bluuebunny/crossref_metadata_2025 huggingface dataset:
A hierarchical framework for investigating epiphyte assemblages: networks, meta‐communities, and scale
Authors: Burns K. C. , Zotz G.
Published: March 2010

Epiphytes are an important component of many forested ecosystems, yet our understanding of epiphyte communities lags far behind that of terrestrial‐based plant communities. This discrepancy is exacerbated by the lack of a theoretical context to assess patterns in epiphyte community structure. We attempt to fill this gap by developing an analytical framework to investigate epiphyte assemblages, which we then apply to a data set on epiphyte distributions in a Panamanian rain forest. On a coarse scale, interactions between epiphyte species and host tree species can be viewed as bipartite networks, similar to pollination and seed dispersal networks. On a finer scale, epiphyte communities on individual host trees can be viewed as meta‐communities, or suites of local epiphyte communities connected by dispersal. Similar analytical tools are typically employed to investigate species interaction networks and meta‐communities, thus providing a unified analytical framework to investigate coarse‐scale (network) and fine‐scale (meta‐community) patterns in epiphyte distributions. Coarse‐scale analysis of the Panamanian data set showed that most epiphyte species interacted with fewer host species than expected by chance. Fine‐scale analyses showed that epiphyte species richness on individual trees was lower than null model expectations. Therefore, epiphyte distributions were clumped at both scales, perhaps as a result of dispersal limitations. Scale‐dependent patterns in epiphyte species composition were observed. Epiphyte–host networks showed evidence of negative co‐occurrence patterns, which could arise from adaptations among epiphyte species to avoid competition for host species, while most epiphyte meta‐communities were distributed at random. Application of our “meta‐network” analytical framework in other locales may help to identify general patterns in the structure of epiphyte assemblages and their variation in space and time.
Demographics of increasing populations of the giant barrel sponge Xestospongia muta in the Florida Keys
Authors: McMurray Steven E. , Henkel Timothy P. , Pawlik Joseph R.
Published: March 2010

The structure of Caribbean coral reef communities has been altered by numerous anthropogenic and natural stressors. Demographic studies of key functional groups have furthered efforts to describe and understand these changes. Little is known, however, about the demographics of sponges on coral reefs, despite their abundance and the important functions they perform (e.g., increased habitat complexity, water filtration). We have monitored permanent plots on reefs off Key Largo, Florida, USA, to study the demography of a particularly important species, the giant barrel sponge, Xestospongia muta. From 2000 to 2006, population densities of X. muta significantly increased at sites on Conch Reef by a mean of 46% (range = 16–108%) and on Pickles Reef by a mean of 33%. In 2006, densities of X. muta on Conch Reef ranged from 0.134 to 0.277 sponges/m2, and mean sponge volume was 1488 cm3/m2, with the largest size class of sponges constituting 75% of the total volume. Increased population density resulted from a significant increase in the number of sponges in the smallest size class. Recruit survival did not significantly change through time; however, a significant interaction between season and year on recruitment suggests that large recruitment pulses are driving population increases. Mean yearly recruitment rates ranged from 0.011 to 0.025 recruits·m−2·yr−1, with pulses as high as 0.036 recruits/m2.

To explore the demographic processes behind the population increase and determine future population growth of X. muta under present reef conditions, a stage‐based matrix modeling approach was used. Variable recruitment pulses and mortality events were hypothesized to be large determinants of the demographic patterns observed for X. muta. Elasticity and life table response analysis revealed that survival of individuals in the largest size class has the greatest effect on population growth. Projections indicate that populations of X. muta will continue to increase under present conditions; however population growth may be negatively affected by continued mortality of the largest individuals from a recently described pathogenic syndrome.
Biology, chance, or history? The predictable reassembly of temperate grassland communities
Authors: Petermann Jana S. , Fergus Alexander J. F. , Roscher Christiane , Turnbull Lindsay A. , Weigelt Alexandra , Schmid Bernhard
Published: March 2010

Many studies have examined invasion resistance in plant communities, but few have explored the mechanisms of invasion and how subsequent community reassembly affects community functioning. Using natural dispersal and deliberate seed addition into grassland communities with different compositional and richness histories, we show that invaders establish in a nonrandom manner due to negative effects of resident functional groups on invading species from the same functional group. Invaders hence complement communities with originally low richness levels. Consequently, communities converge toward similar levels of species richness, high functional richness, and evenness, but not always maximum productivity. Invasion processes are faster but qualitatively similar when the effect of chance, in the form of dispersal stochasticity, is reduced by seed addition. Thus, dispersal limitation may influence community assembly, but it does not override functionally predictable assembly mechanisms. Some of the most productive communities prior to invasion are unstable in the face of invasion, leading to decreased productivity following invasion. We suggest that invasion into such communities occurs possibly because a pathogen‐free niche is available rather than a resource niche. Thus, pathogens in addition to resource niches may be important biological drivers of community assembly.
Roles of human disturbance, precipitation, and a pathogen on the survival and reproductive probabilities of deer mice
Authors: Previtali M. Andrea , Lehmer Erin M. , Pearce-Duvet Jessica M. C. , Jones Jeremy D. , Clay Christine A. , Wood Britta A. , Ely Patrick W. , Laverty Sean M. , Dearing M. Denise
Published: March 2010

