bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carrying capacity in a heterogeneous environment with habitat connectivity
Authors: Zhang Bo , Kula Alex , Mack Keenan M. L. , Zhai Lu , Ryce Arrix L. , Ni Wei‐Ming , DeAngelis Donald L. , Van Dyken J. David 
Published: July 2017

AbstractA large body of theory predicts that populations diffusing in heterogeneous environments reach higher total size than if non‐diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here, we extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially diffusing laboratory populations of yeast. Consistent with previous theory, we predicted and experimentally observed that spatial diffusion increased total equilibrium population abundance in heterogeneous environments, with the effect size depending on the relationship between r and K. Refuting previous theory, however, we discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species diffusion. Our results provide rigorous experimental tests of new and old theory, demonstrating how the traditional notion of carrying capacity is ambiguous for populations diffusing in spatially heterogeneous environments.
Climate warming: a loss of variation in populations can accompany reproductive shifts
Authors: Massot Manuel , Legendre Stéphane , Fédérici Pierre , Clobert Jean 
Published: July 2017

AbstractThe most documented response of organisms to climate warming is a change in the average timing of seasonal activities (phenology). Although we know that these average changes can differ among species and populations, we do not know whether climate warming impacts within‐population variation in phenology. Using data from five study sites collected during a 13‐year survey, we found that the increase in spring temperatures is associated with a reproductive advance of 10 days in natural populations of common lizards (Zootoca vivipara). Interestingly, we show a correlated loss of variation in reproductive dates within populations. As illustrated by a model, this shortening of the reproductive period can have significant negative effects on population dynamics. Consequently, we encourage tests in other species to assess the generality of decreased variation in phenological responses to climate change.
Factors controlling the stable isotope composition and C:N ratio of seston and periphyton in shallow lake mesocosms with contrasting nutrient loadings and temperatures
Authors: Trochine Carolina , Guerrieri Marcelo , Liboriussen Lone , Willems Priscila , Lauridsen Torben L. , Søndergaard Martin , Jeppesen Erik 
Published: July 2017

Summary

Carbon (C) and nitrogen (N) stable isotope composition (15N:14N, δ15N and 13C:12C, δ13C) have been widely used to elucidate changes in aquatic ecosystem dynamics created by eutrophication and climate warming, often, however, without accounting for seasonal variation.

Here, we aim to determine the factors controlling the stable isotope composition and C:N ratio of seston and periphyton in shallow lakes with contrasting nutrient loadings and climate; for this purpose, we followed the monthly stable isotope composition (c. 1 year) of seston (SES) and periphyton (PER) in 24 mesocosms mimicking shallow lakes with two nutrient treatments (enriched and unenriched) and three temperature scenarios (ambient, +3 and +5°C).

Nutrient enrichment and warming had a stronger impact on the δ15N and δ13C values of seston than on periphyton, and the temporal isotopic variability in both communities was large.

δ15NPER did not differ markedly between nutrient treatments, whereas δ15NSES was lower in the enriched mesocosms, possibly reflecting higher N2‐fixation by cyanobacteria. δ15NSES was higher in winter in the heated mesocosms and its dynamics was linked with that of NH4‐N, whereas δ15NPER showed a stronger association with NO3‐N. δ15NSES demonstrated a positive relationship with mean monthly temperature, indicating less isotope fractionation among autotrophs when production increased.

δ13CSES was lowest in the enriched mesocosms during winter, whereas δ13CPER did not differ between nutrient treatments. δ13CSES and δ13CPER were positively related to pH, likely reflecting a pH‐induced differential access to dissolved carbon species in the primary producers. The positive δ13C‐temperature relationship suggested less fractionation of CO2 and HCO3− and/or larger use of HCO3− at higher temperatures.

