Showing papers in "American Midland Naturalist in 1981"

Species composition and life histories of aquatic insects in a lowland Sonoran Desert Stream.

Abstract: Ninety-nine taxa of aquatic insects and a total 104 macroinvertebrate taxa were collected in Sycamore Creek, Arizona, from July 1977 to November 1979. The fauna is primarily composed of organisms restricted to the American Southwest, although many widespread Nearctic taxa are also present. Life histories of 17 taxa were examined with emphasis on total developmental time (egg to adult), reproductive period and dormancy. Ephemeroptera, small Diptera and the corixid Graptocorixa serrulata developed rapidly (1-3 weeks) and reproduced continuously. Aquatic beetles (Dytiscidae and Hydrophilidae) developed in 4-8 weeks and reproduced only in spring and after summer rains. Two Trichoptera species required 6-7 weeks for development and reproduced continuously. Degree-day developmental rates (ca. 1200) were similar for some desert and temperate species. Dormant stages were restricted to stoneflies (egg diapause) and tabanids (larval diapause). Drought and flooding markedly influenced life histories. Adaptations to drought are habitat selection by ovipositing adults and rapid development. Adaptations to floods are behavioral avoidance, rapid development and seasonal reproduction. Floods also contribute to the rarity of dormancy, thus aerial adults become the life stage resistant to disturbance. Floods, which do not occur in temporary lentic systems, are an important selective pressure in temporary lotic systems.

Postflood Recolonization Pathways of Macroinvertebrates in a Lowland Sonoran Desert Stream

Abstract: Most macroinvertebrate taxa recolonizing after floods in Sycamore Creek did so via aerial pathways. After frequent winter flooding, most aerial colonists were aquatic adults (Coleoptera and Hemiptera), whereas ovipositing adults (Ephemeroptera and Diptera) dominated after summer flooding. Drift and upstream movements by relatively few taxa contributed most individuals after floods. Upstream movements were greater during high discharge than during low discharge periods. Few taxa and individuals were present in sediments below 10 cm. INTRODUCTION Stream macroinvertebrates are periodically decimated by various natural catastrophes, such as ice scour, floods and drought. An important aspect of recovery after a catastrophe is to be found in the palthways of recolonization. These pathways influence community composition and suggest common selective forces on -the life histories of species present. Williams and Hynes (1976) identified four principal recolonization pathways of stream benthos: aerial movements, downstream drift, upstream movements and vertical movements from deep substrates. Although all four may contribute colonists, previous studies indicate that one pathway usually dominates. In permanent streams, downstream drift is most important (Townsend and Hildrew, 1976; Williams and Hynes, 1976), while in intermittent streams, aerial movements and vertical movements from deeper substrates are the two main pathways. Harrison (1966) and Hynes (1975) found aerial sources dominant in two African streams. Organisms using this pathway were aquatic adults (Coleoptera and Hemiptera) and ovipositing adults (e.g., Ephemeroptera and Diptera). Williams (1977) found vertical movements predominant in two Canadian streams subject to drying. Organisms were present in dormant stages until water returned. Recolonization processes are integral to macroinvertebrate community dynamics in intermittent desert streams as a consequence of frequent disruption by floods. Floods occur during two distinct rainy seasons in the Sonoran Desert, winter (November to April) and summer (July to October). Winter precipitation results from large-scale frontal systems that affect large areas, producing floods and extended high flows lasting from days to weeks. Summer rains, caused by locally intense thunderstorms, affect variable portions of the watershed resulting in "flash" floods that typically last only a few hours (Deacon and Minckley, 1974). In both seasons, floods scour substrates and eliminate 80-100% of the benthic fauna (Gray, 1980). Recolonization studies of benthic invertebrates were conducted at Sycamore Creek, Arizona (33?45'N, 111?30'W), a lowland Sonoran Desert stream (see Fisher and Minckley, 1978, for a description of the Sycamore Creek watershed). In addition to descriptive studies of each recolonization pathway during stable-flow periods, the hypothesis that aerial pathways are used by most taxa to recolonize after flooding was tested for winter and summer floods. This hypothesis was suggested by observations on species composition and life history characteristics of Sycamore Creek macroinvertebrates (Gray, 1980). Forty of the 104 taxa present have long-lived aquatic adults capable of flight (Coleoptera and Hemiptera), and most remaining species (e.g., mayflies, caddisflies and small dipterans) reproduce throughout the year and lack dormant stages in substrates. Few taxa exhibit dormancy [e.g., Mesocapnia arizonensis (Baumann and Gaufin) and Tabanus dorsifer Walker]; thus vertical movements of these

Movement Patterns and Home Range of the Gopher Tortoise

Abstract: Movement patterns and home ranges of gopher tortoises {Gopherus polyphemus) in southwestern Georgia varied seasonally and were determined largely by social interaction. Adults congregated in breeding colonies on droughty sites in early spring. During spring and summer, females were more sedentary than males; burrow preferences and movements of males were largely determined by mate-seeking and hierarchial behaviors. Individuals began to disperse from breeding colonies by late summer and about half moved to adjacent autumn-win ter range on more mesic soils, likely due to the better food supply. Adults used a minimum of three burrows during an activity season (x = four for females, seven for males) and did not co-occupy burrows overnight. Juveniles typically moved short distances and used only 1 or 2 burrows, but usually left the vicinity of breeding colonies before or during the years as subadults. This dispersal is apparently an important mechanism for adding young adults to sparsely populated colonies and for forming new colonies.

