Showing papers by "Colorado State University published in 2007"

Adaptive versus non‐adaptive phenotypic plasticity and the potential for contemporary adaptation in new environments

Abstract: Summary 1The role of phenotypic plasticity in evolution has historically been a contentious issue because of debate over whether plasticity shields genotypes from selection or generates novel opportunities for selection to act. Because plasticity encompasses diverse adaptive and non-adaptive responses to environmental variation, no single conceptual framework adequately predicts the diverse roles of plasticity in evolutionary change. 2Different types of phenotypic plasticity can uniquely contribute to adaptive evolution when populations are faced with new or altered environments. Adaptive plasticity should promote establishment and persistence in a new environment, but depending on how close the plastic response is to the new favoured phenotypic optimum dictates whether directional selection will cause adaptive divergence between populations. Further, non-adaptive plasticity in response to stressful environments can result in a mean phenotypic response being further away from the favoured optimum or alternatively increase the variance around the mean due to the expression of cryptic genetic variation. The expression of cryptic genetic variation can facilitate adaptive evolution if by chance it results in a fitter phenotype. 3We conclude that adaptive plasticity that places populations close enough to a new phenotypic optimum for directional selection to act is the only plasticity that predictably enhances fitness and is most likely to facilitate adaptive evolution on ecological time-scales in new environments. However, this type of plasticity is likely to be the product of past selection on variation that may have been initially non-adaptive. 4We end with suggestions on how future empirical studies can be designed to better test the importance of different kinds of plasticity to adaptive evolution.

Microbial stress‐response physiology and its implications for ecosystem function

Abstract: Microorganisms have a variety of evolutionary adaptations and physiological acclimation mechanisms that allow them to survive and remain active in the face of environmental stress. Physiological responses to stress have costs at the organismal level that can result in altered ecosystem-level C, energy, and nutrient flows. These large-scale impacts result from direct effects on active microbes' physiology and by controlling the composition of the active microbial community. We first consider some general aspects of how microbes experience environmental stresses and how they respond to them. We then discuss the impacts of two important ecosystem-level stressors, drought and freezing, on microbial physiology and community composition. Even when microbial community response to stress is limited, the physiological costs imposed on soil microbes are large enough that they may cause large shifts in the allocation and fate of C and N. For example, for microbes to synthesize the osmolytes they need to survive a single drought episode they may consume up to 5% of total annual net primary production in grassland ecosystems, while acclimating to freezing conditions switches Arctic tundra soils from immobilizing N during the growing season to mineralizing it during the winter. We suggest that more effectively integrating microbial ecology into ecosystem ecology will require a more complete integration of microbial physiological ecology, population biology, and process ecology.

The highways and byways of mRNA decay.

Abstract: Turnover of mRNA is a key mechanism in regulated gene expression. In addition to turnover pathways for normal transcripts, there are surveillance mechanisms that degrade aberrant mRNAs. mRNA decay is regulated in response to cellular signals and coordinated with other mRNA-metabolic processes. When considering the control of gene expression, the focus has traditionally been on transcriptional regulation. Recently, however, the large contribution made by mRNA decay has become difficult to ignore. Large-scale analyses indicate that as many as half of all changes in the amounts of mRNA in some responses can be attributed to altered rates of decay. In this article, we discuss some of the mechanisms that are used by the cell to mediate and regulate this intriguing process.

Homogenization of regional river dynamics by dams and global biodiversity implications.

Abstract: Global biodiversity in river and riparian ecosystems is generated and maintained by geographic variation in stream processes and fluvial disturbance regimes, which largely reflect regional differences in climate and geology. Extensive construction of dams by humans has greatly dampened the seasonal and interannual streamflow variability of rivers, thereby altering natural dynamics in ecologically important flows on continental to global scales. The cumulative effects of modification to regional-scale environmental templates caused by dams is largely unexplored but of critical conservation importance. Here, we use 186 long-term streamflow records on intermediate-sized rivers across the continental United States to show that dams have homogenized the flow regimes on third- through seventh-order rivers in 16 historically distinctive hydrologic regions over the course of the 20th century. This regional homogenization occurs chiefly through modification of the magnitude and timing of ecologically critical high and low flows. For 317 undammed reference rivers, no evidence for homogenization was found, despite documented changes in regional precipitation over this period. With an estimated average density of one dam every 48 km of third- through seventh-order river channel in the United States, dams arguably have a continental scale effect of homogenizing regionally distinct environmental templates, thereby creating conditions that favor the spread of cosmopolitan, nonindigenous species at the expense of locally adapted native biota. Quantitative analyses such as ours provide the basis for conservation and management actions aimed at restoring and maintaining native biodiversity and ecosystem function and resilience for regionally distinct ecosystems at continental to global scales.

