Bryophyte Layer Research Articles

Decomposition of bryophyte material in two Dutch chalk grasslands

The decomposition of Calliergonella cuspidata material in litterbags was followed for a period of 2½ years on a north- and a south-facing chalk grassland in South Limburg (The Netherlands). Measurements were made of the dry weight and of the nitrogen, phosphorus and potassium content of the bryophyte material During the first month almost half of the N and P leached out. Later the total amount of N and P in the material increased again. Loss of dry weight was faster on the north-facing slope than on the south-facing slope. On the north-facing slope the biomass decreased by almost 50% during the observation period. In these experiments decomposition does not appear to depend on season. However, it may be expected that in the field leaching of nutrients from the bryophyte layer will happen mainly in summer and will supply significant amounts of nutrients to the system.

ARONIA MEDIK. IN THE NETHERLANDS II. ECOLOGY OF A. x PRUNIFOLIA (MARSH) REHD. IN THE DUTCH HAF DISTRICT

SUMMARY Aronia x prunifolia has run wild in a number of reed marsh nature reserves in the western part of The Netherlands. Both in open Sphagnum-dominated communities and below the canopy of woodland the bushes can maintain themselves and reproduce, although performance in open vegetation seems to be better. On gaining dominance in the vegetation both the herb and the bryophyte layer become strongly reduced. From laboratory experiments environmental circumstances as encountered in reed marshes do not seem to affect the germination of Aronia adversely. No significant relations could be detected between the composition of the vegation and the amounts of nutrients available in the ground water at sites where Aronia was present. Only high cover percentages of Aronia were correlated with elevated amounts of NH+4. The species may be found over a wide range from more or less oligotrophic conditions to slightly brackish and moderately eutrophic conditions. Factor analysis of the vegetation data produced no obvious relations with abiotic conditions. The density of Aronia and the structure of the vegetation dominated the first two factors, accounting for 47% of the variance in the data.

Vegetation and nutrient status of northern Michigan bogs and conifer swamps with a comparison to fens

The vegetation and shallow groundwater were sampled at six bog and four conifer swamp sites in northern Lower Michigan in the same manner as at five previously described fen sites.The bogs were characterized by well-developed field (low shrub, herb, and fern), and bryophyte layers and strongly acid waters (pH 3.8–4.3). The most prevalent field-layer plants were Chamaedaphne calyculata and Carex oligosperma while Sphagnum spp. dominated the bryophyte layer. The number of vascular plant species in the field layer was 14 ± 4 (mean ± SD). The conifer swamps were characterized by well-developed tree and field layers and circumneutral waters (pH 7.0–7.4). Thuja occidentalis strongly dominated the tree layer and Mitella nuda, Abies balsamea, and Maianthemum canadense were the most prevalent field layer plants. The number of vascular plant species in the field layer was 57 ± 7 (mean ± SD).The bogs, conifer swamps, and fens are related developmentally (successionally) but differ strongly in floristics, species density, proportion of evergreen species, role of symbiotic nitrogen fixing species, role of Sphagnum spp., and water chemistry. Although these wetland types are often grouped together under the term "bog" or are considered successional stages of "bog," they differ markedly in vegetation and water chemistry, and are best considered as separate but related wetland types.

Some Microclimatic Characteristics of Habitats of Endemic and Disjunct Bryophytes in the Southern Blue Ridge

Precipitation and maximum and minimum tem- peratures (air and bryophyte layer) were measured for six- month periods for two and one-half years in the gorge region of the southern Blue Ridge notable for its rich bryophytic flora with many endemics and disLunct species with af- finities. Stations were maintained both in and outside the gorges. The region receives high precipitation (85-100 inches per year) which is very reliable from year to year. There is some indication that the highest rainfall is at the heads of the gorges near the top of the lower escarpment (2,500-3,000 feet elevation). Both air and bryophyte temperatures in the gorges were more moderate than those outside. High tem- peratures never occurred within the gorges, and the gorge bryophyte habitats never dried out as did the bryophyte habitats on the ridges and in the valleys below. This mild, wet mountain environment is unique in eastern North America. It is postulated that the endemic and disjunct tropical bryo- phytes remained in the gorges in relatively mild and moist microenvironments during the whole of the Pleistocene. The southern Appalachian Mountains have provided refugia for many disjunct and endemic species of plants through the Pleistocene and into the present. The number of bryophytes in this group of species is particularly high (Sharp 1937, 1939, 1941; Anderson 1954; Iwatsuki 1958). An especially high concentration of these dis- juncts and endemics occurs in the extreme southern part of the Blue Ridge escarpment where it faces south along the North Carolina- South Carolina-Georgia boundaries. Here there is a prominent south- facing embayment in the Blue Ridge divide between the Atlantic and Mississippi River drainages (Fig. 1). In this Atlantic slope embayment, about 28 miles wide from east to west and up to nine or ten miles deep from north to south, are the head-waters of an unusual concentration of small rivers having a high annual dis- charge rate. The rivers are, from east to west, the Eastatoe, Toxaway, Horsepasture, Thompson. Whitewater, and Chattooga.

Bark Factors Affecting the Distribution of Corticolous Bryophytic Communities

The intensive study of the composition and ecology of bryophytic communities has been markedly lacking in America compared to the great amount of bryocoenological research which has been carried on by Europeans. This lack, perhaps, may be explained by the fact that we do not yet know much about the structure and environment of the larger forest communities which, as a result, occupy the greater part of the American ecologist's time and interest. However, the forest community is found almost always to be a phytocoenosis composed of two or more synusiae. It is not possible to understand truly the phytocoenosis as a whole unless each synusia has been thoroughly studied. It is impossible to isolate any synusia from its phytocoenosis and to treat it as a separate association (Gleason, 1936). On the other hand, each synusia, no matter how small or obscure, has some effect on the development and structure of the whole phytocoenosis and, therefore, intensive studies of the several synusiae are the foundation-stones in any research which would truly portray the life and composition of a complex forest community. In the virgin hardwood forests of the Great Smoky Mountains of eastern Tennessee, the bryophytic synusia not only occurs on rocks, rotting logs, and occasionally soil, but also extends some distance up the trunks of the large trees. The bryophyte layer in all of these types of habitats is made up of readily discernable communities or (Sirgo, 1935) dominated by one or two species. The present paper is confined to a study of only those bryophytic unions on the trunks of living trees. It is an attempt to learn the effect of various bark factors on the distribution of these unions on the trunks of several species of trees of the dominant synusia. Definite knowledge of the ecology of these bryophytic micro-communities should lead to a better understanding of this synusia and its place in the virgin forest phytocoenosis.