Midland Naturalist Research Articles

Dynamics of the Boreal Forest in Northwestern Ontario

-Histories of stand establishment and development in seven boreal forest types, dominated by Picea mariana, Pinus banksiana, Populus tremuloides and Abies balsamea, are analyzed. The initially established tree cohort in the stand appears to be the major determinant of compositional development. The short fire interval accounts for the preponderance of young communities and prevents deterioration of stands. Spruce budworm infestations are a possible factor in the perpetuation of Abies balsamea forests. INTRODUCTION In spite of relative compositional and structural simplicity and apparently uncomplicated vegetation-environment relationships, the course and mechanisms of successional development in central Canadian boreal forest are poorly understood. A few recent studies (Shafi and Yarranton, 1973a, b; Carleton and Maycock, 1978) have described the dynamic status of forests in eastern Ontario. Temporal changes in jack pine (Pinus banksiana) forests were examined by Yarranton and Yarranton (1975), Carleton (1982) and Kenkel (1986), and those in black spruce (Picea mariana) communities by Carleton and Wannamaker (1987) and Taylor et al. (1987). Gregory (1979) provided data on tree reproduction in the southern portion of northwestern Ontario, whereas Cogbill (1985) analyzed forest development in the Laurentian Highlands of western Quebec. No comparable data on forest dynamics exist for northwestern Ontario. Consequently, the goal of the present study is to address problems of tree establishment, early community development and indications of expected compositional changes in boreal forest communities in this region. STUDY AREA The region of study is roughly circular, ca. 700 km in diam (Fig. 1). The western limit is the Ontario-Manitoba border, and the southern is the shore of Lake Superior and the Ontario-Minnesota border. The northernmost sites are located at Big Trout Lake; from there, the eastern limits pass through Kasabonika and Webequie, S to White River and Lake Superior. The region has warm, short and relatively wet summers, and very cold, long and dry winters (Chapman and Thomas, 1968). A N-S gradient of increasing temperature is superimposed on a W-E gradient of increasing moisture. The landscape, except for the rugged shores of Lake Superior, is composed of gently rolling knobs of Precambrian rocks, extensive boggy plains, and various glacial deposits (Zoltai, 1961, 1963, 1965). Mineral soils are coarse and thin, while peat deposits are substantially thicker. Podzols and organic soils (fibrisols and mesisols) are the most characteristic and widespread types. I Present address: Acres International Ltd., 5259 Dorchester Road, P.O. Box 1001, Niagara Falls, Ontario L2E 6W1, Canada. 289 This content downloaded from 157.55.39.209 on Sun, 11 Jun 2017 18:33:43 UTC All use subject to http://about.jstor.org/terms 290 THE AMERICAN MIDLAND NATURALIST 124(2) 96' 95' 96' 9392' 91' 90e9' e8' 87' 66' 65' 8 8' 82

Effects of Flooding and Root Competition on Growth of Shaded Bottomland Hardwood Seedlings

Effects of Flooding and Root Competition on Growth of Shaded Bottomland Hardwood Seedlings

Assemblage Organization of Stream Fishes: The Effect of Rivers on Adventitious Streams

Assemblage Organization of Stream Fishes: The Effect of Rivers on Adventitious Streams

Inferences in the Classroom and Everyday Life

Research Article| May 01 1986 Inferences in the Classroom and Everyday Life Richard J. Medve, Richard J. Medve Search for other works by this author on: This Site PubMed Google Scholar Frank A. Pugliese Frank A. Pugliese Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1986) 48 (5): 272–277. https://doi.org/10.2307/4448291 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Richard J. Medve, Frank A. Pugliese; Inferences in the Classroom and Everyday Life. The American Biology Teacher 1 May 1986; 48 (5): 272–277. doi: https://doi.org/10.2307/4448291 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright 1986 The National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

