bluuebunny/crossref_metadata_2025_split huggingface dataset:
RECRUITMENT IN DEGRADED MARINE HABITATS: A SPATIALLY EXPLICIT, INDIVIDUAL‐BASED MODEL FOR SPINY LOBSTER
Authors: Butler Mark J. , Dolan Thomas W. , Hunt John H. , Rose Kenneth A. , Herrnkind William F. 
Published: June 2007

Coastal habitats that serve as nursery grounds for numerous marine species are badly degraded, yet the traditional means of modeling populations of exploited marine species handle spatiotemporal changes in habitat characteristics and life history dynamics poorly, if at all. To explore how nursery habitat degradation impacts recruitment of a mobile, benthic species, we developed a spatially explicit, individual‐based model that describes the recruitment of Caribbean spiny lobster (Panulirus argus) in the Florida Keys, where a cascade of environmental disturbances has reconfigured nursery habitat structure. In recent years, the region has experienced a series of linked perturbations, among them, seagrass die‐offs, cyanobacteria blooms, and the mass mortality of sponges. Sponges are important shelters for juvenile spiny lobster, an abundant benthic predator that also sustains Florida's most valuable fishery.In the model, we simulated monthly settlement of individual lobster postlarvae and the daily growth, mortality, shelter selection, and movement of individual juvenile lobsters on a spatially explicit grid of habitat cells configured to represent the Florida Keys coastal nursery. Based on field habitat surveys, cells were designated as either seagrass or hard‐bottom, and hard‐bottom cells were further characterized in terms of their shelter‐ and size‐specific lobster carrying capacities. The effect of algal blooms on sponge mortality, hence lobster habitat structure, was modeled based on the duration of exposure of each habitat cell to the blooms. Ten‐year simulations of lobster recruitment with and without algal blooms suggest that the lobster population should be surprisingly resilient to massive disturbances of this type. Data not used in model development showed that predictions of large changes in lobster shelter utilization, yet small effects on recruitment in response to blooms, were realistic. The potentially severe impacts of habitat loss on recruitment were averted by compensatory changes in habitat utilization and mobility by larger individuals, coupled with periods of fortuitously high larval settlement. Our model provides an underutilized approach for assessing habitat effects on open populations with complex life histories, and our results illustrate the potential pitfalls of relying on intuition to infer the effects of habitat perturbations on upper trophic levels.
RELATIVE STRENGTH OF TOP‐DOWN, BOTTOM‐UP, AND CONSUMER SPECIES RICHNESS EFFECTS ON POND ECOSYSTEMS
Authors: Wojdak Jeremy M. 
Published: June 2007

Theory and experiments demonstrate that the number of species in a local area can determine rates of ecosystem processes, but we know little about how the strength of that control compares with other influences or how it might vary across ecological gradients. Here I report results of a pond mesocosm experiment where consumer (snail) species richness, predation intensity, and nutrient availability were crossed in a full‐factorial design. This design allowed a direct comparison of the strength of the different factors on food web properties and ecosystem functioning (i.e., system‐level fluxes of energy or matter), and an evaluation of how the factors may interact.Systems with higher snail species richness had greater secondary production, consumer biomass, ecosystem respiration, and macrophyte stem growth, and lower epiphyton and periphyton biomass. However, snail species richness effects on periphyton and epiphyton were context dependent; predators reduced the effect of increasing snail richness on the biomass of attached algae. Species richness effects were most often the result of a biological mechanism (e.g., differential resource use), rather than being solely artifacts of the experimental design (e.g., sampling effects). The effects of nutrient enrichment and predation were mostly predictable from simple food chain models; increases in nutrient availability led to increased algal biomass, primary production, and snail biomass, while predators decreased snail biomass and indirectly augmented algae.Snail species richness effects on the biomass of many functional groups were as strong or stronger than those of a substantial nutrient enrichment or of the addition of a voracious predator (Belostoma flumineum). Nutrient enrichment had the most pronounced effects on several system‐level processes (e.g., primary production, sedimentation). Species richness had weaker effects on ecosystem properties than on particular functional groups, probably because of compensatory responses among different producer functional groups. In summary, this experiment suggests that the number of consumer species in a system can have large and meaningful effects on the distribution of biomass in a food web, and that these effects can depend on ecological context.
INVERTEBRATE BIODIVERSITY IN AGRICULTURAL AND URBAN HEADWATER STREAMS: IMPLICATIONS FOR CONSERVATION AND MANAGEMENT
Authors: Moore Aaron A. , Palmer Margaret A. 
Published: June 2007

