bluuebunny/crossref_metadata_2025 huggingface dataset:
Energetics of the Lizard Cnemidophorus Tigris and Life History Consequences of Food‐Acquisition Mode
Authors: Anderson Roger A. , Karasov William H.
Published: April 2006

Energy budgets for the wide—foraging "arthropodivorous" lizard Cnemidophorus tigris were constructed for the reproductive season using doubly labeled water measurements of field metabolic rate (FMR). Rates of body mass change, clutch sizes, and clutch intervals were also investigated. FMRs of both sexes (males, 298 J · g—1 · d—1; females, 247 J · g—1 · d—1) were greater in the reproductive season than during the postreproductive season. This was not due to differences in resting metabolism, but, instead, was due to higher activity costs during the reproductive season. Although males had significantly higher FMR than females, males and females had similar feeding rates (as reflected by water influx rates). The ratio of energy intake to expenditure was higher in females than in males. Females produced eggs but did not grow. Large males did not grow, but small 1st—yr males similar in size to females did grow. Females laid at least two consecutive clutches during a single reproductive season; clutch interval was ≈25 d. Clutch size varied with time of laying (first or second clutch), female body size, and year. We compare the reproductive energetics of C. tigris and other wide—foraging Cnemidophorus with the energetics of ambush iguanids. The wide forager C. tigris and the ambusher Uta stansburiana apparently do not differ in the proportion of the energy budget devoted to reproductive production (reproductive effort, REp). But total reproductive effort, REt, which includes metabolism associated with reproduction, is much lower in Cnemidophorus tigris. Review of the literature indicates Cnemidophorus tend to lay smaller clutches and larger eggs than iguanids, but the number of eggs laid per unit time generally equals that of most iguanids. Cnemidophorus also deposit energy into their eggs at rates almost 60% higher than ambush iguanids. We consider higher rates of production in wide foragers to be permitted by their higher rates of net energy intake while foraging, compared with most ambushers. These higher rates of production in Cnemidophorus apparently allow them either to reach a larger size than iguanids of similar age at first reproduction or to be younger than iguanids of the same size at first reproduction. Life history characters may be influenced by differences in rates of production associated with different food—acquisition modes.
Competition, Habitat Selection, and the Bathymetric Segregation of Two Rockfish (Sebastes) Species
Authors: Larson Ralph J.
Published: April 2006

Sebastes carnatus and Sebastes chrysomelas are morphologically and ecologically similar residents of rocky reefs off the coast of California. They segregate bathymetrically, with S. chrysomelas occurring shallower than S. carnatus. Each species extended its depth distribution where its congener was removed, and no distributional changes occurred in a control area. Thus both species tolerated conditions beyond their normal depth ranges, and were limited in part of their normal depth ranges by interspecific competition. Their segregation was apparently initiated by the preferential settlement of young fish from the plankton, S. chrysomelas in shallow water and S. carnatus deeper. Their segregation was maintained by interspecific territoriality. The distribution of S. chrysomelas, the socially dominant species, may also have been affected by a strong preference for food—rich areas that occurred mainly in shallow water. I postulate that such a preference would be due to the advantage of smaller home ranges in shallow water, where strong wave surge makes the shelter hole a more important part of a fish's territory. This postulated preference, along with aggression from S. carnatus, limited S. chrysomelas to shallow water. Because of its social dominance, S. chrysomelas aggressively excluded S. carnatus from preferred areas in shallow water.
Herbivory and Defensive Characteristics of Tree Species in a Lowland Tropical Forest
Authors: Coley Phyllis D.
Published: April 2006

Rates of herbivory and defensive characteristics of young and mature leaves were measured for saplings of 46 canopy tree species in a lowland tropical rain forest (Barro Colorado Island, Panama). Grazing rates were determined in the field for sample periods in the early wet, late wet, and dry seasons. Leaf properties such as pubescence, toughness, water, protein, fiber, and phenolic contents explained over 70% of the variation among plant species in the rates of herbivory on mature leaves. Leaf toughness was most highly correlated with levels of herbivory, followed by fiber content and nutritive value. Phenol content and phenol: protein ratios were not significantly correlated with damage. Mature leaves of gap—colonizing species were grazed six times more rapidly than leaves of shade—tolerant species. Gap—colonizers have less tough leaves, lower concentrations of fiber and phenolics, higher levels of nitrogen and water, shorter leaf lifetimes, and faster growth rates than do shade—tolerant species. Gap—colonizers did not escape discovery by herbivores to any greater extent than shade—tolerant species, as measured by the spatial distribution of plants or by the intraspecific distribution of herbivore damage under natural or experimentally manipulated conditions. In 70% of the species, young leaves suffered higher damage levels than mature leaves. Although young leaves are more nutritious and less tough and fibrous, they have two to three times the concentrations of phenols. The temporal appearance of young leaves was not correlated with the distribution of herbivory among individuals of a species. Interspecific patterns of defense mechanisms are discussed in terms of current theories of plant apparency, and an alternative model for the evolution of plant defenses is presented.
Fire and Other Factors Controlling the Big Woods Vegetation of Minnesota in the Mid‐Nineteenth Century
Authors: Grimm Eric C.
Published: April 2006