The C:N ratios varied seasonally and the differences between the enriched and unenriched mesocosms were stronger for seston than for periphyton. Particularly, the C:NSES ratios did not indicate deficiencies in N as opposed to the C:NPER ratios, supporting the observed changes in δ15N and suggesting that seston and periphyton have access to different sources of nutrients. We did not observe any clear effect of temperature warming on the C:N ratios.

Our study provides evidence of strong seasonality in the isotopic composition and C:N ratios of seston and periphyton across nutrient and temperature levels; also, we identified several factors that are likely to modulate the strength and variability in stable isotopes values and stoichiometry of sestonic and periphytic communities under these scenarios.
Tropical lotic primary producers: Who has the most efficient photosynthesis in low‐order stream ecosystems?
Authors: Branco Ciro C. Z. , Riolfi Thaís A. , Crulhas Bruno P. , Tonetto Aurélio F. , Bautista Anna I. N. , Necchi Júnior Orlando 
Published: July 2017

Abstract

Photosynthetic performance was assessed for the main groups of primary producers of low‐order tropical streams, comprising macroalgae (11 taxa of Chlorophyta, Rhodophyta and Xanthophyta plus Cyanobacteria), bryophytes (2), angiosperms (3), and the periphytic community, by means of the Chl‐a fluorescence and oxygen evolution techniques.

Samples of primary producer were collected in nine stream reaches within the same drainage basin that were characterised as open or partially shaded.

Low values of compensation irradiance (Ic) were found for all species tested, suggesting that they are able to maintain an autotrophic metabolism even under very low irradiances.

Parameters derived from photosynthesis–irradiance curves revealed high values of the saturation parameter (Ik), associated with relative low values of photosynthetic efficiency (αETR) and photoinhibition (βETR) for species of Chlorophyta and the periphyton, suggesting adaptation to high irradiance conditions.

Species of Rhodophyta, Xanthophyta, Bryophyta and angiosperms showed, in general low values of Ik and moderate to high values of αETR and βETR, indicating typical photosynthetic responses of shade‐adapted plants.

Chlorophyta and the periphyton showed high photosynthetic efficiency in high irradiance, and rhodophytes, bryophytes and angiosperms seemed to be more efficient in shaded stream stretches.

Considering that Cyanobacteria showed high values of the photosynthesis/respiration (P/R) ratio, we suggest that this group is the most efficient primary producer in a wide range of low‐order tropical streams. This physiological trait could be a feature that favours the abundance of Cyanobacteria in the benthic primary producer community, as is often reported in the literature.
Multi‐century tree‐ring precipitation record reveals increasing frequency of extreme dry events in the upper Blue Nile River catchment
Authors: Mokria Mulugeta , Gebrekirstos Aster , Abiyu Abrham , Van Noordwijk Meine , Bräuning Achim 
Published: July 2017

AbstractClimate‐related environmental and humanitarian crisis are important challenges in the Great Horn of Africa (GHA). In the absence of long‐term past climate records in the region, tree‐rings are valuable climate proxies, reflecting past climate variations and complementing climate records prior to the instrumental era. We established annually resolved multi‐century tree‐ring chronology from Juniperus procera trees in northern Ethiopia, the longest series yet for the GHA. The chronology correlates significantly with wet‐season (r = .64, p < .01) and annual (r = .68, p < .01) regional rainfall. Reconstructed rainfall since A.D. 1811 revealed significant interannual variations between 2.2 and 3.8 year periodicity, with significant decadal and multidecadal variations during 1855–1900 and 1960–1990. The duration of negative and positive rainfall anomalies varied between 1–7 years and 1–8 years. Approximately 78.4% (95%) of reconstructed dry (extreme dry) and 85.4% (95%) of wet (extreme wet) events lasted for 1 year only and corresponded to historical records of famine and flooding, suggesting that future climate change studies should be both trend and extreme event focused. The average return periods for dry (extreme dry) and wet (extreme wet) events were 4.1 (8.8) years and 4.1 (9.5) years. Extreme‐dry conditions during the 19th century were concurrent with drought episodes in equatorial eastern Africa that occurred at the end of the Little Ice Age. El Niño and La Niña events matched with 38.5% and 50% of extreme‐dry and extreme‐wet events. Equivalent matches for positive and negative Indian Ocean Dipole events were weaker, reaching 23.1 and 25%, respectively. Spatial correlations revealed that reconstructed rainfall represents wet‐season rainfall variations over northern Ethiopia and large parts of the Sahel belt. The data presented are useful for backcasting climate and hydrological models and for developing regional strategic plans to manage scarce and contested water resources. Historical perspectives on long‐term regional rainfall variability improve the interpretation of recent climate trends.
A reversal of the shift towards earlier spring phenology in several Mediterranean reptiles and amphibians during the 1998–2013 warming slowdown
Authors: Prodon Roger , Geniez Philippe , Cheylan Marc , Devers Florence , Chuine Isabelle , Besnard Aurelien 
Published: July 2017

