Showing papers in "Ecological Monographs in 1970"
TL;DR: Large increases in streamwater concentration were observed for all major ions, except NH4+, SO4 = and HCO3—, approximately five months after the deforestation, and an inverse relationship between sulfate and nitrate concentrations in stream water was observed in both undisturbed and deforested situations.
Abstract: All vegetation on Watershed 2 of the Hubbard Brook Experimental Forest was cut during November and December of 1965, and vegetation regrowth was inhibited for two years by periodic application of herbicides. Annual stream—flow was increased 33 cm or 39% the first year and 27 cm or 28% the second year above the values expected if the watershed were not deforested. Large increases in streamwater concentration were observed for all major ions, except NH4+, SO4 = and HCO3—, approximately five months after the deforestation. Nitrate concentrations were 41—fold higher than the undisturbed condition the first year and 56—fold higher the second. The nitrate concentration in stream water has exceeded, almost continuously, the health levels recommended for drinking water. Sulfate was the only major ion in stream water that decreased in concentration after deforestation. An inverse relationship between sulfate and nitrate concentrations in stream water was observed in both undisturbed and deforested situations. Average streamwater concentrations increased by 417% for Ca++, 408% for Mg++, 1558% for K+ and 177% for Na+ during the two years subsequent to deforestation. Budgetary net losses from Watershed 2 in kg/ha—yr were about 142 for NO3—N, 90 for Ca++, 36 for K+, 32 for SiO2—Si, 24 for Al+++, 18 for Mg++, 17 for Na+, 4 for Cl—, and 0 for SO4—S during 1967—68; whereas for an adjacent, undisturbed watershed (W6) net losses were 9.2 for Ca++, 1.6 for K+, 17 for SiO2—Si, 3.1 for A1+++, 2.6 for Mg++, 7.0 for Na+, 0.1 for C1—, and 3.3 for SO4—S. Input of nitrate—nitrogen in precipitation normally exceeds the output in drainage water in the undisturbed ecosystems, and ammonium—nitrogen likewise accumulates in both the undisturbed and deforested ecosystems. Total gross export of dissolved solids, exclusive of organic matter, was about 75 metric tons/km2 in 1966—67, and 97 metric tons/km2 in 1967—68, or about 6 to 8 times greater than would be expected for an undisturbed watershed. The greatly increased export of dissolved nutrients from the deforested ecosystem was due to an alteration of the nitrogen cycle within the ecosystem. The drainage streams tributary to Hubbard Brook are normally acid, and as a result of deforestation the hydrogen ion content increased by 5—fold (from pH 5.1 to 4.3). Streamwater temperatures after deforestation were higher than the undisturbed condition during both summer and winter. Also in contrast to the relatively constant temperature in the undisturbed streams, streamwater temperature after deforestation fluctuated 3—4°C during the day in summer. Electrical conductivity increased about 6—fold in the stream water after deforestation and was much more variable. Increased streamwater turbidity as a result of the deforestation was negligible, however the particulate matter output was increased about 4—fold. Whereas the particulate matter is normally 50% inorganic materials, after deforestation preliminary estimates indicate that the proportion of inorganic materials increased to 76% of the total particulates. Supersaturation of dissolved oxygen in stream water from the experimental watersheds is common in all seasons except summer when stream discharge is low. The percent saturation is dependent upon flow rate in the streams. Sulfate, hydrogen ion and nitrate are major constituents in the precipitation. It is suggested that the increase in average nitrate concentration in precipitation compared to data from 1955—56,as well as the consistent annual increase observed from 1964 to 1968, may be some measure of a general increase in air pollution.
1,188 citations
TL;DR: At least two species of predators are supported at different shore levels at San Juan Island, whereas only one species occupies the whole intertidal shore in Scotland, and a predator, T. emarginata, has evolved to specialize at these upper levels.