Bearing—tree data from the original land—survey records of 1847—1850 were used to reconstruct the vegetation of the Big Woods and adjacent areas along the prairie—woodland border in south—central Minnesota. The characteristic tree taxa of the Big Woods were elm (Ulmus), basswood (Tilia americana), sugar maple (Acer saccharum), ironwood (Ostrya virginiana), bitternut hickory (Carya cordiformis), butternut (Junglans cinerea), and ash (Fraxinus). The most common tree was elm, which comprised 27% of the bearing trees. A buffer zone of fire—tolerant oaks and aspen generally lay between the Big Woods and prairie. The width of this zone depended on topography and on the presence of additional firebreaks, which in places formed sharp boundaries between the Big Woods and oak—aspen. The prairie—woodland border was characteristically a sharp boundary along firebreaks (water bodies and physiographic breaks). In some places very effective firebreaks formed sharp boundaries between prairie and the Big Woods, with no intervening oak—aspen zone. The vegetation was most strongly correlated with the fire—probability pattern, which was a function of both abiotic and biotic factors. Soils influenced the probability of fire, but they also were the major factor controlling the vegetation within areas of similar fire probability. Soil drainage was the most important factor controlling vegetation within the units of the overall pattern. Because the locations of firebreaks and the existing pattern of vegetation controlled the fire probability pattern, sites with virtually identical physical characteristics supported qualitatively different types of persistent or stable vegetation.
Carbon and Nitrogen Dynamics During the Decomposition of Litter and Roots of a Chihuahuan Desert Annual, Lepidium Lasiocarpum
Authors: Parker L. W. , Santos P. F. , Phillips J. , Whitford W. G.
Published: April 2006

Carbon and nitrogen dynamics were analyzed during the decomposition of litter and roots of the desert ephemeral pepperweed (Lepidium lasiocarpum). We treated litter bags with the insecticide chlordane and the fungicides benomyl and captan to eliminate or restrict groups of soil biota. The mass losses of buried litter (51, 39, and 25% for untreated, insecticide—treated, and fungicide—insecticide—treated material, respectively) were higher than those of the respective root treatments (35, 18, and 15%) at 96 d. The mass loss of untreated material was correlated with numbers of detritivorous—fungivorous microarthropods, and only a small percentage of this loss was as CO2: 27 and 42% for litter and roots, respectively. In the absence of microarthropods a higher percentage of mass—loss carbon could be accounted for as CO2: 33 and 76% for litter and roots, respectively, indicating that mass loss was due primarily to litter removal by microarthropod activity and not to mineralization. Litter removal by microarthropods was less dependent on abiotic constraints such as soil moisture (r = 0.65, P < .001) than was mass loss when microarthropods were absent (r = 0.79, P < .001). In the absence of microarthropods, mass loss was more closely coupled with biomass of grazers, such as nematodes, which require free water for activity (r = 0.99, P < .0001). Unlike mass loss, carbon mineralization was highest in untreated roots, suggesting a stimulation of microbial activity by microarthropods, while in untreated litter no stimulation was observed when compared to insecticide treatments. This difference was primarily a function of fungivorous microarthropod density, with overgrazing occurring in the untreated litter. Nitrogen budgets indicated the importance of microarthropods in the turnover of root nitrogen. In the presence of microarthropods 132% of the initial root nitrogen could be accounted for after 96 d, while in the absence of microarthropods 270% could be accounted for. This net immobilization of nitrogen was primarily in the soil organic fraction around the roots and was associated with fungal development. Data from this study re—emphasize the importance of microarthropods as regulators of decomposition in deserts and suggest that predation by nematodes or protozoa on bacteria and fungi contributes to rate regulation. Nitrogen flux data suggest that when spring ephemeral plant production is high, decomposition of ephemeral roots with attendant nitrogen immobilization can reduce the nitrogen available to creosotebush, Larrea tridentata, thus reducing shrub production. Higher taxa of soil biota, i.e., nematodes and microarthropods, may thus be important regulators of nitrogen fluxes and of mass loss in decomposition.
Dynamism in the Barrier‐Beach Vegetation of Great South Beach, New York
Authors: Clark James S.
Published: April 2006

Pollen data were used to reconstruct the past 340 yr of vegetational changes at Great South Beach, a system of barrier beaches east of Fire Island Inlet, Long Island, New York. The data came from cores taken along 16 transects, 6 of which are described in detail. Dates and stratigraphy from individual cores provided local environmental histories that were combined to reconstruct temporal and spatial patterns of vegetation on local and regional scales. Changes in inlet status and local disturbances accounted for much of the dynamism in vegetation. Salt marshes fringed back—barrier lagoons only when many inlets were open and saline conditions prevailed (1760 to 1835; 1931 to the present). Cyperaceae dominated marshes throughout the remainder of postsettlement time. Inlets affected vegetation by altering tidal range and salinity in back barrier lagoons and provided new substrates for marsh establishment when flood—tide deltas were abandoned by inlet channels. At least once every 100 yr along the six transects, sufficient sand was deposited to destroy all vegetation. The composition of invading assemblages on primary substrates was regulated mainly by physical factors. Annual herbs, shrubs, or high—marsh plants each were "pioneers" at different localities and times. Putative "pioneer" annuals were not limited to the early stages of succession. Fluctuating water tables played an important role in determining composition of freshwater wetlands. Biotically controlled trends in plant composition could not be positively identified. The reconstructions on Great South Beach indicate tight environmental control of plant distribution but emphasize that vegetation does not achieve an equilibrium with the physical environment. Present distributions are largely the product of historical events acting together with existing conditions.
An Analysis of the Dynamics of a Weddell Seal Population
Authors: Siniff D. B. , DeMaster D. P. , Hofman R. J. , Eberhardt L. L.
Published: April 2006