Climate change, human disturbance, and disease can have large impacts on the dynamics of a species by affecting the likelihood of survival and reproduction of individuals. We investigated the roles of precipitation, off‐road vehicle (ORV) alteration of habitat, and infection with Sin Nombre virus on the survival and reproductive probabilities of deer mice (Peromyscus maniculatus). We used generalized linear mixed models to estimate the effects of these factors and their interactions by fitting capture–recapture data collected seasonally from 2002 to 2007 at 17 sites in the Great Basin Desert of central Utah, USA. During periods with high precipitation, we found no difference in survival and reproductive probabilities between seasons, but during drier periods, we found a reduction of overwinter survival and fall reproductive activity. Precipitation also interacted with disturbance to affect survival probabilities and female reproduction; in periods with low precipitation, deer mice on highly disturbed sites had extremely low survival probabilities and low reproductive probabilities of females compared to those of individuals from low‐disturbance sites. However, high precipitation ameliorated the effect of disturbance on both parameters. Deer mice from sites with high impact of ORV disturbance also had low survival over summer. Additionally, male reproductive probabilities were diminished on highly disturbed sites in both seasons; in contrast, they were reduced only in the fall on low‐disturbance sites. Density had an overall negative effect on survival and reproductive probabilities of deer mice. For females, the negative effect on reproductive activity was amplified in highly disturbed sites. We found no effect of hantavirus infection on survival probabilities of deer mice. Overall, this study revealed complexity in the determinants of deer mouse survival and reproduction given by the effects of a number of significant interactions among explanatory variables. Thus, factors that may not appear to have a strong effect when investigated alone can still be influential by modulating the effect of a different factor.
Plant diversity effects on soil microorganisms support the singular hypothesis
Authors: Eisenhauer N. , Beßler H. , Engels C. , Gleixner G. , Habekost M. , Milcu A. , Partsch S. , Sabais A. C. W. , Scherber C. , Steinbeiss S. , Weigelt A. , Weisser W. W. , Scheu S.
Published: March 2010

The global decline in biodiversity has generated concern over the consequences for ecosystem functioning and services. Although ecosystem functions driven by soil microorganisms such as plant productivity, decomposition, and nutrient cycling are of particular importance, interrelationships between plant diversity and soil microorganisms are poorly understood. We analyzed the response of soil microorganisms to variations in plant species richness (1–60) and plant functional group richness (1–4) in an experimental grassland system over a period of six years. Major abiotic and biotic factors were considered for exploring the mechanisms responsible for diversity effects. Further, microbial growth characteristics were assessed following the addition of macronutrients. Effects of plant diversity on soil microorganisms were most pronounced in the most diverse plant communities though differences only became established after a time lag of four years. Differences in microbial growth characteristics indicate successional changes from a disturbed (zymogeneous) to an established (autochthonous) microbial community four years after establishment of the experiment. Supporting the singular hypothesis for plant diversity, the results suggest that plant species are unique, each contributing to the functioning of the belowground system. The results reinforce the need for long‐term biodiversity experiments to fully appreciate consequences of current biodiversity loss for ecosystem functioning.
Termites, vertebrate herbivores, and the fruiting success of Acacia drepanolobium
Authors: Brody Alison K. , Palmer Todd M. , Fox-Dobbs Kena , Doak Dan F.
Published: March 2010

In African savannas, vertebrate herbivores are often identified as key determinants of plant growth, survivorship, and reproduction. However, plant reproduction is likely to be the product of responses to a suite of abiotic and biotic factors, including nutrient availability and interactions with antagonists and mutualists. In a relatively simple system, we examined the role of termites (which act as ecosystem engineers—modifying physical habitat and creating islands of high soil fertility), vertebrate herbivores, and symbiotic ants, on the fruiting success of a dominant plant, Acacia drepanolobium, in East African savannas.

Using observational data, large‐scale experimental manipulations, and analysis of foliar N, we found that Acacia drepanolobium trees growing at the edge of termite mounds were more likely to reproduce than those growing farther away, in off‐mound soils. Although vertebrate herbivores preferentially used termite mounds as demonstrated by dung deposits, long‐term exclusion of mammalian grazers did not significantly reduce A. drepanolobium fruit production. Leaf N was significantly greater in trees growing next to mounds than in those growing farther away, and this pattern was unaffected by exclusion of vertebrates. Thus, soil enrichment by termites, rather than through dung and urine deposition by large herbivores, is of primary importance to fruit production near mounds.

Across all mound–herbivore treatment combinations, trees that harbored Crematogaster sjostedti were more likely to fruit than those that harbored one of the other three ant species. Although C. sjostedti is less aggressive than the other ants, it tends to inhabit large, old trees near termite mounds which are more likely to fruit than smaller ones.

