bluuebunny/crossref_metadata_2025 huggingface dataset:
LONG‐TERM ASSESSMENT OF TEMPERATE OCTOCORAL MORTALITY PATTERNS, PROTECTED VS. UNPROTECTED AREAS
Authors: Coma Rafel , Pola Emilià , Ribes Marta , Zabala Mikel
Published: June 2007

Coastal marine protected areas (MPAs) are usually established with an aim to protect areas of special ecological value. However, protected areas tend to attract more tourism and associated recreational activities, thereby exposing the biota to new risks such as high diving activity. The effects of these drawbacks are still little known for low‐dynamic systems such as one of the most characteristic and fragile Mediterranean communities, the coralligenous community. Mortality rates were assessed in both heavily dived and lightly dived areas to evaluate the effect of diving on the survival of the gorgonian Paramuricea clavata. The study was designed to distinguish human‐induced causes from natural causes of gorgonian mortality and to provide criteria for sustainable management of protected areas. We examined total and partial mortality of adult colonies (>10 cm in height) at four locations, two each representing one of the two situations, heavily dived (MPA) and lightly dived (control), annually over a 9‐yr period (1992–2000).

High levels of recreational activity did not affect the degree of injury of the colonies. On average, the proportion of live tissue of the colonies remained steady at ∼91%. Colony death by detachment was the main source of mortality at the MPA, four times higher than death due to overgrowth. Mortality rate due to overgrowth remained constant at both areas with an average of 1.2%/yr. Natural mortality rate in sites with low diving activity was estimated to be about 2.7%/yr, whereas high diving activity was estimated to increase the natural mortality rate of the species by a factor of three, up to ∼7.4%/yr. The demographic characteristics of long‐lived low‐turnover structural components of ecosystems makes them especially vulnerable to disturbance events. Since an increase in diving activity seems to be unavoidably brought about by the creation of any MPA, strict regulation of recreational activity must be guaranteed in areas with low‐turnover communities.
ROOT AND LEAF HERBIVORY ON LYTHRUM SALICARIA: IMPLICATIONS FOR PLANT PERFORMANCE AND COMMUNITIES
Authors: Hunt-Joshi Tamaru R. , Blossey Bernd , Root Richard B.
Published: June 2007

Herbivores can have major direct impacts on plant performance, carbon and nitrogen content of plant tissues, nutrient cycling, and important ecosystem processes such as decomposition. Herbivory on a dominant plant can alter competitive interactions, which may have profound effects on plant community composition. We investigated the impact of herbivory by a root weevil (Hylobius transversovittatus) and a leaf beetle (Galerucella calmariensis) on purple loosestrife (Lythrum salicaria) in large walk‐in cages established in an invaded wetland in upstate New York, USA, from 1997 to 2000. We monitored how herbivory affected L. salicaria performance (growth and biomass allocation), litter dynamics, plant community composition, and changes in canopy temperature, humidity, and the amount of light penetrating through the canopy. Leaf herbivory had the greatest effect, reducing the height of L. salicaria shoots, reproductive effort, and aboveground biomass. Root herbivory also reduced L. salicaria leaf, stem, and inflorescence biomass and the number of stems but did not affect shoot height. Both root and leaf herbivore damage to L. salicaria resulted in increased light availability within the canopy but had no effect on canopy temperature or humidity. Whereas existing wetland plants grew larger in plots where L. salicaria was damaged by leaf herbivores, plant species richness did not vary among treatments. Leaf herbivory also accelerated decomposition of L. salicaria leaves and stems. Leaf and root herbivory did not interact, suggesting that (1) beetles did not compete for resources via their shared host plants and (2) attack by multiple herbivores did not increase or accelerate herbivore impact on L. salicaria over our four‐year study. Our results show that the competitive dominance of L. salicaria in North American wetlands can be curtailed by herbivores introduced as biological control agents, but it also demonstrates the need for long‐term investigations to capture cumulative herbivore impacts on plant individuals and communities.
USING SPECIES–HABITAT MODELS TO TARGET CONSERVATION: A CASE STUDY WITH BREEDING MALLARDS
Authors: Newbold Steve , Eadie John M.
Published: June 2007

To make effective conservation decisions, managers must understand the ecology of species targeted for conservation and be able to apply that knowledge in decision‐making. Most conservation research to date has focused on the first of these requirements, but lately ecologists and others have begun to address more systematically the decision‐making component of conservation. In this paper, we develop an explicit model of species– habitat relations and incorporate it into an optimization framework for prioritizing sites for management. We then present a case study that applies these concepts to choosing sites for wetlands restoration to benefit breeding Mallards (Anas platyrhynchos) in the Central Valley of California, USA. First, a model of habitat selection by Mallards was estimated using count regression techniques. Our results indicate that breeding Mallard abundances depend not only on the amount of each land use type present, but also on the interspersion of particular land use types in the vicinity of each survey location. We then used the estimated parameters in an optimization model to predict the differences in the expected total Mallard abundance under three generalized strategies for wetlands restoration. Our results suggest that using the spatial habitat preferences of Mallards to target restoration can lead to a greater‐than‐proportional increase in Mallard abundances: a simulated 50% increase in the total area of wetlands resulted in a nearly 80% increase in the total abundance of breeding Mallards. In contrast, simulated strategies for choosing restoration sites that did not account for the spatial habitat preferences of Mallards resulted in 13–33% increases in total abundance. Accounting for the spatial arrangement of preferred habitats when setting restoration priorities can enhance conservation effectiveness considerably.
THE INFLUENCE OF FOREST MANAGEMENT ON HEADWATER STREAM AMPHIBIANS AT MULTIPLE SPATIAL SCALES
Authors: Stoddard Margo A. , Hayes John P.
Published: June 2007

