bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrasting effects of repeated summer drought on soil carbon efflux in hydric and mesic heathland soils
Authors: SOWERBY ALWYN , EMMETT BRIDGET A. , TIETEMA ALBERT , BEIER CLAUS 
Published: May 2008

AbstractCurrent predictions of climate change include altered rainfall patterns throughout Europe, continental USA and areas such as the Amazon. The effect of this on soil carbon efflux remains unclear although several modelling studies have highlighted the potential importance of drought for carbon storage. To test the importance of drought, and more importantly repeated drought year‐on‐year, we used automated retractable curtains to exclude rain and produce repeated summer drought in three heathlands at varying moisture conditions. This included a hydric system limited by water‐excess (in the UK) and two mesic systems with seasonal water limitation in Denmark (DK) and the Netherlands (NL). The experimental rainfall reductions were set to reflect single year droughts observed in the last decade with exclusion of rain for 2–3 months of the year resulting in a 20–26% reduction in annual rainfall and 23–38% reduction in mean soil moisture during the drought period. Unexpectedly, sustained reduction in soil moisture over winter (between drought periods) was also observed at all three sites, along with a reduction in the maximum water‐holding capacity attained. Three hypotheses are discussed which may have contributed to this lack of recovery in soil moisture: hydrophobicity of soil organic matter, increased water use by plants and increased cracking of the soil. The responses of soil respiration to this change in soil moisture varied among the sites: decreased rates were observed at the water‐limited NL and DK sites whilst they increased at the UK site. Reduced sensitivity of soil respiration to soil temperature was observed at soil moisture contents above 55% at the UK site and below 20% and 13% at the NL and DK sites, respectively. Soil respiration rates recovered to predrought levels in the NL and DK sites during the winter re‐wetting period that indicates any change in soil C storage due to changes in soil C efflux may be short lived in these mesic systems. In contrast, in the hydric UK site after 2 years of drought treatment, the persistent reduction in soil moisture throughout the year resulted in a year‐round increase in soil respiration flux, a response that accelerated over time to 40% above control levels. These findings suggest that carbon‐rich soils with high organic matter content may act as a significant source of CO2 to the atmosphere following repeated summer drought. Nonrecovery of soil moisture and a persistent increase in soil respiration may be the primary mechanism underlying the reported substantial losses of soil carbon from UK organic soils over the last 20 years. These findings indicate that the water status of an ecosystem will be a critical factor to consider in determining the impact of drought on the soil carbon fluxes and storage.
Diagnostic assessment of European gross primary production
Authors: JUNG MARTIN , VERSTRAETE MICHEL , GOBRON NADINE , REICHSTEIN MARKUS , PAPALE DARIO , BONDEAU ALBERTE , ROBUSTELLI MONICA , PINTY BERNARD 
Published: May 2008

AbstractWe present an approach to estimate gross primary production (GPP) using a remotely sensed biophysical vegetation product (fraction of absorbed photosynthetically active radiation, FAPAR) from the European Commission Joint Research Centre (JRC) in conjunction with GPP estimates from eddy covariance measurement towers in Europe. By analysing the relationship between the cumulative growing season FAPAR and annual GPP by vegetation type, we find that the former can be used to accurately predict the latter. The root mean square error of prediction is of the order of 250 gC m−2 yr−1. The cumulative growing season FAPAR integrates over a number of effects relevant for GPP such as the length of the growing season, the vegetation's response to environmental conditions and the amount of light harvested that is available for photosynthesis. We corroborate the proposed GPP estimate (noted FAPAR‐based productivity assessment+land cover, FPA+LC) on the continental scale with results from the MOD17+radiation‐use efficiency model, an artificial neural network up‐scaling approach (ANN) and the Lund–Potsdam–Jena managed Land biosphere model (LPJmL). The closest agreement of the mean spatial GPP pattern among the four models is between FPA+LC and ANN (R2= 0.74). At least some of the discrepancy between FPA‐LC and the other models result from biases of meteorological forcing fields for MOD17+, ANN and LPJmL. Our analysis further implies that meteorological information is to a large degree redundant for GPP estimation when using the JRC‐FAPAR. A major advantage of the FPA+LC approach presented in this paper lies in its simplicity and that it requires no additional meteorological input driver data that commonly introduce substantial uncertainty. We find that results from different data‐oriented models may be robust enough to evaluate process‐oriented models regarding the mean spatial pattern of GPP, while there is too little consensus among the diagnostic models for such purpose regarding inter‐annual variability.
Variability in 20th century climate change reconstructions and its consequences for predicting geographic responses of California mammals
Authors: PARRA JUAN L. , MONAHAN WILLIAM B. 
Published: May 2008