A breeding population of the Weddell seal (Leptonychotes weddelli) was studied annually during the 2 1/2—mo pupping and breeding season in McMurdo Sound, Antarctica, from 1969 through 1974. Components of the population were estimated by direct counts of adult ♂ ♂ with pups, by capture—recapture studies of nonparous ♀ ♀ and adult ♂ ♂, and by aerial counting. Total population size was estimated as being on the order of 2,500—3,000 seals. The Seber—Jolly method was adapted to circumstances of the present study. Reproductive rates (measured in terms of successful pupping) were ~ 0.5 pups/♀ for the entire breeding colony, and ~ 0.7 pups/♀ for a subset of tagged ♀ ♀ observed for 4 yr in sequence. Age—specific reproductive data were also obtained, and it appears that full reproductive activity of ♀ ♀ is achieved at ~ age 7. The annual survival rate for adult ♀ ♀ is in the range of 0.80 to 0.85, as determined (by several methods) from tagging data. Survival rates for adult ♂ ♂ are lower (perhaps 0.50), but are not as well established. Little information was obtained on the subadult class (1 to 3 yr of age). Underwater territories of adult °° on one breeding colony were studied by acoustic tagging and found to be steadily patrolled by dominant ♂ ♂.Two experimental colonies having different densities ties of ♂ ♂ with pups demonstrated increased interactions at higher densities, but lower weight losses on the part of the °° (presumably due to isolated location of the colonies). We infer from the available data that the McMurdo Sound population is somehow regulated by a physiological or social connection between the number of adult ♀ ♀ at the pupping colonies and subsequent years' pup population.
The Epizootiology and Ecological Significance of Malaria in Hawaiian Land Birds
Authors: van Riper Charles , van Riper Sandra G. , Goff M. Lee , Laird Marshall
Published: April 2006

Laboratory and field experiments were conducted on the island of Hawaii from 1977—1980 in an effort to determine the impact of avian malaria on the forest birds. At 16 study sites from sea level to tree line in mesic and xeric habitat, birds were captured and bled to determine the host and altitudinal distribution of blood parasites. In the laboratory, six bird species were challenged with malarial parasites to measure host susceptibility. Distributions, activity cycles, and transmission potentials of malarial parasite vectors were also analyzed. One species of Plasmodium was present from sea level to tree line, concentrated in the mid—elevational ranges in the ecotonal area where vectors and native birds had the greatest overlap. Native forest birds were: (a) more susceptible to malaria than were introduced species; (b) most likely to have malaria during the nonbreeding, wet season; (c) found ranging lower in xeric than in mesic forests; and (d) found to have a lower prevalence of malaria in xeric forests. Temporal as well as elevational differences in prevalence and parasitemia levels of wild birds were apparent throughout the annual cycle, a result of differing host and parasite responses to biotic and abiotic factors. Avian malaria probably did not reach epizootic proportions on Hawaii until after ≈1920. However, since that time it has had a negative impact on the population dynamics of the native forest birds and is today a major limiting factor, restricting both abundance and distribution of these species on the island. In response, a number of native bird species have developed immunogenetic and behavioral responses that reduce the impact of the parasite on host populations.
Some Physical and Biological Determinants of Coral Community Structure in the Eastern Pacific
Authors: Glynn Peter W.
Published: April 2006

Various physical and biological factors affecting coral community structure were investigated by direct observation and periodic censusing (supplemented with laboratory observations and experiments) on three coral reefs off the Pacific coast of Panama from 1970 to 1975. The physical environment has a strong control over coral growth at shallow depth; physical factors are also important subtidally (light, sediment transport). However, paralleling the pattern on temperate shores, biological processes (competition, predation, bioturbation, mutualism) assume an increasing influence on community structure in deeper and more diverse reef assemblages. Coral zonation is marked on these biologically simple and small reefs; the following assemblages are recognized: drying reef flat–live coral cover moderate, species diversity low; reef crest and upper reef slope–highest cover, lowest diversity; lower reef slope and reef base–cover moderate to low, diversity highest. Coral populations in the different zones, though spatially close, are affected by unique sets of conditions. Recurrent extreme tidal exposures devastate reef flat corals (Pocillopora mortality = 40%—60%). The mortality rate of pocilloporid corals is higher than for other corals; this has a diversifying effect on the reef flat assemblage. Acanthaster normally feeds in deep reef zones and numerically its major prey are the predominant pocilloporid corals (most often small colonies and broken branches). Electivity indices and prey choice experiments indicate that less abundant, nonbranching corals are preferred over Pocillopora. Large, branching pocilloporid colonies harbor crustacean symbionts (Trapezia and Alpheus) which can repulse Acanthaster and therefore protect this group of corals. Experimental removal of the symbionts results in a shift of prey preference from nonbranching corals towards the branching pocilloporids. Crustacean symbionts were present in all large Pocillopora colonies sampled, but the density of Trapezia in colonies on the reef flat was about twice that in colonies from deep zones where Acanthaster forages. Further, small pocilloporid colonies and fragments contained relatively few (and a high proportion of juvenile) symbionts. The variety of preferred coral prey present along the seaward reef flanks and the relatively low abundance of Pocillopora in this habitat are considered important factors affecting the distribution of Acanthaster. In addition, a continuous live cover of pocilloporid corals, which Acanthaster avoids, can protect reef zones (e.g., the reef flat) or preferred prey species from attack. The selective destruction of nonpocilloporid corals by Acanthaster tends to lower both live coral cover and species diversity (H'). This trend is evident on the Uva Island study reef where a significant decline in coral cover (47%—18%) and H' (1.06—0.58) occurred over a 4—mo period.
Forest Changes in Minnesota at the End of the Pleistocene
Authors: Amundson Donna C. , Wright H. E.
Published: April 2006