Understanding how habitat structure at multiple spatial scales influences vertebrates can facilitate development of effective conservation strategies, but until recently most studies have focused on habitat relationships only at fine or intermediate scales. In particular, patterns of amphibian occurrence across broad spatial scales are not well studied, despite recent concerns over regional and global declines. We examined habitat relationships of larval and neotenic Pacific giant salamanders (Dicamptodon tenebrosus), larval and adult Pacific tailed frogs (Ascaphus truei) (hereafter “tailed frogs”), and torrent salamanders (Rhyacotriton spp.) at three spatial scales (2‐m sample unit, intermediate, and drainage). In 1998 and 1999, we captured 1568 amphibians in 702 sample units in 16 randomly chosen drainages in the Oregon Coast Range. We examined species–habitat associations at each spatial scale using an information‐theoretic approach of analysis to rank sets of logistic regression models developed a priori. At the 2‐m sample unit scale, all groups were negatively associated with proportion of small substrate and positively associated with stream width or elevation. At the intermediate scale, Pacific giant salamanders, adult tailed frogs, and torrent salamanders were positively associated with presence of a 46‐m band of forested habitat on each side of the stream, and larval tailed frogs were positively associated with presence of forest >105 years old. Aspect was important for Pacific giant salamanders and larval tailed frogs at the intermediate scale. At the drainage scale, all groups except torrent salamanders were positively associated with proportion of stream length having forested bands >46 m in width, but further analysis suggests narrower bands may provide adequate protection for some groups. Population‐ and community‐level responses at broad spatial scales may be reflected in species‐level responses at fine spatial scales, and our results suggest that geophysical and ecological characteristics, as well as measures of instream habitat, can be used together to prioritize conservation emphasis areas for stream amphibians in managed landscapes.
MIGRATORY SUCCESS OF JUVENILES: A POTENTIAL CONSTRAINT ON CONNECTIVITY FOR POND‐BREEDING AMPHIBIANS
Authors: Rothermel Betsie B.
Published: June 2007

The persistence of pond‐breeding amphibians in highly fragmented landscapes may be constrained by the need for connectivity between aquatic breeding sites and suitable terrestrial habitat, an example of landscape complementation. Although migratory ability determines the spatial scale at which landscape complementation operates, the factors influencing migratory success of amphibians, especially of juveniles, are poorly understood. This study is the first to investigate whether juvenile amphibians possess any innate, long‐distance orientation mechanisms that might improve their chances of locating suitable terrestrial habitat. I conducted experimental releases of spotted salamanders (Ambystoma maculatum) and American toads (Bufo americanus) from 18 artificial pools in replicate pastures at distances of 5–50 m from the nearest forest edges. Using circular drift fences with pitfall traps, I captured, individually marked, and released metamorphosed salamanders (n = 323) and toads (n = 203) leaving each pool. Salamanders exhibited nonrandom orientation at nine pools, but at only one was the mean movement direction consistent with the direction to the nearest forest edge. Emigrating salamanders probably responded to microtopographic or other distinct features of each pool, rather than to distant cues. Migratory success was determined by recaptures of marked juveniles at drift fences along the forest edges. I used logistic regression to model probability of recapture and evaluated alternative models using an information‐theoretic approach. Migratory success of both species was primarily a function of distance to nearest forest. Of salamanders and toads released from 50‐m pools, <15% reached the forest, suggesting that few juvenile amphibians would be able to migrate greater distances across pastures. Breeding sites lacking connectivity to suitable terrestrial habitat may be population sinks due to high mortality of juveniles during emigration. Additional research is needed to determine appropriate threshold distances between breeding sites and terrestrial habitat, as well as the potential effectiveness of movement corridors for migrating amphibians.
A BEHAVIOR‐BASED MODELING APPROACH TO REDUCING SHOREBIRD–SHELLFISH CONFLICTS
Authors: Caldow Richard W. G. , Beadman Helen A. , McGrorty Selwyn , Stillman Richard A. , Goss-Custard John D. , Durell Sarah E. A. le V. dit , West Andrew D. , Kaiser Michel J. , Mould Kim , Wilson Andrew
Published: June 2007

Bottom cultivation of mussels on intertidal flats is practiced throughout the world. This often generates conflicts between commercial interests and competing birds such as oystercatchers. At the Menai Strait, United Kingdom, the overwinter consumption of 242 tonnes (1 metric tonne = 1000 kg) of commercially harvestable mussels (>40 mm) by oystercatchers in 1999–2000 was worth £133 000 ($226 000 U.S. dollars). This represents 19% of the value of the landings. We used a behavior‐based simulation model to predict the extent to which such losses can be reduced by novel commercial management practices, and to explore the consequences for the oystercatcher population.

