Henry J. Oosting

Ecological processes and vegetation of the maritime strand in the Southeastern United States

The sand strands bordering oceans and large lakes have attracted the interest of ecologists and others in many parts of the world for a long time. Studies have been made of their origin, of dune formation, of the plants and animals and their zonation and special characteristics, the factors of strands and their limiting or controlling effects on the vegetation. There is, as a result, a considerable body of literature which would have to be brought together to summarize all that is known about strands, and assembling it and getting it published would be a tremendous undertaking. However, the sand strands of the southeastern United States have a certain unity regarding origin, physiographic features and vegetation, and have been studied more or tess intensively throughout. A review restricted to them should be of value as a summary of a fairly large segment of the knowledge of sand strands and their vegetation. Sand strands occur discontinuously along the entire Atlantic Coast from southern New England to the tip of Florida. From here they continue as a feature of the irregularly spaced keys which occur in a long curve southwestward to the Dry Tortugas. The west coast of Florida has little sand strand, but northwest Florida and westward along much of the Gulf Coast is again discontinuously bordered by strand. Much of this sand strand is on the mainland, but as often as not it appears on offshore banks or islands which are separated from the mainland by a usually narrow sound. Sometimes, however, the banks lie ten or 12 miles offshore. No attempt will be made to review the details of sometimes conflicting opinion on the origin of banks nor the voluminous literature on sand dune formation. Comprehensive treatments of the subject are available (28, et al.) as are certain more recent ideas applying to the area in par-

Water and Light in Relation to Pine Reproduction

Seedlings of certain species of pine often become established along the margins of forests (fig. 1) although they rarely become established within the forests. Seedlings growing at the margin must compete for water and minerals with the roots of trees comprising the stand but they are exposed to light of much higher intensity than if they were growing in the interior of the stand. These circumstances provide an opportunity to study the relative importance of light and water with respect to the establishment of pine seedlings. It is well known that in the Piedmont pine (Pinus taeda L., P. echinata Mill., P. virginiana Mill.) usually fails to reproduce under either pine or hardwood stands while many species of hardwoods grow under both pines and hardwoods. It was generally assumed at one time that failure of tree seedlings to survive under a forest canopy was the result of lack of light, and species failing to survive under such conditions were described as shade intolerant. Results of certain trenched-plot experiments performed during the past 40 years have been interpreted, however, as indicating that lack of water is more important than shade in the failure of seedlings to survive. It has been observed that if small areas under forest stands are protected from the root competition of the surrounding vegetation by trenching, seedlings of intolerant species sometimes become established. The only demonstrable environmental difference between such trenched plots and adjacent untrenched control plots is that the trenched plots usually contain more available soil moisture during periods of drought. It has therefore been argued that lack of available soil moisture rather than lack of light is responsible for the failure of intolerant species, such as many species of pine, to become established under a forest canopy. It seemed probable to the writers that the supply of water is as low in the marginal zone where pine seedlings survive as it is within the forest where they fail to survive. If this. were true it would suggest that pine seedlings are able to become established in the margin of a forest because they are exposed to higher light intensity than within the stand. In other words, possibly pine seedlings are more drought resistant in the open than in the shade. Therefore, it was decided to measure the moisture content of the soil along a transect extending from within the forest across the marginal fringe of pines into an adjacent open field to learn whether significant differences exist.

Plant Succession on Granite Rock in Eastern North Carolina

1. The transition between Piedmont and Coastal Plain provinces, called the fall line, has numerous outcrops of granitic rock scattered along its length throughout North Carolina, South Carolina, and Georgia. 2. Rocks are unfavorable habitats for plant colonization and these are particularly so because of the long dry summers with high temperatures. Especially adapted plants, including several rock endemics, grow here in spite of the extreme conditions. Succession on the North Carolina rocks follows two major lines, originating (1) anywhere on the rock surface and (2) in depressions. The depressions may be dry, moist, or pools. 3. The bare rock surface is invaded by Grimmia or crustose lichens. The latter do not contribute to further succession. Grimmia forms mats which are successively invaded by stages dominated by (1) Cladonia-Selaginella, (2) Polytrichum, (3) Andropogon, (4) conifers. 4. Dry depressions retain little water and are floored with a clayey soil. The soil is too thin to support species which lead to a successional series and too deep to permit the beginnings of a normal rock succession. They support scattered succulents like Talinum and Portulaca, and sometimes dry, fibrous individuals like Fimbristylis and Stenophyllus. 5. Damp depressions represent the best development on the rocks. The stages are essentially like those on the rock surface but the additional moisture results in richer and more rapid growth, with hardwoods appearing in the later stages. 6. Pools are usually intermittent but regularly support marsh species. The margins have the normal rock series spreading from the pool and Cyperaceae predominate among the soil builders in the water or mud. Late stages are dominated first by mesophytic shrubs and later by hardwoods. 7. Margins are irregular. Where seepage occurs there may be small boggy areas dominated by Sphagnum. Dry margins are usually fixed and rarely show evidence of migration upon the rocks. Shaded margins, protected from washing, produce a distinctive pioneer community upon the debris which accumulates. Entodon is the dominant. 8. The exposures must owe their origin to factors which caused the fall line. Considering the time since this line was formed and the rate of plant succession, it is proposed that the rocks were once entirely covered although probably not so richly forested as the surrounding country. The activities of man resulted in repeated fires and erosion which again uncovered the rock, and today drought, wind-throw, and fire undoubtedly maintain them in their semi-barren condition.