Ecological consequences of food limitation for adult mantids (Tenodera ardifolia sinensis Saussure).

Abstract: Comparative studies between adult mantids (Tenodera ardifolia sinensis) in field populations and cohorts maintained in the laboratory on ad lib. diets suggest that females in field populations were food-limited. Food limitation apparently occurred in two cases during the time of acquiring energy to produce oothecae and in one case prior to maturation. In each case the net result was decreased fecundity. We recognize two distinct components to the life history food requirements of this species: (1) the food re- quired to reach maturity, and (2) the additional food required by females to produce oothecae. Our data suggest that food availability for nymphs affects initial sizes of adults, which in turn determines potential weight gain during the adult portion of the life cycle. Both the magnitude of this potential and the extent to which it is realized affects fecundity. The constraints imposed on either food component by membership in, and reliance upon, a seasonal insect community have implications for the ecological

Tolerance of Headwater vs. Mainstream Fishes for Abrupt Physicochemical Changes

Abstract: A headwater cyprinid (Phoxinus oreas) of the Roanoke River drainage (Virginia) was compared to three mainstream cyprinids (Notropis ardens, N. albeolus and N. cerasinus) for tolerance of abrupt changes in dissolved oxygen, temperature and pH. A darter common in the headwaters (Etheostoma flabellare) was compared to two mainstream darters (E. podostemone and Percina roanoka) for tolerance of low oxygen. In all interspecific comparisons, species characteristic of intermittent headwaters were more tolerant than those restricted to the more environmentally stable mainstream. Etheostoma flabellare from intermittent headwaters were more tolerant of low oxygen conditions than conspecifics from the river mainstream.

The Effect of Seed Size and Relative Emergence Time on Fitness in a Natural Population of Impatiens capensis Meerb. (Balsaminaceae)

Abstract: The importance of seed size and relative emergence time to survivorship and fecundity in natural populations of the woodland annual Impatiens capensis was assessed by "close-interval" censusing techniques applied to populations growing in Concord, Massachusetts. Emergence time was important, but neither the effect of seed size nor the size X emergence time interaction was significant. Introduction Plant ecologists have often concerned themselves with the population biology of monospecific stands of annual plants. Such populations often experience severe mortality (Yoda et al, 1963; Hiroi and Monsi, 1966), much of it seemingly due to competition among individual plants (Mack and Harper, 1977). Substantial variation in the demographic parameters of individuals results (Ross and Harper, 1972; Obeid et al, 1967; Cook, 1979, 1980). These situations offer insight into the mechanics and evolutionary importance of competitive interactions. How much mortality is actually caused by competition? Is this mortality, as Williams (1975) supposes, a selective process: Are successful plants genetically different from less successful ones? Is there selection for 'competitive ability/ and can we understand the basis of this elusive trait? This paper considers the effect of certain seedling traits on 'competitive ability/ measured as the fitness of individual plants growing in monospecific stands. The most important process that accompanies growth of these populations is the development of a 'dominance hierarchy' (Koyama and Kira, 1956; Obeid et al, 1967; Ford, 1975). As the stand of plants develops, certain individuals preempt increasing amounts of space. Ultimately, the stand is composed of a few large, dominant individuals and many smaller, less vigorous, suppressed individuals. Initially, seedling size has nearly a normal distribution, but as growth proceeds it develops an increasingly negative skew and ultimately assumes a log-normal or bimodal form (Koyama and Kira, 1956; Obeid et al, 1967; Ford, 1975; Rabinowitz, 1979). This skewness develops as the result of the rapid, nearly exponential growth of the dominant individuals, and the much slower growth of the suppressed plants. Eventually, the populations enter a 'self-thinning' stage (Harper and McNaughton, 1962) in which there is substantial mortality. There are important differences in the demographic parameters of dominant and suppressed plants. Smaller individuals are more likely to die than large ones (White and Harper, 1970; Black, 1957), and large individuals often produce vastly greater numbers of offspring than the smaller ones (Salisbury, 1942; Gottlieb, 1977). These demographic differences raise the question of the evolutionary status of dominant individuals. Do they represent a 'genetic elite' (Dobzhansky, 1964), composed of 'sisyphean genotypes' (Williams, 1975), the grim remnant of a period of intense selection for 'competitive ability'? Alternatively, can we explain the phenomenon of self-thinning without reference to natural selection (e.g., Gottlieb, 1977) ? One approach to these questions seeks to understand the influence of various seedling characteristics on the development of the dominance hierarchy. A number of workers have studied this issue. Black (1956, 1957, 1958) conpresent address: Department of Botany, Duke University, Durham, North Carolina 27706.