Mating Reduces Predation on Male Milkweed Beetles

Previous articleNext article No AccessNotes and CommentsMating Reduces Predation on Male Milkweed BeetlesDavid E. McCauley, and Ellen C. LawsonDavid E. McCauley Search for more articles by this author , and Ellen C. Lawson Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 127, Number 1Jan., 1986 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/284472 Views: 4Total views on this site Citations: 21Citations are reported from Crossref Copyright 1986 The University of ChicagoPDF download Crossref reports the following articles citing this article:Madison Hernandez, Paul Masonick, Christiane Weirauch Crowdsourced online images provide insights into predator-prey interactions of putative natural enemies, Food Webs 21 (Dec 2019): e00126.https://doi.org/10.1016/j.fooweb.2019.e00126P. A. Lagos A review of escape behaviour in orthopterans, Journal of Zoology 303, no.33 (Sep 2017): 165–177.https://doi.org/10.1111/jzo.12496Danilo G. Muniz, Glauco Machado Experimental limitation of oviposition sites affects the mating system of an arachnid with resource defence polygyny, Animal Behaviour 109 (Nov 2015): 23–31.https://doi.org/10.1016/j.anbehav.2015.08.007Taís M. Nazareth, Glauco Machado, Claude Wicker-Thomas Egg Production Constrains Chemical Defenses in a Neotropical Arachnid, PLOS ONE 10, no.99 (Sep 2015): e0134908.https://doi.org/10.1371/journal.pone.0134908Gustavo S. Requena, Glauco Machado Lack of costs associated with nest-related behaviors in an arachnid with exclusive paternal care, Oikos 124, no.33 (Sep 2014): 372–380.https://doi.org/10.1111/oik.01641Amanda M. Franklin, Zoe E. Squires, Devi Stuart-Fox, Therésa M. Jones Does Predation Risk Affect Mating Behavior? An Experimental Test in Dumpling Squid (Euprymna tasmanica), PLoS ONE 9, no.1212 (Dec 2014): e115027.https://doi.org/10.1371/journal.pone.0115027Giovanni Benelli, Gabriele Gennari, Alessandra Francini, Angelo Canale Longevity costs of same-sex interactions: first evidence from a parasitic wasp, Invertebrate Biology 132, no.22 (May 2013): 156–162.https://doi.org/10.1111/ivb.12017Stephen F. Matter Abundance of an Herbivorous Beetle: Factors Affecting Dispersal and Local Reproduction, The American Midland Naturalist 162, no.11 (Jul 2009): 19–28.https://doi.org/10.1674/0003-0031-162.1.19Maria Almbro, Cecilia Kullberg The downfall of mating: the effect of mate-carrying and flight muscle ratio on the escape ability of a pierid butterfly, Behavioral Ecology and Sociobiology 63, no.33 (Oct 2008): 413–420.https://doi.org/10.1007/s00265-008-0675-4Stephen F. Matter Changes in landscape structure decrease mortality during migration, Oecologia 150, no.11 (Jul 2006): 8–16.https://doi.org/10.1007/s00442-006-0491-3Rickey D. Cothran Precopulatory mate guarding affects predation risk in two freshwater amphipod species, Animal Behaviour 68, no.55 (Nov 2004): 1133–1138.https://doi.org/10.1016/j.anbehav.2003.09.021O. Y. Martin, D. J. Hosken Copulation reduces male but not female longevity in Saltella sphondylli (Diptera: Sepsidae), Journal of Evolutionary Biology 17, no.22 (Dec 2003): 357–362.https://doi.org/10.1046/j.1420-9101.2003.00668.xQiao Wang, Wenyu Zeng , Environmental Entomology 33, no.33 ( 2004): 657.https://doi.org/10.1603/0046-225X-33.3.657L. M. Hanks INFLUENCE OF THE LARVAL HOST PLANT ON REPRODUCTIVE STRATEGIES OF CERAMBYCID BEETLES, Annual Review of Entomology 44, no.11 (Jan 1999): 483–505.https://doi.org/10.1146/annurev.ento.44.1.483Gary A. Polis, Joseph D. Barnes, Mary K. Seely, Joh R. Henschel, Margit M. Enders PREDATION AS A MAJOR COST OF REPRODUCTION IN NAMIB DESERT TENEBRIONID BEETLES, Ecology 79, no.77 (Oct 1998): 2560–2566.https://doi.org/10.1890/0012-9658(1998)079[2560:PAAMCO]2.0.CO;2Carin Magnhagen Predation risk as a cost of reproduction, Trends in Ecology & Evolution 6, no.66 (Jun 1991): 183–186.https://doi.org/10.1016/0169-5347(91)90210-O Andrew Sih , James Krupa , and Steven Travers An Experimental Study on the Effects of Predation Risk and Feeding Regime on the Mating Behavior of the Water Strider, The American Naturalist 135, no.22 (Oct 2015): 284–290.https://doi.org/10.1086/285044Darryl T. Gwynne Does copulation increase the risk of predation?, Trends in Ecology & Evolution 4, no.22 (Feb 1989): 54–56.https://doi.org/10.1016/0169-5347(89)90144-4BENGT GUNNARSSON Local adjustment of sex ratio in the spider Pityohyphantes phrygianus, Journal of Zoology 217, no.11 (Mar 2009): 1–7.https://doi.org/10.1111/j.1469-7998.1989.tb02470.xAndrew Sih The effects of predators on habitat use, activity and mating behaviour of a semi-aquatic bug, Animal Behaviour 36, no.66 (Nov 1988): 1846–1848.https://doi.org/10.1016/S0003-3472(88)80129-5Kikuo IWABUCHI Mating Behavior of Xylotrechus pyrrhoderus BATES (Coleoptera : Cerambycidae) : IV. Mating Frequency, Fecundity, Fertility, and Longevity, Applied Entomology and Zoology 23, no.22 (Jan 1988): 127–134.https://doi.org/10.1303/aez.23.127

