Dune Vegetation Research Articles

Internal Geometry and Origin of Vegetated Coastal Sand Dunes

ABSTRACT Frequency distributions of dip angles, azimuths, and elevations of 209 eolian cross-bed sets from Monomoy Island, Cape Cod, Massachusetts, were analyzed and compared with similar data from the coastal sand dunes of Mustang Island, Texas (McBride and Hayes, 1963), Sapelo Island, Georgia (Land, 1964), Praia de Leste, Brazil (Bigarella and others, 1969), and Israel (Yaalon and Laronne, 1971). These analyses from five widely scattered localities show that vegetated coastal sand dunes have a distinctive internal dune geometry. At all five locations, azimuth distributions correlate with the prevailing winds, either directly or with a bimodal azimuth distribution bisected by the prevailing wind vectors. Also, the dip distributions center around two modes, 11°-15° and 25°-35°. The smaller of the two modes is present at each of the five locations; the dip distribution is bimodal at three (and perhaps four) of the locations. Whereas the smaller dip mode tends to have a unimodal azimuth distribution, the larger dip modes (25°-35°) have bimodal azimuth distributions. It is suggested that the high-angle dips form as pyramidal wind shadow dunes via slip-face accretion behind large vegetation hummocks, which results in the distinct bimodal azimuth distribution. For the Monomoy dunes, the cross-bed dip angles are mostly low (x = 11.2°) in all azimuth directions, at all dune elevations, on all sides of the dunes, and at all sample localities. Pyramidal wind shadows are rare on Monomoy. The combined azimuths show a statistically significant correlation with the three prevailing northwest, southwest, and southeast wind directions rather than with the dominant northeast storm winds. This association is valid for cross-bed sets at any dune elevation. The azimuth distribution varies appreciably among sample localities, with the cross-bed sets tending to dip seaward on all sides (i.e., away from the center of the island). Biweekly field observations and numerous aerial photographs of Monomoy coastal dunes made during a three-year period suggest that the Monomoy internal dune geometry is closely dependent on growth of dune vegetation, especially Marram grass (Ammophila arenaria). The grasses act as baffles, trapping sand moved by the prevailing winds, which results in low-angle cross-bed sets (i.e., lower dip mode) formed by the vertical accumulation of sand behind vegetation hummocks on the gently undulatory, nearly horizontal upper surface of the dunes. Thus, vegetation plays a distinctive role in the formation and internal geometry of vegetated coastal sand dunes.

Experiments On Dispersal, Late-Larval Predation, and Pupation in the Cinnabar Moth (Tyria Jacobaeae L.) With a Radioactive Label (192Ir)

A number of experiments is described from which it is concluded that a predating ant, Lasius alienus Forst, locally has a very important influence on the population dynamics of the Cinnabar Moth. Moreover, Tyria appears to be absent in some of the dry dune vegetations and it is suggested that this is due to the presence of Lasius in high densities in those areas. The distribution pattern of pupae in the field could be explained by preference for certain pupation sites. The applied technique of labelling, with an external radioactive mark, proved satisfactory.

Computer analysis of sand dune vegetation in norfolk, England, and its implications for conservation

An account is given of the application of a new computer analysis technique to the primary survey of dune vegetation in North Norfolk, England. Quadrat groupings are produced by this analysis and their distribution and significance is discussed, together with a description of their flora. The origins and inter-relationships of these groups is suggested and some consideration is given to their implications in sand dune conservation.

Computer analysis of sand dune vegetation in norfolk, England, and its implications for conservation

Computer analysis of sand dune vegetation in norfolk, England, and its implications for conservation

Vegetation studies in the Simpson Desert, N.T.