Prey capture by the crab spider Misumena vatia (Clerck) (Thomisidae) on three common native flowers.

Abstract: I compared the capture methods and prey of crab spiders Misumena vatia (Clerck) hunting on pasture rose (Rosa carolina L.), common milkweed (Asclepias syriaca L.) and goldenrod (Solidago j?ncea Ait.). Individual spiders occupied milkweed and goldenrod inflorescences significantly longer than rose flowers. They also captured significantly larger biomasses of prey on milkweed and goldenrod than on rose. During the day, spiders captured a larger biomass of prey on goldenrod than on milkweed; however, when nighttime captures on milkweed (entirely moths) were added, it was the most profitable feeding site. The low captures of prey on pasture rose were partly a consequence of the short period during which it attracted insects each day. Overall, bumblebees (Bombus spp.) were the most important prey in terms of biomass, although small syrphid flies (Toxomerus marginatus) were the most frequently captured prey. The only other frequently captured items were honeybees (Apis mellifera) and moths, both primarily on milkweed. Only on milkweed was there sign of nocturnal hunting. Spiders hunting on roses invested considerable time finding new flowers each day and also took longer to process prey than did spiders on other flowers.

Tree Invasion of Montane Meadows in Oregon

Abstract: Mesic montane meadows in the Cascade Mountains of central and southern Oregon have been invaded recently by trees from the adjacent forests. Cessation of sheep grazing coincides with the initiation of the tree invasions, but the absence of frequent fires and cool moist weather both may have contributed to the conditions which favored the unstable ecotones.

The distribution of plant water stress and vegetation characteristics in southeastern California chaparral.

Abstract: Plant xylem pressure potentials and various shrub characteristics were measured in seven chaparral stands located between the coastal and inland boundaries of the chaparral vegetation in southern California. Early summer xylem pressure potentials decreased progressively from the boundaries of chaparral to the center of the chaparral zone, with increasing stand age and with increasing foliage-area index. Pressure potentials increased with annual precipitation. Stem elongation, leaf size and leaf density were related more to stand age and transpiration per unit leaf-area index than to annual precipitation per se. The boundaries of the chaparral occur where transpiration is ca. 200 mm/year per unit leaf-area index, which occurs with an annual precipitation of about 400 mm/year. With increasing precipitation, the leaf-area index can increase such that transpiration per unit leaf-area index remains at ca. 200 mm/year.

Food Partitioning in Three Sympatric Species of Map Turtle, Genus Graptemys (Testudinata, Emydidae)

Abstract: Three species of map turtle, Graptemys geographica, G. ouachitensis and G. pseudo geo graphic a, inhabit the Mississippi River near Stoddard, Vernon Co., Wiscon- sin. Adult females of all three species are of similar size and are distinctly larger than males. One species, G. geographica, has a notably wider head than the other two. Quan- titative analysis of fresh stomach contents of 113 adult females, qualitative analysis of 74 others and feeding observations confirm that the three species use different foods and feeding strategies. Graptemys geographica is a carnivore specializing on mollusks. Grap- temys ouachitensis is an omnivore, but specializes in surface feeding. Graptemys pseudo- geographica is a general omnivore, overlapping the other two species both in food and feeding areas. Graptemys geographica seems to be limited by food availability. Graptemys ouachitensis represents 66% of the Graptemys in the study area and may be best at exploiting an apparently unlimited food resource of aquatic vegetation and insect larvae. In Arkansas, G pseudo geo graphica is a mollusk specialist, possibly due to lack of com- petition from G geographica and competition from the ubiquitous generalist, Pseudemys scripta, and the strict vegetarian, Pseudemys concinna.

Courtship solicitation by colias females lepidoptera pieridae

Abstract: Females in the Colias eurytheme C. philodice species complex may sometimes approach and chase patrolling males. Chases that were elicited by presenting tethered males to free-flying females generally lasted less than 4 sec and their duration was not related to any of several measures of female reproductive condition. However, the probability that mated females approached males was directly related to the degree of depletion of the contents of spermatophores received in previous matings. These observations suggest that females that approach males are doing so to solicit male courtship attempts and potentially remate to receive a fresh spermatophore. These results are compared and contrasted with reports of similar behavior in other butterflies.

