Showing papers in "Ecology in 1945"

Tolerance to Salt Spary of Plants of Coastal Dunes

Abstract: Salt spray is injurious to many plants and consequently is an important factor in the environment of vegetation on coastal dunes. Its effects are most apparent after severe storms during which plants near the ocean may have been continuously wetted. Then also other plants are subjected to salt spray which ordinarily are not exposed to it because of their distance from the ocean or because of protecting dunes. Usually such storms are accompanied by rain which reduces the effectiveness of the spray. But, when no rain falls during or immediately after a storm, as happens occasionally, damage to coastal vegetation resulting from salt spray may be disastrous. Many trees and shrubs are then killed, or at least their tops are partially killed-back, and as some of these may be of considerable age they must have survived previous storms. Since plants of some species are affected much more than others the evidence indicates a "selective" action of salt spray which permits the growth and survival of a limited number of tolerant species along the coast and thus controls indirectly the communities and their development. Wells and Shunk ('38) suggested the probability "that the distinctive composition of the dune community is based primarily upon the species adaptations to the spray factor." Later ('39) Wells recognized a "salt spray climax" on the same basis. Variation in tolerance to spray among herbaceous plants is indicated by a zonation of herbs along the North Carolina coast (Oosting and Billings, '42) which is correlated with intensity of salt spray but with no other apparent factors. Also, there are several species which grow only along the coast and others which grow more abundantly there than elsewhere. If these species are tolerant to spray their abundance along the coast may be explained by the reduced competition from intolerant species which are largely eliminated. It would appear then that the characteristic species of coastal dunes and their vicinity comprise a "select" group which is more or less tolerant to salt spray. That there should be variation in sensitivity to spray is also reasonable to suppose. To verify these assumptions and particularly to check the range of tolerance of some of the common coastal plants an experiment was set up at the Duke Marine Laboratory which is on Pivers Island, in the harbor at Beaufort, North Carolina.

Coagulation Film Anoxia in Fishes

Abstract: One hundred and ten goldfish were carried in water of controlled hydrogen-ion concentration and oxygen content, to which various substances could be added as desired. The lethality of sulfuric acid to goldfish results from decreased permeability of the gill membrane system to oxygen, as a result of the precipitation of the mucus on the gill filaments. Lead nitrate (5.0 gms./liter) causes death to goldfish by precipitation of the mucus on the gills, thereby interfering with the oxygen intake in the same manner as sulfuric acid. The lethality of lactic acid to goldfish seems to be independent of the oxygen level, and as no precipitation of mucus was observed on the gill filaments except in very strong solutions, it is suggested that lactic acid diffuses into the blood, and death results from the systemic effects of the absorbed acid. These findings are helpful in interpreting the reactions of fishes to chemical alterations of the environment, either due to natural causes, as acid streams from certain volcanic areas, sulfur deposits, and coal veins, or to various industrial effluents.

The Distribution of Stream Fish in the Vicinity of Mountain Lake, Virginia

Abstract: From both taxonomic and ecological standpoints the streams in the vicinity of the University of Virginia's Mountain Lake Biological Station offer favorable locale for the study of fish distribution. In the first place Salt Pond Mountain, on which the station is located, is one point on the divide between Atlantic and Mississippi valley drainage systems. The streams flowing from the west slopes are tributaries of the New River which flows into the Ohio, whereas streams on east slope enter the James River and flow thence to the Atlantic ocean. Due to the irregularity of the mountain ranges in this part of Virginia the streams may run parallel to each other a few miles apart, but eventually flow in opposite directions and belong to different drainage systems (fig. 1). Secondly, variations in altitude produce a variety of environmental conditions, often within a few miles of the same stream. Finally, the streams of the region have been only moderately polluted or otherwise disturbed by man, and the upper reaches are of special interest as good trout streams. The collections and field observations on which this paper is based are almost entirely the work of Burton who started field work in the summer of 1938 under the direction of Prof. Maurice G. Brooks and continued for the following three summers. During the summer of 1941 Odum worked with Burton in the field. When Burton entered the armed forces Odum undertook to arrange and interpret the data for publication. All identifications have been made by Dr. Carl L. Hubbs, Curator of Fishes, Museum of Zoology, University of Michigan, or have been made by the authors by comparison with material determined by him. The writers express their great appreciation to Dr. Hubbs, who also critically read the manuscript. Certain

