferum was dominant, and were selected from within an area 15 X 15 m, lying partly beneath the spruce crowns but also comprising a. small clearing among the trees. The field layer was mostly sparse and consisted of scattered Vaccinium inyrtillus and V. vitis idaea. The light intensities, as shown in Figs. 1 & 2,

Tree mycorrhiza: Chiefly Field Notes

Summary (a) The association with a mycorrhizal fungus commences, in the case of birch, while the seedling is very young, almost immediately after germination, and it exhibits no indication of injury, accruing from the fact that the whole of its root system immediately developes mycorrhiza. (b) The whole of the water absorbed by such a seedling must pass through the mantle. It contains dissolved colloid substances from the surrounding matrix. Water is readily absorbed and readily yielded by the mantle. (c) Roots of woodland trees, oak and beech, for example, creep over the surface of the soil, where there is an abundance of moss, and entering the lower layers of the moss carpet develop mycorrhiza. A chemotoxic action is apparently set up within the decaying moss. (d) There are indications that in cases of severe drought when much mycorrhiza has been destroyed, certain trees, notably, birches of all sizes, and hornbeam stools, lose vitality and become specially subject to attacks from microfungi such as Melanconis stilbostoma (Fr.) Tul. and Pseudovalsa lanciformis (Fr.) Ces. and de Not. (5). I am much indebted to Dr Somerville Hastings for the photographs of mycorrhiza in situ and to the Essex Field Club for the loan of two blocks.