Foraging Ecology of Seed-Harvesting Ants, Pheidole spp. in a Chihuahuan Desert Ecosystem

Abstract: Seasonal activity, factors affecting foraging activity and forage selection were studied in three species of Pheidole (Hymenoptera: Formicidae) on a watershed in the southern New Mexico Chihuahuan Desert. Pheidole spp. exhibited a seasonal pattern in numbers of active colonies with most colonies active in July coincident with onset of summer rains and seed drop by annual plants. Pheidole militicida occurred only on the deeper soils of the lower watershed while Ph. rugulosa and Ph. xerophila occurred on the entire watershed. The three Pheidole spp. were active only at soil temperatures between 15-35C and were most active at sunrise. Analysis of factors affecting foraging intensity using a stepwise discriminant function and regression showed evaporation and soil surface temperature to be the strongest influences and seed availability to rank second. However, the factors included in the analysis accounted for less than 50% of the variance in all three species. Pheidole militicida collected mostly forb seeds while Ph. xerophila utilized primarily grass seeds, especially the seeds of fluff grass Erioneuron pulchellum. Introduction Seed-harvesting ants (Pogonomyrmex sp., Veromessor pergandii (Mayr) and Pheidole sp.) are important components of desert ecosystems (Whitford, 1978; Davidson, 1977). The ecology of Pogonomyrmex sp. has been studied extensively by Whitford (1976, 1978), Whitford et al (1976), Whitford and Ettershank (1975) and Rogers (1974). Tevis (1958), Went et al. (1972), Clark and Comanor (1973), Wheeler and Rissing (1975a, b,) and Rissing and Wheeler (1976) reported on aspects of the ecology of Veromessor pergandii. However, studies on the foraging ecology of desert-inhabiting species of Pheidole are limited (Davidson, 1977). Studies of Pheidole are necessary to assess the relative impact of seed-harvesting ants in desert ecosystems. Brown and Davidson (1977) showed that the density of Pheidole sp. increased in areas where seed-eating rodents were excluded, indicating that these seed harvesters responded quickly to the removal of competitors whereas the large-bodysize, seed-harvesting ants of the genus Pogonomyrmex appeared not to be affected. The work of Brown and Davidson suggests potentially important differences between Pheidole and Pogonomyrmex and point to a need for information concerning the foraging ecology of desert species of Pheidole. Our studies were designed to examine the foraging ecology of Pheidole militicida (Wheeler), Pheidole rugulosa (Gregg) and Pheidole xerophila (Wheeler), the most numerous species of Pheidole in several plant communities on a Chihuahuan desert watershed. Methods Studies were conducted on the Jornada Validation Site watershed 40km NNE of Las Cruces, Dona Ana Co., New Mexico. The watershed is an alluvial fan to the ? and E of Mt. Summerford, Dona Ana Mountains, which drains into a small ephemeral lake. The upper portion of the watershed at the base of the mountain (elevation ca. 2000 m) is a black grama (Bouteloua eriopoda) (Torr.) grassland which shifts abruptly to a creosote bush (Larrea tridentata) (DC)-dominated desert pavement community on shallow soils. On the highly dissected slopes of the watershed, the creosote bush community supports a variety of annual plants which occur at low densities during summer rainy periods (ca. lO^OO'ha-1) (Whitford, 1973). 1 Permanent address : Department of Zoology and Entomology, Monash University, Clayton, Victoria, Australia.

Periphyton Production in an Appalachian Mountain Trout Stream

Abstract: Periphyton primary production was investigated in a second-order Appalachian Mountain stream and two of its tributaries. Using 14C fixation in recirculating chambers, estimates averaged 2.27 mg C m-2 h-1 in the mainstream and 1.65 and 1.37 mg C m~2 h-1 in the two tributaries. Abiotic factors most influential on primary production rates were light, streamflow and inorganic carbon. Based on annual budgets, the estimated stream energy input attributable to autochthonous primary production was about 3% of allochthonous inputs. However, because of high nutritive value and timing, autochthony may be more important than indicated by annual budgets. Introduction Many studies have indicated that allochthonous organic material is the major energy base for low-order streams {e.g., Nelson and Scott, 1962; Minckley, 1963; Hynes, 1963; Maciolek, 1966; Minshall, 1967; Fisher and Likens, 1972, 1973; Cummins, 1974). However, Minshall (1978) argued that belief in a general dependency of streams on allochthonous organic materials has resulted from a concentration of research effort in small streams in deciduous forests. In studies of such streams, the role of autotrophy has often been disregarded as negligible and not measured. In a recent review on lotie primary production, Wetzel (1975a) emphasized that in any attempt to effectively evaluate the efficiency and dynamics of a detritus-based system, it is essential to measure the magnitude and fluctuations of autotrophy. In general, quantitative measurements of annual primary production in lotie ecosystems are scarce (Likens, 1975). Of the few measurements made of annual primary production in low-order woodland streams, nearly all have been of tangential interest within more general studies and were usually accomplished by biomass accumulation techniques. Biomass accumulation techniques as measures of photosynthetic rate are considered error-prone for various reasons (Wetzel, 1975a). Hoskin (1959, as cited by Wetzel, 1975a) and Hall (1972) used the diurnal oxygen curve method in relatively small streams, but in most low-order streams, relatively high gradients and turbulence preclude using open system oxygen methods. Hansmann (1969) studied three streams, using the oxygen method but employing recirculating chambers to avoid problems produced by turbulence. Chambers improve measurements but in many cases, where primary production is relatively low, accurate measurement requires more sensitive methods than gas exchange techniques. Carbon-14 methodology is about 50 times more sensitive than gas exchange methods (Wetzel, 1975b) and therefore is particularly useful in low-order woodland streams. In this study we have coupled the advantages of using recirculating chambers and carbon-14 methodology to investigate carbon fixation rates in a second-order Appalachian Mountain trout stream and two of its tributaries. Description of Study Area Primary productivity measurements were made in Guys Run, a second-order tributary of the Calfpasture River (James River Basin, Rockbridge Co., Virginia; 79?39' W long, 38?58' ? lat) and in two tributaries, Glade Brook and Piney Branch. Most of the 19 km2 watershed of Guys Run is located within the Goshen Wildlife address correspondence to J. R. Webster.