Abstract: On San Juan Island, Washington, three species of intertidal barnacles (Balanus glandula, Balanus cariosus and Chthamalus fissus) are the main prey of several species of predators, the commonest being three species of snails, Thais emarginata, Thais canaliculata and Thais lamellosa. Larvae of B. glandula settle throughout the intertidal zone but, except in quiet bays, survive to maturity only in a narrow zone at the top of the shore. In quiet bays, where predators of barnacles were scarce, and in areas of turbulent water where predators were excluded by other circumstances, adult B. glandula occurred over the whole intertidal zone. From the lower part of the intertidal zone. Predators were evidently eliminating all B. glandula from the lower part of the intertidal zone. The rates of feeding of Thais lamellosa and Thais emarginata were measured in cages on the shore. The existing population of Thais could account for all of the mortality of B. glandula which occurred at low shore levels in mid and late summer. By late autumn these predators could eat all the remaining B. glandula of that year's settlement at low levels, but at upper shore levels the Thais population could not account for all the mortality of B. glandula in summer. The Thais populations shift upwards from the lower shore levels in the autumn and it is very probable that this increased predation is enough to eliminate the barnacles at the middle and upper shore within the next year. The recruitment of B. glandula every year was quite regular. The breeding population in the narrow "refuge" zone at the top of the intertidal zone was capable of replacing itself as well as colonizing the middle and lower shore. The settlement below the refuge zone can be regarded simply as a regular food supply for the predator population. Because of the dependability of this food supply at upper shore levels, a predator, T. emarginata, has evolved to specialize at these upper levels. In Scotland, where the recruitment of barnacles is irregular, no such specialization is possible. Thus at least two species of predators are supported at different shore levels at San Juan Island, whereas only one species occupies the whole intertidal shore in Scotland. In Scotland, much of the mortality of young barnacles was caused by intraspecific crowding in dense populations, and these deaths provide food for scavengers, rather than predators. In contrast, at San Juan Island of the mortality of young barnacles is caused by predators. Thus the predators at San Juan Island are more efficient than those in Scotland, since they eat a much higher proportion of the available prey. Whereas in Scotland the distribution and abundance of barnacles is largely determined by competition for space, at San Juan Island the barnacles is largely determined by competition for space, at San Juan Island the barnacles are limited by predation.
498 citations
TL;DR: Mixed—species flocks of birds composed of chickadees, titmice, woodpeckers, nuthatches, creepers, kinglets, and wood warblers were studied in several habitats in Louisiana, Maryland, and Maine and appear to be an effective adaptation to difficult conditions.
Abstract: Mixed—species flocks of birds composed of chickadees, titmice, woodpeckers, nuthatches, creepers, kinglets, and wood warblers were studied in several habitats in Louisiana, Maryland, and Maine. Chickadees and titmice usually led these groups. Both the size of the flock and density of birds varied with the habitat. An inverse relation existed between the density of birds in a habitat and the percentage of them that were species participating in flocks. Individuals of species regularly participating in flocks sometimes were found away from them. The tendency for such an individual to be in a flock was inversely related to the density of birds in the habitat. Hostile interactions were infrequent in flocks, being mostly of an intraspecific nature. A dominance hierarchy existed between the different species in flocks. A definite distance was maintained between individuals. As flock size increased the area occupied per individual decreased. The larger flocks were, the faster they usually moved. Each species favored certain parts of the habitat when foraging, though overlap existed between almost all pairs of species. The commonest species (Chickadees, titmice, kinglets) overlapped heavily. Subordinate species foraging in the presence of dominant species changed their areas of foraging, but little or no tendency was seen for subordinates to affect the foraging of dominants. Subordinates might either spread out over alternative foraging areas or concentrate their activities more strongly in a few areas. Most flock members responded markedly to predators; however, few predators were observed during the study. Many of the responses seen were delivered to inappropriate stimuli. Several factors suggest a direct relationship between population density and food supply. Flocking appears to be an effective adaptation to difficult conditions. If a species adjusts its foraging in the presence of another species, possibilities of hostilities should be minimized. Subordinate species usually moved to parts of the habitat to which they were well—adapted. If dominant species are absent, however, opportunism by the subordinate may allow it to take advantage of otherwise unused resources. Dominants may obtain a more predictable portion of the food supply by participating in flocks that if solitary. Constant movement may insure that birds obtain the most readily available food. Large flocks may move rapidly because their individuals are more crowded than those in small flocks. With this restriction either increased speed or more concentrated foraging would be predicted. The low frequency of predators suggests that evasive responses of flock members may have been more advantageous than at present.
476 citations
TL;DR: A prolonged evolutionary interaction between rodent—like, arboreal mammals and the reproductive organs of the modern genera in the family Pinaceae is consistent with the fossil record.