AbstractHerps, especially amphibians, are particularly susceptible to climate change, as temperature tightly controls many parameters of their biological cycle—above all, their phenology. The timing of herps’ activity or migration period—in particular the dates of their first appearance in spring and first breeding—and the shift to earlier dates in response to warming since the last quarter of the 20th century has often been described up to now as a nearly monotonic trend towards earlier phenological events. In this study, we used citizen science data opportunistically collected on reptiles and amphibians in the northern Mediterranean basin over a period of 32 years to explore temporal variations in herp phenology. For 17 common species, we measured shifts in the date of the species’ first spring appearance—which may be the result of current changes in climate—and regressed the first appearance date against temperatures and precipitations. Our results confirmed the expected overall trend towards earlier first spring appearances from 1983 to 1997, and show that the first appearance date of both reptiles and amphibians fits well with the temperature in late winter. However, the trend towards earlier dates was stopped or even reversed in most species between 1998 and 2013. We interpret this reversal as a response to cooling related to the North Atlantic Oscillation (NAO) in the late winter and early spring. During the positive NAO episodes, for certain species only (mainly amphibians), the effect of a warm weather, which tends to advance the phenology, seems to be counterbalanced by the adverse effects of the relative dryness.
Long‐term changes in abundances of Sonoran Desert lizards reveal complex responses to climatic variation
Authors: Flesch Aaron D. , Rosen Philip C. , Holm Peter 
Published: July 2017

AbstractUnderstanding how climatic variation affects animal populations and communities is essential for addressing threats posed by climate change, especially in systems where impacts are projected to be high. We evaluated abundance dynamics of five common species of diurnal lizards over 25 years in a Sonoran Desert transition zone where precipitation decreased and temperature increased across time, and assessed hypotheses for the influence of climatic flux on spatiotemporal variation in abundances. We repeatedly surveyed lizards in spring and summer of each year at up to 32 sites, and used hierarchical mixture models to estimate detection probabilities, abundances, and population growth rates. Among terrestrial species, abundances of a short‐lived, winter–spring breeder increased markedly by an estimated 237%–285% across time, while two larger spring–summer breeders with higher thermal preferences declined by up to 64%. Abundances of two arboreal species that occupy shaded and thus sheltered microhabitats fluctuated but did not decline systematically. Abundances of all species increased with precipitation at short lag times (1–1.5 years) likely due to enhanced food availability, but often declined after periods of high precipitation at longer lag times (2–4 years) likely due to predation and other biotic pressures. Although rising maximum daily temperatures (Tmax) are expected to drive global declines of lizards, associations with Tmax were variable and weak for most species. Instead, abundances of all species declined with rising daily minimum temperatures, suggesting degradation of cool refugia imposed widespread metabolic or other costs. Our results suggest climate warming and drying are having major impacts on lizard communities by driving declines in species with traits that augment exposure to abiotic extremes and by modifying species interactions. The complexity of patterns we report indicates that evaluating and responding to the influence of climate change on biodiversity must consider a broad array of ecological processes.
Warming drives a front of white spruce establishment near western treeline, Alaska
Authors: Miller Amy E. , Wilson Tammy L. , Sherriff Rosemary L. , Walton James 
Published: July 2017