Genome sequence of Aedes aegypti, a major arbovirus vector

Abstract: We present a draft sequence of the genome of Aedes aegypti, the primary vector for yellow fever and dengue fever, which at approximately 1376 million base pairs is about 5 times the size of the genome of the malaria vector Anopheles gambiae. Nearly 50% of the Ae. aegypti genome consists of transposable elements. These contribute to a factor of approximately 4 to 6 increase in average gene length and in sizes of intergenic regions relative to An. gambiae and Drosophila melanogaster. Nonetheless, chromosomal synteny is generally maintained among all three insects, although conservation of orthologous gene order is higher (by a factor of approximately 2) between the mosquito species than between either of them and the fruit fly. An increase in genes encoding odorant binding, cytochrome P450, and cuticle domains relative to An. gambiae suggests that members of these protein families underpin some of the biological differences between the two mosquito species.

Global-Scale Similarities in Nitrogen Release Patterns During Long-Term Decomposition

Abstract: Litter decomposition provides the primary source of mineral nitrogen (N) for biological activity in most terrestrial ecosystems. A 10-year decomposition experiment in 21 sites from seven biomes found that net N release from leaf litter is dominantly driven by the initial tissue N concentration and mass remaining regardless of climate, edaphic conditions, or biota. Arid grasslands exposed to high ultraviolet radiation were an exception, where net N release was insensitive to initial N. Roots released N linearly with decomposition and exhibited little net N immobilization. We suggest that fundamental constraints on decomposer physiologies lead to predictable global-scale patterns in net N release during decomposition.

Potential impacts of global climate change on freshwater fisheries

Abstract: Despite uncertainty in all levels of analysis, recent and long-term changes in our climate point to the distinct possibility that greenhouse gas emissions have altered mean annual temperatures, precipitation and weather patterns. Modeling efforts that use doubled atmospheric CO2 scenarios predict a 1–7°C mean global temperature increase, regional changes in precipitation patterns and storm tracks, and the possibility of “surprises” or sudden irreversible regime shifts. The general effects of climate change on freshwater systems will likely be increased water temperatures, decreased dissolved oxygen levels, and the increased toxicity of pollutants. In lotic systems, altered hydrologic regimes and increased groundwater temperatures could affect the quality of fish habitat. In lentic systems, eutrophication may be exacerbated or offset, and stratification will likely become more pronounced and stronger. This could alter food webs and change habitat availability and quality. Fish physiology is inextricably linked to temperature, and fish have evolved to cope with specific hydrologic regimes and habitat niches. Therefore, their physiology and life histories will be affected by alterations induced by climate change. Fish communities may change as range shifts will likely occur on a species level, not a community level; this will add novel biotic pressures to aquatic communities. Genetic change is also possible and is the only biological option for fish that are unable to migrate or acclimate. Endemic species, species in fragmented habitats, or those in east–west oriented systems will be less able to follow changing thermal isolines over time. Artisanal, commercial, and recreational fisheries worldwide depend upon freshwater fishes. Impacted fisheries may make it difficult for developing countries to meet their food demand, and developed countries may experience economic losses. As it strengthens over time, global climate change will become a more powerful stressor for fish living in natural or artificial systems. Furthermore, human response to climate change (e.g., increased water diversion) will exacerbate its already-detrimental effects. Model predictions indicate that global climate change will continue even if greenhouse gas emissions decrease or cease. Therefore, proactive management strategies such as removing other stressors from natural systems will be necessary to sustain our freshwater fisheries.

The invasion paradox: reconciling pattern and process in species invasions.