Simulations of novel lay management practices indicated that the losses of commercially harvestable mussels to oystercatchers can be considerably reduced by altering the shore level and/or extent of the commercial lays. We propose a novel management strategy for the bottom cultivation of mussels in intertidal areas. Seed mussels (15–20 mm) should be laid relatively far upshore, where losses to oystercatchers will be minimal. As the mussels grow over the next 2–3 years, they should be moved progressively further downshore such that the largest mussels spend their last season prior to harvest in a relatively small area, lower on the shore than all mussels earlier in the cultivation cycle. Support for the effectiveness of this proposed management strategy can be found in the reports of commercial operators who have incorporated this management strategy in new management practices in the last few years. They report an increase in the ratio of the live mass of harvested to seeded mussels from the previous norm of 1:1 to 4:1. By accepting greater losses of mussels earlier in the cultivation cycle, rather than later, the feeding conditions for oystercatchers might even be improved under this system. With appropriate management, the interest of shellfish growers and competing shorebirds need not conflict.
LANDSCAPE COMPOSITION, PATCH SIZE, AND DISTANCE TO EDGES: INTERACTIONS AFFECTING DUCK REPRODUCTIVE SUCCESS
Authors: Horn David Joseph , Phillips Michael L. , Koford Rolf R. , Clark William R. , Sovada Marsha A. , Greenwood Raymond J.
Published: June 2007

Prairies and other North American grasslands, although highly fragmented, provide breeding habitat for a diverse array of species, including species of tremendous economic and ecological importance. Conservation and management of these species requires some understanding of how reproductive success is affected by edge effects, patch size, and characteristics of the landscape. We examined how differences in the percentage of grassland in the landscape influenced the relationships between the success of nests of upland‐nesting ducks and (1) field size and (2) distance to nearest field and wetland edges. We collected data on study areas composed of 15–20% grassland and areas composed of 45–55% grassland in central North Dakota, USA during the 1996 and 1997 nesting seasons. Daily survival rates (DSRs) of duck nests were greater in study areas with 45–55% grassland than with 15–20% grassland. Within study areas, we detected a curvilinear relationship between DSR and field size: DSRs were highest in small and large fields and lowest in moderately sized fields. In study areas with 15–20% grassland, there was no relationship between probability of hatching and distance to nearest field edge, whereas in study areas with 45–55% grassland, there was a positive relationship between these two variables. Results of this study support the conclusion that both landscape composition and configuration affect reproductive success of ground‐nesting birds. We are prompted to question conservation strategies that favor clustering moderately sized patches of nesting habitat within agricultural landscapes because our results show that such patches would have low nest success, most likely caused by predation. Understanding the pattern of nest success, and the predator–prey mechanisms that produce the pattern, will enable design of patch configurations that are most conducive to meeting conservation goals.
WILD BEE ABUNDANCE AND SEED PRODUCTION IN CONVENTIONAL, ORGANIC, AND GENETICALLY MODIFIED CANOLA
Authors: Morandin Lora A. , Winston Mark L.
Published: June 2007

The ecological impacts of agriculture are of concern, especially with genetically modified and other intensive, modern cropping systems, yet little is known about effects on wild bee populations and subsequent implications for pollination. Pollination deficit (the difference between potential and actual pollination) and bee abundance were measured in organic, conventional, and herbicide‐resistant, genetically modified (GM) canola fields (Brassica napus and B. rapa) in northern Alberta, Canada, in the summer of 2002. Bee abundance data were collected using pan traps and standardized sweep netting, and pollination deficit was assessed by comparing the number of seeds per fruit from open‐pollinated and supplementally pollinated flowers. There was no pollination deficit in organic fields, a moderate pollination deficit in conventional fields, and the greatest pollination deficit in GM fields. Bee abundance was greatest in organic fields, followed by conventional fields, and lowest in GM fields. Overall, there was a strong, positive relationship between bee abundance at sampling locations and reduced pollination deficits. Seed set in B. napus increased with greater bee abundance. Because B. rapa is an obligate outcrossing species, the lack of pollination deficit in the organic (B. rapa) fields likely was due to the high bee abundance rather than a lower dependence of B. rapa on pollinators than B. napus canola. Our study illustrates the importance of wild bees to agricultural production and suggests that some agroecosystems may better sustain wild bee abundance, resulting in greater seed production. Further research on why some cropping systems, such as genetically modified, herbicide‐resistant canola, have low wild bee abundance would be useful for management of agroecosystems to promote sustainability of food production.
EVALUATING THE STEADY STATE ASSUMPTION: SIMULATIONS OF GORILLA NEST DECAY
Authors: Walsh Peter D. , White Lee J. T.
Published: June 2007