The Late—Wisconsin spruce forest that characterized most of Minnesota (and the rest of the Middle West) differed from the modern Boreal Forest of Canada not only in the absence of pine but also in the apparent admixture of black ash, oak, and elm and in the presence of openings in which Artemisia was abundant. Close—interval pollen analyses at 3 sites in Minnesota show some of the details in the transformation of this spruce forest to pine or hardwood forests. At Kirchner Marsh in southeastern Minnesota, the spruce forest was replaced abruptly about 10 000 yr ago birch, ald and temperate hardwoods before pine (jack pine?) entered the region for a short period. At Wolf Creek in central Minnesota, pine arrived from the east virtually at the moment when spruce declined. At Lake of the Clouds in northeastern Minnesota, spruce forest had succeeded tundra about 10 000 yr ago, but simultaneously pine (jack pine?) and the temperate hard woods (especially elm) appeared in quantity. The spruce and hardwood components then declined about 9300 yr ago as pine (red pine?) increased to dominance during the next 400 yr. Charcoal counts for the 3 sites provide no support for the hypothesis that increased fire incidence explains the forest transformation from spruce to pine. Climatic change must instead be the primary cause. The apparent openness of the spruce forest can be attributed to the continued presence of the wasting ice sheet just to the north, which favored a dry and windy climate, perhaps with relatively mild winters. As the ice sheet withdrew, its influence decreased. Differential rates of tree immigration as well as progressive leaching of upland soils may have been additional factors effecting changes in forest composition.
Associations of Plants and Insects in Deciduous Forest
Authors: Futuyma Douglas J. , Gould Fred
Published: April 2006

Phytophagous insect larvae (Lepidoptera and Tenthredinoidea) in the leaf—chewing guild were sampled from accessible parts of all the 18 species of common woody plants in a mature upland forest in New York State, in early and in late June. Among the procedures used to describe patterns of associations between plants and insects are principal components analysis and the clustering techniques of numerical taxonomy, whereby the faunistic similarity among plant species is described. We introduce a weighting factor for cluster analysis that weights a character (in this case the density of an insect species on a plant) in proportion to its deviation from the norm. During June, both the abundance and variety of insects declined on most plant species, which vary greatly in both these aspects of their fauna. Insect species that are either quite highly specialized or generalized in diet appeared to be prevalent; those with intermediate diet breadth were less so. Clustering plant species by faunal similarity revealed some clusters of taxonomically related species, but the correspondence between faunal similarity and taxonomic affinity is not strong. Few plant species have a highly distinct, specialized fauna. The complexity of distribution of insects over plants indicates that insects are responding to many factors that differentiate plant species.
Ecosystem Dynamics of a Subtropical Floodplain Forest
Authors: Frangi Jorge L. , Lugo Ariel E.
Published: April 2006

The carbon, phosphorus, and water cycles of a subtropical floodplain forest, and related ecosystem characteristics, were studied. Located at 750 m elevation in Puerto Rico (latitude 18°N) the forest had 27 tree species, 3059 stems/ha, a basal area of 42.4 m2/ha, maximum height of 17 m, and a leaf area index of 3.3. Palm (Prestoea montana) dominated the forest, and, with two other species, accounted for 68% of the dominance. Throughfall, stemflow, interception, runoff, transpiration, and evapotranspiration accounted for 81.6, 9.8, 8.6, 77.7, 13.7, and 22.3% of annual rainfall (3725 mm) respectively. The stand carbon storage was 28.77 kg/m2, distributed as follows: aboveground 35.4%, vegetation 44.2%, soil to 1 m depth 55%, palms 10.9%. Vegetation biomass was partitioned as follows: leaves 9.8% (75% are palm leaves), wood 68%, and roots 21.8%. Net aboveground primary carbon productivity (NPP) was 876 g°m—2°yr—1. Average litterfall was 2.4 g°m—2°d—1 (palm leaves 32%, other leaves 39%, and wood 10%). Half—lives of decaying material were 188, 306, 462, and 576 d, respectively, for palm leaves still attached to the parent tree, dicotyledonous leaves, palm leaves on the ground, and palm trunks. Total organic carbon concentrations in stream water increased with increasing stream discharge (from 2 g/m3 to 30 g/m3). Watershed export of carbon was 50 g°m—2°yr—1 (including 12 g°m—2°yr—1 in the form of leaf litter). Mean P concentration in palm leaves (1.18 mg/g) was twice that in dicotyledonous leaves (0.64 mg/g). Compared to a rainfall phosphorus input to the watershed of 63 mg°m—2°yr—1, leaching from the canopy was high (167 mg°m—2°yr—1), as was the loss of P from the watershed (611 mg°m—2°yr—1). Phosphorus—conserving mechanisms included a high rate of retranslocation in palms (504 mg°m—2°yr—1). In spite of these mechanisms, there was a net P loss from the watershed that ranged from 136 to 544 mg°m—2°yr—1. Periodic flooding, poor soil aeration, intensive year—round rainfall, and low atmospheric saturation vapor pressure deficits are believed to be the main driving forces of the floodplain forest, which exhibits many characteristics typical of lowland rain forests and floodplain wetlands. Rates of NPP, litterfall, and biomass turnover (residence time of 14—17 yr) are faster than expected for the climatic conditions, whereas rates of wood production and storage of organic matter in the vegetation and soil profile are lower than expected for the climate.
Nutrient Dynamics of Aboveground Detritus in Lodgepole Pine (Pinus contorta ssp. latifolia) Ecosystems, Southeastern Wyoming
Authors: Fahey Timothy J.
Published: April 2006