Abstract: Field observations of discriminatory feeding behavior of squirrels indicate that in the process of maximizing their own feeding efficiency squirrels act as selective agents on several characteristics of plant reproduction Calorimetric measurements of the energy content of plant reproductive organs confirm the evolutionary effects of discriminatory feeding by squirrels The reproductive characteristics of conifers which are affected include several details of cone anatomy, the number of seeds per cone, the time at which cones shed their seeds, the thickness of seed coats, and annual fluctuations in the size of cone crops A prolonged evolutionary interaction between rodent—like, arboreal mammals and the reproductive organs of the modern genera in the family Pinaceae is consistent with the fossil record A general analysis of selective pressure influencing terrestrial plant reproduction indicates that seed eaters could have a marked influence on the evolution of plant reproduction Among the interrelated selective pressures that influence the coevolution of conifers and squirrels, the physical environment is the independent variable The effect of one predator feeding on two species of prey is the divergent evolution of defense mechanisms in the two prey species However, one species of predator can cause convergent evolution in the pattern of variation in the production of prey, which may also be considered a defense mechanism
300 citations
TL;DR: The vegetation and peatland types of the Lake Agassiz Peatlands Natural Area are related to topography, waterflow patterns, water chemistry, and the evolution of the landscape as recorded by peat stratigraphy.
Abstract: The vegetation and peatland types of the Lake Agassiz Peatlands Natural Area are related to topography, waterflow patterns, water chemistry, and the evolution of the landscape as recorded by peat stratigraphy. Eight peatland types are distinguished: (1) minerotrophic swamp, (2) weakly minerotrophic swamp, (3) string bog and patterned fen, (4) forest island and fen complex, (5) transitional forested bog, (6) semi—ombrotrophic bog, (7) ombrotrophic bog (raised bog), and (8) raised bog drain. Consistent differences in pH, Ca, and Mg were found between waters of contrasting peatland types. These differences agree with the division of peatland types by degree of mineral soil water influence (minerotrophy). A general topographic alignment of vegetation and peatland types agrees with the hypothesis of chemical controls. Vegetation types often have sharp boundaries related to changes in water properties, peat surface configuration, and paths of waterflow. Landscape evolution included five phases: (1) Recession of...
249 citations
TL;DR: Correlations between chydorids and chemical—physical properties of lakes, plus evidence from relative abundances and frequencies of each species found in each lake type, suggests that most species prefer those waters best termed oligotrophic and dystrophic.
Abstract: Surficial sediments from 77 Danish lakes were processed for chydorid remains for the purpose of establishing relationships of species occurrence to lake type. A total of 35 species of chydorids was recovered; 3 species were new for Denmark, while 3 others previously reported from Danish lakes were not found. The lakes sampled were subjectively grouped according to physical—chemical measurements into 1 of 3 groups–clear—water lakes (1), ponds and bogs (2) and polluted, clear—water lakes (3). Correlations between chydorids and chemical—physical properties of lakes, plus evidence from relative abundances and frequencies of each species found in each lake type, suggests that most species prefer those waters best termed oligotrophic and dystrophic. The exceptions of Chydorus sphaericus and Alona rectangula which, when found in high percentages, typify eutrophic or polluted sites. These data correlated well with species diversity values–high values were found in clear—water lakes (1) and ponds and bogs (2), while low diversities were typical of polluted sites (3). These data suggested that species diversity is a function of available habitat (rooted aquatics), and hence to a large extent the distribution of most chydorid species within a region is determined by habitat diversity (structure). Grane Langso (an oligotrophic, Jutlandic lake) and Esrom S° (an eutrophic, Zealandic lake) were selected for paleo—studies because of their differences, which resulted in contrasting lake development. Postglacial gyttja sediment in Grane Langso extended to 431 cm below the mud—water surface interface. Pollen zonation, and a radiocarbon date of ±9500 BP placed the lowest organic deposits into Pre—Boreal time. Two chydorid species were important in Grane Langso Late—glacial sands underlying the gyttja (Alona affinis and Chydorus sphaericus). Chydorid faunas developed through the Pre—Boreal and early Boreal; by late Boreal chydorid populations were most diverse, and presumably stable. A decrease in species diversity during Atlantic time was due to unstable conditions within the lake, evidenced by deposition of sand; Chydorus piger was abundant during this period. Sub—Boreal organic deposits overlay the Atlantic sands. High percentages of Pleuroxus during mid—Sub—Boreal were attributed to man's activity, and a lower water level. The most recent change in chydorid assemblages occurred within the past 100 yrs; this change was increased percentages of Alonella nana–a species normally associated with low alkalinities in Denmark. Postglacial calcareous gyttja deposits in Esrom So extended to 380 cm below the mud water interface. Calcareous clay extended from 381—840 cm, and glacial till occurred below 840 cm. Pollen preservation was poor in Esrom, but the lowermost gyttja was probably Pre—Boreal (Zone IV). No pollen counts were attributable to Zone VI. Few chydorid remains were found in Late—glacial clays, and extensive development of populations began in Pre—Boreal time (370 cm). Chydorid assemblages characteristic of discriminant Group 1 were present throughout most of the postglacial deposits; benthic species were prevalent during most of the lake's history. Littoral forms did increase in Sub—Boreal time, but by Sub—Atlantic chydorid assemblages were again dominated by benthic groups. In Esrom, postglacial chydorid fluctuations were dampened by its morphological and chemical characteristics, while Grane Langso fossil assemblages were sensitive to minor variations in the lake's environs. Pioneer chydorid species in northern Europe are Chydorus sphaericus, Alona affinis, A. quadrangularis, Acroperus harpae, and Alonella nana.