The urbanization of agricultural lands is currently one of the dominant patterns of land use change in developed countries. In the United States and parts of Europe, this has led to the implementation of agricultural land preservation programs and riparian protection and replanting efforts along urban streams. The ecological benefits of such programs for the conservation of freshwater biodiversity have yet to be fully explored. We designed a study to investigate the patterns of stream macroinvertebrate community structure along a gradient of agriculture to urban development, and the patterns among urban streams that vary in the amount of intact riparian buffer. In 2001 and 2002, we sampled the 29 small headwater streams comprising the outlying tributaries of four watersheds just north of Washington, D.C., in Montgomery County, Maryland, USA. This region has had dramatic urban development over the last 50 years, yet significant efforts have been made to maintain riparian buffers and promote preservation of agricultural land.Macroinvertebrate richness was strongly related to land use, with agricultural streams exhibiting the highest macroinvertebrate diversity. Taxa richness was related negatively and linearly (no statistical threshold) to the amount of impervious surface cover. For the urban streams, there was a strong positive relationship between invertebrate diversity and riparian forest cover. Urban streams with high amounts of intact riparian forest exhibited biodiversity levels more comparable to less urban areas despite high amounts of impervious cover in their catchments. The agricultural headwater streams in this study were not only more diverse than the urban headwaters, but their levels of macroinvertebrate diversity were high compared to other published estimates for agricultural streams. These higher richness values may be due to widespread use of “best management practices” (BMPs), including no‐till farming and the implementation of woody and herbaceous riparian buffers, which may alleviate many acute stressors caused by cultivation. These findings suggest that, if managed properly, the preservation of agricultural land from development may help conserve stream invertebrate biodiversity, and that maintenance of riparian forests even in highly urbanized watersheds may help alleviate ecological disturbances that might otherwise limit macroinvertebrate survival.
GAUSSIAN ERROR PROPAGATION APPLIED TO ECOLOGICAL DATA: POST‐ICE‐STORM‐DOWNED WOODY BIOMASS
Authors: Lo Ernest 
Published: June 2007

Error analysis using Gaussian error propagation (GEP) can be used to analytically determine the error or uncertainty produced by multiple and interacting measurements or variables. The technique is especially useful for studies that involve step‐by‐step calculations, where measurements taken at a smaller temporal or spatial scale are used to estimate a value at larger scales (e.g., daily total tree‐crown carbon assimilation is estimated from carbon assimilation rate per unit leaf area per unit time).The GEP technique is not well known and rarely used in ecology. The purpose of this paper is to illustrate the concepts and methods of GEP in a manner that is accessible and relevant to students and researchers in ecology. The technique is also extended to calculate the “error budget” and “sensitivity indices” of error sources. The concept of the “error structure” of an experiment or calculation is introduced, and different partitioning methods and optimization strategies for analyzing and reducing error, which further develop the potential usefulness of GEP, are shown. An example of its application to ecological data is demonstrated using the post‐ice‐storm‐downed woody‐biomass data set, previously reported by M. C. Hooper, K. Arii, and M. J. Lechowicz. Both the data and the error analysis can be viewed as being representative of and relevant to a general class of step‐by‐step and scaling‐up ecological calculations. Finally the use of GEP reveals that the error structure is a scale‐dependent quantity, a result that is relevant to both scaling theory and experimental design.
MULTISCALE CONTROLS ON WOODY PLANT DIVERSITY IN WESTERN OREGON RIPARIAN FORESTS
Authors: Sarr Daniel A. , Hibbs David E. 
Published: June 2007