A transect of contiguous quadrats was used to study the sand dune vegetation of a small area of the Simpson Desert. The study was carried out shortly after a period of abundant precipitation which resulted in optimum winter growth conditions for both ephemeral and perennial species. The frequency data of 54 species were analysed by computer programmes that grouped the 729 quadrats according to similarity of species composition. Seven habitat types could be distinguished: swale hard clayey sand, lower slope clayey sand, mid-slope clayey sand, mid-slope Triodia mound, upper slope loose sand, steep slope loose sand, and crest mobile sand. Rather than sharply defined plant communities corresponding to these habitat types, the species groupings tended to form a continuum from swale to crest. Additional description of the vegetation is provided by studies of two permanent plots and of the size class distributions of eight shrub and tree species. An appendix listing all species collected during the study period is included.

Variation in Fixed Dune Vegetation at Newborough Warren, Anglesey

Although much work has been reported on the vegetation of sand dunes, there is little information on point to point variation within the main vegetation types. The observations reported here are a contribution to an understanding of variation in one type of fixed dune complex. They were made at Newborough Warren National Reserve on the west coast of Anglesey (Grid Ref. SH 4065), an extensive dune system the main features of which have been described by Ranwell (1958, 1959, 1960). The area selected for the present study was a portion 320 x 100 m lying towards the landward site of the Warren, within the part mapped by Ranwell (1958) as 'closed low dune and Salix slack associes'. Physiognomically, the area was predominantly a pasture community dominated by Festuca rubra, but included patches of relict dune with Ammophila arenaria.

The amounts of drainage water and solutes from lysimeters planted with either oak, pine or natural dune vegetation, or without any vegetation cover

The amounts of drainage water and solutes from lysimeters planted with either oak, pine or natural dune vegetation, or without any vegetation cover

DUTCH STUDIES ON COASTAL SAND DUNE VEGETATION, ESPECIALLY IN THE DELTA REGION

A short history of Dutch dune vegetation research is presented as an introduction to the present research in the Delta region. Remarkably enough the main results of dune research were presented as dissertations. The classics F. Holkema, L. Vuyck, J. Jeswiet, J. Bijhouwer and W. van Dieren are mentioned. The broadening basis is marked by the outstanding thesis of V. Westhoff, the first all-round phytosociological and ecological study of Dutch dunes. New ideas from this work are mentioned. The work of some pupils and collaborators of Westhoff is discussed. The new approach consists of concentration of the research in the Delta region, development of new ideas and establishment of field stations in the dunes. The scientific value of the Delta dunes is treated. Especially the Voorne dunes are considered as outstanding. Some future changes that threaten the area, are mentioned. The organisation of the Delta dune research is discussed, especially the work of a special Research Group, operating from the Biological Station “Weevers’ Duin” at Voorne. The current botanical problems are treated. It is stressed that they are placed in the framework of the ecological relation theory of C. G. van Leeuwen, which is a new, highly stimulating, system-theoretical approach. This relation theory is introduced and commented. Four environmental types are treated, the uniform, the variegated, the ecotone and the ecocline environment. The dune environment is discussed as a system of gradients. The main gradients are mentioned: the zonation of dry dunes, zonation of slacks, gradient from sea dunes towards estuaries, the complex salt-fresh gradient, the complex wet-dry gradient, and the complex gradient in the human and animal factors. The dune vegetation is treated as a continuum. 24 vegetational series are mentioned. A series consists of closely related communities, forming a continuum. Some problems concerning selection and sampling are discussed. The controversy between Anglo-American and Zurich-Montpellier scholars is elucidated on some points. The Braun-Blanquet scale of combined estimation is advocated. The study of pattern and instability in vegetation research is emphasized. Some methods in structure analysis are mentioned. Recent problems in vegetation systematics are discussed. The application of methods in the Delta research is consequently mentioned. An extensive bibliography, covering important botanical work in Dutch dunes, ends the paper.