Diel Activity Rhythms of the Rodents, Microtus Ochrogaster and Sigmodon Hispidus Hispidus

Abstract: In the vicinity of Nashville, Davidson County, Tennessee there occur two species of rodents which frequent the same or neighboring fields. These two species are the prairie meadow mouse, Microtus ochrogaster (Wagner), and the cotton rat, Sigmodon hispidus hispidus Say and Ord. In their major adjustments to the community of which they are a part these two rodents seem to be ecologically equivalent (Allen, 1870-71; Bailey, '31). In the more southern latitudes of the United States Sigmodon replaces Microtus. Sigmodon is a much larger animal and, therefore, constructs larger surface and underground runways. The adult weight of Sigmodon is approximately 125 grams whereas that of Microtus is 45 grams. According to Hamilton ('43) the above area lies at the extreme southern range of Microtus ochrogaster and the extreme northern range of Sigmodon hispidus hispidus in the eastern United States. We find that the opinions of field workers based on trapping data vary greatly in regard to the time of day at which Microtus is most active. A diurnality was found by Bailey ('31) for M. mexicanus in New Mexico and by Jackson ('08) for M. pennsylvanicus in Wisconsin. However, both Kennicott ('56) and Lyon ('36) found M. pennsylvanicus to be mainly nocturnal. Johnson ('30), Bailey ('26), and Goodwin ('35) state that M. pennsylvanicus is arhythmic, although there is a tendency for an increase in activity at dusk and during the early morning hours. A similar situation appears to exist in regard to cotton rats. Aldrich and Bole

Season of Attachment and Growth of Sedentary Marine Organisms at Oakland, California

Abstract: The attachment of sedentary marine organisms is not only of general interest to the biologist but is of very great economic importance because of the fouling of ships' bottoms and other submerged surfaces. Our knowledge of the season of attachment and growth of marine fouling organisms in various harbors is not extensive, especially for the west coast of America. Coe ('32) and Coe and Allen ('37) studied the season of attachment and growth of sedentary organisms at La Jolla, California where open coastal conditions prevail. Johnson and Miller ('35) investigated fouling in Puget Sound. Kofoid and Miller ('27) reported on the marine borers of San Francisco Bay. However, there is very little information available regarding the season of settling of the true fouling organisms of San Francisco Bay. It is the purpose of this paper to present the results of studies made with test panels set out over a period of more than a year in Oakland Estuary at Oakland, California. The writers wish to acknowledge their indebtedness to Dr. Lucile Mason for identification of algae; to Dr. Olga Hartmann for identification of Annelids; to Mr. C. R. Shoemaker for identification of amphipods; to Mr. J. 0. Maloney for identification of isopods; and to Miss Elizabeth Loudon and Miss Mary North for technical assistance.

Axillary Cleistogenes in Stipa Leucotricha and their Role in Nature

Abstract: Texas needlegrass (Stipa leucotricha Trin. and Rupr.) is the principal and usually the only stipa on the prairies of the eastern half of Texas. In this area it is widely recognized and appreciated by ranchers because of its winter-growth habit. Locally it is commonly known as winter speargrass, or, curiously enough, as "stipa." Its most common associate in pastures is buffalo grass (Buchloe dactyloides (Nutt.) Engelm.). On some severely overgrazed pastures, particularly those with deep, heavy, clay soils, stipa is the principal perennial grass. During 1943 and 1944 stipa was studied intensively on the Fort Worth Prairie, west of the city of Fort Worth, Texas. Here it is abundant in overgrazed pastures, though ordinarily absent on lands subjected to no greater disturbance than removal of an annual crop of native hay. Its ability to withstand intensive grazing use and the fact that it is the only native perennial grass providing considerable green pasturage during winter, cause itto be of especial interest. This interest is heightened because it is the only stipa in continental United States reported by Hitchcock ('35) to have cleistogenes. Concerning Stipa leucotricha, he stated "Cleistogamous spikelets with glumes obsolete and lemma nearly awnless are borne in basal sheaths just after maturity of panicle." The r6le of these plump, commonly subterranean, grains is apparently little known. The morphology of axillary cleistogenes in several American grasses has been treated by Chase ('18) whose article also prompted this study into autecological aspects because of the statement " I surmise that the grains germinate within the sheath and push root and shoot through the internerves but this has not been proved by experiment." PURPOSE AND METHODS OF STUDY