222 citations
TL;DR: The biogeochemical, productivity, and ecological data obtained from this study are representative of a mature ecosystem in dynamic balance with regional and local controlling factors, i.e., climate, geology, and topography.
Abstract: The synecology of tree species was studied in a mature second—growth forest in the Hubbard Brook ecosystem. The forest, on a 13—ha undisturbed watershed ecosystem covering a 245—m range of elevation, has a basal area of about 23 m2ha—1. Dominance is shared by Acer saccharum, Fagus grandifolia, and Betula alleghaniensis. Direct gradient analysis and regression analysis indicated a strong response in both stand and species characteristics to an elevational complex gradient. Basal area per hectare, basal area per tree, deciduousness, and canopy height decreased with increasing elevation, whereas density, evergreenness, and species diversity increased. A lower rate of net primary productivity is correlated with higher elevations. Gradient analyses indicated that no two tree species have identical patterns of importance values over the elevational complex gradient. Sugar maple shows a decreasing trend; balsam fir, paper birch, and mountain ash show increasing trends. Beech, red spruce, mountain maple, and striped maple show intermediate patterns. Seedlings and saplings respond to the elevational gradient as do larger trees; however, the behavior of trees, seedlings, and saplings of the same species is clearly different. The Hubbard Brook ecosystem is located in relation to the vegetational zonation systems of earlier authors. The only generally agreed upon vegetational boundary, ca. 760 m (2,500 ft), is accounted for by a steepened rate of environmental change in the vicinity of that elevation. Various lines of evidence indicate that the present second—growth forest at Hubbard Brook approximates old—age mature northern hardwood forest. Therefore, the biogeochemical, productivity, and ecological data obtained from this study are representative of a mature ecosystem in dynamic balance with regional and local controlling factors, i.e., climate, geology, and topography.
195 citations
TL;DR: A year's study was made of 13 species of mammals in a desert community in southeastern Arizona, finding that a dominant species may be more important in the cycling of matter in the community, while nondominants may beMore important in stabilizing the community and sustaining the higher trophic levels.
Abstract: A year's study was made of 13 species of mammals in a desert community in southeastern Arizona. Mammal density averaged 17.4/ha: 66% Dipodomys merriami and 10.5% Onychomys torridus. Average biomass was 1130 g/ha: 40% D. merriami and 40% Lepus californicus. Annual energy flow of mammals was 105,950 kcal/ha: 55% by a granivore (D. merriami), 22% by a browser (L. californicus) and 6.5% by an insectivore (O. torridus). 94.6% of the energy flow was spent in maintenance and 5.4% in growth. The secondary productivity of the dominant D. merriami was 1.2% of its energy flow; that of Peromyscus eremicus, the resident species with the lowest and least stable density, was 1.7%. A dominant species may be more important in the cycling of matter in the community, while nondominants may be more important in stabilizing the community and sustaining the higher trophic levels. Since the mammals dissipated only 1.95% of the net annual above ground plant production, their importance must be in their controlling actions on the...
176 citations
TL;DR: The dynamics of naturally occurring high (zone 1) and low (zone 2) populations of the limpet, Acmaea scabra, were investigated on Bodega Head in Sonoma County, California.