Abstract: The invasion paradox describes the co-occurrence of independent lines of support for both a negative and a positive relationship between native biodiversity and the invasions of exotic species. The paradox leaves the implications of native-exotic species richness relationships open to debate: Are rich native communities more or less susceptible to invasion by exotic species? We reviewed the considerable observational, experimental, and theoretical evidence describing the paradox and sought generalizations concerning where and why the paradox occurs, its implications for community ecology and assembly processes, and its relevance for restoration, management, and policy associated with species invasions. The crux of the paradox concerns positive associations between native and exotic species richness at broad spatial scales, and negative associations at fine scales, especially in experiments in which diversity was directly manipulated. We identified eight processes that can generate either negative or positive native-exotic richness relationships, but none can generate both. As all eight processes have been shown to be important in some systems, a simple general theory of the paradox, and thus of the relationship between diversity and invasibility, is probably unrealistic. Nonetheless, we outline several key issues that help resolve the paradox, discuss the difficult juxtaposition of experimental and observational data (which often ask subtly different questions), and identify important themes for additional study. We conclude that natively rich ecosystems are likely to be hotspots for exotic species, but that reduction of local species richness can further accelerate the invasion of these and other vulnerable habitats.

Carbon allocation in forest ecosystems

Abstract: Carbon allocation plays a critical role in forest ecosystem carbon cycling. We reviewed existing literature and compiled annual carbon budgets for forest ecosystems to test a series of hypotheses addressing the patterns, plasticity, and limits of three components of allocation: biomass, the amount of material present; flux, the flow of carbon to a component per unit time; and partitioning, the fraction of gross primary productivity (GPP) used by a component. Can annual carbon flux and partitioning be inferred from biomass? Our survey revealed that biomass was poorly related to carbon flux and to partitioning of photosynthetically derived carbon, and should not be used to infer either. Are component fluxes correlated? Carbon fluxes to foliage, wood, and belowground production and respiration all increased linearly with increasing GPP (a rising tide lifts all boats). Autotrophic respiration was strongly linked to production for foliage, wood and roots, and aboveground net primary productivity and total belowground carbon flux (TBCF) were positively correlated across a broad productivity gradient. How does carbon partitioning respond to variability in resources and environment? Within sites, partitioning to aboveground wood production and TBCF responded to changes in stand age and resource availability, but not to competition (tree density). Increasing resource supply and stand age, with one exception, resulted in increased partitioning to aboveground wood production and decreased partitioning to TBCF. Partitioning to foliage production was much less sensitive to changes in resources and environment. Overall, changes in partitioning within a site in response to resource supply and age were small (o15% of GPP), but much greater than those inferred from global relationships. Across all sites, foliage production plus respiration, and total autotrophic respiration appear to use relatively constant fractions of GPP ‐ partitioning to both was conservative across a broad range of GPP ‐ but values did vary across sites. Partitioning to aboveground wood production and to TBCF were the most variable ‐ conditions that favored high GPP increased partitioning to aboveground wood production and decreased partitioning to TBCF. Do priorities exist for the products of photosynthesis? The available data do not support the concept of priorities for the products of photosynthesis, because increasing GPP increased all fluxes. All facets of carbon allocation are important to understanding carbon cycling in forest ecosystems. Terrestrial ecosystem models require information on partitioning, yet we found few studies that measured all components of the carbon budget to allow estimation of partitioning coefficients. Future studies that measure complete annual carbon budgets contribute the most to understanding carbon allocation. Nomenclature:

Plant trait responses to grazing – a global synthesis

Abstract: Herbivory by domestic and wild ungulates is a major driver of global vegetation dynamics. However, grazing is not considered in dynamic global vegetation models, or more generally in studies of the effects of environmental change on ecosystems at regional to global scale. An obstacle to this is a lack of empirical tests of several hypotheses linking plant traits with grazing. We, therefore, set out to test whether some widely recognized trait responses to grazing are consistent at the global level. We conducted a meta-analysis of plant trait responses to grazing, based on 197 studies from all major regions of the world, and using six major conceptual models of trait response to grazing as a framework. Data were available for seven plant traits: life history, canopy height, habit, architecture, growth form (forb, graminoid, herbaceous legume, woody), palatability, and geographic origin. Covariates were precipitation and evolutionary history of herbivory. Overall, grazing favoured annual over perennial plants, short plants over tall plants, prostrate over erect plants, and stoloniferous and rosette architecture over tussock architecture. There was no consistent effect of grazing on growth form. Some response patterns were modified by particular combinations of precipitation and history of herbivory. Climatic and historical contexts are therefore essential for understanding plant trait responses to grazing. Our study identifies some key traits to be incorporated into plant functional classifications for the explicit consideration of grazing into global vegetation models used in global change research. Importantly, our results suggest that plant functional type classifications and response rules need to be specific to regions with different climate and herbivory history.