Log Decomposition in Donaldson's Woods, Spring Mill State Park, Indiana

Abstract: Stem maps of the 4rees on 8.16 ha of Donaldson's Woods were used to help identify logs and estimate their ages on the forest floor. I collected 162 samples from 126 different logs representing 10 different genera. Logs were assigned to age classes based on information from the stem maps and assigned to decay classes by physical appearance. Total log frequency was 37.6 logs/ha. Mean log input rate was 2.52 log/ha/year. Oak-log biomass, area and volume were calculated. Oak-log decay was calculated as Y = .5402 exp (-0.0295 t), where Y = density in g/cc, t = time in years (n = 62, r2 = 0.949). An average oak log takes ca. 75 years to decay to 1/10 its original density. INTRODUCTION An essential step in ecosystem nutrient cycling is the decay of plant litter, and since logs represent a relatively large pool of nutrients temporarily stored on the forest floor (Lang and Forman, 1978), studies of log accumulation and decomposition are important to estimates of total nutrient budgets (Bormann and Likens, 1979; Waring and Franklin, 1979). However, tree death and subsequent decomposition of woody material is a largely unknown component in forest nutrient cycles. There are considerable data on leaf-litter decomposition and nutrient cycling in both deciduous and coniferous forests (e.g., Edwards et al., 1970; Duvigneaud and Denaeyer-DeSmet, 1970), but there is much less information on decomposition and nutrient turnover from larger woody inputs such as downed tree trunks (Bormann and Likens, 1979; Waring and Franklin, 1979). Estimates of woody litter production were reported by Bray and Gorham (1964), McFee and Stone (1966), Cromack (1973), Cromack and Monk (1975), Grier and Logan (1977), Lang and Forman (1978), Bormann and Likens (1979) and Waring and Franklin (1979). Woody litter accumulation is widely variable, depending on climatic conditions, density of stand stocking, availability of nutrients and decay rates. Decay rates of woody litter are difficult to measure. In three studies that have been done, McFee and Stone (1966) described decay of logs over 100 years old, but they did not report a decay rate. J. E. Means (pers. comm.) reported a decay rate for Douglas fir logs in Oregon, and Odum (1970) reported a decay rate for logs in a Puerto Rican rain forest. Like decay of leaves and small branches, log decomposition appears to be correlated with climate and with substrate quality of the wood (Fogel and Cromack, 1977). Since summers in southern Indiana are warm and wet, decomposition rates are expected to be rapid (cf. Olson, 1963). The objectives of this study were to measure the number of logs/ha, and to calculate input rate, woody biomass and decay rate of logs found in a deciduous forest in S-central Indiana. A secondary objective was to test the applicability of a five-class scheme that allowed categorization of logs into different decay classes. SITE DESCRIPTION Donaldson's Woods, the site of this study (38?45'N and 86025'W) is a nearly classic example of Braun's (1950) western mesophytic deciduous forest, or using Bailey's (1976) classification, it is on the border between the beech-maple and oakhickory forests, and contains white oaks (Quercus alba) over 90 cm diam and tulip trees (Liriodendron tulipifera) over 112 cm diam. Because the Woods is an Indiana State Nature Preserve, and living trees cannot be cut or harmed, I could not increment-bore any trees to estimate the age classes. The area studied was 3.35 ha at the northern end

An integrated multivariate analysis of forest communities of the Central Great Smoky Mountains.