The Kelp Beds of the Monterey Region

Abstract: The giant kelp beds and especially their associated animals have attracted little attention. The kelp beds of this particular region have not been studied heretofore. The author investigated the beds near Friday Harbor in Puget Sound in 1922 and found a great variety of species. Some of them appeared to be dependent upon holdfasts for some of their life history stages (Andrews, '?5). In a study dealing with the larger communities and their variations, Shelford et al. ('35) classified these kelp beds as the NereocystisLaminaris-Lacuna faciation, listing the more important algae and the representative animal species. 1 The material here presented is included in a dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate School of the University of Illinois.

Frost Pocket and Other Microclimates in Forests of the Northern Allegheny Plateau

Abstract: Open valley bottoms characterize many otherwise forested drainages in the High Plateau section of western Pennsylvania In some cases these openings have persisted for many years, following the original logging, even though forest growth has been re-established on adjacent slopes The object of this study was to determine the chief reasons for the failure of natural tree regeneration to reclaim these sites Local climatic factors which might limit tree growth and the browsing by deer and rabbits were given special consideration Early observations over a wide territory showed the presence of eastern hemlocks (Tsuga canadensis (L) Carr) 2 with densely clustered branches in many of these open valley sites, and it was also noted that browsing of the scattered hardwoods and small hemlocks by deer was prevalent It was not, however, until weather records had been kept during 1932-1939 in a shallow open valley on the Kane Experimental Forest that the greater severity of the microclimate at this station compared with nearby forested stations began to be appreciated, and not until later did the exclosure of deer and rabbits begin to show results

The Ecological Relations of Pike, Esox Lucius, L., and Waterfowl

Abstract: During the summers of 1940 and 1941, four months were spent by the author in studying the relations of pike and waterfowl on the water areas of the Saskatchewan River delta. During this period over 3,000 pike were caught and determinations of age, sex, length, weight and stomach contents were made. Pike held in confinement were fed specimens of ducklings, chicks, young grebes, young terns, shrews, mice, pieces of muskrat flesh, goldeyes and perch. The pike were examined at intervals after feeding in order to determine the rate of digestion of different types of food. By intensive fishing in one body of water data concerning the total pike population were obtained. Observations on the feeding habits of the pike were made by using wooden and metal lures armed with multiple hooks.

The Effect of Overhead Shade on the Survival of Loblolly Pine Seedlings

Abstract: Loblolly pine (Pinus taeda) 1 seedlings, if they succeed in germinating under overhead shade and survive the first season or two, will almost inevitably die at some later period unless this competition is removed. This makes it impossible either to practice the single tree or pure selection system of silviculture, or to maintain successfully for an indefinite period a "normal" growing stock on the same area, from which only an amount equal to the annual growth is removed annually or even at 10-year intervals. Under such practice, conditions originally favoring the establishment of loblolly pine, caused by past cutting and fires, are gradually altered to favor the dominance of hardwoods of inferior species and quality, leading ultimately to elimination of loblolly pine. On the other hand, if loblolly pine seedlings start in the same year with competing hardwood sprouts, they have a more than even chance of outgrowing and dominating the hardwoods in spite of their lesser height growth in the first year compared with sprouts. Full sunlight or freedom from overhead shade permits loblolly pine rapidly to assume its normal rate of growth in height, which can exceed that of all competitors except red gum (Liquidambar styraciflua) by from 25 to 50 per cent. Gum, due to its narrow crown, is not always a serious competitor if the pine develops at the same time, but, with oaks and other hardwoods, it becomes so if it starts 2-3 years earlier. Observers are often confused by the fact that in a rather mature high forest of mixed pine and hardwoods, especially among the hardwoods, great numbers of young loblolly pine seedlings and small