Distribution and Habitat Requirements of the Ozark Cavefish, Amblyopsis rosae

Distribution and Habitat Requirements of the Ozark Cavefish, Amblyopsis rosae

Stochasticity and Assemblage Organization in an Indiana Stream Fish Assemblage

Site d'etude: zone situee sous le barrage de Markles; problemes d'echantillonnage; nombre d'especes incluses dans l'analyse. Inclusion des jeunes d'un an dans cette analyse; interpretation et nouvelle analyse des modeles alternatifs

Effects of Tubificid Worms on the Germination and Establishment of Typha

and subalpine forest succession along a topographic gradient in Wyoming. Ecology 62:319-326. Rundel, P. W., D. J. Parsons, and D. T. Gordon. 1977. Montane and subalpine vegetation of the Sierra Nevada and Cascade Ranges. Pages 5 59-599 in M. G. Barbour and J. Major, editors. Terrestrial vegetation of California. Wiley-Interscience, New York, New York, USA. Schmelz, D. V., and A. A. Lindsey. 1965. Size-class structure of old-growth forests in Indiana. Forest Science 11: 258-264. Vankat, J. L., and J. Major. 1978. Vegetation changes in Sequoia National Park, California. Journal of Biogeography 5:377-402. Whipple, S. A., and R. L. Dix. 1979. Age structure and successional dynamics of a Colorado subalpine forest. American Midland Naturalist 101:142-158.