AbstractRegional warming has led to increased productivity near the boreal forest margin in Alaska. To date, the effects of warming on seedling recruitment have received little attention, in spite of forecasted forest expansion. Here, we used stand structure and environmental data from 95 white spruce (Picea glauca) plots sampled across a longitudinal gradient in southwest Alaska to explore factors influencing spruce establishment and recruitment near western treeline. We used total counts of live seedlings, saplings, and trees, representing five life stages, to evaluate whether geospatial, climate, and measured plot covariates predicted abundance, using current abundance distributions as a surrogate for climate conditions in the past. We used generalized linear models to test the null hypothesis that conditions favorable for recruitment were similar along the environmental gradient represented by longitude, by exploring relationships between per‐plot counts of each life stage and the covariates hypothesized to affect abundance. We also examined the relationship between growing degree days (GDD) and seedling establishment over a period of three decades using tree‐ring chronologies obtained from cores taken at a subset of our sites (n = 30). Our results indicated that seedling, sapling, and tree abundance were positively correlated with temperature across the study area. The response to longitude was mixed, with earlier life stages (seedlings, saplings) most abundant at the western end of the gradient, and later life stages (trees) most abundant to the east. The differential relationship between longitude and life‐stage abundance suggests a moving front of white spruce establishment through time, driven by changes in environmental conditions near the species’ western range limit. Likewise, we found a positive relationship between periods of seedling establishment and GDD, suggesting that longer summers and/or greater heat accumulation might enhance establishment, consistent with the positive relationship we found between life‐stage abundance and temperature.
Aquatic export of young dissolved and gaseous carbon from a pristine boreal fen: Implications for peat carbon stock stability
Authors: Campeau Audrey , Bishop Kevin H. , Billett Michael F. , Garnett Mark H. , Laudon Hjalmar , Leach Jason A. , Nilsson Mats B. , Öquist Mats G. , Wallin Marcus B. 
Published: July 2017

AbstractThe stability of northern peatland's carbon (C) store under changing climate is of major concern for the global C cycle. The aquatic export of C from boreal peatlands is recognized as both a critical pathway for the remobilization of peat C stocks as well as a major component of the net ecosystem C balance (NECB). Here, we present a full year characterization of radiocarbon content (14C) of dissolved organic carbon (DOC), carbon dioxide (CO2), and methane (CH4) exported from a boreal peatland catchment coupled with 14C characterization of the catchment's peat profile of the same C species. The age of aquatic C in runoff varied little throughout the year and appeared to be sustained by recently fixed C from the atmosphere (<60 years), despite stream DOC, CO2, and CH4 primarily being sourced from deep peat horizons (2–4 m) near the mire's outlet. In fact, the 14C content of DOC, CO2, and CH4 across the entire peat profile was considerably enriched with postbomb C compared with the solid peat material. Overall, our results demonstrate little to no mobilization of ancient C stocks from this boreal peatland and a relatively large resilience of the source of aquatic C export to forecasted hydroclimatic changes.
The role of protected areas in land use/land cover change and the carbon cycle in the conterminous United States
Authors: Lu Xiaoliang , Zhou Yuyu , Liu Yaling , Le Page Yannick 
Published: July 2017