Abstract: The dynamics of naturally occurring high (zone 1) and low (zone 2) populations of the limpet, Acmaea scabra, were investigated on Bodega Head in Sonoma County, California. Populations at different intertidal heights can be considered separate because migration between levels is precluded by the homing behavior of A. scabra. Each population was investigated by means of 400—cm² quadrats containing marked individuals; the quadrats were censused approximately every 2 months and yielded information on density, size distribution, dispersion, recruitment, growth, and mortality. Samples were collected from each population approximately every 2 weeks to determine the seasonal pattern of reproduction and changes in size—specific weights. In zone 1 the probable pattern of food availability was distinctly seasonal because of the interaction of tides and climate. Growth and reproduction in this zone were also seasonal, probably increasing and decreasing with the food supply. Seasonal changes in size—specific weights were correlated with the reproductive cycle. Dispersion in zone 1 was always contagious. Recruitment was lower in zone 1, resulting in lower densities and a lower rate of mortality. Annual growth was greater in zone 1 because of the lower densities; consequently limpets in zone 1 were larger and biomass was greater than in zone 2. The population in zone 1 was susceptible to density—independent (catastrophic) mortality and corresponds to a population on the "edge" of the species' range. In zone 2 food was probably more constantly available because this zone was submerged more regularly and to a greater extent than zone 1. As a result there were more constant rates of growth and reproduction, and since reproduction was less variable, there were no seasonal changes in size—specific weights. Dispersion in zone 2 was random or, occasionally, uniform. Recruitment was higher in zone 2 resulting in higher densities and a higher mortality rate. Annual growth was lower because of the higher densities; consequently limpets in zone 2 were smaller and biomass was lower than in zone 1. The population in zone 2 was less susceptible to density—independent (catastrophic) mortality and corresponds to a population in the "center" of the species' range. Zone 2 is the "center" of the species' range, yet individual performance was poor because of the high densities; the probability of dying was high, growth rates were low, and the animals remained small. In both zones competition for food limited biomass, but lack of food did not cause mortality, i.e., regulate density.
168 citations
TL;DR: The herb and shrub layers of the control northern hardwood forest ecosystem at Hubbard Brook contain 96 species of plants and ninety—three per cent of the current growth was localized in eight species in the 1966 summer growth aspect.
Abstract: The herb and shrub layers of the control northern hardwood forest ecosystem at Hubbard Brook contain 96 species of plants. This ecosystem, 13.2 ha in size, has a southeast—facing aspect, an average slope of 26%, and an altitudinal range of 545 to 791 m. Vascular cryptogams, woody saplings, shrubs, tree seedlings, and herbaceous phanerogams contributed 38%, 22%, 18%, 13%, and 8% respectively to the aboveground current growth in the herb—shrub layer. Ninety—three per cent of the current growth was localized in eight species in the 1966 summer growth aspect. Dryopteris spinulosa, Viburnum alnifolium, Acer saccharum, and Fagus grandifolia contributed 67% of the cover in the herb layer, and, respectively, made up 70% of the current growth of herbs, 83% of shrubs, 61% of tree seedlings, and 90% of saplings. For the ecosystem as a whole, the herbaceous layer contained 1.8 kg/ha K, 0.3 Mg, 0.3 Ca, 0.1 S, 0.09 Mn, 0.007 Fe, 0.008 Zn, 0.001 Na, and 0.001 Cu in the aboveground current growth. The herb—shrub layer re...
154 citations
TL;DR: Density of adult garibaldi can be limited by supply of resources for survival or, where these are abundant, by minimal space requirements of nesting males, as well as by some form of intraspecific competition.
Abstract: The garibaldi, Hypsypops rubicunda, is a California pomacentrid fish inhabiting the rocky subtidal between 0 and 25 m. Garibaldi feed almost exclusively on benthic organisms. Adults defend a territory which includes a shelter hole, grazing area, and for some males, a nest site. The territory is defended all year and against some other species as well as other garibaldi. The nest site is a small patch of red algae cultured by the male. The same site is used over a period of several years by the same male and probably by his successors. The female is allowed in the territory only to spawn; the eggs are guarded by the male. The young receive no parental care; they disperse into the plankton and settle out in shallow water. Age estimates from scales indicate that garibaldi assume adult coloration and mature at age 5 or 6 years and may live 13 or more years. Garibaldi have no obvious important predators or diseases. From age structures of several populations the mortality rate is estimated at about 9% of the adult population per year. In most cases potential recruitment more than balances mortality, indicating that population density is limited by some resource in the area and regulated by some form of intraspecific competition. Density and dispersion of both fish and resources (food, shelter, and nest sites), sex ratio, and age structure were determined in several study areas. From these data and a series of repopulation experiments, the most likely limiting and regulating factors are proposed. Density of adult garibaldi can be limited by supply of resources for survival or, where these are abundant, by minimal space requirements of nesting males. Exclusion by territory defense helps regulate density to limits set by food, space, etc. There is no evidence of feedback between density and the density limiting or regulating effects of territorial behavior. Territorial behavior seems to have evolved as a means of increasing reproductive success. Population effects, though beneficial, are probably incidental. There is no support for the hypothesis that territorial behavior in the garibaldi has evolved because it limits or regulates density.
TL;DR: It is suggested that preferred temperatures may shift during the day, but that these levels cannot always be maintained; head temperatures may be regulated more precisely than those of the body.