On the Origin of the Field Plants of the Northeastern United States

Old fields have dominated studies of terrestrial plant succession in the eastern United States. In spite of the tremendous amount of work on old field succession, fundamental questions remain. One such question is the subject of the present paper: In the primeval landscape, where were the plants that are abundant today in old fields? The question holds interest not only for interpretation of the northeastern landscape but also for understanding of the habitats in which field plants evolved. The plants of fallow agricultural fields are widely assumed to be early successional species, i.e., plants adapted to move from one temporary opening to another, but did they really evolve as successional plants? Many of the plants that grow in abandoned fields today are not native to North America and were thus not part of the landscape prior to European settlement. Bard (1952) reported that between one fifth and one third of the plant species in old fields in New Jersey were alien to North America. It is of the remaining two thirds (roughly 100 species) that we can ask, Where was a sun-loving field flora growing in a landscape that was heavily forested? According to Braun (1950, p. 7), "When the first settlers colonized the Atlantic seaboard ... they found an endless expanse of forest broken only by swamps and bogs, by cliffs or river bluffs too steep for forest, by windfalls and burns, by small grassy openings such as the serpentine barrens of the northern Piedmont, and by the prairie patches and 'barrens' of the interior.' Four hypotheses can be suggested to account for the location of native field plants in the presettlement landscape. (1) They evolved on agricultural land abandoned by Indians far back in time. (2) Native field plants migrated eastward from prairies and savannas at the western margin of the deciduous forest with the onset of extensive clearing for settlement and agriculture and with the development of continuous east-west corridors of open field habitat along railroads and canals. (3) Native field plants were true pioneer or early successional species that colonized temporary forest openings caused by wind, fire, and other kinds of

Niche Breadth Calculation Based on Discriminant Analysis

Pyke, G. H. 1981. Optimal nectar production in a hummingbird-pollinated plant. Theoretical Population Biology 20:326-343. Reincke, D. C., and W. L. Bloom. 1979. Pollen dispersal in natural populations: a method for tracking individual grains. Systematic Botany 4:223-229. Schaal, B. A. 1975. Population structure and local differentiation in Liatris cylindracea. American Naturalist 109: 511-528. 1980. Measurement of gene flow in Lupinus texensis. Nature 284:450-45 1. Schlising, R. A., and R. A. Turpin. 1971. Hummingbird dispersal of Delphinium ccardinale pollen treated with radioactive iodine. American Journal of Botany 58:401-406. Schmitt, J. 1980. Pollinator foraging behavior and gene dispersal in Senecio (Compositae). Evolution 34:934-943. Snedecor, G. W., and W. G. Cochran. 1967. Statistical methods, sixth edition. Iowa State University Press, Ames, Iowa, USA. Stockhouse, R. E. 1976. A new method for studying pollen dispersal using micronized fluorescent dusts. American Midland Naturalist 96:241-245. Thomson, J. D. 1981. Spatial and temporal components of resource assessment by flower-feeding insects. Journal of Animal Ecology 50:49-59. Thomson, J. D., and R. C. Plowright. 1980. Pollen carryover, nectar rewards, and pollinator behavior, with special reference to Diervilla lonicera. Oecologia (Berlin) 46:6874. Waddington, K. D. 1981. Factors influencing pollen flow in bumblebee-pollinated Delphinium virescens. Oikos 37:153159. Waser, N. M. 1976. Food supply and nest timing of broadtailed hummingbirds in the Rocky Mountains. Condor 78:133-135. . 1978. Competition for pollination and sequential flowering in two Colorado wildflowers. Ecology 59:934944. Waser, N. M., and M. V. Price. 1982, in press. Optimal and actual outcrossing in plants, and the nature of plant-pollinator interaction. In C. E. Jones and R. J. Little, editors. Handbook of experimental pollination biology. Van Nostrand Reinhold, New York, New York, USA. Waser, N. M., and L. A. Real. 1979. Effective mutualism between sequentially flowering plant species. Nature 281:670-672. Waser, N. M., R. K. Vickery, Jr., and M. V. Price. 1982, in press. Patterns of seed dispersal and population differentiation in Mimulus guttatus. Evolution.