Termites play a key role in generating patches of nutrient‐rich habitat important to the reproductive success of A. drepanolobium in East African savannas. Enhanced nutrient acquisition from termite mounds appears to allow plants to tolerate herbivory and the reduced defense by a relatively ineffective ant partner. Our results underscore the importance of simultaneously examining top‐down and bottom‐up effects to understand those factors most important to plant reproductive success.
Flowering phenology in subalpine meadows: Does climate variation influence community co‐flowering patterns?
Authors: Forrest Jessica , Inouye David W. , Thomson James D.
Published: March 2010

Climate change is expected to alter patterns of species co‐occurrence, in both space and time. Species‐specific shifts in reproductive phenology may alter the assemblages of plant species in flower at any given time during the growing season. Temporal overlap in the flowering periods (co‐flowering) of animal‐pollinated species may influence reproductive success if competitive or facilitative interactions between plant species affect pollinator services. We used a 33‐year data set on flowering phenology in subalpine meadows in Colorado, USA, to determine whether interannual variation in snowmelt date, which marks the start of the growing season, affected co‐flowering patterns. For two of four species considered, we found a significant relationship between snowmelt timing and composition of the assemblage of co‐flowering plants. In years of early snowmelt,Lathyrus lanszwertiivar.leucanthus(Fabaceae), the species we investigated in most detail, tended to overlap with earlier‐flowering species and with fewer species overall. In particular, overlap with the flowering period ofLupinus polyphyllusvar.prunophilus, with whichLathyrus leucanthusshares pollinators, was significantly reduced in early‐snowmelt years. The observed association between timing of snowmelt and patterns of flowering overlap could not have been predicted simply by examining temporal trends in the dates of peak flowering of the dominant species in the community, as peak flowering dates have largely shifted in parallel with respect to snowmelt date. However, subtle interspecific differences in responsiveness of flowering time, duration, and intensity to interannual climate variation have likely contributed to the observed relationship. Although much of the year‐to‐year variation in flowering overlap remains unexplained by snowmelt date, our finding of a measurable signal of climate variation suggests that future climate change may lead to altered competitive environments for these wildflower species.
Phosphorus and soil development: Does the Walker and Syers model apply to semiarid ecosystems?
Authors: Selmants Paul C. , Hart Stephen C.
Published: March 2010

The Walker and Syers model of phosphorus (P) transformations during pedogenesis is widely accepted for the development of humid ecosystems, but long‐term P dynamics of more arid ecosystems remain poorly understood. We tested the Walker and Syers model in semiarid piñon–juniper woodlands by measuring soil P fractions under tree canopies and in intercanopy spaces along a well‐constrained, ∼3000 ka (1 ka = 1000 years) volcanic substrate age gradient in northern Arizona, USA. The various pools of soil P behaved largely as predicted; total soil P and primary mineral P declined consistently with substrate age, labile inorganic P increased early in soil development and then declined at later stages, and organic phosphorus increased consistently across the chronosequence. Within each site, soils under tree canopies tended to have higher concentrations of labile and intermediately available P fractions compared to intercanopy soils. However, the degree of spatial heterogeneity conferred by tree islands was moderated by the stage of soil development. In contrast, tree islands had no influence on within‐site distribution of more recalcitrant soil P pools, which appear to be controlled solely by the stage of pedogenesis. Coincident with declines in total P, primary mineral P, and labile inorganic P, we found that phosphatase enzyme activity increased with substrate age; a result consistent with greater ecosystem‐level P demand on older, more highly weathered substrates. Our results suggest that, compared to humid climates, reduced inputs of water, energy, and acidity to semiarid ecosystems slow the rate of change in P fractions during pedogenesis, but the overall pattern remains consistent with the Walker and Syers model. Furthermore, our data imply that pedogenic change may be an important factor controlling the spatial distribution of labile P pools in semiarid ecosystems. Taken together, these data should both broaden and unify terrestrial ecosystem development theory.
Ecological drivers of the evolution of public‐goods cooperation in bacteria
Authors: Brockhurst Michael A. , Habets Michelle G. J. L. , Libberton Ben , Buckling Angus , Gardner Andy
Published: March 2010

The role of ecological processes in the evolution of social traits is increasingly recognized. Here, we explore, using a general theoretical model and experiments with bacteria, the joint effects of disturbance frequency and resource supply on the evolution of cooperative biofilm formation. Our results demonstrate that cooperation tends to peak at intermediate frequencies of disturbance but that the peak shifts toward progressively higher frequencies of disturbance as resource supply increases. This appears to arise due to increased growth rates at higher levels of resource supply, which allows cooperators to more rapidly exceed the density threshold above which cooperation is beneficial following catastrophic disturbance. These findings demonstrate for the first time the importance of interactions between ecological processes in the evolution of public‐goods cooperation and suggest that cooperation can be favored by selection across a wide range of ecological conditions.
Temperature sensitivity of soil carbon fractions in boreal forest soil
Authors: Karhu Kristiina , Fritze Hannu , Hämäläinen Kai , Vanhala Pekka , Jungner Högne , Oinonen Markku , Sonninen Eloni , Tuomi Mikko , Spetz Peter , Kitunen Veikko , Liski Jari
Published: March 2010