Large mammal surveys are often based on indices of animal abundance such as dung or, for great apes, sleeping nests. They also tend to rely on the “steady state” assumption that the rate at which an index is deposited in the environment is exactly balanced by the rate at which it disappears (decays). Here we use a data set on western gorilla (Gorilla gorilla) sleeping nest decay rates to show that this assumption is likely to be strongly violated often and in ways that have serious implications for our ability to accurately survey and monitor a wide range of endangered species, particularly in tropical forests. We first fit the data using a model describing the daily probability of nest decay as a function of nest age and monthly rainfall. We then use this decay model to simulate time series of gorilla nest standing stock, given observed rainfall regimes from a series of sites in the equatorial African country of Gabon. These simulations suggest that, within a given site, the relationship between nest standing stock and true gorilla density fluctuates wildly and is, on average, tens of percent away from the mean nest decay time for the empirical data set. The behavior of nest standing stock is extremely sensitive to variability in rainfall, not just annual mean rainfall. Differences between sites in rainfall variability produce counterintuitive differences between sites in nest standing stock. Multiyear trends in the mean and variance of rainfall produce the spurious impression of trends in animal abundance. Furthermore, heterogeneity in rainfall exists at all spatial and temporal scales, so that attempts to use regression models based on rainfall measurements taken at one location or time are not likely to accurately predict the nest decay regime at other places or times. We close with some suggestions on alternative estimation methods that do not rely on extrapolations of environmental conditions from one time or place to another.
THE IMPACT OF LOW‐HEAD DAMS ON FISH SPECIES RICHNESS IN WISCONSIN, USA
Authors: Cumming Graeme S.
Published: June 2007

Communities that live in linear systems such as streams or riparian zones may be particularly sensitive to changes in habitat connectivity. I examined the relationship between environmental variables, the number of low‐head dams downstream of each reach, and fish species richness in first‐order streams in Wisconsin, USA. The analysis was based on an extensive database of 13 628 localities and ∼180 000 individual collection records. The environmental variables included climate, elevation, distance from nearest town, and network‐specific measures such as link number (the number of first‐order tributaries upstream of the current reach), downstream link number, stream order, and fractal dimension. The link number of the downstream reach was the strongest broad‐scale correlate of fish species richness in first‐order streams. Path analysis of a simple directed graph suggested that, although downstream dams have a significant effect on fish species richness, this effect is small by comparison to the influence of water quantity and summer maximum temperatures. From a management perspective, the results imply that modifications of water volume and temperature are greater threats to fish communities than the decrease in connectivity that results from low‐head dams.
SPATIAL RESPONSES OF WOLVES TO ROADS AND TRAILS IN MOUNTAIN VALLEYS
Authors: Whittington Jesse , St. Clair Colleen Cassady , Mercer George
Published: June 2007

Increasing levels of human activity in mountainous areas have high potential to inhibit animal movement across and among valleys. We examined how wolves respond to roads, trails, and other developments. We recorded the movements of two wolf packs for two winters by following their tracks in the snow and simultaneously recording positions with a hand‐held global positioning system. We then used matched case‐controlled logistic regression to compare habitat covariates of wolf paths (cases) to multiple paired random locations (controls). This analysis emphasized the differences within pairs of cases and controls, rather than differences in their overall distribution, making it useful to assess fine‐scale habitat selection and path data. Both packs selected low elevations, shallow slopes, and southwest aspects. They selected areas within 25 m of roads, trails, and the railway line and more strongly selected low‐use roads and trails compared to high‐use roads and trails. One pack strongly avoided distances between 26 and 200 m of high‐use trails; otherwise, the wolves weakly selected or avoided this distance class. Both packs avoided areas of high road and trail density. We concluded that roads and trails have a cumulative effect on wolf movement and that management of trails, in addition to roads, may be needed to retain high‐quality habitat for wolves, particularly in known movement corridors.
OCEAN WARMING EFFECTS ON GROWTH, REPRODUCTION, AND SURVIVORSHIP OF SOUTHERN CALIFORNIA ABALONE
Authors: Vilchis L. Ignacio , Tegner Mia J. , Moore James D. , Friedman Carolyn S. , Riser Kristin L. , Robbins Thea T. , Dayton Paul K.
Published: June 2007

Traditional fisheries management in southern California has failed, in part because it is based on an assumption of an unvarying environment and is focused on size limits rather than insuring the persistence of aggregations of large fecund individuals. The combined effect of low frequency climatic variability and anthropogenic perturbations can have dramatic consequences for abalone in southern California. Abalone species are tightly linked to kelp forest ecosystems that, besides furnishing habitat, also provide the main food source for abalone. In southern California, kelp canopies are very sensitive to oceanographic climate because the kelp depend upon high nutrients in the water column. Oceanic warming, in turn, results in decreased nutrients in the surface water, and this is correlated with marked reductions in giant kelp biomass.