Geographic reconnaissance of Western Australian Seashore vegetation

Field study of 32 sites along the Western Australian coast showed that pioneer vegetation includes 110 species in 40 angiosperm families. Less than 25 % are exotic, only 10 % are endemic, and the bulk are shared with the interior or with other coasts of Australia. Regional ranges and microdistributions, described from herbarium records and 50 sample transects, are diverse. Although unique in detail, species distributions show broadly coherent relationships between geographic origins and present habitat patterns. Sheltered intertidal shores have two discrete types of land vegetation. Mangroves, sea-dispersed outliers of a richer Indo-Malayan assemblage, form extensive estuarine forests on the tropical coast, where tidal ranges are large, and a few stands of one species occur along the temperate coast. Low-growing chenopods and similar halophytes, with major populations in saline interior basins, are scattered discontinuously along the coast in shallowly flooded tidal marshes. They are subject to no apparent climatic control within the region. Rocky coasts are even more disjunct and also lack any unique, autochthonous vegetation. Wet pockets in the spray zone bear ordinary salt marsh plants while dry rock shores and outcrops in the dunes have vegetation differing mainly quantitatively from neighboring sand areas. Open beaches and dunes offer the most extensive coastal habitats and bear the most complex vegetation. Species groups derived from different geographic sources are loosely segregated by zones parallel to the shore. Toward the rear of the active dunes, some plants are simply outrunners from the stabilized inland sand vegetation : these are important dune pioneers in the drier sectors. Generally, the active dune zone is dominated by species peculiar to it, some endemic but mostly shared with temperate coasts east of the study region. All are adapted to tolerate salt spray, sand blast, and other special habitat conditions. Sclerophylions shrubs predominate, grading into small trees on parts of the moister, tem~erate coasts. Prostrate succulents, rhizomatous grasses and sedges, and other types of evergreen perennials are minor components. The active dune vegetation is floristically richer and more regionally diversified towards its inner limits, the few species native to the outer dunes having comparatively wide coastwise ranges. On the outer faces of the foredunes and on the storm beach, the otherwise almost purely Australian sand vegetation is joined by exotics. Sea-dispersed paleotropical and pantropical beach vines, grasses, and other low-growing plants range along the north coast and a few penetrate beyond the tropic. A different, primarily inland group of old immigrants may have arrived indirectly via the arid interior to provide the extreme outpost vegetation of the drier coasts. Along the moister, temperate coasts, a belt seaward of the native dune vegetation is occupied by recently naturalized annuals and other low-growing herbs from temperate African and European beaches.Except close to roads and settlements, little recent modification of the coastal vegetation is evident. Some blowouts, particularly on the drier margin of the tem- perate region, may stem from dune burning, but generally the plant cover regenerates rapidly after fire.

Ecological studies on the vegetation of coastal sand bars. : II. Succession in vegetation and developmental processes of dunes.

Ecological studies on the vegetation of coastal sand bars. : II. Succession in vegetation and developmental processes of dunes.

KRITISCHE BEMERKUNGEN UND VORSCHLÄGE ZUR QUANTITATIVEN VEGETATIONSANALYSE

Starting from the general principles of the Zürich-Montpellier school for the description of vegetation by means of field estimations of abundance, cover etc., the authors criticise the scales adopted by most workers, and some of their interpretations. The following analytical characters of vegetation, and methods of estimation, are discussed: height (layering, recognition of synusiae), peripheral and internal cover, density, abundance, sociability, vitality, fertility, and phenological stage of taxa or layers. The main weaknesses of the usual scales for estimation of these characters (see list of references) are considered to be: 1. The use of combined scales for estimation of abundance and cover, and of vitality and fertility. 2. The lack of equivalence in the range of values for each class in most of the existing scales. 3. The limited range of some of the scales, and the absence of provision for more detailed estimations. 4. The inexact definition of degrees of abundance and sociability in the Braun-Blanquet scale. 5. The confusion about the concept of density. A number of proposals is made for the use of scales with closer intervals, based on decimal, logarithmic or other systems. These leave less room for personal interpretation, and are more suitable for subsequent calculations and autecological studies. A method of reducing errors by carrying out certain estimations in two successive steps is suggested, e.g. by estimating peripheral and internal percentage cover (Fig. 1) separately and multiplying both values to obtain real cover. The proposed scales have been tested in routine field work by the authors and other workers in a wide range of vegetation types. An example is given of an analysis of Dutch coastal sand dune vegetation in which some of the proposed scales have been applied. The authors hope that their proposals for a more accurate description of vegetation will help to consolidate the basic principles underlying the Braun-Blanquet system of classification.