Feedback to climate warming from the carbon balance of terrestrial ecosystems depends critically on the temperature sensitivity of soil organic carbon (SOC) decomposition. Still, the temperature sensitivity is not known for the majority of the SOC, which is tens or hundreds of years old. This old fraction is paradoxically concluded to be more, less, or equally sensitive compared to the younger fraction. Here, we present results that explain these inconsistencies. We show that the temperature sensitivity of decomposition increases remarkably from the youngest annually cycling fraction (Q10 < 2) to a decadally cycling one (Q10 = 4.2–6.9) but decreases again to a centennially cycling fraction (Q10 = 2.4–2.8) in boreal forest soil. Compared to the method used for current global estimates (temperature sensitivity of all SOC equal to that of the total heterotrophic soil respiration), the soils studied will lose 30–45% more carbon in response to climate warming during the next few decades, if there is no change in carbon input. Carbon input, derivative of plant productivity, would have to increase by 100–120%, as compared to the earlier estimated 70–80%, in order to compensate for the accelerated decomposition.
Nonconsumptive effects of a generalist ungulate herbivore drive decline of unpalatable forest herbs
Authors: Heckel Christopher D. , Bourg Norman A. , McShea William J. , Kalisz Susan
Published: March 2010

High herbivore pressure is expected to benefit unpalatable species that co‐occur with palatable browsed species. However, for five unpalatable understory species we found no evidence of benefit from deer browse. Detailed studies of one species in natural populations,Arisaema triphyllum, revealed surprising changes in its population structure and demography: deer browse level on a palatable species significantly correlates with reduced plant size and seed rain and male‐biased sex ratios of co‐occurringArisaemapopulations. Analyses of individual size in five unpalatable forest plant species in long‐term experimental paired deer exclosure/deer access plots corroborate the natural site results; all five species were smaller in deer access plots. Analyses of abiotic variables in natural and experimental sites suggest one potential mechanism for indirect effects of deer. Deer‐mediated soil quality declines included increased soil penetration resistance and decreased leaf litter depth, which are known to hinder plant growth. Our results are likely applicable to other unpalatable forest species and have clear consequences for understory biodiversity. Unpalatable plant species in forests experiencing high deer numbers may be in decline along with their palatable neighbors. Our study implicates deer overabundance in the cascade of forest species decline and the urgency of this conservation issue in North America.
Soil biota community structure and abundance under agricultural intensification and extensification
Authors: Postma-Blaauw Maria B. , de Goede Ron G. M , Bloem Jaap , Faber Jack H. , Brussaard Lijbert
Published: March 2010

Understanding the impacts of agricultural intensification and extensification on soil biota communities is useful in order to preserve and restore biological diversity in agricultural soils and enhance the role of soil biota in agroecosystem functioning. Over four consecutive years, we investigated the effects of agricultural intensification and extensification (including conversion of grassland to arable land and vice versa, increased and decreased levels of mineral fertilization, and monoculture compared to crop rotation) on major soil biota group abundances and functional diversity. We integrated and compared effects across taxonomic levels to identify sensitive species groups.

Conversion of grassland to arable land negatively affected both abundances and functional diversity of soil biota. Further intensification of the cropping system by increased fertilization and reduced crop diversity exerted smaller and differential effects on different soil biota groups. Agricultural intensification affected abundances of taxonomic groups with larger body size (earthworms, enchytraeids, microarthropods, and nematodes) more negatively than smaller‐sized taxonomic groups (protozoans, bacteria, and fungi). Also functional group diversity and composition were more negatively affected in larger‐sized soil biota (earthworms, predatory mites) than in smaller‐sized soil biota (nematodes). Furthermore, larger soil biota appeared to be primarily affected by short‐term consequences of conversion (disturbance, loss of habitat), whereas smaller soil biota were predominantly affected by long‐term consequences (probably loss of organic matter). Reestablishment of grassland resulted in increased abundances of soil biota groups, but since not all groups increased in the same measure, the community structure was not completely restored.