Here we address the additive effects of ocean warming on two species of California abalone (the red abalone, Haliotis rufescens; and the green abalone, H. fulgens) by subjecting them to varied environmental conditions similar to cool, normal, and warm phases of the California current in the southern California Bight. Our experimental design simultaneously tested the synergistic effects of temperature and food quantity and quality on survivorship, growth, and reproduction. For red abalone, warm temperatures increased the onset of withering syndrome, a fatal abalone disease, and halted growth and reproduction. In contrast, green abalone survivorship, growth, and reproduction were relatively robust irrespective of temperature, while their growth and reproduction were most strongly influenced by food quantity. We found clear evidence suggesting that, combined with overfishing, California abalone populations are adversely affected by ecosystem responses to ocean warming: Cool‐water red abalone suffer stronger consequences in warm water than do green abalone. Conservation, restoration, and recovery plans of remnant California abalone populations must consider these relationships when taking any action.
PATTERNS OF PLANT SPECIES RICHNESS, RARITY, ENDEMISM, AND UNIQUENESS IN AN ARID LANDSCAPE
Authors: Stohlgren Thomas J. , Guenther Debra A. , Evangelista Paul H. , Alley Nathaniel
Published: June 2007

Most current conservation literature focuses on the preservation of hotspots of species diversity and endemism, as if the two were geographically synonymous. At landscape scales this may not be the case. We collected data from 367 1000‐m2 plots in the Grand Staircase–Escalante National Monument, Utah, USA, to show that: (1) the vast majority of plant species are locally rare; (2) species‐rich areas are generally in rare, mesic, or high‐elevation habitats such as aspen stands or riparian zones high in soil N and P; (3) endemic species (to the Colorado Plateau and the Monument) were generally found in relatively species‐rich, but low‐elevation, xeric vegetation type areas low in soil P; (4) unique species assemblages were found in areas moderately high in endemism and species richness; and (5) nonnative plant species were widely distributed, but more prevalent in species‐rich, mesic sites high in soil fertility or disturbed sites, and significantly less prevalent in plots with endemic species. We show that primary hotspots of species richness, high endemism, and unique species assemblages are not co‐located on the landscape. Hence, conservation strategies may have to consider a much broader concept of “hotspots” to adequately preserve native plant species and the processes that foster persistence.
COUNTRYSIDE BIOGEOGRAPHY OF NEOTROPICAL HERBACEOUS AND SHRUBBY PLANTS
Authors: Mayfield Margaret M. , Daily Gretchen C.
Published: June 2007

As human impacts on the environment intensify, the future of plant and animal biodiversity will depend increasingly on the floras surviving in human‐dominated “countryside” habitats. To begin to characterize these floras for the Neotropics, we investigated the richness and composition of herbaceous and shrubby plant communities in six forested and deforested habitats, in three replicated study areas (7.5‐km in diameter), of southern Costa Rica. We chose habitat types that are common throughout the tropics, to begin building a general understanding of both the habitats of origin and the diversity of countryside floras. Focal forest habitats were understory, 1‐ to 2‐year‐old tree‐fall gaps, and riverbanks, all in primary forest. Focal deforested habitats were ungrazed road verges, grazed pasture, and riverbanks in grazed pasture. Non‐riverbank habitats were sampled both near and far from forest edge. In total, we sampled 772 species from 79 families, ∼40% of the non‐tree plant diversity of the region. Only 6% of identified species are known to be exotic. In each study area, understory and pasture plots were consistently species poor, while tree‐fall gaps and road verges near forest were consistently the most species‐rich habitats. In each study area, we found the same proportion of species restricted to forested habitats (∼45%) and deforested habitats (∼37%), and the same proportion of “countryside‐habitat generalists” (∼18%) occurring in both forested and deforested habitats. However, different forested habitats supported different proportions of countryside‐habitat generalists in each study area, although understory plots consistently supported the fewest generalists. Among forested habitats, riverbanks were the most similar floristically to deforested habitats. Pasture riverbanks and road verges near forest supported plant communities most similar to those in forested habitats. The uniqueness and richness of each habitat suggests that countrysides with diverse land uses can support many native herbaceous and shrubby plant species. As it becomes increasingly difficult to protect large tracts of undisturbed tropical forest, we suggest that conservation goals expand to encompass maintenance of heterogeneity in countryside landscapes.
THE ROLES OF FISHING AND CLIMATE IN THE POPULATION DYNAMICS OF BOCACCIO ROCKFISH
Authors: Tolimieri Nick , Levin Phillip S.
Published: June 2007

Climate is an important force influencing the dynamics of populations and communities in many terrestrial, aquatic, and marine systems. The precipitous decline of stocks of bocaccio (Sebastes paucispinis) since the mid‐1970s has been attributed to a combination of a shift in the climate regime in the eastern Pacific Ocean during the winter of 1976–1977 (leading to lower productivity) and overfishing. We used a bocaccio recruitment time series (1959–1997) and indices of climate and ocean condition (e.g., sea surface temperature, Northern Oscillation Index, El Niño–Southern Oscillation Index, and upwelling indices) to examine the relationship between bocaccio productivity (recruits per spawning output, R/S) and both interannual (e.g., ENSO) and interdecadal (regime shifts) scale variation in climate and ocean conditions.