Storage and fluxes on N, P, Ca, Mg, and K in aboveground detritus were measured in six contrasting lodgepole pine (Pinus contorta ssp. latifolia) stands in southeastern Wyoming. Litterfall was predominantly leaves (67—80%) in 80—100 yr old stands, while woody litter was more important in an older stand (240 yr old). Leaf litter nutrient concentrations were very low compared with other pine forests, particularly for N (0.40% dry mass). Dry mass loss from decomposing leaf litter was slow (15%/yr in first 2 yr), and summer rates did not differ significantly from winter rates beneath the insulating snowpack. Significant amounts of N, P, and Ca were added to decomposing leaves during the first winter, and N and Ca addition continued for 2 yr. Potassium and magnesium were rapidly lost from decomposing leaves. Rates of mass and nutrient loss from decomposing bark, twigs, and cones were comparable to those observed in other studies of temperate—zone forests. Mass loss from decaying bole wood appeared to be exponential through 40 yr, with an average decay coefficient (k) of 0.016, which is comparable to that in other cold temperate forests. Nitrogen content of decaying boles doubled between 30 and 55 yr following tree death, while smaller additions of P, Ca, K, and Mg also were noted. Relatively large accumulations of organic matter and nutrients were observed in the forest floor, leading to very high steady—state residence times for dry mass (mean = 18 yr), N (54 yr), P (39 yr), Ca (35 yr), Mg (21 yr), and K (18 yr). Deadfall contributed by the present forest generation was a minor component of the aboveground detritus except in an old—age stand and in a dense, self—thinning forest site. In contrast, dead wood inherited from the previous forest generation (killed by fire) was a major detrital storage component, exceeding forest floor mass by several—fold in 80—100 yr old stands. High nutrient immobilization in the dead wood led to storage values which were similar to those of the forest floor in these stands.
A Comparative Analysis of Potential Nitrification and Nitrate Mobility in Forest Ecosystems
Authors: Vitousek Peter M. , Gosz James R. , Grier Charles C. , Melillo Jerry M. , Reiners William A.
Published: April 2006

The controls of potential nitrogen mineralization, nitrate production, and nitrate mobilization in a wide range of forest ecosystems were investigated through a combination of field and laboratory experiments. Trenched plot experiments were performed in 17 forests, and laboratory incubation studies of potential ammonium and nitrate production were made on soils from 14 of these sites. The site with the greatest potential for nitrate production in the laboratory was a New Hampshire northern hardwoods forest. Several other sites, including New Hampshire balsam fir, Indiana maple—beech, New Mexico aspen, and Oregon western hemlock forests, also had high potential nitrate production. All of these sites also had rapid nitrate movement to below the rooting zone following trenching in the field. Of nine processes which could be important in preventing or delaying solution losses of nitrate from disturbed forests, two appeared most important among the forests we examined. Low net nitrogen mineralization (caused by either nitrogen immobilization or low gross nitrogen mineralization) and lags in nitrification (probably caused by either low initial populations of nitrifying bacteria or the allelochemic inhibition of nitrification) were identified as important in several sites and in different regions. A direct relationship between the amount of nitrogen in annual litterfall and the proportion of forest floor nitrogen mineralized in laboratory incubations was observed, suggesting that refractory organic nitrogen compounds are produced in nitrogen—poor sites. An inverse relationship was found between the amount of nitrogen in litterfall in these and other sites and the carbon:nitrogen ratio of that litterfall, suggesting that the immobilization capacity of litter is increased in nitrogen—poor sites. The presence and length of lags in nitrification were inversely correlated with the mean concentration of mineral nitrogen in mineral soil. These patterns suggest that nitrogen retention within disturbed forest ecosystems can be caused by low nitrogen availability prior to disturbance.
Stabilization of the Rate of Nitrogen Accumulation by Larvae of the Cabbage Butterfly on Wild and Cultivated Food Plants
Authors: Slansky Frank , Feeny Paul
Published: April 2006