The Occurrence of Lunularia cruciata in California

The Occurrence of Lunularia cruciata in California

An Integrated Multivariate Analysis of Forest Communities of the Central Great Smoky Mountains

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

Reproduction in a Nebraska Sandhills Population of the Northern Prairie Lizard Sceloporus undulatus garmani

Reproduction in a Nebraska Sandhills Population of the Northern Prairie Lizard Sceloporus undulatus garmani

Indirect Mutualism: Variations on a Theme by Stephen Levine

Indirect Mutualism: Variations on a Theme by Stephen Levine

Some Ecological Characteristics of the Ants of a Desert-Shrub Community in Southeastern Arizona

Ants were studied principally by analysis of collections at 66 stations on a 30.3-m grid baited with honey solution and peanut butter. Twenty-three species were collected, which is an exceptionally diverse ant fauna for a small area. Analyses suggest there are several bases for coexistence of these species: (1) Mean body weights of most species are significantly different from each other, and always so within three general feeding categories (seeds; nectar, honeydew and insects; omnivorous). The mean ratio of dry weight of workers of pairs of nearest species was 1.66 within feeding categories and 1.28 between categories. (2) Forage items showed some distinctiveness of food habits among species. (3) Some species were clearly diurnal and others nocturnal in August. (4) Only four species were active up in shrubs in the daytime, and they had their peak numbers in different months or different species of shrubs. (5) Hierarchical classification of stations by species characteristics showed some patterns of distribution of groups of sites according to topography and unknown factors. Other data are given on importance curves, enrichment of species collected with time and space sampled1, species-area relationship, species interactions, and patterns of daily dispersal of workers. Introduction Ants are often assumed to be important components of ecosystems, and in a few cases their importance has been specifically documented, e.g., in terms of energy flow (Golley and Gentry, 1964), modification of soil chemistry and plant distribution (Gentry and Stiritz, 1972), and effects on microsuccession and composition of vegetation (Talbot, 1953; Tevis, 1958). This study concerns a particularly diverse fauna of 23 species of ants within a creosote bush desert community in southeastern Arizona. Simple techniques were used to determine the general ecological characteristics of the ant fauna of the study site, as a prelude to a more extensive study. In particular, ants were collected at bait stations, intensively over a short period of time in August 1972. The collections provided information on species diversity and equitability of the fauna, importance curves, body sizes of species, patterns of diel activity and foraging, patterns of distribution of species in space, and interactions of species. These data, together with information on food habits and activity through a year's time, provide a good initial understanding of the possible bases of coexistence of the ant species of the community. Since the fieldwork was done, several authors have shown that the use of baits, in spite of their artificiality, is a productive way of determining some aspects of ant ecology (Pressick, 1972; Hunt, 1973; Culver, 1974). 33 This content downloaded from 157.55.39.111 on Sat, 17 Sep 2016 06:12:02 UTC All use subject to http://about.jstor.org/terms 34 The American Midland Naturalist 98(1)

Changes in the Phytosociology of Boreal-Conifer-Hardwood Forests on Mackinac Island, Michigan, 1934 to 1974