Varying Hare and Forest Succession

Abstract: The varying hare or snowshoe rabbit (Lepus americanus Erxleben) is the characteristic lagomorph of the northern coniferous forest of North America. In the eastern United States, it occurs in the northern parts of the Lake States and New England and along the mountains to Virginia. Under pristine conditions, it appears that hares occupied the whole of New York, which was then clad in forests having a high component of conifers spruce in the north, hemlock and pine in the south. The Indians were too few and scattered to have more than local effect upon rabbit populations. With the advent of the white man came wanton exploitation of all natural resources, including wildlife. The hares suffered severely, not only from the direct effects of hunting but also from the more fundamental changes wrought by the reduction of much of their forest habitat to farmland and by the lessening of the proportion of evergreens in the remaining woods. In 1842 DeKay observed that "it lives exclusively in elevated and dry forests of pines and firs, never venturing upon cleared or cultivated lands." At present, the species is rather strictly confined to softwood swamps. The clearing of the greater portion of central and southern New York reduced both the absolute number of snowshoe rabbits and the proportion of the range that they were able to occupy. The present center of greatest abundance and most continuous range is in the forested Adirondacks; elsewhere the animals persist only in scattered colonies. The varying hare is a vegetarian. It is generally agreed that the summer diet consists of succulent plant material clovers, grasses and forbs whereas in winter they subsist on buds, bark and the foliage of certain evergreens. Among woody plants, Seton ('29) lists poplar, willow, birch and tainarac (sic.), as well as "white cedar and spruce leaves." In the Lake States (Anon. '36), "young aspen, willow and the birches are preferred foods. In the coniferous group, the rabbits show a decided preference for jack pine, white pine and tamarack. Other evergreens . . . include Norway pine, white spruce, Scotch pine and white cedar. Black spruce and balsam fir are much less often utilized." The authors' own experience indicates that the hares will eat a great variety of forbs and grasses, as well as the buds and bark of hardwood and softwood trees and shrubs. Considerable preference is exhibited, certain plants being especially favored while others are definitely passed by. So long as the snowshoe rabbit fed upon forest plants and wild tree seedlings, its activities elicited little notice. It was not until its feeding began to interfere with man's economic interests that it became a matter of more than casual concern. Aldous and Aldous ('44) are of the opinion that "it has probably always destroyed a great many young coniferous trees, but this fact was not given serious attention until . . . large-scale (forest) planting was begun." In the Lake States, the problem is particularly acute because of extensive forest plantings in hare territory. "If snowshoe damage to natural seedlings of pine and spruce could be determined, we might find that it exceeds the current annual loss from fire" (Wilson, '42). Hosley ('31) states that, in New England, "the white hares . . . seldom cause serious damage." That statement would be equally true for New York, where the rabbits are too few to do noticeable damage. Valcour Island, on which this study

The Effect of Physical Factors Upon Catch of the Beet Leafhopper (Eutettix Tenellus (BAK.)) By A Cylinder and two Sweep-Net Methods

Abstract: Sweep nets have been used to catch insects since the early history of entomology. The first-known adaptation of this method as an index of insect abundance was that used by Bremi-Wolf ('46) to catch Diptera. Dahl ('08) recommended that a definite number of sweeps be made with the sweep net to determine insect abundance, and since that time many workers have studied and published data on insect abundance on the herb and shrub strata obtained by this method. De Long ('32) stated that certain physical factors influenced the proportion of insects caught by the net, and mentioned temperature and wind velocity as the most important. Other factors of lesser importance were also listed such as humidity, plant size and density, shadow cast by the operator, and the operator's route with respect to wind direction, but the author did not support his statements with data. The writer collected the beet leafhopper, Eutettix tenellus (Bak.), from stands of Russian-thistle, Salsola pestifer A. Nels., throughout New Mexico with the sweep net during the summers of 1928 and 1929. This work showed that catch by the net was affected by a number of factors, of which temperature and wind velocity seemed to be the most important. In order to determine how much effect these two factors, as well as others, might have upon the sweep-net catch it was necessary to develop a quantitative method presumably free from the effect of physical factors for comparison with the sweep-net method. Data presented to show the effect of various physical factors upon the catch of the beet leafhopper are not intended to offer a correction, but merely to point out the relative importance of the various factors upon the catch as indicated by a cylinder and two net methods.