Larvae of Pieris rapae (Lepidoptera: Pieridae) were reared on several crucifer species and varieties which differed in their nitrogen content, either naturally or because they had been fertilized with NH4NO3. Growth rates, food consumption rates, and efficiencies of food utilization were determined for fifth instar larvae on all plants, using standard methods. Larvae on low—nitrogen plants consumed food faster, utilized it less efficiently, and utilized N more efficiently than larvae on high—nitrogen plants. As a result, growth rates and rates of accumulation of N into larval biomass were as high on plants of 1.5% (dry wt) N as on plants of 4.8% (dry wt) N. There was no correlation between larval growth rate and reported patterns of glucosinolate content in the food plants. We attribute low N accumulation rates and growth rates on Lepidium virginicum, Lunaria annua, and Thlaspi arvense to the presence in these plants of unique secondary compounds or atypical glucosinolate breakdown products. Larvae fed on Dentaria diphylla and on the most highly fertilized collards (6.1% dry wt N) accumulated N and grew at unusualy high rates. This may be because N in these plants was more digestible than in the other food plants. We suggest that larvae of P. rapae adjust their feeding rates to maximize the rate at which they can accumulate N, and thus the rate at which they can grow, on any given food plant. There is a limit to the rate at which N can be accumulated, because N is utilized less efficiently as it is consumed faster. We conclude that the growth of P. rapae larvae is limited by the availability of N in their food plants, that N budgets for such larvae are of greater ecological significance than energy budgets, and that, in this case at least, natural selection favors the rate (power output) rather than the efficiency of a biological process.
Population Dynamics and Habitat Suitability of the Intertidal Sea Anemones Anthopleura elegantissima and A. xanthogrammica
Authors: Sebens Kenneth P.
Published: April 2006

Population dynamics of the intertidal sea anemones Anthopleura elegantissima (Brandt) and A. xanthogrammica (Brandt) were investigated by long—term monitoring and experimental manipulation of populations in Washington State. Sizes of individual A. xanthogrammica and A. elegantissima fluctuated seasonally, increasing during the spring and early summer and shrinking or reaching a pleateau the rest of the year. Data from marked individual A. xanthogrammica showed that adults (>6.5 cm) moved very little and may persist for at least several decades. Only 3 of 160 mapped adult anemones disappeared over 2 yr. Juveniles moved more often and thus appeared and disappeared at much higher rates. Growth of A. xanthogrammica in control and experimental removal areas was compared by a new technique. One—year growth increments were used to compare growth in each size class by analysis of variance and were also used to plot long—term growth trajectories and expected reproductive success (habitat suitability, Fretwell 1972). Growth was much more rapid in areas with experimentally reduced density than in control areas. The control area with the lowest density had the greatest individual growth rates. Differences in growth trajectories and expected reproductive success between control areas and the experimental areas indicate that adult density affects growth of most size classes. The mechanism is probably both noninterference competition for prey and direct interference by adult tentacle crowns blocking capture by smaller individuals. Clonal aggregations are formed by longitudinal fission of A. elegantissima. (A. xanthogrammica never reproduce asexually.) Monitored clonal aggregations of A. elegantissima showed that fission rate is greatest during the fall and winter, averaging 0.17 divisions per clonal individual per year in all areas. Only the larger individuals in each clone divided and a single individual never divided more than once in a given year. Rate of fission was independent of mean individual size within clones. Therefore, clones in more suitable habitats produced larger individuals and thus had greater gonad (offspring) production. Clones in the high intertidal were composed of very small individuals, had the lowest rates of fission, and were clearly occupying a marginal habitat.
Biogeochemistry of Thoreau's Bog, Concord, Massachusetts
Authors: Hemond Harold F.
Published: April 2006

Thoreau's Bog in Concord, Massachusetts, is a floating—mat Sphagnum bog developed in a glacial kettle hole. Low shrub vegetation of the open mat is dominated by Chamaedaphne calyculata; trees include scattered Picea mariana and Larix laricina. Hydrological investigations show the bog to be ombrotrophic, with an annual water input of 1.45 m and an annual runoff of 0.24 m. Corresponding metal inputs are 88, 132, and 54 mg°m—2°yr—1 for K, Mg, and Pb, respectively. K and Mg are vertically distributed in the bog profile in accord with the inhomogeneous ion exchange chemistry of peat, while lead is distributed in accord with historical trends in atmospheric lead fallout. Isotopic dating using 210Pb is a valuable tool for determining net peat accumulation rate, which is 180 g°m—2°yr—1. Annual storage rates of K, Mg, and Pb in peat amount to 36, 54, and 46 mg°m—2°yr—1, respectively. Bog acidity (pH = 3.8) is maintained by organic acids at concentrations of 10—3 eq/L. The effect of cation exchange on bog acidity is modest, while the much larger contribution of "acid rain" is offset by alkalinity increases of the same magnitude resulting from sulfate reduction and nitrate uptake. These latter processes are, in effect, a strong buffer mechanism against acid rain. 210Pb dating and historical records suggest that the floating mat is relatively young, perhaps as few as 500 yr old. These data raise the possibility that the bog is not a relict of colder, early postglacial periods, but instead, may have developed under modern climatic conditions.
Pseudoreplication and the Design of Ecological Field Experiments
Authors: Hurlbert Stuart H.
Published: April 2006