Stands studied in 1934 by Potzger (1941) were restudied in 1974 revealing changes in the composition of the Mackinac Island, Michigan, boreal-conifer-hardwood forest. Hardwood stands on the higher center of the island were dominated by Acer saccharum, Quercus borealis maxima, Abies balsamea, Betula papyrifera and Fagus grandifolia in order of basal area. By 1974, Fagus had become second in basal area and first in importance value. Hardwood tree stands increased in basal area from 33.85 to 42.57 m2/ha for an average annual increase of 0.22 m2/ha, while the number of trees in the 2500 m2 sample remained almost the same. A boreal conifer forest occupies the lower island periphery, dominated in both years by Thuja occidentalis, unlike surrounding mainland areas where Picea glauca and Abies balsamea are the dominants. The main change was the increase in dominance of Pinus strobus from fifth to second and the decline in dominance of Picea glauca and Abies balsamea. Also conifer stands are being invaded by Acer saccharum. Conifer stand basal area increased from 48.24 to 53.60 m2/ha, with a reduction in number of trees of 833 to 522 in the 2500 m2 sample. INTRODUCTION In 1934 Potzger (1941) began a 3-year study of Mackinac Island forests. In 1974 I investigated those aspects thought to be of most value. Mackinac Island, located in the Straits of Mackinac, is composed largely of limestone and is approximately 5 km long and 3.5 km wide. Part of its value as a study area today lies in the relative lack of disturbance, with State Park activities largely of a historical-reclamation nature. The present general appearance of the vegetation is of a fringe circle of coniferous trees with hardwood forests in the higher center of the island, much as they appeared to Potzger. METHODS Potzger's methods were duplicated as nearly as possible. His areas were relocated and investigated by 100 m2 quadrats, 10 m on a side. Tree species were tallied by diameter classes (Tables 1 and 2). Five stands of conifers and five of hardwoods were sampled with five quadrats each. Tables 1 and 2 give numbers of trees in each size class, total trees by species, constancy and frequency index comparing data from 1935 and 1974. Frequency index is the percentage of the 25 quadrats (five 317 This content downloaded from 157.55.39.138 on Thu, 19 May 2016 04:28:01 UTC All use subject to http://about.jstor.org/terms 318 THE AMERICAN MIDLAND NATURALIST 96(2) B > H dz C?) 4 m ' ? U ? Q a) 1 l C g *SN1 O noN+ c+ +NOn c>+ NC+b>N Q~~~~~~~~~Locq q c O~~~~~~~~~~ o I 1 O4-4 C 9 Lo -00l 0 C, OR C qw (. C0 LQ OC~ C\l LO rn C ? H + + + + + + + + n t rCD b mQ-Q o M; ~~~~~~~~~~~Ct i CD C m CD CD CDr C't U 0 m WZs E+ O Ob d~~~~~~~~~~~~~~~~~~~~~~~~~~~~ci M .4 0 LO1 LO oo .

Resource Division in an Understory Herb Community: Responses to Temporal and Microtopographic Gradients

Resource Division in an Understory Herb Community: Responses to Temporal and Microtopographic Gradients

Distribution and Accumulation of Rat Damage in Hawaiian Sugarcane

Distribution and Accumulation of Rat Damage in Hawaiian Sugarcane

The Shape of Plant Stems

Based on experiment, functional relationships are found that give, with considerable precision, the loading, the normal stress and the radius as a function of stem height. Using the functional relationship for the loading and for the normal stress, a theoretical expression for the radius distribution in the stem and for the volume of the stem is developed. By optimizing the total volume of the stem with respect to the stress parameter a and using the functional relationship for the loading, a theoretical (optimal) stress distribution and a theoretical (optimal) radius are found. These particular distributions lead to a minimumvolume stem. Experiments with plants having different load functions show that the actual values of the normal stress and radius agree with the theoretical (minimum-volume) predictions. INTRODUCTION Sequoia gigantea! Standing near this largest of all living things leads to astonishment and then to speculation, for some at least. An engineer might ask: Why does the stem grow in such a shape? How does the load affect the shape? These questions can be applied to all plants, and this paper attempts to answer them for some singlestemmed plants (Markwardt, 1930; Markwardt and Wilson, 1935). The following abbreviations are used throughout: A, area of cross section, ft2; C, constant of integration; E, Young's modulus in compression, lbf/ft2; F, total load of plant from the tip [L] to x, lbf; L, height of stem from datum, ft; k, number of stem segments; r, radius of stem, ft; x, height above datum, ft; V, volume of stem from the tip [L] to x, ft3; Vt, total volume of the stem, ft3; W, distributed load of plant, lbf/ft; Y, vertical displacement, ft; a, stress parameter, dimensionless; ,B, radius parameter, dimensionless; y, load parameter, dimensionless; A, difference operator; a, nominal normal stress, lbf/ft2. EXPERIMENTAL OBSERVATION S Plants of the type that have a single stem were examined to determine the loading, the normal stress and the radius as a function of stem height and, further, to see if some approximating functions could describe the measured values of these properties with precision. Using the definition o(x) F (x) L .JL W(x)dx (2.1) A (x) A (x) where a(x) = nominal normal stress, lbf/ft2 F (x) = total load of the plant from the tip [L] to x, lbf A(x) = 7r r2(x) = area of cross section of stem, ft2 x = height above datum, ft W (x) = distributed load of the plant, lbf/ft r(x) radius of stem, ft measurements on three types of plant were taken. 371 This content downloaded from 207.46.13.80 on Thu, 11 Aug 2016 06:26:47 UTC All use subject to http://about.jstor.org/terms 372 THE AMERICAN MIDLAND NAT URALIST 86(2) Figure 1 shows a typical plot of the three properties F (x), a(x) and r(x). In the figure, the point of maximum normal stress defines the separation between the root and the stem. This paper deals with the stem only. It was found that the three properties could be represented closely on this basis, by the functional relationships F(x) = F. (1x ) (2.2) u(X) = uo(1X a (2.3) and r(x) Xr (1 X I, (2.4) Specifically, each plant to be measured experimentally was cut off at the ground, and the total load of the plant and diam of the cut were measured and the nominal normal stress ul computed. Starting in the root-flare region, a series of small cuts were made, and with the ith cut the total load of the plant and the diam of the cut were measured, and the nominal nonnal stress ui computed. This process was continued until un = un+1, and the neighborhood of the maximum normal