The Ecology of Uniola paniculata L. in the Dune‐Strand Habitat of North Carolina

INTRODUCTION Sinee the turn of the century interest in salnd luItes and their vegetation has been centered about four ia~joi areas: the vegetation and flora, the comnlarviative anatomny of some of the dune species, the phvsiography of the dunes, and environmental factors hi relation to the vegetation. A significant body of wNork seeiiis to have been triggered by a classic paper MI t\o in elach area. One such study was by Kearney (1900) oii the vegetation of Ocracoke Island. Sevenrtl papei s followed dealing with strand and dune v-egetatioii iii Ahlabaia (Mohr 1901), Mississippi and LoliSiana ('Lloyd & Tracy 1901), Delaware (Snow 1902), NewN Jersey (Harshberger 1900), South Carolitia ((oker 1905), Florida (Millspaugh 1907), Maryland (Shieve 1910), and California (Raimaley 1918), to cite justa few. In these early papers habitat deS(Ii1)tiofls were coupled with species lists usually with soMIW .8ttelIi)t to group the plants into conmmunities o' it least by Zones. Concurrent with these early e(tifoitt, to (describe the composition and structure of tle (lille-strand vegetation was a series of studies of the ;il a)to1ii of various dune plants attempting to ililt(elI)et tbe iole of the special dune environment in Mi dini i n e t eita in xeronmorphic, features. Chrysler (1904), tble prolifie Harshberger (190S, 1909) and P'urier (19:-,6) typify this approach to the problem of (lulle vegetation versus dune environment. TI'he pliysiographbi ap)proach to the problems of dUleS and their vegetation seems; to have started with ('owles' remiiarkable work on the Lalke Michigan dunes (1899). Other examples of this approach are OlssonSeffer (1909), Salisbury (1922), and more recently Olson (1958). In the years since World War II there has been a great blossonming of interest in Great Britain in this physiographic aspect with such studies as Ranwell (1958, 1959), Willis & Yeiniii (1961), Wilson (1960) and mtiany others. An example of the environmental approach is the group of papers dealing with salt spray, its nature and effects starting with Wells & Shunk (1938), and later Oosting & Billings (1942), the excellent a8ward-winning research on the salt spray community by Boyce (1954), and the studies of Tsuda (1961) in Japan. Only some of the highlights of dune research have been cited here and grouped to indicate the more obvious trends. Conspicuously missing from this rather impressive body of research have been studies of individual components of the dune vegetation and their relationship to the whole. A few papers dealing with certain aspects of the ecology of Ammophila arenaria (L.) Link in Great Britain have been published by Greig-Smith, Gemniell & Giimiinghami (1947), Gemmnell, Greig-Smith & Gimingham (1953), and Greig-Sinith (1961) and in this country a more comprehensive study of the closely related Am mo)hila )reiriligulata Fern. (Laing 1958). These studies apparently represent the current level of research on autecology of the dune-strand flora, a rather surprising state of affairs considering the accessibility of the dunes of this country and the conspicuous

OBSERVATIONS ON NATURAL CLONES OF TRIFOLIUM REPENS L.