Abstract: Amphibolurus inermis occurs throughout Australia except for the eastern third of the continent, the north—central coast, and the southwestern tip. It inhabits sandy soils. Body temperature rises in the morning, levels off and remains rather constant between 1000 and 1600 hr, and falls after 1600 hr. Thermoregulation involves changes in location and posture, color change, basking, burrowing, shade—seeking, and panting. The level of temperature maintained depends on geographic locality and immediate weather conditions and may depart widely from the temperature preferred in a laboratory gradient. The relative importance of specific behavioral responses varies with locality; burrowing and shade—seeking may be interchangeable. Amphibolurus inermis functions either as a thigmotherm or a heliotherm depending on local conditions and time of day. It is one of the most heat—resistant species known; the mean body temperature which causes loss of coordination is 48.5° C, and the lethal temperature is 49.3° C. Because of the extreme environments it occupies, A. inermis has narrow minimum thermal safety margins even though it has high temperature tolerances. Burrows tend to be located near thermoregulatory perches. When the sun—perch and the shade—perch are close together, an individual may have only one burrow; if the perches are further apart, a burrow will usually be located near each. If widely separated, auxiliary burrows may occur between the two types of perches. Burrows sometimes become too hot to serve in thermoregulation. Active individuals are found at all hours between sunrise and sunset in summer. However, individuals may seek shelter at midday. In winter the activity period is restricted to a few hours at midday. It is suggested that preferred temperatures may shift during the day, but that these levels cannot always be maintained. Head temperatures may be regulated more precisely than those of the body.
TL;DR: The following eight community types in the Olympic Mountains, delimited from an ordination of 38 plots, are described: the cushion plant type occurring in dry habitats on exposed knolls or ridge tops, the dry grass—forb type occurring on steep, dry, south— to west—facing slopes, and the moist Saussaurea forbtype occurring in shallow gullies kept moist by melting snowbanks or shallow streams.
Abstract: The following eight community types in the Olympic Mountains, delimited from an ordination of 38 plots, are described: (1) the cushion plant type occurring in dry habitats on exposed knolls or ridge tops; (2) the dry grass—forb type occurring on steep, dry, south— to west—facing slopes; (3) the mesic grass type occurring on mesic, south— to west—facing slopes; (4) the moist Saussaurea forb type occurring in shallow gullies kept moist by melting snowbanks or shallow streams; (5) the moists Valeriana forb type occuring on steep, northeast—facing slopes; (6) the tall sedge type mostly occurring at higher elevations on many aspects and topographic situations, depending on location in the Olympic Mountains; (7) the heath shrub type occurring in cool habitats where snow remains until mid— to late July; and (8) the dwarf sedge type occurring in high subalpine to alpine areas where snow remains until late July to early August. Soils are mostly poorly developed (Entisol and Inceptisol), but some have well—developed horizons (Spodosol). The less developed soils generally had higher amounts of available nutrients. Physical properties differed little between soils in each community, except for the fraction >2 mm which varied from a high of 82% in the dry grass—forb community to a low of 31% in the tall sedge community. Solar radiation, wind velocity, precipitation, atmospheric moisture, temperature, and soil moisture were monitored in the dry grass—forb, mesic grass, and Saussaurea forb communities. Total solar radiation received was similar in the summers of 1966 and 1967. Wind velocity was low in all communities; the highest average for a summer was 1.2—1.6 m/sec in the mesic grass community. Temperatures and vapor pressure deficits were highest in the dry grass—forb community and lowest in the moist Saussaurea forb community. Precipitation differed little among stations. Soil moisture in 1967 was available for the shortest period in the dry grass—forb community and 3 and 5 weeks longer in the mesic grass and moist Saussaurea forb communities, respectively. Shoot productivity was determined in three communities, and standing crop of shoots and roots was determined in five communities. Productivity values were 1.2, 2.7, and 11.4 g/m2 per day in the dry grass—forb, mesic grass, and moist Saussaurea forb communities, respectively. Peak shoot production, ranked from low to high, was dry grass—forb (107 g/m2), dwarf sedge (157 g/m2), mesic grass (245 g/m2), tall sedge (395 g/m2), and moist Saussaurea forb (502 g/m2). Peak root production ranged from a high of 3,257 g/m2 in the tall sedge community to a low of 1,234 g/m2 in the moist Saussaurea forb community. Chlorophyll content in the five communities followed the same trend as shoot production. The correlation between ovendry weight of shoots and chlorophyll content was high (r = .70, p < .01). Differences in water potentials were small among the species from the dry grass—forb, mesic grass, and moist Saussaurea forb communities, and the lowest water potentials were mostly between —14 and —16 bars. The effect of light, temperature, and soil moisture on photosynthesis was determined for Caltha leptosepala (wet site species), Saussaurea americana (moist site species), Festuca idahoensis and Lupinus latifolius (mesic site species), and Eriophyllum lanatum (dry site species). Except for the temperature response of Caltha and Eriophyllum, response of the five species to the three environmental factors helped to explain their natural distribution.