We did not detect an effect of the 1976 climate regime shift on bocaccio productivity. Mean log R/S and the frequency of “good” recruitment years (log R/S > 1 sd above the long‐term mean) were the same before and after the 1976 regime shift. Good recruitment years occurred about 13% of the time in both regimes. At an interannual time scale, cooler ocean temperatures during the period spanning egg production to the end of the larval stage correlated with higher log R/S both before and after the regime shift. Prior to the 1976 shift, high log R/S values were more likely when upwelling was low during the settlement period, but there was no relationship after the regime shift. A matrix population model suggested that in the absence of fishing a “good” recruitment year needs to occur 15% of the time to achieve a nonnegative population growth rate of (λ ≥ 1.0), similar to the observed frequency of good recruitment events. Good recruitment years needed to occur >90% of the time under historic levels of fishing mortality to achieve a population growth rate ≥1.0. Taken together, these results suggest that the 1976 regime shift did not contribute to the decline in bocaccio stocks through processes affecting recruitment, and that the degree to which populations of bocaccio can withstand fishing depends on the frequency of climatic conditions that promote strong recruitment.
CHANGES IN FROG AND TOAD POPULATIONS OVER 30 YEARS IN NEW YORK STATE
Authors: Gibbs James P. , Whiteleather K. Kristian , Schueler Frederick W.
Published: June 2007

Lack of historical data against which to measure population trends greatly hampers understanding the status of amphibians. In 2001–2002 we resurveyed a hitherto unexamined baseline of monitoring data established in 1973–1980 at some 300 sites in western, central, and northern New York State, USA, and contrasted population transitions with environmental conditions to identify correlates of population change in American toads (Bufo americanus), northern spring peepers (Pseudacris crucifer), western chorus frogs (Pseudacris triseriata), leopard frogs (Rana pipiens), and wood frogs (Rana sylvatica). At the regional level, loss of habitats along roadsides has been substantial (minimally 7– 12% of sites), yet within remaining wetlands, populations of most anurans have not declined. At the local level, population disappearance was associated with elevated levels of acid deposition (in American toad, spring peeper, western chorus frog, and leopard frog), urban development (American toad and spring peeper), increased forest cover (western chorus frog), and high‐intensity agriculture (spring peeper); whereas population persistence was associated with increased deciduous forest cover (American toad, spring peeper, and wood frog) and low‐intensity agriculture (American toad and western chorus frog). Habitat configurations at surprisingly large spatial scales (5–10 km from surveyed populations) were most closely associated with transitions in local anuran populations, implying that large‐scale extinction–recolonization dynamics influence population transitions, a result land managers should consider in conservation planning.
NOTHOFAGUS REGENERATION DYNAMICS IN SOUTH‐CENTRAL CHILE: A TEST OF A GENERAL MODEL
Authors: Pollmann William , Veblen Thomas T.
Published: June 2007

Studies in Southern Hemisphere temperate forests have yielded a general model of how the successional status of shade‐intolerant Nothofagus is related to site conditions and disturbance. According to model predictions, regeneration of most Nothofagus species is dependent on coarse‐scale disturbance at favorable sites where shade‐tolerant rain forest species co‐occur. In contrast, at suboptimal sites where tree species richness is low, regeneration is not dependent on coarse‐scale disturbance. We used variation in forest composition and structure as well as disturbance patterns in the forests of Puyehue National Park, Chile, to test several predictions from this general model. The study area presents a complex mosaic of disturbance patterns, including the effects of the strong 1960 earthquake as well as fire and wind disturbance. We reconstructed stand development on sites affected by these disturbances, and compared these patterns with the structure of old‐growth forests along an elevation gradient from species‐rich montane rain forest to monotypic subalpine Nothofagus forests.

Tree age data indicate that both the Nothofagus and many of the rain forest tree species are long‐lived, often reaching ages greater than 600 years. Regeneration of Nothofagus was abundant in stands recently disturbed by landslides, fire, or blowdown across the entire elevation gradient, and Nothofagus also regenerated in old‐growth high‐elevation forests. In contrast, regeneration of Nothofagus was scarce or absent in undisturbed stands and at lower elevation. In comparison with the rain forest species, Nothofagus species are more tolerant of the unfavorable site conditions associated with increasing elevation. Thus, there is a gradient of decreasing interspecific tree competition with increasing elevation, so that the dependence of regeneration of Nothofagus on coarse‐scale disturbance is much less at higher elevation. This study confirms that changes in forest composition may be explained by simple processes occurring in accordance with the main predictions of the general model of Nothofagus forest dynamics: At low elevations, coarse‐scale disturbance is required for Nothofagus regeneration; at higher elevations under decreasing competition the regeneration of Nothofagus is less dependent on coarse‐scale disturbance. Thus, for the Puyehue landscape, patterns of forest structure and disturbance history are congruent with the major features of the general model of Nothofagus dynamics.
DELAYED EFFECTS OF FLOOD CONTROL ON A FLOOD‐DEPENDENT RIPARIAN FOREST
Authors: Katz Gabrielle L. , Friedman Jonathan M. , Beatty Susan W.
Published: June 2007