Notes on the Biology of the Central American Squirrel, Sciurus richmondi

Additional specimens of Sciurus richmondi are reported, along with comments on variation, distribution, reproduction and molt in this little kno.on squirrel. As presently understood, S. richmondi occurs only in the Caribbean rain forests of Nicaragua. Significant secondary sexual variation in adults was found only in zygomatic breadth, in which females are the larger. Available evidence reveals that the breeding season extends at least from February to September, and suggests two seasonal molts annually. INTRODUCTION Sciurus richmondi was named and described by Nelson (1898: 146), based on a series of specimens collected by Charles W. Richmond in 1892 on the Rio Escondido above Bluefields, Departamento Zelaya, Nicaragua. Subsequently, ]. A. Allen (1908:660; 1910: 104) recorded several specimens from the Caribbean drainage of central Nicaragua, but we are unaware of reports of additional material since Allen's second paper. In recent studies in Nicaragua, 53 specimens of S. richmondi have been collected, providing noteworthy data on the biology of this poorly known sciurid. VARIATION In the original description and in subsequent publications '(Nelson, 1899:101; Hall and Kelson, 1959:395), Sciurus richmondi has been characterized as closely related to S. granatensis, recorded from northern Costa Rica southward into South America. Nelson (1898: 147) supposed it probable that the two intergraded. S. richmondi differs principally from the North American subspecies of S. granatensis-hoffmanni of Costa Rica, chiriquensis of Costa Rica and Panama (these two represent but a single subspecies according to Harris, 1943:9-10) and morulus (choco, a synonym according to, Handley, 1966:777) of Panama-in being smaller, both externally and cranially, slightly less richly colored overall, and in having conspicuously paler bands on the hairs of the tail (tawny ochraceous as opposed to fulvous or buffy orange). We agree that richmondi resembles granatensis in general features and admit the possibility that the two may be found to be conspecific. Nevertheless, we are reluctant at this time to consider richmondi as a subspecies of granatensls because of the great size difference in the specimens available to us. The smallest adult granatensis that we have seen is a female '(KU 60478) from El Dragon, 26 km S San Jose, Costa Rica, in which the greatest length of skull is 53.1 mm, whereas the largest richmondi is a male from El Rccreo with a greatest length of skull of 51.5 mrn (Table 1). The only indication of possible intergradation now available between the two taxa is revealed by a male (skin only) from Cataratas San Carlos, Costa Rica (AMNH 141922), which differs from other Costa Rican granatensis in that both dorsal and ventral sides of the tail are considerably less reddish-orange; the tail of this specimen thus closely resembles those of our Nicaraguan squirrels 'in color. Jones & Genoways in American Midland Naturalist (July 1971) 86(1). Copyright 1971, University of Notre Dame. Used by permission.