TL;DR: About 1,200 Microtus pennsylvanicus and M. ochrogaster were collected over a 3—year period by sequential trapping of snap—trap lines in southern Indiana to determine whether weight at sexual maturity, pregnancy rate, living embryo production, prenatal mortality, and body weight varied in relation to fluctuations in numbers.
Abstract: About 1,200 Microtus pennsylvanicus and 1,000 M. ochrogaster were collected over a 3—year period by sequential trapping of snap—trap lines in 15 grassland areas in southern Indiana. Peak densities were reached in 1966 for all but two of the populations studied. Reproductive data were obtained to determine whether weight at sexual maturity, pregnancy rate, living embryo production, prenatal mortality, and body weight varied in relation to fluctuations in numbers. The rate of winter breeding was high in both species of vole between the cyclic increase and cyclic peak years. Breeding was continued at a reduced level during the fall of the cyclic peak and was greatly reduced during the winter between the cyclic peak and decline. In both species sexual maturity occurred at higher weights in periods of peak population density and lower weights in periods of low density. Only heavy individuals remained fecund during the winter months of November—February. Sexual maturity was reached at the same weight in males and in females. Litter size was correlated with body size. In M. pennsylvanicus litter size was not significantly different in multiparous and primiparous females, and litter size remained constant in the summer breeding seasons of the increase, peak, and decline years. Difference between seasons was significant, the fall—winter—spring periods having a 14% lower litter size than the summer period. In M. ochrogaster living embryo counts were 25% lower during the period of cyclic peak in multiparous females than they were during the years of cyclic increase or decline. This observation was confirmed independently in a population that was out of synchrony. A decline in litter size was not associated with the year of cyclic decline in either species. Corpora lutea counts were correlated with body size. The pattern established for living embryo counts was nearly identical to the ovulation pattern. Prenatal mortality did not change significantly, either seasonally or yearly, and thus was not higher in the decline phase for either species. Testes weight and body weight were correlated. The testes weight of non—fertile Microtus pennsylvanicus differed little among the summers of population increase, peak, or decline. Testes development was inhibited during fall and winter. Fertile males taken during the summer of population peak and the summer of decline had heavier testes than males taken during the summer of increase. A midsummer drop in testes weight was observed during three breeding seasons. Non—fertile M. ochrogaster had only slightly reduced testes weight during the winter between the population increase and peak, but testes weight declined significantly during the winter following the population peak. Testes weights of fertile males changed little during the summer of population increase, but they increased steadily during the summer of population peak. A significant decline in testicular weight occurred during the winter following the population peak. High body weights were associated with peak populations in both species of Microtus. The pattern of change in weight distributions was similar to that described for other cyclic voles and lemmings.
TL;DR: The ecological differences between the three species seem to indicate that H. gentilis is the most generalized (primitive) form, which survives here in marginal habitats, particularly areas recently modified by man.
Abstract: Three species of the blenniid genus Hypsoblennius, H. gilberti, jenkinsi, and gentilis, coexist in the shallow waters of the San Diegan Warm Temperate Region. Extensive field and laboratory studies were carried out to determine the degree of ecological differentiation present in these species. The dominant species, H. gilberti and H. jenkinsi show both behavioral and ecological specializations which are lacking in H. gentilis. These differences include: Habitat preference; H. gilberti inhabits the rocky intertidal and adjacent subtidal cobble; H. jenkinsi is found only subtidally, inhabiting boring clam burrows, Serpulorbis tubes or mussel beds. Adult motility: H. gilberti is a meandering species commonly including a radius as large as 15 m within its home range. Individuals return to "home" pools at low tide and homing has been demonstrated for displacements as great at 45 m. H. jenkinsi is sedentary rarely wandering more than a meter from its home refuge. Homing was not demonstrated in this species, even for displacements as small as 5 m. Territoriality: Degree of territoriality correlates with movement, the sedentary species is highly territorial while this phenomena is less easily demonstrated in the meandering form. The above differences have been experimentally verified in the laboratory. All species are omnivorous, differences in gut content seem to represent different habitat associations. Reproduction occurs from spring through late summer; the eggs are guarded by the male. Hatching occurs in 4—18 days depending on temperature; the larvae are pelagic for about three months. Adult size differences reflect differing larval and first year growth plus differing longevity; determinate growth has not been demonstrated. Adult size varies between the species and is an important ecological factor. In the small tubiculous species H. jenkinsi, tube size controls fish size (habitat matching) probably through predator selection. Habitats made up of different tube sizes support populations of significantly different mean fish size. In Newport Bay, population structures are altered by a viral infection, Lymphocystis which reaches epidemic levels during the warm months. The ecological differences between the three species seem to indicate that H. gentilis is the most generalized (primitive) form. The specializations of its congeners adapt them to coexistence with limited competition. H. gentilis unspecialized and unable to compete in Southern California survives here in marginal habitats, particularly areas recently modified by man.