SummaryAn attempt was made to map the distributions of some of the individual clones of Trifolium repens in an area of about 600 sq. yd of fixed dune vegetation. The field observations were checked in culture by morphological examination and by cross‐pollination. Most of the clones were limited to small patches of land (up to 6 yd across) and in relation to the vigorous vegetative spread of the species this might indicate a maximum age of genotype of about 20 years. However, one clone was found to be distributed in five discrete patches, each of small size but collectively giving a discontinuous spread of more than 20 yd. The five patches were limited to a narrow ecological zone suggesting specialization in ecological tolerance. The presence of a second genotype which occurred in two patches ecologically similar to one another but contrasting strongly with those of the first genotype indicated differentiation of ecological tolerance between genotypes within the population. These results are contrasted with those published earlier for Festuca. It is pointed out that if vegetative spread is limited by ecological factors the size of the area occupied by a clone cannot be regarded as a function of age, and that consequently the Trifolium genotypes observed might be just as ancient as those of Festuca.

Destruction of indigenous heath vegetaion in Victorian sea-bird colonies

The sclerophyllous heath and scrub which occupies undisturbed granite coasts is essentially a vegetation of infertile, acid soils deficient in available phosphorus and nitrogen and sometimes in potassium and certain microelements. In sea-bird colonies soil reaction and fertility are altered by the deposition of guano, which is rich in phosphorus, nitrogen, and potassium, and the indigenous heath and scrub are destroyed. Mechanical disturbance and chemical changes hinder the accumulation of surface peat. Toxicity of guano in summer leads to a specialized flora and limits the total number of species. Comparison of floristic data from sea-bird islands and nearby control areas with no nesting sea-birds illustrates the widely divergent nature of the flora in the two habitats. Heath species are almost non-existent in the rookeries, and sclerophylls, switch plants, and woody plants much rarer than in the control areas. Conversely, succulents, annuals, biennials, and aliens are considerably more abundant in the rookeries. Man is the primary introducer of alien plants; but gulls are also important in this respect, and all colonial sea-birds make the habitat more suitable for invasion by ruderals in the autumn when mechanical disturbance ceases and guano becomes diluted to beneficial concentrations. Where man has access to the rookeries large areas may become dominated by introduced weeds which are seldom able to establish themselves on unmodified heath soils. The vegetation of sand dunes (to which few nutrients are being added and from which few have been leached) lies between that of the leached soils of heaths and the guano-rich soils of rookeries overlying granite in all the above characters, in spite of the markedly different physical nature of the substratum, and contains a higher proportion of creeping plants than either. Guano and sea salt have parallel effects on vegetation, and the presence of sea-birds leads to a broadening of the coastal belt of salt-resistant plants and elimination of the indigenous, more inland type of flora. Pteridium esculentum and Leptospermum laevigatum are important species in the transition zone between either saline or guano-rich habitats and the surrounding heath.

Studies on European calcareous fixed dune communities

Along the European coast from the Bay of Biscay to the Danish waters there is behind the mobile sand dunes dominated by vigorous Ammophila mostly a zone in which the dunes are green. In these more consolidated dunes Ammophila will be less abundant and the ground covered by bryophytes and, mostly low, herbaceous plants. This community was by WARMING (1909, pp. 87-88, 121-125) termed greensward dune and in part moss dune. British workers call it calcareous fixed dune vegetation. Farther from the coast, where the wind does not convey appreciable amounts of basic sand particles, a leaching of the stabilized dune soil may result in the development of a grey dune, i.e. a vegetation especially characterized by Cladonia and other acidophilous species. In westernmost Europe, e.g. in the British Isles, where the sand contains much lime, calcareous fixed dunes play an important part, while the grey dune (Corynephorus-Cladina) is often absent. On the other hand calcareous fixed dune communities in many Danish dune areas, will only occur as fragments or untypically, while the grey dune will cover large areas. At the same time as the two dune vegetations, which ecologically tend in opposite directions and which for the sake of convenience we shall term the green and the grey dune vegetation, in each direction in Europe come to hold a more and more modest position, the contents of species of the two types will be changed. There will partly be a thinning-out among their most characteristic species and partly a mixture of their species. Important contributions to a sociological account of the calcareous dune communi ties have been given by HOCQUETTE (1927) and BRAUN-BLANQUET & DE LEEUW (1936). There the association Tortuleto-Phleetum arenarii is mentioned, which has later been investigated in detail both in Holland(WESTHOFF 1947) and West Germany (TOXEN 1937). According to WESTHOFF the main occurrence of the Tortuleto-Phleetum is in Southwestern Europe. Its period of growth mainly falls in the winter half-year; therefore it selects in the north the regions mildest in winter. Along the west coast of Jutland there is just a narrow zone with relatively high winter temperatures, which in connexion with the content of lime in the sand enables occurrences of communities closely related to the Tortuleto-Phleetum. Our ecological understanding of the zonation of the vegetation in dune areas is to a great extent due to British investigations, first of all by SALISBURY (1925), later supplefmented by MOORE (1931), HEPBURN (1944), and GIMINGHAM, GEMMEL & GREIG SMITH (1948). From Danish quarters there are some investigations of belt transects in Jutland, on Lxs0, and in Zealand (BOCHER 1941, 1945 pp. 78-79, 101-102). The Danish transects show the occurrence of the green dune vegetation between the white and the grey one. It requires pH values about the neutral point or higher. The electrical conductivity of the soil (K 200 X 106; for acid soils corrected for hydrogen ions; (K 200 K 200(H+)) X 106) shows values above 50, while in the typical grey dune it drops to