The downstream effects of dams on riparian forests are strongly mediated by the character and magnitude of adjustment of the fluvial–geomorphic system. To examine the effects of flow regulation on sand‐bed streams in eastern Colorado, we studied the riparian forest on three river segments, the dam‐regulated South Fork Republican River downstream of Bonny Dam, the unregulated South Fork Republican River upstream of Bonny Dam, and the unregulated Arikaree River. Although Bonny Dam significantly reduced peak and mean discharge downstream since 1951, there was little difference in forest structure between the regulated and unregulated segments. On all river segments, the riparian forest was dominated by the native pioneer tree, Populus deltoides, which became established during a period of channel narrowing beginning after the 1935 flood of record and ending by 1965. The nonnative Elaeagnus angustifolia was present on all river segments, with recruitment ongoing. The lack of contrast in forest structure between regulated and unregulated reaches resulted primarily from the fact that no large floods occurred on any of the study segments since dam construction. Most of the riparian forest in the study area was located on the broad narrowing terrace, which was rarely inundated on the unregulated segments, resulting in little contrast with the regulated segment. A minor dam effect occurred on the small modern floodplain, which was actively disturbed on the unregulated segments, but not on the regulated segments. Although Bonny Dam had the potential to significantly influence downstream riparian ecosystems, this influence had not been expressed, and may never be if a large flood does not occur within the lifetime of the dam. Minor dam effects to riparian systems can be expected downstream of large dams in some settings, including the present example in which there was insufficient time for the dam effects to by fully expressed.
THE EVOLUTION OF LACTATION STRATEGIES IN PINNIPEDS: A PHYLOGENETIC ANALYSIS
Authors: Schulz Tyler M. , Bowen W. Don
Published: June 2007

Pinnipeds are a diverse group of aquatic carnivores that exhibit wide variation in body size, milk composition, lactation strategies, and the length of maternal care. We used 12 pinniped life‐history and ecological traits to test hypotheses concerning the influence of phylogeny, maternal body size, breeding substrate, and other factors on the evolution of lactation strategies. We used independent contrasts to account for phylogenetic effects on correlations between traits. Our findings indicate that the negative relationships between maternal mass and lactation length and between maternal mass and the percentage of time spent at sea by females during lactation are not recent adaptations, but likely a result of phylogenetic history and an evolutionary grade shift in lactation length, which occurred when the phocids diverged from the otariids. Differences in body size between the ancestral phocid and otariid impacted their foraging strategies and metabolic rates, which subsequently influenced lactation strategies. The fat‐storage abilities of large phocids may have allowed them to exploit remote and patchy prey resources and thereby reduce time spent feeding during lactation. We also suggest that an early divergence in the mammary gland structure of phocids and otariids is a fundamental influence on pinniped lactation strategies. Although estimates are lacking for several key species, body size appears to have little adaptive influence on the lactation length of extant species. Instead, an abbreviated lactation period seems to be adaptive in minimizing the relative milk energy expended over lactation, although it may have initially evolved to reduce maternal overhead, especially in ancestral fasting phocids. Subsequently, a brief lactation in phocids was also selected through the effects of terrestrial predation, the instability of breeding on pack‐ice, and the energy benefits of increasing milk energy output.
AVIAN COMMUNITY DYNAMICS IN A FRAGMENTED TROPICAL LANDSCAPE
Authors: Borgella René , Gavin Thomas A.
Published: June 2007

As humans alter habitats worldwide, developing reliable methods of assessing biodiversity and community attributes of interest (e.g., species richness, turnover, and extinction rates) is important. Frequently, estimates of community‐level attributes are biased because the estimators make assumptions of the data that are violated; many published studies assume equal detectability across species, sites, or time. The accuracy of estimators of species richness and community‐level vital rates (e.g., extinction and colonization) can be increased by using probabilistic estimation methods, which do not assume that all species are detected, or that the data assume a particular statistical distribution.

Using these estimation methods, we examined avian community dynamics in a fragmented tropical landscape using data from five years of a mark–release–recapture study. For the resident understory avifauna in each of five small (∼0.3–20 ha), isolated forest fragments in southern Costa Rica, we estimated species richness, rate of change in species richness, extinction and turnover rates of species, and the number of colonizing species over temporal scales of one month, one year, and two years. We expected that community dynamics would be higher in smaller fragments than in larger fragments, reflecting greater temporal variability of avian communities in relatively small habitat patches. Additionally, a selective logging operation was conducted at one of our sites during the midpoint of this study, which gave us the opportunity to examine how community‐level vital rates may reflect the effects of that perturbation.