Correlation of the highest-energy cosmic rays with nearby extragalactic objects.

Abstract: Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrate that there is a correlation between the arrival directions of cosmic rays with energy above {approx} 6 x 10{sup 19} eV and the positions of active galactic nuclei (AGN) lying within {approx} 75 Mpc. We reject the hypothesis of an isotropic distribution of these cosmic rays at over 99% confidence level from a prescribed a priori test. The correlation we observe is compatible with the hypothesis that the highest energy particles originate from nearby extragalactic sources whose flux has not been significantly reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources.

Defining Strategic Communication

Abstract: This article examines the nature of strategic communication, which is defined as the purposeful use of communication by an organization to fulfill its mission. Six relevant disciplines are involved in the development, implementation, and assessment of communications by organizations: management, marketing, public relations, technical communication, political communication, and information/social marketing campaigns. The nature of the term strategic is examined, and key aspects of communication are identified. This article is based, in part, on a panel discussion involving the journal's editors and international scholars at the International Communication Association in May 2005 in New York.

Restoration of the Mississippi Delta: Lessons from Hurricanes Katrina and Rita

Abstract: Hurricanes Katrina and Rita showed the vulnerability of coastal communities and how human activities that caused deterioration of the Mississippi Deltaic Plain (MDP) exacerbated this vulnerability. The MDP formed by dynamic interactions between river and coast at various temporal and spatial scales, and human activity has reduced these interactions at all scales. Restoration efforts aim to re-establish this dynamic interaction, with emphasis on reconnecting the river to the deltaic plain. Science must guide MDP restoration, which will provide insights into delta restoration elsewhere and generally into coasts facing climate change in times of resource scarcity.

Weak northern and strong tropical land carbon uptake from vertical profiles of atmospheric CO2

Abstract: Measurements of midday vertical atmospheric CO2 distributions reveal annual-mean vertical CO2 gradients that are inconsistent with atmospheric models that estimate a large transfer of terrestrial carbon from tropical to northern latitudes. The three models that most closely reproduce the observed annual-mean vertical CO2 gradients estimate weaker northern uptake of –1.5 petagrams of carbon per year (Pg C year–1) and weaker tropical emission of +0.1 Pg C year–1 compared with previous consensus estimates of –2.4 and +1.8 Pg C year–1, respectively. This suggests that northern terrestrial uptake of industrial CO2 emissions plays a smaller role than previously thought and that, after subtracting land-use emissions, tropical ecosystems may currently be strong sinks for CO2.

Life-cycle assessment of net greenhouse-gas flux for bioenergy cropping systems

Abstract: Bioenergy cropping systems could help offset greenhouse gas emissions, but quantifying that offset is complex. Bioenergy crops offset carbon dioxide emissions by converting atmospheric CO2 to organic C in crop biomass and soil, but they also emit nitrous oxide and vary in their effects on soil oxidation of methane. Growing the crops requires energy (e.g., to operate farm machinery, produce inputs such as fertilizer) and so does converting the harvested product to usable fuels (feedstock conversion efficiency). The objective of this study was to quantify all these factors to determine the net effect of several bioenergy cropping systems on greenhouse-gas (GHG) emissions. We used the DAYCENT biogeochemistry model to assess soil GHG fluxes and biomass yields for corn, soybean, alfalfa, hybrid poplar, reed canarygrass, and switchgrass as bioenergy crops in Pennsylvania, USA. DAYCENT results were combined with estimates of fossil fuels used to provide farm inputs and operate agricultural machinery and fossil-fuel offsets from biomass yields to calculate net GHG fluxes for each cropping system considered. Displaced fossil fuel was the largest GHG sink, followed by soil carbon sequestration. N2O emissions were the largest GHG source. All cropping systems considered provided net GHG sinks, even when soil C was assumed to reach a new steady state and C sequestration in soil was not counted. Hybrid poplar and switchgrass provided the largest net GHG sinks, .200 g CO2e-Cm � 2 � yr � 1 for biomass conversion to ethanol, and .400 g CO2e-Cm � 2 � yr � 1 for biomass gasification for electricity generation. Compared with the life cycle of gasoline and diesel, ethanol and biodiesel from corn rotations reduced GHG emissions by ;40%, reed canarygrass by ;85%, and switchgrass and hybrid poplar by ;115%.