Soil conditions of the maritime and dune vegetation is the vicinity of Kanazawa, Ishikawa Prefecture.

Soil conditions of the maritime and dune vegetation is the vicinity of Kanazawa, Ishikawa Prefecture.

The Vegetation of the Sand Dunes of the Camel Estuary, North Cornwall

A considerable number of papers have already appeared, describing the vegetation occurring on sand dunes in the British Isles, and the pioneer stages in the colonization of mobile dunes seem to conform generally to a well-marked type. When, however, the sand has become partially fixed, a large number of non-maritime species are able to gain a foothold, and in this stage the composition of the vegetation as it passes into 'fixed dune' shows a great variety in the areas which have been studied. The species occurring must clearly depend to a large extent on the proximity of seed parents and also on the power of a particular species to survive in sand which is still partially mobile. The ultimate vegetation must also be influenced by the nature of the sand. The front dunes in all areas which have been studied seem to be generally alkaline, largely as a result of their salt content. Where the sand contains little CaCO3, however, the older dunes tend to become acid and the subsequent vegetation is accordingly influenced. The chief interest in the present study lies in the fact that the sand, even in the oldest and most fixed portions of the area, is always highly calcareous and contains at least 50% CaCO3, with a pH exceeding 8-0. The other feature of interest about these Cornish dunes is that they include a well-defined area of dunes which have recently been formed and whose age is known with some accuracy. These dunes show the early stages of colonization very clearly. It will be seen from the lists of species included in this paper that this area is no exception in supporting a very varied flora, including some species which do not seem to have been recorded from similar habitats elsewhere. An analysis of the vegetation occurring on more or less fixed dunes in a number of localities in the British Isles and Ireland has been included at the end of this paper. This list, besides showing something of the great variety of the flora, shows that a number of non-maritime species occur in this type of habitat with considerable regularity. It had been hoped to include in this paper studies of the more extensive sand-dune areas along the north Cornish coast, at Perranporth and elsewhere, but transport difficulties have unfortunately made this impossible. The area studied is situated on the east side of the Camel estuary on the coast of north Cornwall, opposite the little port of Padstow (see Fig. 1). The front of the dunes extends from a point just south of Brea Hill to the village of Rock, a distance of about 2Ikm. Behind this is a large area of fixed dune and blown sand, which extends in some places for a distance of over I km. from the water's edge and reaches as far north as Daymer Bay. The blown sand covers, usually thickly, an area of slate or diabase, and much of it lies over 30 m. above the sea. The vegetation of the whole blown-sand area is very similar to that on the lower lying fixed dunes nearer the sea, which were more intensively studied for the detailed lists in this paper. Much of the blown-sand area is occupied by the St Enodoc Golf Course, with the result that the vegetation on the fairways and greens has been considerably modified.