Our results demonstrate that avian communities in the larger fragments were more stable than those in the smaller fragments, and that the selectively logged fragment was the most unstable of all. We found that extinction rates were more similar across our sites than were colonization rates, and that the higher instability of the small fragments was due primarily to higher levels of colonization. Although our sample size (n = 5) precludes strong inference, our findings are consistent with the prediction of higher local dynamics within small fragments and after logging. Taken together, these findings suggest that smaller fragments are more dynamic over time, and that ecological processes and multitrophic relationships at these dynamic sites may be in a constant state of flux.
MODELING GROSS PRIMARY PRODUCTION OF AN EVERGREEN NEEDLELEAF FOREST USING MODIS AND CLIMATE DATA
Authors: Xiao Xiangming , Zhang Qingyuan , Hollinger David , Aber John , Moore Berrien
Published: June 2007

Forest canopies are composed of photosynthetically active vegetation (PAV, chloroplasts) and nonphotosynthetic vegetation (NPV, e.g., cell wall, vein, branch). The fraction of photosynthetically active radiation (PAR) absorbed by the canopy (FAPAR) should be partitioned into FAPARPAV and FAPARNPV. Gross primary production (GPP) of forests is affected by FAPARPAV. In this study we developed and validated a satellite‐based vegetation photosynthesis model (VPM; GPP = εg × FAPAPPAV × PAR) that incorporates improved vegetation indices derived from the moderate resolution imaging spectroradimeter (MODIS) sensor. Site‐specific data from the CO2 flux tower site (evergreen needleleaf forest) at Howland, Maine, USA, were used. The enhanced vegetation index (EVI) better correlated with the seasonal dynamics of GPP than did the normalized difference vegetation index (NDVI). Simulations of the VPM model were conducted, using both daily and eight‐day composites of MODIS images (500‐m spatial resolution) and climate data (air temperature and PAR), respectively. Predicted GPP values in 2001 agree reasonably well with estimated GPP from the CO2 flux tower site. There were no significant differences in VPM‐predicted GPP (from eight‐day MODIS composites) among one pixel (∼500‐m resolution), 3 × 3 pixel block (∼1.5‐km resolution), and 5 × 5 pixel block (∼2.5‐km resolution). The differences between VPM‐predicted and observed GPP were smaller for simulations using eight‐day MODIS composites than for simulations using daily MODIS images. The results of this study have shown the potential of MODIS data (both daily and eight‐day composites) and the VPM model for quantifying seasonal and interannual variations of GPP of evergreen needleleaf forests.
DIFFERENT MOOSE DENSITIES AND ACCOMPANIED CHANGES IN TREE MORPHOLOGY AND BROWSE PRODUCTION
Authors: Persson Inga-Lill , Danell Kjell , Bergström Roger
Published: June 2007

Large herbivores affect the morphology and productivity of their food plants, which in turn affects food availability and foraging efficiency. These effects can occur directly, through tissue removal, or indirectly through additions of nutrients in dung and urine. Although influences of herbivores on plant communities are well established for grazers, less is known about the effects of browsers. We studied how tree morphology (number of shoots, shoot mass, and mean yearly height increase) and production of winter browse of Scots pine (Pinus sylvestris) and birch (Betula pubescens and B. pendula) responded to simulated moose herbivory in Swedish boreal forests. We simulated browsing, defecation, and urination to represent effects of four levels of moose density in each of eight exclosures. To be able to study the whole range of moose impact and obtain better mean estimates from the ecosystem perspective, the eight exclosures were placed along a forest productivity gradient. Treatments were applied for three consecutive years. For both birch and pine, the mean average number of shoots per tree and the mean yearly height increase decreased with increasing biomass removal. Mass of individual shoots increased for birch, but not for pine. The mean yearly production of winter browse (per m2) was significantly reduced by biomass removal. The responses of birch followed a threshold model predicting no effect up to a low to moderate level of biomass removal, and thereafter a linear decrease, although the model describing constant linear decrease not could be ruled out (model selection based on Akaike Information Criterion). The response of pine followed a threshold model. We concluded that winter browse might be in shortage at high browsing pressure over extended time, but most woody plants eaten by moose should sustain browsing pressure at moose densities common in many areas in Sweden.
LANDSCAPE CHARACTERISTICS INFLUENCE POND OCCUPANCY BY FROGS AFTER ACCOUNTING FOR DETECTABILITY
Authors: Mazerolle M. J. , Desrochers A. , Rochefort L.
Published: June 2007

Many investigators have hypothesized that landscape attributes such as the amount and proximity of habitat are important for amphibian spatial patterns. This has produced a number of studies focusing on the effects of landscape characteristics on amphibian patterns of occurrence in patches or ponds, most of which conclude that the landscape is important. We identified two concerns associated with these studies: one deals with their applicability to other landscape types, as most have been conducted in agricultural landscapes; the other highlights the need to account for the probability of detection. We tested the hypothesis that landscape characteristics influence spatial patterns of amphibian occurrence at ponds after accounting for the probability of detection in little‐studied peatland landscapes undergoing peat mining. We also illustrated the costs of not accounting for the probability of detection by comparing our results to conventional logistic regression analyses. Results indicate that frog occurrence increased with the percent cover of ponds within 100, 250, and 1000 m, as well as the amount of forest cover within 1000 m. However, forest cover at 250 m had a negative influence on frog presence at ponds. Not accounting for the probability of detection resulted in underestimating the influence of most variables on frog occurrence, whereas a few were overestimated. Regardless, we show that conventional logistic regression can lead to different conclusions than analyses accounting for detectability. Our study is consistent with the hypothesis that landscape characteristics are important in determining the spatial patterns of frog occurrence at ponds. We strongly recommend estimating the probability of detection in field surveys, as this will increase the quality and conservation potential of models derived from such data.