Riparian forests are known to be floristically diverse and influenced by multiscale phenomena, yet few studies have explicitly compared how these factors contribute to various aspects of riparian plant diversity. We analyzed woody riparian plant species and environmental data from four western Oregon watersheds distributed across a wide climate‐driven productivity gradient at three scales (40‐m2 sample plots [alpha diversity], 1‐ha plots, and species pools from 16 1‐ha plots in each watershed) to compare three hypotheses of control on species diversity: (1) local control, (2) direct climatic control, and (3) indirect climatic control. We used a process model (3‐PG) to model gross primary productivity (GPP) as a functional climate index across our study area. We performed multiple linear regression to determine the best predictors of alpha (sample‐plot scale) diversity, compositional change within riparian forests (beta diversity), and hectare‐scale diversity and used path analysis to explore hypothesized causal linkages between climate and other factors and species diversity. We also analyzed a companion data set of gap and forest environments from a subset of the same sites to determine the influence of disturbance on species diversity across the gradient.We found evidence for strong spatial patterning in woody plant richness consistent with indirect climatic control on woody plant richness. Climate (GPP) showed negative relationships with alpha diversity and hectare richness of trees, shrubs, and woody plant species and was the most commonly selected explanatory variable in regression analyses. GPP and Rubus spectabilis cover increased from the least to most productive climates while understory light and moisture heterogeneity across the riparian area decreased. These environmental changes coincided with declines in alpha, beta, and hectare‐scale diversity. Disturbance gaps yielded higher richness at most sites, but differences in species richness between gap and forest sample plots did not increase at high levels of GPP, as hypothesized.This study points toward an integrated conceptual model whereby regional and landscape scale controls such as climate and watershed position complement and interact with local controls (i.e., vegetation structure, environmental gradients) to jointly govern woody plant diversity in riparian forests.
TUNDRA CO2 FLUXES IN RESPONSE TO EXPERIMENTAL WARMING ACROSS LATITUDINAL AND MOISTURE GRADIENTS
Authors: Oberbauer Steven F. , Tweedie Craig E. , Welker Jeff M. , Fahnestock Jace T. , Henry Greg H. R. , Webber Patrick J. , Hollister Robert D. , Walker Marilyn D. , Kuchy Andrea , Elmore Elizabeth , Starr Gregory 
Published: June 2007

Climate warming is expected to differentially affect CO2 exchange of the diverse ecosystems in the Arctic. Quantifying responses of CO2 exchange to warming in these ecosystems will require coordinated experimentation using standard temperature manipulations and measurements. Here, we used the International Tundra Experiment (ITEX) standard warming treatment to determine CO2 flux responses to growing‐season warming for ecosystems spanning natural temperature and moisture ranges across the Arctic biome. We used the four North American Arctic ITEX sites (Toolik Lake, Atqasuk, and Barrow [USA] and Alexandra Fiord [Canada]) that span 10° of latitude. At each site, we investigated the CO2 responses to warming in both dry and wet or moist ecosystems. Net ecosystem CO2 exchange (NEE), ecosystem respiration (ER), and gross ecosystem photosynthesis (GEP) were assessed using chamber techniques conducted over 24‐h periods sampled regularly throughout the summers of two years at all sites.At Toolik Lake, warming increased net CO2 losses in both moist and dry ecosystems. In contrast, at Atqasuk and Barrow, warming increased net CO2 uptake in wet ecosystems but increased losses from dry ecosystems. At Alexandra Fiord, warming improved net carbon uptake in the moist ecosystem in both years, but in the wet and dry ecosystems uptake increased in one year and decreased the other. Warming generally increased ER, with the largest increases in dry ecosystems. In wet ecosystems, high soil moisture limited increases in respiration relative to increases in photosynthesis. Warming generally increased GEP, with the notable exception of the Toolik Lake moist ecosystem, where warming unexpectedly decreased GEP >25%. Overall, the respiration response determined the effect of warming on ecosystem CO2 balance. Our results provide the first multiple‐site comparison of arctic tundra CO2 flux responses to standard warming treatments across a large climate gradient. These results indicate that (1) dry tundra may be initially the most responsive ecosystems to climate warming by virtue of strong increases in ER, (2) moist and wet tundra responses are dampened by higher water tables and soil water contents, and (3) both GEP and ER are responsive to climate warming, but the magnitudes and directions are ecosystem‐dependent.
Physical aggression as a function of perceived fighting ability and provocation: an experimental investigation
Authors: Archer John , Benson David 
Published: June 2007