AbstractEmpirical species distribution models are widely used to predict the effects of climate change on biodiversity distribution but rely on multiple assumptions about the certainty of the locality and climate data. Here, we assess the effect of historical climate data variability when forecasting geographic responses of California mammals to 20th century climate change. We first used two methods to derive gridded climate surfaces from weather station data (ANUSPLIN and PRISM) representing two sampling eras: historic (1900–1940) and current (1980–2005). We then used the two sources of climate data in conjunction with a maximum entropy algorithm (MAXENT) to predict both the historic and current distributions of all major mammal species vouchered historically in California. Results indicate that levels of disagreement between the two climate datasets are considerably greater in the historical era than in the current era. For the bioclimatic variables used in modeling historical mammal distributions, precipitation variables were less concordant than temperature variables. These discrepancies are reflected in the low agreement between historic mammal range predictions and further propagated when the historic models are projected to present day. Nonetheless, some common patterns exist across mammal species and climate estimates. Range stability is the most common prediction between the two eras, followed by expansion and contraction. Jepson ecoregions with relatively high levels of range stability include parts of the Great Central Valley and Sierra Nevada, while other parts of the Central Valley, the Sonoran desert, and Central‐ and Southwestern California yield predictions of range shifts. Historical species distribution modeling can greatly inform studies attempting to describe how species will continue to move geographically in response to future changes in climate. We suggest that alternative estimates of historical climate and their uncertainties are ultimately required in order to provide a quantitative measure of the confidence in predicted changes in distribution.
Modelled effects of precipitation on ecosystem carbon and water dynamics in different climatic zones
Authors: GERTEN DIETER , LUO YIQI , Le MAIRE GUERRIC , PARTON WILLIAM J. , KEOUGH CINDY , WENG ENSHENG , BEIER CLAUS , CIAIS PHILIPPE , CRAMER WOLFGANG , DUKES JEFFREY S. , HANSON PAUL J. , KNAPP ALAN A. K. , LINDER SUNE , NEPSTAD DAN , RUSTAD LINDSEY , SOWERBY ALWYN 
Published: May 2008

AbstractThe ongoing changes in the global climate expose the world's ecosystems not only to increasing CO2concentrations and temperatures but also to altered precipitation (P) regimes. Using four well‐established process‐based ecosystem models (LPJ, DayCent, ORCHIDEE, TECO), we explored effects of potentialPchanges on water limitation and net primary production (NPP) in seven terrestrial ecosystems with distinctive vegetation types in different hydroclimatic zones. We found that NPP responses toPchanges differed not only among sites but also within a year at a given site. The magnitudes of NPP change were basically determined by the degree of ecosystem water limitation, which was quantified here using the ratio between atmospheric transpirational demand and soil water supply. Humid sites and/or periods were least responsive to any change inPas compared with moderately humid or dry sites/periods. We also found that NPP responded more strongly to doubling or halving ofPamount and a seasonal shift inPoccurrence than that to alteredPfrequency and intensity at constant annual amounts. The findings were highly robust across the four models especially in terms of the direction of changes and largely consistent with earlierPmanipulation experiments and modelling results. Overall, this study underscores the widespread importance ofPas a driver of change in ecosystems, although the ultimate response of a particular site will depend on the detailed nature and seasonal timing ofPchange.
Climate change hastens the turnover of stream fish assemblages
Authors: BUISSON LAËTITIA , THUILLER WILFRIED , LEK SOVAN , LIM PUY , GRENOUILLET GAËL 
Published: May 2008