Pseudoreplication is defined as the use of inferential statistics to test for treatment effects with data from experiments where either treatments are not replicated (though samples may be) or replicates are not statistically independent. In ANOVA terminology, it is the testing for treatment effects with an error term inappropriate to the hypothesis being considered. Scrutiny of 176 experimental studies published between 1960 and the present revealed that pseudoreplication occurred in 27% of them, or 48% of all such studies that applied inferential statistics. The incidence of pseudoreplication is especially high in studies of marine benthos and small mammals. The critical features of controlled experimentation are reviewed. Nondemonic intrusion is defined as the impingement of chance events on an experiment in progress. As a safeguard against both it and preexisting gradients, interspersion of treatments is argued to be an obligatory feature of good design. Especially in small experiments, adequate interspersion can sometimes be assured only by dispensing with strict randomization procedures. Comprehension of this conflict between interspersion and randomization is aided by distinguishing pre—layout (or conventional) and layout—specific alpha (probability of type I error). Suggestions are offered to statisticians and editors of ecological journals as to how ecologists' understanding of experimental design and statistics might be improved.
Modern Pollen Assemblages and Vegetation in the Myrtle Lake Peatland, Minnesota
Authors: Janssen C. R.
Published: April 2006

Pollen grains and spores in moss polsters are compared with vegetation along transects across vegetational gradients in a large peatland in northern Minnesota. The distribution, percentage values, and source of 135 pollen and spore types are traced and related to the broad—scale vegetation pattern in the midwestern United States, and to the fine—scale vegetation pattern in the peatland. The pollen assemblages of taxa presently not growing in the peatland constitute the regional pollen deposition, with nearly constant proportions of pollen types distributed across the study area. Regional pollen values are compared for several peatlands in northern Minnesota and with the regional forest composition. The fine—scale pattern of peatland vegetation types corresponds well with the spatial pattern of the local pollen assemblages. Peatland vegetation types are characterized on the basis of these pollen assemblages. Conclusions on development of peatland vegetation can be drawn from local pollen assemblages preserved in sediment cores. Pollen transport for wind—pollinated Abies, Pinus, Betula, Alnus, Fraxinus, and Typha is discernible in the peatland only within 200 m from their source in local plant populations. The dispersal pattern of Abies pollen from an Abies balsamifera stand is related to wind speed and direction and sky cover for as much as 5 yr preceding sample collection. Most peatland pollen types are restricted in distribution to their corresponding vegetation types.
Inputs, Outputs, and Accumulation of Nitrogen in an Early Successional Moss (Polytrichum) Ecosystem
Authors: Bowden Richard D.
Published: April 2006

Measurement of total ecosystem nitrogen accumulation in a moss (Polytrichum) ecosystem after 13 yr of primary succession upon exposed sands of glacial origin in New Hampshire, USA, revealed an N accumulation rate of 10.1 kg · ha—1 · yr—1. Comparison of the measured accumulation with a mass balance analysis of measured inputs (bulk precipitation inorganic N plus biological N2 fixation plus windblown coarse particulate matter) minus outputs (hydrologic losses plus N2O and N2 emissions) revealed that 35% of the inputs required to satisfy the observed rate of N accumulation had not been measured. These unmeasured sources include bulk precipitation organic N, dry deposition, and dew inputs. Total N inputs, including the unmeasured sources, were 10.5 kg · ha—1 · yr—1. Bulk precipitation was the dominant N input, comprising 58% of the annual input. Dinitrogen fixation and coarse particulate organic matter together represented only 7%; unmeasured sources accounted for the remainder (35%). The predominance of bulk precipitation as an input source to the moss ecosystem is in contrast to many other primary successional systems where N2 fixation is the dominant source of N. Nitrogen outputs from the ecosystem were small (0.40 kg · ha—1 · yr—1), with most coming from hydrologic export (0.29 kg · ha—1 · yr—1) and a smaller fraction (0.10 kg · ha—1 · yr—1) from N2O effluxes. No N2 losses were detected. The moss ecosystem was extremely efficient at retaining bulk precipitation N inputs. Additions of 15N—labelled simulated rainfall showed that soil and belowground live moss biomass retained most of the input. The amount of N retained by each component of the ecosystem was related directly to the amount of biomass (living or dead) in the component. Soil organic matter was also important in retaining nitrogen inputs. In a short—term microcosm experiment, soil with a high organic matter content (2.71%) retained 47% of inorganic N in simulated rainfall, compared to only 27% retained in soil with a low organic matter content (0.51%). The moss vegetation exerted control over the N retention efficiency of the ecosystem. Removal of mosses resulted in a short—term retention of N inputs, soon followed by losses that exceeded inputs. Nitrogen retention again resumed following recolonization of the soil by mosses. Development of the moss ecosystem appears to have been enhanced by two positive feedback mechanisms. First, establishment of the mosses led to biomass and soil organic matter accumulation, enhancing N capture and retention, and thus increasing biomass accumulation. Second, development of aboveground biomass further enhanced collection of N in dry deposition and dew, increasing total inputs.
Holocene Paleoecology of the Boreal Forest and Great Lakes‐St. Lawrence Forest in Northern Ontario
Authors: Liu Kam-Biu
Published: April 2006