We concluded that larger‐sized soil biota are more sensitive to agricultural intensification than smaller‐sized soil biota. Furthermore, since larger‐sized soil biota groups had lower taxonomic richness, we suggest that agricultural intensification exerts strongest effects on species‐poor soil biota groups, thus supporting the hypothesis that biodiversity has an “insurance” function. As soil biota play an important role in agroecosystem functioning, altered soil biota abundances and functional group composition under agricultural intensification are likely to affect the functioning of the agroecosystem.
Apparent competition in canopy trees determined by pathogen transmission rather than susceptibility
Authors: Cobb Richard C. , Meentemeyer Ross K. , Rizzo David M.
Published: March 2010

Epidemiological theory predicts that asymmetric transmission, susceptibility, and mortality within a community will drive pathogen and disease dynamics. These epidemiological asymmetries can result in apparent competition, where a highly infectious host reduces the abundance of less infectious or more susceptible members in a community via a shared pathogen. We show that the exotic pathogen Phytophthora ramorum and resulting disease, sudden oak death, cause apparent competition among canopy trees and that transmission differences among canopy trees drives patterns of disease severity in California coast redwood forests. P. ramorum ranges in its ability to infect, sporulate on, and cause mortality of infected hosts. A path analysis showed that the most prolific inoculum producer, California bay laurel (Umbellularia californica), had a greater impact on the mortality rate of tanoak (Lithocarpus densiflorus) than did other inoculum‐supporting species. In stands experiencing high tanoak mortality, lack of negative impacts by P. ramorum on bay laurel may increase bay laurel density and subsequently result in positive feedback on pathogen populations. This study demonstrates the degree to which invasive, generalist pathogens can cause rapid changes in forest canopy composition and that differences in transmission can be more important than susceptibility in driving patterns of apparent competition.
Light, nutrients, and herbivore growth in oligotrophic streams
Authors: Hill Walter R. , Smith John G. , Stewart Arthur J.
Published: March 2010

The light : nutrient hypothesis posits that herbivore growth is increasingly constrained by low food quality as the ratio of light to nutrients increases in aquatic ecosystems. We tested predictions of this hypothesis by examining the effects of large seasonal cycles in light and nutrients on the mineral content of periphyton and the growth rate of a dominant herbivore (the snail Elimia clavaeformis) in two oligotrophic streams. Streambed irradiances in White Oak Creek and Walker Branch (eastern Tennessee, USA) varied dramatically on a seasonal basis due to leaf phenology in the surrounding deciduous forests and seasonal changes in sun angle. Concentrations of dissolved nutrients varied inversely with light, causing light : nitrate and light : phosphate to range almost 100‐fold over the course of any individual year. Periphyton nitrogen and phosphorus concentrations were much lower than the concentrations of these elements in snails, and they bottomed out in early spring when streambed irradiances were highest. Snail growth, however, peaked in early spring when light : nutrient ratios were highest and periphyton nutrient concentrations were lowest. Growth was linearly related to primary production (accounting for up to 85% of growth variance in individual years), which in turn was driven by seasonal variation in light. Conceptual models of herbivore growth indicate that growth should initially increase as increasing light levels stimulate primary production, but then level off, and then decrease as the negative effects of decreasing algal nutrient content override the positive effects of increased food production. Our results showed no evidence of an inflection point where increasing ratios of light to nutrients negatively affected growth. Snail growth in these intensively grazed streams is probably unaffected by periphyton nutrient content because exploitative competition for food reduces growth rates to levels where the demand for nitrogen and phosphorus is small enough to be satisfied by even low levels of these nutrients in periphyton. Competition for limited food resources in habitats where herbivore densities are uncontrolled by predation or other mortality factors should strongly influence the potential for herbivores to be limited by mineral deficits in their food.
Temporal shift in density dependence among North American breeding duck populations
Authors: Murray Dennis L. , Anderson Michael G. , Steury Todd D.
Published: March 2010

Environmental perturbation can have a marked influence on abundance and trend in many animal populations, but information is scant on how numerical change relates to variability in density‐dependent and density‐independent processes acting on populations. Using breeding population estimates for 10 duck species from a survey area of ∼2.2 million km2in central North America (1955–2005), we compared population growth models and related parameters among species and across time. All duck species showed evidence of density‐dependent growth, and the best‐fit relationship between population growth (rt) and population size (Nt) was linear or convex for all species. Density dependence and associated population parameters were not related to an index of species life history strategy. Reanalysis of segmented (1955–1979, 1980–2005)rttime series, where the truncation date coincided with a putative decline in wetland availability on breeding grounds, showed that density‐dependent forces were weakened during the latter time segment. Additionally, in later years most populations experienced increased first‐order autocorrelation in annual counts, decreased intrinsic growth rate, increased nonlinearity in the relationship betweenrtandNt, increased equilibrium return time, and increased inter‐species synchrony in numbers. Such changes were not closely related to species life history strategy or to shifts in mean population size, average trend, and estimated carrying capacity. We speculate that shifts in breeding duck habitat quality altered historical predator–prey dynamics in the system and thereby underlie observed dynamical changes. The paradoxical finding that population abundance and trend do not reveal shifts in population processes highlights the need to go beyond simple numerical assessment when evaluating population responses to environmental perturbation.
Reducing Six-Month Inpatient Psychiatric Recidivism and Costs Through Case Management
Authors: Kolbasovsky Andrew , Reich Leonard , Meyerkopf Neil
Published: March 2010