AbstractStream fish are expected to be significantly influenced by climate change, as they are ectothermic animals whose dispersal is limited within hydrographic networks. Nonetheless, they are also controlled by other physical factors that may prevent them moving to new thermally suitable sites. Using presence–absence records in 655 sites widespread throughout nine French river units, we predicted the potential future distribution of 30 common stream fish species facing temperature warming and change in precipitation regime. We also assessed the potential impacts on fish assemblages' structure and diversity. Only cold‐water species, whose diversity is very low in French streams, were predicted to experience a strong reduction in the number of suitable sites. In contrast, most cool‐water and warm‐water fish species were projected to colonize many newly suitable sites. Considering that cold headwater streams are the most numerous on the Earth's surface, our results suggested that headwater species would undergo a deleterious effect of climate change, whereas downstream species would expand their range by migrating to sites located in intermediate streams or upstream. As a result, local species richness was forecasted to increase greatly and high turnover rates indicated future fundamental changes in assemblages' structure. Changes in assemblage composition were also positively related to the intensity of warming. Overall, these results (1) stressed the importance of accounting for both climatic and topographic factors when assessing the future distribution of riverine fish species and (2) may be viewed as a first estimation of climate change impacts on European freshwater fish assemblages.
The prognostic impact of M‐CSF, CSF‐1 receptor, CD68 and CD3 in prostatic carcinoma
Authors: Richardsen E , Uglehus R D , Due J , Busch C , Busund L‐T R 
Published: May 2008

Aims:  Macrophage colony‐stimulating factor (M‐CSF) binds to colony‐stimulating factor‐1 receptor (CSF‐1R) and stimulates proliferation and differentiation of monocytes, macrophages and their bone marrow progenitors. M‐CSF, CSF‐1R, the macrophage marker CD68, and the pan T‐lymphocyte marker CD3 are increased in many human cancers. Their prognostic importance in primary prostatic carcinoma has not been fully delineated. The aim was to compare the expression of M‐CSF, CSF‐1R, CD68 and CD3 in metastatic and non‐metastatic prostatic cancer.Methods and results:  Digital video analysis of tumour cell areas and tumour stromal areas was performed in 59 cancer specimens: 32 patients with metastases and 27 patients without metastases. Expression of M‐CSF and CSF‐1R was recorded as 0 (negative immunoreactivity), 1 (weak), 2 (moderate) or 3 (strong reactivity). Macrophages (CD68) and T lymphocytes (CD3) were detected as proportions of moderately or strongly immunoreactive cells. Patients with metastatic primary cancers showed higher expression of M‐CSF (P < 0.0001, P = 0.005), CSF‐1R (both P < 0.0001) and CD3 (P = 0.007, P < 0.0001) in both tumour cell areas and tumour stromal areas, compared with the non‐metastatic cancers.Conclusion:  This study suggests that expression of M‐CSF, CSF‐1R and CD3 is a significant prognostic factor in primary prostatic cancers by predicting the development of metastases.
Density‐dependent predation of weed seeds in maize fields
Authors: Westerman Paula R. , Borza Jaclyn K. , Andjelkovic Jelena , Liebman Matt , Danielson Brent 
Published: May 2008