Notes on the Forest Biology of Horn Island, Mississippi

Four islands, 8 to 13 miles f rom the mainland, separate the Mississippi coast from the Gulf of Mexico. These include Cat Island on the west, and Ship Island, Horn Island, and Petit Bois on the east. Horn Island is in Jackson County; the west end of the island, the longest one in the group, is 13 miles southeast of Biloxi, Mississippi, at approximately 300 13' N. and 88? 40' WV. The climate of Horn Island is mild; records available at Pascagoula, Mississippi, some 12 miles northeast, show a mean winter temperature of 52.9? F. and a mean summer temperature of 80.70 F. The highest temperature recorded at Pascagoula is 1010 F. and the lowest 160 F. The mean annual precipitation is about 58 inches, most of which falls during the warmer part of the year. Geologists believe that these coastal islands were at one time a part of the mainland, and that the entire Gulf coast is slowly sinking (McGee, 1891). The islands are separated from the mainland by a depression, which has become filled by the waters of the Gulf of Mexico, forming the Mississippi Sound. Soil samples taken at different places on Horn Island seem to substantiate this hypothesis, for in a number of places the soil is quite similar to that of the mainland. The nature of the bottom of the Sound, which is composed of hard clay, and the shallowness of the Sound, further substantiate this hypothesis of the origin of the islands and the sinking of the coast. Horn Island is 13 miles long and threefourths of a mile wide at its widest part. At the west end of the island is a sand bar approximately 2 miles long and at the east end another bar about one-half mile long (fig. 1). Between these sand bars the island is heavily wooded with slash pine.' Along the south (or Gulf) and north (or Sound) coasts, dune and beach sands form the major soils. In the interior of the island, are many depressions, some of which are inhabited by dune vegetation and others by marsh plants. In both conditions, Plummer fine sand predominates. This soil consists of fine, dark gray sand underlain by fine, white, water-soaked sand. This poorly drained soil supports scattered grass, which affords grazing for a hundred or more cattle. The sand bars at each end of the island are practically barren, the vegetation consisting mainly of widely scattered tufts of grass, with small patches of Croton and Hydrocotyle. Towards the interior of the island the ground rises to about 10 feet above sea level, and slash pine, together with an undergrowth of shrubs constitutes the major vegetation. On a few scattered patches on old dunes prickly pear occurs. At both the west and the east ends of the island sand dunes much higher than in the interior have buried tall pine trees to their crowns. Slash pine, the principal forest species, forms pure stands of various ages; the oldest trees measure 26 inches in diameter at breast height (d.b.h.) and are about 170 years old. Trees 12 inches or more d.b.h. are 90 to 100 years old, and those 8 to 10 inches d.b.h. probably are 40 to 50 years old. The reproduction ranges

Ecological Aspects of Transpiration. II. Pike's Peak and Santa Barbara Regions: Edaphic and Climatic Aspects

1. Radiant energy seems to be the most important factor between sun and shade habitats. Shade vegetation does not respond to any one factor, however, but rather to all of the environmental conditions. 2. Although individual factors varied, the environmental complex at two different stations produced similar functional responses in the coastal chaparral association. 3. The xeric character of the vegetation of the sand dunes is due to an edaphic rather than to a climatic condition. 4. Soil temperature, below approximately 37-39⚬ F., is an important factor in limiting transpiration. Water loss seems to be increased by higher soil temperatures up to a certain point where the curve flattens off. The effect of different soil temperatures requires further study. 5. Transpiration was found to be highest in soils of medium water content, next in saturated soils, and lowest in soils with low water contents. 6. Osmotic values showed a constant decrease with increased soil moisture.

Sand Dune and Subalpine Vegetation in New Zealand

Sand Dune and Subalpine Vegetation in New Zealand