Abstract: An integrated sequence of multivariate techniques was applied to vegetation and site data from 244 stands in the central Great Smoky Mountains National Park. The analyses included cluster analysis, stepwise multiple discriminant analysis with both species and site variables, reciprocal averaging, canonical analysis and canonical correlation. Taken together, they provided a system of successive refinement and cumulative evidence for analysis of vegetation and vegetation-site relationships. Nineteen forest community types were identified and examined. At the broad level, the vegetation pattern was most directly related to elevation, topography and stand history. However, some soil variables were important, specifically soil/?H and clay content of the ? horizon. The most useful measures of topographic effects were topographic position and total annual potential solar irradiation (a function of slope angle and aspect). Number of dead Castanea dentata remains provided a measure of past disturbance which was related to the vegetation pattern. Introduction The Great Smoky Mountains National Park, located in eastern Tennessee and western North Carolina (approximately 83? 30' W longitude, 35? 45' ? latitude), contains large areas of undisturbed and little-disturbed temperate forests. General descriptions of the physiography, climate, flora, general vegetation and land use history are available elsewhere (Cain, 1930, 1931, 1945; Whittaker, 1956, 1966; King and Stupka, 1950; Hoffman, 1964; Frome, 1966; Golden, 1974). Whittaker's (1956) monograph is the most comprehensive treatment of the general vegetation pattern. He provided a direct gradient analysis which related species populations and subjectively defined community types to elevation and to a qualitative moisture "complex-gradient" based on topographic characteristics. He did not obtain any data on soils. His scope was the entire national park and involved data from locations scattered throughout it. The study reported here was designed to supplement previous studies. It employs an integration of several multivariate techniques which have recently become widely used. The scope is the middle elevation forests of the central portion of the park. This was defined as forest stands at 750-1600 m elevation in an area ca. 20,000 ha, roughly centered on Mt. LeConte. Field observation indicated that the vegetation pattern of this area varied significantly in certain details from the general pattern reported by Whittaker (1956). For example, the high elevation Quercus alba communities he reported are absent here, and Tsuga canadensis is more prominent than in the remainder of the park. This paper has two primary purposes: (1) to more clearly define the forest vegetation pattern and forest vegetation-site relationships in the central Great Smoky Mountains, and (2) to illustrate the integrated use of a combination of multivariate techniques for defining and describing such vegetation attributes. Methods and Results data Data from 244 forest stands were used in the analyses and descriptions. Each stand was sampled using a 0.08 ha circular plot in which trees > 12.7 cm dbh were tallied by species in 5-cm dbh classes. Sample locations were selected primarily from topographic maps with the objective of obtaining a reasonable distribution among topographic situations in the elevation range 750-1600 m. Species importance percentages for each stand were computed as one-half the sum of relative density and relative basal area. 37 This content downloaded from 157.55.39.162 on Thu, 11 Aug 2016 04:52:52 UTC All use subject to http://about.jstor.org/terms 38 The American Midland Naturalist 106(1) Only tree species present in at least three stands (30 species) were used in the analyses. Taxonomic nomenclature follows Little (1953). Topographic measurements taken included elevation, slope angle, slope direction and slope position (as percent distance from ridge to cove or valley bottom). The potential annual solar irradiation (in langleys) was estimated for each site from the tables of Frank and Lee (1966). Soil profile descriptions and samples were taken from a soil pit near the center of each plot. Soil p?i and texture for each horizon were determined in the laboratory. numerical analyses An integrated sequence of multivariate procedures, involving both classification and ordination, was used to explore the vegetative and environmental relationships among the communities. The sequencing and integration of the procedures are illustrated in Figure 1. Cluster analysis and similarity sorting. ?Minimum within-group dispersion using standard distance (Orloci, 1967), a polythetic agglomerative clustering algorithm, was used to provide a basis for defining stand groups which represent community types. The data were species importance values. A dendrogram was constructed using output

Seed Production and Seedling Establishment in the Mayapple, Podophyllum peltatum L.

Abstract: Mayapple (Podophyllum peltatum L), a perennial clonai herb, produces flowering and nonflowering stems. Stem densities per clone are fairly constant from year to year, but fruit and seed production is variable, both among clones and among years. Fruit production is positively correlated with flowering stem density per clone. Seven age-specific mortalities are recognized from flowering to seedling establishment: flower abortion, improper pollination, immature fruit loss, failure of fruits and seeds to be removed from clone area, seed pr?dation, failure of seed germination and seedling competition. Improper pollination is responsible for the largest loss of potential seeds; failure of seeds to be removed from the clonai area is the second most important mortality factor. Eastern box turtles (Terrapene carolina) are the only seed dispersal agents so far identified. Turtle-ingested seeds germinate faster and have a higher probability of success than noningested seeds. The survivorship curve for turtle-ingested seeds is Type II. The negative exponential model for seedling mortality best describes the mayapple and predicts a reduction of the initial seed crop to one plant by the 5th year.