Soil carbon saturation: concept, evidence and evaluation

Abstract: Current estimates of soil C storage potential are based on models or factors that assume linearity between C input levels and C stocks at steady-state, implying that SOC stocks could increase without limit as C input levels increase. However, some soils show little or no increase in steady-state SOC stock with increasing C input levels suggesting that SOC can become saturated with respect to C input. We used long-term field experiment data to assess alternative hypotheses of soil carbon storage by three simple models: a linear model (no saturation), a one-pool whole-soil C saturation model, and a two-pool mixed model with C saturation of a single C pool, but not the whole soil. The one-pool C saturation model best fit the combined data from 14 sites, four individual sites were best-fit with the linear model, and no sites were best fit by the mixed model. These results indicate that existing agricultural field experiments generally have too small a range in C input levels to show saturation behavior, and verify the accepted linear relationship between soil C and C input used to model SOM dynamics. However, all sites combined and the site with the widest range in C input levels were best fit with the C-saturation model. Nevertheless, the same site produced distinct effective stabilization capacity curves rather than an absolute C saturation level. We conclude that the saturation of soil C does occur and therefore the greatest efficiency in soil C sequestration will be in soils further from C saturation.

Looking Back and Thinking Ahead: A Decade of Cities and Climate Change Research

Abstract: To many observers of climate change politics, 1997 was an important milestone because of the completion of the Kyoto Protocol negotiations. With considerably less fanfare, 1997 was also the year in...

A study of secondary organic aerosol formation in the anthropogenic-influenced southeastern United States

Abstract: [1] The formation of secondary organic aerosol (SOA) in an anthropogenic-influenced region in the southeastern United States is investigated by a comparison with urban plumes in the northeast. The analysis is based on measurements of fine-particle organic compounds soluble in water (WSOC) as a measure of secondary organic aerosol. Aircraft measurements over a large area of northern Georgia, including the Atlanta metropolitan region, and in plumes from New York City and surrounding urban regions in the northeast show that fine-particle WSOC are spatially correlated with vehicle emission tracers (e.g., CO), yet the measurements indicate that vehicles do not directly emit significant particulate WSOC. In addition to being correlated, WSOC concentrations were in similar proportions to anthropogenic tracers in both regions, despite biogenic volatile organic compounds (VOCs) that were on average 10–100 times higher over northern Georgia. In contrast, radiocarbon analysis on WSOC extracted from integrated filters deployed in Atlanta suggests that roughly 70–80% of the carbon in summertime WSOC is modern. If both findings are valid, the combined results indicate that in northern Georgia, fine-particle WSOC was secondary and formed through a process that involves mainly modern biogenic VOCs but which is strongly linked to an anthropogenic component that may largely control the mass of SOA formed. Independent of the radiocarbon results, a strong association between SOA and anthropogenic sources has implications for control strategies in urban regions with large biogenic VOC emissions.

Alternative Splicing of Pre-Messenger RNAs in Plants in the Genomic Era

Abstract: Primary transcripts (precursor-mRNAs) with introns can undergo alternative splicing to produce multiple transcripts from a single gene by differential use of splice sites, thereby increasing the transcriptome and proteome complexity within and between cells and tissues. Alternative splicing in plants is largely an unexplored area of gene expression, as this phenomenon used to be considered rare. However, recent genome-wide computational analyses have revealed that alternative splicing in flowering plants is far more prevalent than previously thought. Interestingly, pre-mRNAs of many spliceosomal proteins, especially serine/arginine-rich (SR) proteins, are extensively alternatively spliced. Furthermore, stresses have a dramatic effect on alternative splicing of pre-mRNAs including those that encode many spliceosomal proteins. Although the mechanisms that regulate alternative splicing in plants are largely unknown, several reports strongly suggest a key role for SR proteins in spliceosome assembly and regulated splicing. Recent studies suggest that alternative splicing in plants is an important posttranscriptional regulatory mechanism in modulating gene expression and eventually plant form and function.