The objective of this study is to determine the reduction in inpatient psychiatric recidivism and costs associated with an intensive case management (ICM) program among high-risk adults with chronic mental health conditions. An intent-to-treat, historical control design was used to examine utilization differences between 306 intervention group (IG) members eligible to receive ICM services and a cohort of 290 baseline group (BG) members over a six-month outcome period. Members were identified retrospectively using identical criteria during one year prior to implementation of the program. The six-month recidivism rate for BG members was 49.67% compared to 22.07% among IG members. Forward stepwise regression results indicated a significant main effect for the ICM intervention on inpatient psychiatric costs. Inpatient psychiatric costs for the six-month outcome period were $4,982.90 lower per member in the IG group. Additional models demonstrated that the ICM intervention was associated with significantly lower inpatient substance abuse costs and psychiatric emergency department costs. There were no statistically significant increases in utilization associated with the ICM intervention. After factoring in program costs, it is estimated that the ICM services contributed to almost $1,500,000 in cost savings over the six-month outcome period. The ICM intervention was associated with significant reductions in inpatient, psychiatric six-month readmission rates and associated costs among adult members who are at elevated risk of inpatient, psychiatric recidivism. The intervention, enrollment process, and measurement strategies can be adapted for use by health plans looking to reduce psychiatric costs.
When to Stop Screening: A Review of Breast, Gynecologic, and Colorectal Cancer Screening in Women Over Age 65
Authors: Bernstein Rebecca , Dejoseph Daniel , Buchanan Edward M.
Published: March 2010

Because age alone is not an indicator of health, there is no clear consensus among the various cancer screening guidelines on when to stop cancer screening. For breast, cervical, and colorectal cancer, there are recommended screening tests, while, for other gynecologic cancers, there are not. When discussing with older women patients when to stop cancer screening, we encourage practitioners to review the goals of the screening test, assess the health and functional status of the patient, and discuss her values and health goals. To facilitate this discussion, we review proposed frameworks for determining when to screen older patients for cancer. We also review the concepts of “well” and “frail” older adults. Finally, we review the current screening recommendations for breast, gynecological, and colorectal cancers, and the reasoning behind them, from the United States Preventative Screening Task Force, the American Cancer Society, the American College of Obstetricians and Gynecologists, and the American Geriatric Society.
2-D Electrical Resistivity Imaging to Assess Slurry Pond Subsoil Pollution in the Southeastern Region of Murcia, Spain
Authors: Martínez-Pagán Pedro , Cano Ángel Faz , Ramos da Silva Gerson R. , Olivares Ana B.
Published: March 2010

About 2,341 pig farms generate large amounts of slurry in the southeastern Region of Murcia, Spain. Given the nature of the pig slurry as well as its amount produced in livestock, it has become a matter of growing environmental concern. The control of slurry ponds is now a top priority concern to create a safer environment, especially for agricultural production. This study reports the results of a much wider and comprehensive project carried out to collect reliable data on the behavior of slurry, soil, and the infiltration of slurry ponds under semiarid climate. The two-dimensional (2-D) electrical resistivity imaging (ERI) technique was used to qualitatively evaluate the natural permeability of the soils and depth that slurry had reached. The results obtained have shown that ERI is a useful tool in mapping the infiltration, as well as monitoring seasonal changes in the pollutant plume underneath the slurry ponds.
Tillage and Crop Rotation Phase Effects on Soil Physical Properties in the West‐Central Great Plains
Authors: Stone Loyd R. , Schlegel Alan J.
Published: March 2010

Efficient water use is the primary determinant of profitability in dryland crop production of the western Great Plains. For a sustainable increase in precipitation use efficiency (PUE) from that typical of the traditional winter wheat (Triticum aestivum L.)–fallow rotation with conventional stubble‐mulch (sweep) tillage (CT) to occur, decreased use of fallow and tillage is required. Our objective was to quantify the effect of tillage intensity (no‐till [NT], reduced tillage [RT], and CT) and phase of the winter wheat–grain sorghum [Sorghum bicolor (L.) Moench]–fallow rotation on selected soil properties that influence PUE, with emphasis on infiltration and the association between water‐stable aggregates (WSA) and infiltration rate. Soil water content at −1.5 MPa matric potential, concentration of WSA ≥0.5 mm, mean weight diameter of WSA, and ponded steady‐state infiltration rate were significantly greater with NT than RT or CT (infiltration rates: NT, 30.6; RT, 15.3; and CT, 11.4 mm h−1). Infiltration rate was significantly greater in the wheat phase (25.8 mm h−1) than in the sorghum (15.4 mm h−1) or fallow (16.2 mm h−1) phases. The significantly better conditions of aggregate stability and water infiltration with NT management and the lack of development of poor infiltration properties during the wheat season that would need to be alleviated by tillage after harvest reinforce the appropriateness of NT management in crop production systems of the region.
Survey of the Silicon Status of Flooded Rice in Louisiana
Authors: Kraska Joseph E. , Breitenbeck Gary A.
Published: March 2010