Summary

Seed predation can cause substantial losses of newly produced weed seeds and can therefore be important in regulating weed densities. The impact on weed population dynamics is greatest if predation acts in a directly density‐dependent manner.
We investigated the effect of between‐patch variability in seed density on seed removal. For this purpose, artificial weed seed patches were created by broadcasting giant foxtail Setaria faberi, at low (1000 seeds m−2), medium (4500 seeds m−2) and high densities (9500 seeds m−2) over 25 ¥ 25 m areas within three maize fields in August. Changes in giant foxtail seed densities were evaluated 3 weeks and 7 weeks post‐application, using soil surface sampling.
Observations of seed predation rate (seeds seed−1 week−1), using seed cards and exclosure cages, activity–densities of invertebrates using pitfall traps, and population estimates of rodents using Sherman live traps, were conducted to understand and explain the dynamics of seeds on the soil surface.
Three weeks after seed addition, seed predation was strongly and inversely density dependent. After 7 weeks, the net response since the start of the experiment exhibited only a weak inverse density dependence. This means that between 3 weeks and 7 weeks after seed addition, the response had reversed from inverse to almost direct density dependence.
During the August–October period, seeds in maize fields were mainly consumed by invertebrates. The most abundant granivorous invertebrates were crickets Gryllus pennsylvanicus and Allonemobius allardi, and carabid beetles, especially Harpalus pensylvanicus. The insects appeared unable to detect and respond numerically to weed patches, resulting in inversely density‐dependent predation, which favours the persistence of weed patches. The granivorous prairie deer mouse Peromyscus maniculatus bairdi, was present but contributed little to overall seed losses in autumn.
Synthesis and applications. The results of this study indicate that weed densities in maize fields currently are not regulated through directly density‐dependent seed predation, because the time between seed shed and seed movement into soil is too short for invertebrates to respond to and level out spatial differences at the scale of weed patches. However, our results suggest that delaying crop harvest and tillage may provide invertebrate predators with more time to attack weed seeds, and may allow for subsequent predation by vertebrates, which would be directly density‐dependent.
Socioeconomic and psychological variables as risk and protective factors for parental well‐being in families of children with intellectual disabilities
Authors: Olsson M. B. , Hwang C. P. 
Published: May 2008

AbstractBackground  The first aim of the present study was to estimate the extent to which differences in well‐being in parents of children with and without intellectual disability (ID) in Sweden can be accounted for by differences in the presence of the risk factors: (1) child disability; (2) socioeconomic disadvantage; (3) household composition; and (4) parental characteristics.The second aim was concerned with individual variation in well‐being within the group of parents of children with ID. The aim was to estimate if protective factors such as parental personality characteristics (sense of coherence), perceived positive impact of the child and satisfaction with participation in different arenas of life explained variation in well‐being in mothers and fathers of children with ID over and above that explained by the risk factors.Method  Parents of children with ID (62 mothers and 49 fathers) and control children (183 mothers and 141 fathers) completed postal surveys on well‐being, socioeconomic situation, health, sense of coherence, satisfaction with participation in different arenas of life and the child's impact on the family.Results  The results showed that mothers of children with ID had lower levels of well‐being than fathers and control parents, but the presence of a child with ID did not in itself predict poorer maternal well‐being. Rather, differences in economic hardship and self‐rated health were the strongest predictors for well‐being. It was further found that 67.7% of the mothers of children with ID scored within the high well‐being group. The predictive power of the model increased significantly for both fathers and mothers when protective factors were added to the model (42 and 78% explained variance compared with 25% with only risk factors).Conclusions  Well‐being of parents with a child with ID is dependent upon the interplay of risk and protective factors and research needs to address these variables simultaneously.
Sequence differentiation in regions identified by a genome scan for local adaptation
Authors: WOOD HENRY M. , GRAHAME JOHN W. , HUMPHRAY SEAN , ROGERS JANE , BUTLIN ROGER K. 
Published: May 2008