TL;DR: The macrobenthos of Moreton Bay is diverse, with 355 species collected from 400 dredged stations, and frequently occurring species dominate the epifauna and the four most frequent species show seasonal changes.
Abstract: The macrobenthos of Moreton Bay is diverse, with 355 species collected from 400 dredged stations. Many of these species are distributed throughout the Indo—West—Pacific area, others have an Australian distribution (possibly some may also occur in the northern hemisphere), and others are known as yet only from Moreton Bay. The occurrence of the richest sites near the edges of the bay can be attributed to either favorable hydrographic—sedimentary conditions or to the location of these sites on the periphery of areas worked by prawn trawlers. Infrequently occurring species dominate the epifauna, and frequently occurring species dominate the infauna. Neither the infrequent species nor the four most frequent species show seasonal changes, but some seasonal change is evident in other species. Species occurring in more than eight sites usually showed a distribution pattern, but species patterns could not, by inspection, be classified into group patterns. By limiting consideration to the 32 commonest species six ...
TL;DR: Five vegetation zones were recognized in the Similkameen Valley of southern British Columbia and some habitat types correlated well with the soils at a great group level, largely controlled by elevation primarily as a reflection of climate.
Abstract: Five vegetation zones were recognized in the Similkameen Valley of southern British Columbia. These zones were largely controlled by elevation primarily as a reflection of climate. The climate becomes progressively more moist from east to west and with increasing elevation. Two habitat types were described in the Artemisia tridentata zone, three in the Pinus ponderosa zone, five in the Pseudotsuga menziesii zone, five in the Abies lasiocarpa zone, and one in the Alpine zone. Some habitat types correlated well with the soils at a great group level. The Pinus—Festuca habitat type was found mostly on Dark Gray soils, the Pseudotsuga—Festuca habitat type on a variety of soils, the Pseudotsuga—Calamagrostis habitat type on Gray Luvisols, the Festuca—Eriogonum habitat type on Black Chernozems, the Abies—Vaccinium—Calamagrostis habitat type on Dystric Brunisols, and the Abies—Vaccinium, Phyllodoce habitat type on Alpine Dytsric Brunisols soils. A key for the identification of the major habitat types is included....
TL;DR: Comparisons of site chronologies derived from both the skeleton plots and the index routine for each species showed that a number of narrow rings consistently occurred in certain years throughout the Central Mississippi Valley, and analyses of variance indicated that black oak generally responded more to climatic influences than to other factors of the environment.
Abstract: Tree—ring samples (increment cores) from living trees at 61 different forest sites were analyzed by using skeleton plots and several computer routines to determine the effect of climatic influences upon the growth of black oak, white oak, and shortleaf pine. All cores were cross—dated within each species and between species by skeleton plots, and a specific calendar year was assigned to each annual ring. Black oak was easier to cross—date than white oak or pine. Computer—calculated negative mean sensitivity values verified cross—dating by skeleton plots. Comparisons of site chronologies derived from both the skeleton plots and the index routine for each species showed that a number of narrow rings consistently occurred in certain years throughout the Central Mississippi Valley. Within any species the degree of similarity in narrow rings decreased as the distance between sites increased. Major changes in soil types also influenced the number of narrow rings; thus ecological differences may occur within the same species as well as between species. Information about the past history of the stand and its present ecology may be obtained from the increment cores and the ring—width listing routine. Bivariate distribution tables indicated that for each species annual ring widths correlated highest with certain periods of precipitation. Analyses of variance permitted the evaluation of relative similarities and differences of tree—growth response and indicated past stand disturbances as well as the effects of climatic and edaphic influences. Pine has greater tree—to—tree variability on clay soils than on cherty soils. Oaks have more tree—to—tree variability on cherty soils. Analyses of variance also indicated that black oak generally responded more to climatic influences than to other factors of the environment.