Low Si content in rice (Oryza sativaL.), sugarcane (Saccharum officinarumL.), and other Si‐accumulating crops can adversely affect crop performance by increasing susceptibility to abiotic and biotic stresses. Although it is generally assumed in the United States that soils containing appreciable amounts of silicate clays supply adequate Si to meet crop demands, there is little evidence to support this assumption. A survey was conducted to assess the Si status of rice plants at mid‐tiller (Y‐leaf) and at harvest (straw) in 97 rice fields located throughout the rice‐growing regions of Louisiana. On average, Y‐leaves contained 30.5 ± 7.8 g Si kg−1, whereas mature rice straw contained 54.7 ± 12.7 g Si kg−1Low early season Si assimilation occurred in nearly all rice fields, whereas only 36% contained mature straw with <50 g Si kg−1, a level commonly used to indicate sufficiency. Late‐season deficiencies were limited to fields in extreme southwest Louisiana where soils tend to be strongly acidic and have a long history of rice production.
Assessment across the United States of the Benefits of Altered Soybean Drought Traits
Authors: Sinclair Thomas R. , Messina Carlos D. , Beatty Andy , Samples Mitch
Published: March 2010

A number of plant traits have been suggested to ameliorate the effects of water deficits on crop yield. A quantitative response across a range of years and location is needed because many traits that could be beneficial in dry years might also be detrimental in wet years. This analysis was undertaken using a robust simulation model of soybean [Glycine max (L.) Merr.] development and growth to quantify yield changes as a result of modification of five traits: rooting depth extension, rate of leaf area development, decreased stomata conductance at high soil water content, reduced maximum transpiration rate, and drought‐tolerant nitrogen fixation. Simulations were done for 50 yr of weather data for 2655 grid locations of 30 km by 30 km size in the United States. Slow rate of rooting development was a neutral or negative trait in most locations. Slow leaf area development proved beneficial in less than half the years and in wetter years it resulted in yield losses. Water conservation both by early decrease in stomata conductance with soil drying and by reducing the maximum transpiration rate resulted in yield increases in many locations in 70% or more of the years. Both traits resulted in only small yield decreases in the wet years. Drought‐tolerant nitrogen fixation had the greatest benefit of all traits with a yield gain in more than 85% of the years at nearly all locations, and in those cases with no yield increase there was only a very small yield loss.
Sun Position and Cloud Effects on Reflectance and Vegetation Indices of Corn
Authors: de Souza Eduardo G. , Scharf Peter C. , Sudduth Kenneth A.
Published: March 2010

The reflectance characteristics of plants and plant canopies far from solar noon (i.e., at large solar zenith angles) or with cloudy skies are not well known. This is an obstacle to making real‐time, variable‐rate N fertilizer applications based on canopy reflectance because such a system must work under cloudy skies and at all times of day. Our objective was to develop spectral radiometer reflectance corrections for variations in incoming sunlight so that the same reflectance reading would be obtained (and the same N recommendation made) for the same plants regardless of time of day or cloud conditions. Passive spectral radiometers were mounted in a stationary position about 25 cm above the corn (Zea mays L.) canopy. Readings were taken from morning until night over several days with a range of sky conditions (sunny, overcast, and partly cloudy). Experiments were done in the field in April and May on greenhouse‐grown corn ranging from V10 to R2 growth stages. Sun angle, time of day, and cloud cover all influenced reflectance measured from the corn canopy. When regression models were applied to correct reflectance values to reference conditions for these variables, coefficients of variation were reduced by 29 to 56% for vegetation indexes and by 43 to 56% for reflectance values. The near‐infrared/green ratio and the green normalized difference vegetation index were the indices most sensitive to N deficiency among six analyzed indices.
Sugarcane Responses to Water‐Table Depth and Periodic Flood
Authors: Glaz Barry , Morris Dolen R.
Published: March 2010

Sugarcane (Saccharum spp.) is exposed to periodic floods and shallow water tables in Florida due to practices that reduce P discharge to the Everglades. This study examined the yields and juice quality of four sugarcane cultivars (CP 88‐1762, CP 89‐2143, CP 89‐2376, and CP 96‐1252) maintained at constant water‐table depths near 20 (20CWT) and 45 cm (45CWT) and with periodic summer flooding. Prescribed lysimeters were flooded for the first 7 d of five, five, and four 21‐d cycles in 2005 (plant‐cane crop), 2006 (first‐ratoon crop), and 2007 (second‐ratoon crop), respectively. These treatments generally remained flooded during the next 7 d while they received no irrigation or drainage, and were drained to 20 (20FWT) or 45 cm (45FWT) for the final 7 d of each cycle. Water treatment affected CRS only in the plant‐cane crop, where 45CWT had lower CRS than 20CWT, 20FWT, and 45FWT. Yields of cane and sucrose of CP 89‐2143 were least affected by water treatments. Reductions in cane and sucrose yields at a 20 compared with a 45 cm water‐table depth were common for the other three cultivars, but yields under the 20CWT vs. 20FWT or 45CWT vs. 45FWT treatments were generally similar. These results suggest that sugarcane roots function well in flood for up to 14 d, but do not grow well into saturated soil. This provides new options for sustaining high yields of sugarcane exposed to shallow water tables and floods; verification of root responses could enhance strategies to sustain yields while reducing P discharge.
Efficiency Indexes for Melon Crop Optimization
Authors: Castellanos M. T. , Cartagena M. C. , Ribas F. , Cabello M. J. , Arce A. , Tarquis A. M.
Published: March 2010