Vegetation of northern New Jersey before European settlement.

Abstract: The vegetation of northern New Jersey before European settlement was reconstructed from early descriptions and land surveys. The land was forested except for scattered lowland meadows and clearings made by Indians. Several oak (Quercus) species dominated the forests. Chestnut (Castanea dentata) was common in steeper areas and hickory (Carya spp.) was common throughout. Hemlock (Tsuga canadensis) and the northern hardwoods, such as sugar maple (Acer saccharum) and beech (Fagus grandifolia), were present but not abundant. Overall the dominants of the 17thand early 18th-century upland forests were similar to those in today's forests, but with more chestnut and hickory and less birch (Betula spp. ) and maple.

Effects of Age, Sex and Weight on Social Rank in Penned White-tailed Deer

Abstract: Relationships of dominance to age, sex and weight were examined in a herd of penned white-tailed deer (Odocoileus virginianus borealis) for 3 years near Guelph, Ontario. Hierarchies were constructed for each month using a method which minimized dominance triangles. Adult males ranked significantly higher (P <0.05) than adult females in all but 3 months, higher than yearling males in six of 15 months, and higher than other classes in all months with sufficient data for comparisons. Adult females dominated (P<0.05) yearling males in seven of 15 months, primarily in summer and autumn. Adult females ranked significantly above (P<0.05) yearling females until after the peak in rut, but did not rank significantly higher thereafter. Fawn females were uniformly subordinate to adult does, but fawn males began in their first rut to dominate adult and yearling does. Mean rank of yearling males was always higher than yearling females, but statistical comparisons were impossible. Yearling females were usually ranked above fawns although no statistical differences were evident. Difference in mean ranks between male and female fawns was never statistically significant, but mean rank of males was always higher. Partial correlations showed that virtually all variation in rank accounted for by coefficients of multiple determination was explained by weight in males and age in females. Importance of weight in males reflected strength and endurance necessary to win severe fights. Outcome of contests between does depended on conditioning, persistence and experience gained with age.

Seasonal Diets of the Porcupine Caribou Herd

Abstract: Microhistological techniques were used to quantify the diet of the Porcupine Caribou Herd of the northern Yukon during seven phenological periods. Winter diet was characterized by a dominance of lichens (66.7%) and mosses (28.8%). The shift from winter to summer diet was marked by a large increase in the use of vascular vegetation. Sedges comprise the bulk (55.5%) of the spring diet with orthophyll shrubs assuming dominance (over 98%) during the postcalving period. The use of orthophyll shrubs begins to decline during August and by autumn the diet is essentially similar to that during winter.

Low Genetic Variability and High Similarities in the Crayfish Genera Cambarus and Procambarus

Abstract: Electrophoretic analysis of 19 biochemical loci was used to investigate relationships among six species of crayfish inhabiting the Savannah River Plant near Aiken, South Carolina. One species of the genus Cambarus (C. latimanus) and five species of the genus Procambarus (P. ranei. P. pubescens, P. hirsutus, P. acutus, P. troglodytes) were studied. Seven of 19 loci were polymorphic in at least one species while 12 loci were consistently monomorphic in all species. The mean heterozygosity (H) for all species was 0.016?0.01. Nei's identity values (I) were calculated for all species pairs. The average J between Procambarus species was 0.78 ?0.1 and the range was 0.63 to 0.89. The average J between C. latimanus and the Procambarus species was 0.51 ? 0.04. As shown in this and other studies, H in decapod crustaceans is low compared to that of other organisms..

Factors Affecting the Establishment of Natural Vegetation on a Coal Strip Mine Spoil Bank in Southeastern Ohio

Abstract: Soil factors affecting plant establishment on strip mine soils were examined. Soil ?? was below 4.0 and aluminum concentrations averaged from 2.8 to 4.0 meq/100 g, levels considered toxic to plants. Transplant studies with Panicum clandestinum and Andropogon virginicus indicated that they could grow under these extreme conditions. In vegetated island areas with high litter content, establishment occurs readily even though soil pK conditions are similar to the unvegetated area. High soil temperatures and low soil moisture on the spoil inhibit germination and establishment of plants.

Effect of season of burning and mowing on an eastern Nebraska Stipa-Andropogon prairie.

Abstract: The effects of spring and summer mowing and spring burning on species composition and inflorescence phenology were evaluated on an eastern Nebraska bluestem prairie with a history of summer mowing. Portions of the prairie were burned and mowed in April 1978; evaluations were conducted in June and August of the same year. Canopy cover and flowering stem numbers and height of porcupine grass (Stipa sparten), a cool season species, consistently averaged higher on areas mowed in the summer. In contrast, big bluestem (Andropogon gerardti), a warm season grass, was favored by spring burning and mowing. These effects, as well as the responses of other cool and warm season species, suggest that over time, summer treatments will tend to increase the dominance of cool season species whereas spring treatments will increase that of warm season species. Comparisons between treatments suggest that the vegetative responses to spring mowing are more similar to spring burning than summer mowing. Thus, it appears that the time of treatment has a greater impact on potential vegetative change than does the type of management. Consideration of these influences is essential when selecting appropriate practices designed to maintain bluestem prairie in near pristine condition.