Australian Rainfall and Surface Temperature Variations Associated with the Southern Hemisphere Annular Mode

Abstract: Daily variations in Australian rainfall and surface temperature associated with the Southern Hemisphere annular mode (SAM) are documented using observations for the period 1979–2005. The high index polarity of the SAM is characterized by a poleward contraction of the midlatitude westerlies. During winter, the high index polarity of the SAM is associated with decreased daily rainfall over southeast and southwest Australia, but during summer it is associated with increased daily rainfall on the southern east coast of Australia and decreased rainfall in western Tasmania. Variations in the SAM explain up to ∼15% of the weekly rainfall variance in these regions, which is comparable to the variance accounted for by the El Nino–Southern Oscillation, especially during winter. The most widespread temperature anomalies associated with the SAM occur during the spring and summer seasons, when the high index polarity of the SAM is associated with anomalously low maximum temperature over most of central/easter...

TiO2 Nanotube Arrays of 1000 μm Length by Anodization of Titanium Foil: Phenol Red Diffusion

Abstract: We report for the first time fabrication of self-aligned hexagonally closed-packed titania nanotube arrays of over 1000 μm in length and aspect ratio ≈10 000 by potentiostatic anodization of titanium. We describe a process by which such thick nanotube array films can be transformed into self-standing, flat or cylindrical, mechanically robust, polycrystalline TiO2 membranes of precisely controlled nanoscale porosity. The self-standing membranes are characterized using Brunauer−Emmett−Teller surface area measurements, glancing angle X-ray diffraction, and transmission electron microscopy. In initial application, such membranes are used to control the diffusion of phenol red.

Temporal and spatial trends in the occurrence of human and veterinary antibiotics in aqueous and river sediment matrices.

Abstract: The occurrence of 15 antibiotics belonging to three different groups, tetracyclines (TCs), sulfonamides (SAs), and macrolides (MLs), mainly used to prevent or treat illness for humans and also to control disease or to promote the growth for animals was studied in aqueous and sediment matrices. The result of spatial and temporal statistical analysis revealed that measured concentrations of individual antibiotics were significantly different depending on sampling location and time periods for aqueous and sediment samples. High concentrations of human-used antibiotics were detected downstream of a wastewater treatment plant, and animal-used antibiotics were mainly found in a region with significant agricultural activity. Generally, the highest concentrations of antibiotics for both water and sediment samples were measured in winter indicating that low flow conditions and cold-water temperatures might enhance the persistence of these compounds. Furthermore, a pseudo-partitioning coefficient (P-PC) was introdu...

An overview of regional land-use and land-cover impacts on rainfall

Abstract: This paper documents the diverse role of land-use/land-cover change on precipitation. Since land conversion continues at a rapid pace, this type of human disturbance of the climate system will continue and become even more significant in the coming decades.

Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes

Abstract: Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

Toward greater understanding of market orientation and the resource-based view

Abstract: Connor's commentary offers a series of thoughtful comments on the ideas presented in Hult, Ketchen, and Slater (2005). We focus on two of his contentions in our response. First, we argue that the theory underlying our study—the resource-based view—is not tautological. This is because resources and performance are not directly related. Instead, realizing the potential value of resources depends on those resources being exploited through a firm's strategic actions. Second, we disagree with Connor's contention that market-oriented and customer-led firms lie along a continuum. We propose a richer conceptualization centered on a two-by-two matrix that contains market-oriented firms, customer-led firms, and two additional types. Copyright © 2007 John Wiley & Sons, Ltd.

Rain in Shallow Cumulus Over the Ocean: The RICO Campaign

Abstract: Shallow, maritime cumuli are ubiquitous over much of the tropical oceans, and characterizing their properties is important to understanding weather and climate. The Rain in Cumulus over the Ocean (RICO) field campaign, which took place during November 2004–January 2005 in the trades over the western Atlantic, emphasized measurements of processes related to the formation of rain in shallow cumuli, and how rain subsequently modifies the structure and ensemble statistics of trade wind clouds. Eight weeks of nearly continuous S-band polarimetric radar sampling, 57 flights from three heavily instrumented research aircraft, and a suite of ground- and ship-based instrumentation provided data on trade wind clouds with unprecedented resolution. Observational strategies employed during RICO capitalized on the advances in remote sensing and other instrumentation to provide insight into processes that span a range of scales and that lie at the heart of questions relating to the cause and effects of rain from shallow ...