The present study reviews the most common N efficiency indexes with a view to maximizing yield and minimizing N loss, for melon grown in a zone where the water supply has a high nitrate content due to environmental degradation. The N use efficiency (NUE) values of the study were those relating the fruit yield (FY) and the dry weight (DW) with N applied (Nap), N available (Nav), and N uptake (Nup), which were denominated NUE1, NUE2, NUtE, NUE3, NUE4, and NUE5, respectively. A 3‐yr field experiment (2005, 2006, and 2007) was performed from May to September in central Spain. Melon crops were irrigated at 100% of the ETc (crop evapotranspiration) and 11 N rates, ranging from 11 to 393 kg ha−1 (considering N fertilizer [Nf], applied over 10 wk, and N in the irrigation water [Nw], where the NO3− concentration was 5.58, 80.64, and 10.89 mg L−1 in 2005, 2006, and 2007, respectively), were applied to a soil classified as Alfisol Xeralf Petrocalcic Palexeralfs. The results show a clear relationship between crop Nup and both FY and DW. Of the potential yield, 95% could be obtained with a N application of 93 kg ha−1 The maximum FY was observed with a Nup of 155 kg ha−1 The NUE, when related to Nap and Nav, showed an exponential trend and when related to Nup a linear trend, delimiting a range within which the optimum value of N occurs.
Profitability Analysis of Cellulosic Energy Crops Compared with Corn
Authors: James Laura K. , Swinton Scott M. , Thelen Kurt D.
Published: March 2010

The expected profitability of six cellulosic feedstock crops is compared with two corn (Zea mays L.)‐based systems under southern Great Lakes region conditions over a projected 10‐yr period. At 2006–2009 costs and yields from literature, none would be more profitable than the corn‐based systems. Comparative breakeven price analysis identifies the cellulosic feedstock price that would make crops equally profitable with continuous corn. Breakeven prices of cellulose are $110 to $130 Mg−1 for poplar (Populus spp.), switchgrass (Panicum virgatum L.), and mixed grasses. For miscanthus (Miscanthus × giganteus J.M. Greef & Deuter ex Hodk. &Renvoize), breakeven cellulose prices are $200 Mg−1 at current costs, but only $45 Mg−1 if rhizome costs fall to near European levels, well within the range of temporary U.S. farm bill cost share levels for biomass harvest, transportation, and storage. Without targeted subsidies, native prairie and fallow old field systems would not be competitive with corn or the other four cellulosic crops reviewed at current yields and foreseeable prices. Comparative breakeven yields at a cellulose price of $60 Mg−1 would require yield gains above benchmark literature values of 50% for switchgrass, 60% for poplar and mixed grasses, 140% for fallow old fields, 180% for native prairie, and 190% for miscanthus at current rhizome costs, but no added yield for miscanthus with rhizomes at plausible reduced cost.
Identification of Fertility Regimes that Enhance Long‐Term Productivity of Alfalfa Using Cluster Analysis
Authors: Lissbrant S. , Brouder S. M. , Cunningham S. M. , Volenec J. J.
Published: March 2010

Recommendations regarding P and K fertilization and critical soil and tissue concentrations for alfalfa (Medicago sativa L.) are inconsistent. Our objective was to use cluster analysis and binary logistic regression to determine if soil and herbage P and K concentrations can be used as diagnostics of P‐ and K‐limited alfalfa yields across soils with variable P and K soil test values. Samples were obtained from 28 consecutive harvests (four per year) of plots fertilized with four rates of P and five rates of K. Moderate to high rates of both nutrients were required to maintain high yields. Cluster analysis using May 2004 data for mass shoot−1 and shoots m−2 identified six clusters that also differed in yields. Averaged over the seven May harvests the two lowest yielding clusters had low herbage K (10.3–15.9 g kg−1), while intermediate yields were associated with low herbage P (1.6 g kg−1). Herbage P and K of the highest yielding cluster were 2.5 and 21.5 g kg−1, respectively. Plant populations in 2004 were the greatest with intermediate yields (61 m−2) and lowest for the poorest yielding plots (6 m−2). High taproot N reserves were associated with high yields. Prediction of acceptable (high‐yielding clusters) vs. unacceptable (low yielding clusters) performance was best achieved using the combination of herbage K and P concentrations and their ratio as independent variables. Results illustrate a varying, interdependent nature for alfalfa critical P and K tissue concentrations and suggest the need to account for both nutrients simultaneously.