Behavior of the Evening Bat Nycticeius humeralis at a Nursery Roost

Abstract: Roosting behavior was investigated in the evening bat Nycticeius humeralis during the summer of 1971 in northern Missouri. Adult females arrived at maternity colonies by early May. They gave birth by mid-June and had all begun their southern migration by mid-September. Females nursed their own offspring during the 1st 2 weeks subsequent to birth; then they nursed any approaching young until weaning. Weaning and foraging flights by the young occurred simultaneously. Adults were found at higher temperatures during lactation than during pregnancy or postlactation. Following weaning, juveniles were found at higher temperatures than postlactating adults. Movement patterns appear to be related to thermor?gulation and to water conservation.

Spring Ground Layer Vegetation 50 Years After Harvesting in Northern Hardwood Forests

Abstract: Ground layer vegetation on four approximately 50-year-old silviculture research plots at the Upper Peninsula Experimental Forest, Michigan, was surveyed in the spring of 1976. Species composition was typical of northern hardwood forests and similar among plots. The vegetation was denser but less diverse on clear-cut harvest plots than on less severely but more frequently disturbed selection harvest plots. Periodic reharvests of the selection harvest plots promoted development of an intermediate layer of tree seedlings and shrubs that was probably responsible for the differences in ground layer vegetation among harvest methods.

Feeding Behavior of a Plant: Differential Prey Capture in Old and New Leaves of the Pitcher Plant (Sarracenia purpurea)

Abstract: The functional response of the carnivorous pitcher plant (Sarracenia purpurea L.) was determined using Drosophila melanogaster as prey. These plants exhibit a sigmoid-shaped curve in response to an increase in prey availability. Plants with newly opened leaves captured significantly more Drosophila in 24 hr than plants without new leaves. The number of Drosophila caught was related to the size of the leaf opening in plants that did not have newly opened leaves. This relationship did not occur in plants that had newly opened leaves. There was no increase in the number of Drosophila caught as the number of leaves per plant increased. INTRODUCTION The response of predators to changes in the number of prey available has been widely studied. Soloman (1949) first noted two such responses: the numerical response in which there is a change in the density of predators and the functional response in which there is a change in the predator's capture rate. Holling (1959) categorized three types of functional responses typical of different animals: Type 1 curves are characteristic of animals which consume food at a rate proportional to the rate of encounter (e.g., filter feeders). This response increases linearly with increasing prey availability until it reaches an asymptote. Type 2, or the "invertebrate" curve, rises at a negatively accelerating rate and is characteristic of animals that require a certain amount of time to capture and digest their prey. Type 3, or sigmoid-shaped curves, are typical of animals which exhibit some form of learning behavior. The sigmoid curve results because the animals do not respond readily to changes in density when the prey is scarce; it is only when the prey is relatively abundant that the capture rate of the predators goes up quickly, and then the response is a curvilinear rise up to a plateau. While functional responses have been demonstrated for a wide range of animal species (Holling, 1959; Hassell, et al., 1977), the response to increased prey density has not been examined in carnivorous plants -plants that supplement their nutrition by capturing and digesting animal prey (Schnell, 1976). Pitcher plants (Sarracenia purpurea L.) capture insects passively by means of hollow tube-shaped leaves. The leaves grow for approximately 2-3 weeks before the opening of the leaf is revealed by the splitting open of the top or leaf hood. When the hood opens, insects are attracted to the leaf by a nectar secreted from glands on the internal surface of the leaf (Adams and Smith, 1977). They are then directed by downward-pointing hairs onto a slippery inner surface, causiig them to fall into the leaf liquid composed of rainwater and symbiotic organisms (Fish and Hall, 1978). Captured insects drown in the liquid and are digested by leaf-secreted enzymes (Heslop-Harrison, 1976) and bacterial exozymes. In this, the sarcophageal region of the leaf, foliar absorption of nutrients occurs (Plummer and Kethley, 1964). Previous work has shown that the prey-capture ability of a pitcherplant leaf is greatest in the 1st month after the flap opens (Fish and Hall, 1978). After 30 days, the number of prey captured by the leaf declines. The purpose of this laboratory study was to determine the functional response of pitcher plants to changes in prey density (Drosophila melanogaster) and how this response differs between plants with newly opened leaves ( < 30 days old) and those without 1 Present address: 222 Sheraton Drive, Montreal West, Quebec H4X IN4. Department of Botany, University of Toronto, Toronto, Ontario, Canada M55 7A7