AbstractIn three studies, Resource Holding Power (RHP) and provocation were manipulated in scenarios involving a young person in a bar with friends. In Study 1, teenage men reported lower likelihood of responding with physical aggression when insulted as levels of three RHP cues (size, allies and reputation) increased, effects that were accentuated by combinations of high‐RHP cues; in the second part of this study, they consistently rated an insult to their girlfriend as the most provoking from a range of possible provocations, chosen on theoretical and empirical grounds. Study 2 replicated the results of the first part of Study 1 in samples of men and women in their twenties, although the effects were weaker at low levels of RHP. Study 3 combined a high‐ or low‐provoking event, with low, medium or high RHP, and a wider range of response choices. As expected, direct aggression increased as provocation increased and RHP decreased. Delayed aggressive responses, including revenge fantasies, were highest in response to high provocation and high RHP. Findings are discussed in relation to theoretical models of aggressive motivation. Aggr. Behav. 34:9–24, 2008. © 2007 Wiley‐Liss, Inc.
Sliding mode control for an induction machine submitted to large variations of mechanical configuration
Authors: Betin Franck , Capolino Gérard‐André 
Published: June 2007

AbstractIn this paper, a variable structure control (VSC) algorithm with a time‐varying switching surface is combined with an indirect field‐oriented control in order to control the position of an induction machine shaft submitted to large variations of mechanical configuration such as inertia or load torque changes. The introduction of a time‐varying switching surface guarantees the existence of a sliding mode since the beginning of the shaft motion without any chattering effects. Indeed, this moving switching surface allows the reaching phase elimination and the motor behaviour is insensitive to unknown mechanical configuration changes. The algorithm has been first tested in simulation and then implemented using a low‐cost DSP platform combined with a numerical coprocessor. Finally, an advanced test bed is used in order to evaluate the tracking properties and the robustness capacities of the VSC law with variations of the mechanical configuration. Copyright © 2007 John Wiley & Sons, Ltd.
Nanostructured photoactive films synthesized by a flame aerosol reactor
Authors: Thimsen Elijah , Biswas Pratim 
Published: June 2007

AbstractA flame aerosol reactor (FLAR) system was used to deposit nanostructured photocatalytic films of titanium dioxide with well controlled morphologies. Nanoparticles were generated in the aerosol phase and then deposited onto a water‐cooled substrate via thermophoresis. Two important parameters that influenced film characteristics were the titanium precursor feed rate and substrate temperature, through their effect on particle sintering dynamics on the substrate. The size of the particles as they arrived at the substrate was controlled by varying the titanium precursor feed rate. When the size was below ∼8 nm, sintering was completed in the time available to obtain films with columnar nanostructures. Larger particle sizes resulted in granular, particulate films. The temperature of the substrate was also an important parameter as it controlled the sintering rate and the resultant crystal phase of the film. The thickness of the films was controlled by varying the precursor feed rate and deposition time. The performance of the as‐synthesized photocatalytic films was established by measuring the resultant photocurrents. Well sintered columnar morphologies and thicker films (in the range of 40–900 nm) resulted in the largest photocurrents. © 2007 American Institute of Chemical Engineers AIChE J, 2007
Human skeletal remains from Sabana de Bogotá, Colombia: A case of Paleoamerican morphology late survival in South America?
Authors: Neves Walter A. , Hubbe Mark , Correal Gonzalo 
Published: June 2007