Virgin Hemlock Forest Segregates in the Joyce Kilmer Memorial Forest of Western North Carolina

1. Two segregates can be readily distinguished in the virgin hemlock forest which occupies the flats and lower slopes in the Joyce Kilmer Memorial, a part of the Nantahala National Forest in western North Carolina. The first of these types, restricted to the flats and lowermost parts of the slopes along the streams, is characterized by a dense undergrowth of Rhododendron and a sparse herb layer. The other type, occurring higher up on the slopes, has a very open shrub stratum but a fairly dense and diversified herb layer. 2. Tsuga canadensis is the dominant tree species in both types, with Fagus grandifolia, Tilia americana, Betula lenta, Fraxinus pennsylvanica, and Halesia carolina as almost constant associates. Liriodendron tulipifera and Acer saccharum are more abundant in the Herb type, while Betula lutea is restricted to the Rhododendron type. The total tree density is lower, but the BA is greater in the latter type (60% more). Hemlock reproduction is about equivalent at the seedling stage, but saplings are considerably less numerous in the Rhododendron type. Age-diameter relationships in hemlock indicate that the species is able to stand suppression relatively well but not so long as some other climax conifers. 3. Herbs which are constants for both types include Mitchella repens and Viola rotundifolia, observed in every stand, and Tiarella cordifolia, Laportea canadensis, Trillium sessile, Dryopteris spinulosa var. intermedia, and Oxalis montana, with lower presence values. In spite of their general distribution, these are the important herbs of the Rhododendron type. The characteristic herbs of the Herb type are therefore those numerous additional species which appear. Among these, Carex plantaginea, Medeola virginiana, Adiantum pedatum, and Polygonatum pubescens are exclusive and constant. 4. The soils are very similar under both types. They are sandy loams with an A-C profile, good incorporation of organic matter, and good structure. The better growth of dominant components in the Rhododendron type is attributed to better soil-water relations, owing to topography and possibly to microclimatic differences. 5. A comparison is made with the two types (Rhododendron and Polycodium) of virgin hemlock forest found in Ravenels Woods. Differences in species composition and in growth of hemlock lead to the conclusion that there are at least four types of hemlock cove forest, which are believed to be relic association-segregates of Brauns Tertiary Mesophytic Climax. The considerably greater BA of hemlock in Ravenels Woods and the differences in associated species are attributed to differences in general climate (higher precipitation and lower temperature). 6. The sampling method used in this study is discussed. It consists of a strip random sampling in which each strip is in turn systematically subsampled at a 50% intensity.

Ecological Composition of Pulpwood Forests in Northwestern Maine

Within the State of Maine are few, if any, relicts of the original northeastern coniferous forest. Extensive areas of forest land are covered with second-growth forest, the main source of pulpwood for the local papermills. Silvicultural considerations have had little weight in determining the management of these forests in the past. Demand for and accessibility of timber have regulated the extent of each years cut. Modern methods of operation, particularly clear-cutting, suggest the future value and usefulness of silvical and ecological information pertinent to tlhe nature of these second-growth forest commuinities. Sound silvicultural practices can be initiated and applied successfully only as ecological and silvical information accumulates. The Swain and Reed Lumber Company of Roxbury, Maine, provided special facilities in the summer of 1940 which made possible an ecological survey of the pulpwood forests in the general vicinity of the watershed of Swift River, a tributary of the Androscoggin River, located in northern Oxford County, Maine. After reconnaissance, several stands were selected as representative of the pulpwood forests of the region, and these were studied intensively on a phytosociological basis. This is a report on the findings of the study with conclusions drawn from the data obtained.