This paper presents pollen and macrofossil stratigraphies derived from sediment cores taken near the deepest parts of Nina Lake (46°36' N, 81°30' W), Jack Lake (47°19' N, 81°46' W), and Lake Six (48°24' N, 81°19' W), which are situated along a transect across the ecotone between the boreal forest and the Great Lakes—St. Lawrence forest in northern Ontario. Paleoecological data from this region of steep climatic gradient and varied landforms provide sensitive records of postglacial vegetational and climatic changes. These data are used to evaluate questions concerning the occurrence of late—glacial vegetation communities without modern analog. Hypsithermal ecotonal movements, and individualistic species response to climatic change and soil development. The early postglacial boreal forest that colonized the Canadian Shield upland after ca. 10 000 BP was dominated by white spruce with little or no black spruce, and probably contained more oak, elm, poplar, and heliophytic herbs and shrubs than its modern counterpart. Its lack of modern analog is probably due to the widespread occurrence of fresh, unleached soil in a newly deglaciated landscape. Spruce declined and was replaced by jack pine after ca. 9000 BP as the climate continued to warm. The boreal forest was enriched floristically by the successive immigration of species such as Myrica. Alnus crispa, and A. rugosa. Boreal forest was transformed into Great Lakes—St. Lawrence forest ca. 7400 yr ago when white pine, beech, and hemlock immigrated to Nina Lake. Species of the Great Lakes—St. Lawrence forest responded individualistically to Hypsithermal climatic changes. White pine populations continued to spread northward during ca. 7000—3000 BP, causing the boreal forest/Great Lakes—St. Lawrence forest ecotone to advance ca. 140 km north of its present position, only constrained by the physiographic boundary between the Clay Belt and the Canadian Shield upland. During 6000—4500 BP northern white cedar proliferated in the Clay Belt lowlands due to a warmer and drier climate. The regional water table was lowered, permitting Thuja populations that were otherwise restricted to the margins of swamps and open peatlands to spread to the center. This vegetation response was landform selective, being more pronounced in the Clay Belt than on the Canadian Shield upland. The predominance of calcareous substrates and wetland habitats in the Clay Belt was favorable to the expansion of Thuja under a suitable climate. Neoglacial cooling decimated the populations of northern white cedar in the Clay Belt and those of white pine in the whole region. Spruce, jack pine, and balsam fir increased over the last 4000 yr. The ecotone retreated from near Lake Six after 3000 BP, reaching Jack Lake at ca. 2600 BP, and was stabilized in its modern position during the last millennium.
Ecomorphology, Performance Capability, and Scaling of West Indian Anolis Lizards: An Evolutionary Analysis
Authors: Losos Jonathan B.
Published: April 2006

Studies of ecomorphology–the relationship among species between morphology and ecology–contain two implicit and rarely tested hypotheses: (1) that morphological differences among species result in differences in performance capability at ecologically relevant tasks, which, in turn, produce differences in behavior and ecology; and (2) that morphology, performance capability, ecology and behavior have evolved synchronously. I tested these hypotheses using the Anolis lizards of Jamaica and Puerto Rico. I measured morphological and performance variables on recently caught lizards. Movement, display rate and microhabitat measurements were made on lizards observed in the field. Body size explained most of the variation in morphology and performance ability, but was not correlated with the ecological or behavioral variables. When the effect of body size is removed from the morphological and performance variables, the ecomorphological hypotheses were confirmed. Species that were similar morphologically were also similar in performance ability, ecology, and behavior. Evolutionary changes in morphology, performance, and ecology and behavior (ecobehavior) were correlated. The morphology–ecobehavior comparison revealed that: long—legged, heavy—bodied lizards jump farther in nature, jump and display more often, walk less often, and use wide perches that are distant from the nearest available perches; and that species with many subdigital lamellae perch lower, use narrower supports, and walk more frequently. Inclusion of performance parameters revealed a relationship, in agreement with biomechanical models, between body proportions and running and jumping capability; in turn, performance capability related to locomotor patterns and microhabitat use. Despite the relationship between lamellae number and ecobehavioral variables, clinging performance did not contribute to the correlations with either morphology or ecology.
Comparisons of Treatments After an Analysis of Variance in Ecology
Authors: Day R. W. , Quinn G. P.
Published: April 2006

The statistical literature on tests to compare treatments after the analysis of variance is reviewed, and the use of these tests in ecology is examined. Monte Carlo simulations on normal and lognormal data indicate that many of the tests commonly used are inappropriate or inefficient. Particular tests are recommended for unplanned multiple comparisons on the basis of controlling experimentwise type I error rate and providing maximum power. These include tests for parametric and nonparametric cases, equal and unequal sample sizes, homogeneous and heterogeneous variances, non—independent means (repeated measures or adjusted means), and comparing treatments to a control. Formulae and a worked example are provided. The problem of violations of assumptions, especially variance heterogeneity, was investigated using simulations, and particular strategies are recommended. The advantages and use of planned comparisons in ecology are discussed, and the philosophy of hypothesis testing with unplanned multiple comparisons is considered in relation to confidence intervals and statistical estimation.