AbstractHuman skeletal remains of the first Americans are scarce, especially in North America. In South America the situation is less dramatic. Two important archaeological regions have generated important collections that allow the analysis of the cranial morphological variation of the Early Americans: Lagoa Santa, Brazil, and Sabana de Bogotá, Colombia. Human crania from the former region have been studied by one of us (WAN) and collaborators, showing that the cranial morphology of the first South Americans was very different from that prevailing today in East Asia and among Native Americans. These results have allowed for proposing that the New World may have been colonized by two different biological populations in the final Pleistocene/early Holocene. In this study, 74 human skulls dated between 11.0 and 3.0 kyr, recovered in seven different sites of Sabana de Bogotá, Colombia, were compared with the world cranial variation by different multivariate techniques: Principal Components Analysis, Multidimensional Scaling, and Cluster of Mahalanobis distance matrices. The Colombian skeletal remains were divided in two chronological subgroups: Paleocolombians (11.0–6.0 kyr) and Archaic Colombians (5.0–3.0 kyr). Both quantitative techniques generated convergent results: the Paleocolombians show remarkable similarities with Lagoa Santa and with modern Australo‐Melanesians. Archaic Colombians exhibited the same morphological patterns and associations. These findings support our long‐held proposition that the early American settlement may have involved two very distinct biological populations coming from Asia. On the other hand, they suggest the possibility of late survivals of the Paleoamerican pattern not restricted to isolated or marginal areas, as previously thought. Am J Phys Anthropol, 2007. © 2007 Wiley‐Liss, Inc.
Role of wild plant foods among late Holocene hunter‐gatherers from Central and North Patagonia (South America): An approach from dental evidence
Authors: Bernal Valeria , Novellino Paula , Gonzalez Paula N. , Perez S. Ivan 
Published: June 2007

AbstractThis study evaluates the role of plant foods in the subsistence of hunter‐gatherers that inhabited the Central East, Northwest, and Northeast Patagonia (Argentina) during the late Holocene (ca. 3,000–500 years BP). The goal of the present study is to assess the temporal variation of dental caries ratio and wear rate in skeletal samples to ascertain if the biological information supports the dietary shift toward greater consumption of wild plant foods around 1,500 years BP, suggested by other types of evidence. The authors registered caries, antemortem and postmortem tooth loss, and tooth wear from eight samples belonging to hunter‐gatherers from Patagonia for which chronological sequences from early late Holocene (ca. 3,000–1,500 years BP) up to final late Holocene (ca. 1,500–500 years BP) are available. The results indicate that caries percentages in Patagonian samples fall within the range established for hunter‐gatherers but there are significant geographical differences. In addition, caries ratio does not change significantly through time, so the amount of carbohydrates consumed seems to have remained fairly constant since 3,000 years BP. In contrast, there is a marked temporal trend toward the reduction of wear rates in the three areas, suggesting a faster rate in early late Holocene than in final late Holocene. These results would reflect a change to less hard and/or abrasive diets in the final late Holocene, probably owing to differences in food processing methods employed. Am J Phys Anthropol, 2007. © 2007 Wiley‐Liss, Inc.
The stochastic unit root model and fractional integration: An extension to the seasonal case
Authors: Caporale Guglielmo Maria , Gil‐Alana Luis A. 
Published: June 2007

AbstractIn a recent paper, Yoon (Working Paper, Department of Economics and Related Studies, University of York, 2003. Presented at the ESF‐EMM Second Annual Meeting, Rome, Italy, 2003) asserts that the stochastic unit root (STUR) model is closely related to long memory processes, and, in particular, that it is a special case of an I(d) process, with d = 1.5. In this paper we question this claim by using parametric and semiparametric techniques for modelling long memory. We extend the analysis by considering both non‐normality and seasonality, and shed light, theoretically and by means of Monte Carlo methods, on the relationship between the seasonal STUR and the seasonal I(d) models. The results show that methods that are specifically designed for testing I(d) statistical models are not appropriate for testing the STUR model. Moreover, they have in some cases very low power against STUR alternatives. Copyright © 2007 John Wiley & Sons, Ltd.