AbstractGenome scans using large numbers of randomly selected markers have revealed a small proportion of loci that deviate from neutral expectations and so may mark genomic regions that contribute to local adaptation. Measurements of sequence differentiation and identification of genes in these regions is important but difficult, especially in organisms with limited genetic information available. We have followed up a genome scan in the marine gastropod,Littorina saxatilis, by searching a bacterial artificial chromosome library with differentiated and undifferentiated markers, sequencing four bacterial artificial chromosomes and then analysing sequence variation in population samples for fragments at, and close to the original marker polymorphisms. We show that sequence differentiation follows the patterns expected from the original marker frequencies, that differentiated markers identify independent and highly localized sites and that these sites fall outside coding regions. Two differentiated loci are characterized by insertions of putative transposable elements that appear to have increased in frequency recently and which might influence expression of downstream genes. These results provide strong candidate loci for the study of local adaptation inLittorina. They demonstrate an approach that can be applied to follow up genome scans in other taxa and they show that the genome scan approach can lead rapidly to candidate genes in nonmodel organisms.
Mutation in the rel gene of Sorangium cellulosum affects morphological and physiological differentiation
Authors: Knauber Tina , Doss Sabrina D. , Gerth Klaus , Perlova Olena , Müller Rolf , Treuner‐Lange Anke 
Published: May 2008

SummaryInterruption of the (p)ppGpp synthetase gene (rel) of Sorangium cellulosum So ce56 resulted in loss of ppGpp accumulation after norvaline treatment during exponential growth phase. The rel mutant failed to produce wild‐type levels of the polyketides chivosazol and etnangien in production media. In wild‐type cells expression of the chivosazol biosynthetic operon can be significantly increased by norvaline or α‐methylglucoside. This induction does not occur in the rel mutant. The rel mutant also lost the capability to form multicellular fruiting bodies under nutrient starvation.
The holin of bacteriophage lambda forms rings with large diameter
Authors: Savva Christos G. , Dewey Jill S. , Deaton John , White Rebecca L. , Struck Douglas K. , Holzenburg Andreas , Young Ry 
Published: May 2008

SummaryHolins control the length of the infection cycle of tailed phages (the Caudovirales) by oligomerizing to form lethal holes in the cytoplasmic membrane at a time dictated by their primary structure. Nothing is currently known about the physical basis of their oligomerization or the structure of the oligomers formed by any known holin. Here we use electron microscopy and single‐particle analysis to characterize structures formed by the bacteriophage λ holin (S105) in vitro. In non‐ionic or mild zwitterionic detergents, purified S105, but not the lysis‐defective variant S105A52V, forms rings of at least two size classes, the most common having inner and outer diameters of 8.5 and 23 nm respectively, and containing approximately 72 S105 monomers. The height of these rings, 4 nm, closely matches the thickness of the lipid bilayer. The central channel is of unprecedented size for channels formed by integral membrane proteins, consistent with the non‐specific nature of holin‐mediated membrane permeabilization. S105 present in detergent‐solubilized rings and in inverted membrane vesicles showed similar sensitivities to proteolysis and cysteine‐specific modification, suggesting that the rings are representative of the lethal holes formed by S105 to terminate the infection cycle and initiate lysis.
A Sinorhizobium meliloti osmosensory two‐component system required for cyclic glucan export and symbiosis
Authors: Griffitts Joel S. , Carlyon Rebecca E. , Erickson Jacob H. , Moulton Jason L. , Barnett Melanie J. , Toman Carol J. , Long Sharon R. 
Published: May 2008

SummaryA screen for novel symbiotic mutants of the nitrogen‐fixing legume symbiont Sinorhizobium meliloti uncovered a crucial role for the putative response regulator FeuP in the symbiotic infection process. Transcriptome analysis shows that FeuP controls the transcription of at least 16 genes, including ndvA, which encodes an ATP‐dependent exporter of cyclic β glucans. Loss of feuP function gives rise to traits associated with cyclic β glucan biosynthetic defects, including poor growth and motility under hypoosmotic conditions, and the inability to invade plant tissue during the early stages of symbiotic infection. Analysis of cyclic glucans indicates that the feuP mutant is able to synthesize intracellular cyclic β glucans, but is unable to export them. Cyclic β glucan export can be restored to feuP mutant cells by constitutive expression of ndvA; likewise, the symbiotic phenotype of a feuP mutant is rescued by ectopic ndvA expression. We further show that the linked sensor kinase gene, feuQ, is also important for modulating ndvA transcription, and that signalling through the FeuP/FeuQ pathway is responsive to extracellular osmotic conditions, with low osmolarity stimulating ndvA expression.