AbstractProtected areas (PAs) cover about 22% of the conterminous United States. Understanding their role on historical land use and land cover change (LULCC) and on the carbon cycle is essential to provide guidance for environmental policies. In this study, we compiled historical LULCC and PAs data to explore these interactions within the terrestrial ecosystem model (TEM). We found that intensive LULCC occurred in the conterminous United States from 1700 to 2005. More than 3 million km2 of forest, grassland and shrublands were converted into agricultural lands, which caused 10,607 Tg C release from land ecosystems to atmosphere. PAs had experienced little LULCC as they were generally established in the 20th century after most of the agricultural expansion had occurred. PAs initially acted as a carbon source due to land use legacies, but their accumulated carbon budget switched to a carbon sink in the 1960s, sequestering an estimated 1,642 Tg C over 1700–2005, or 13.4% of carbon losses in non‐PAs. We also find that PAs maintain larger carbon stocks and continue sequestering carbon in recent years (2001–2005), but at a lower rate due to increased heterotrophic respiration as well as lower productivity associated to aging ecosystems. It is essential to continue efforts to maintain resilient, biodiverse ecosystems and avoid large‐scale disturbances that would release large amounts of carbon in PAs.
Teeth bleaching with low concentrations of hydrogen peroxide (6%) and catalyzed by LED blue (450 ± 10 nm) and laser infrared (808 ± 10 nm) light for in‐office treatment: Randomized clinical trial 1‐year follow‐up
Authors: Vildósola Patricio , Bottner Jessica , Avalos Francisca , Godoy Isidora , Martín Javier , Fernández Eduardo 
Published: July 2017

AbstractObjectivesThe aim of this study was to evaluate color longevity after a year of in‐office bleaching with gel (6% hydrogen peroxide HP, LED blue/laser infrared activation system) compared to a 35% control concentration in a split‐mouth study model.Materials and MethodsThirty‐one patients were initially treated. The bleaching procedure with 6% or 35% gel HP was performed randomly in the upper half arcade of each patient. The color was measured at baseline and at 1 week, 1 month, and 1 year using the spectrophotometer Vita Easyshade, Vita Bleached, and Vita classical Shade guide organized by value. During the 1‐year recall, the color was assessed before and after dental prophylaxis.ResultsOnly 27 patients were assessed in the 1‐year recall. There was a significant difference in the ΔE between the two groups at all times assessed (P < .011). The ΔL, Δa, and Δb showed significant difference between both groups at all assessed times (P < .038). There was no significant difference between the ΔSGU at all times (P > .05) except for the Vita bleachedguide postprophylaxis comparison (P < .05).ConclusionThe two compounds remained effective at 1 year. When objectively evaluated, color difference between groups was found, not seen when subjectively determined.CLINICAL SIGNIFICANCEA low concentration hydrogen peroxide bleaching agent can reach good clinical results at 1 year of follow‐up.
Assessing attitudes and actions of pediatric dentists toward childhood obesity and sugar‐sweetened beverages
Authors: Wright Robin , Casamassimo Paul S. 
Published: July 2017

AbstractObjectivesChildhood obesity is a major US health concern, and oral health professionals have opportunities to participate in an interprofessional effort to intervene owing to their access to young patients and their abilities in addressing obesity‐related dietary habits like consumption of sugar‐sweetened beverages (SSBs). This study determined attitudes, behaviors, future intentions, and perceived barriers of pediatric dentists regarding efforts to prevent childhood obesity and reduce children's consumption of SSBs.MethodsThe American Academy of Pediatric Dentistry conducted an online electronic survey with a convenience sample of approximately 7,450 pediatric dentists and pediatric dental residents during spring 2016.ResultsOver 17 percent of pediatric dentists offer childhood obesity interventions. Of those not providing interventions, 67 percent were interested in offering obesity‐prevention services. Nearly 94 percent of pediatric dentists offer information or other interventions on consumption of SSBs. Statistically significant barriers to providing healthy weight interventions were fear of offending parents, appearing judgmental, or creating parent dissatisfaction and a lack of parental acceptance of guidance about weight management from a dentist. Significant barriers to SSB interventions were sufficient time and health professional education.ConclusionsMore pediatric dentists stated they offer childhood obesity interventions than in previous surveys reporting 6 percent, but respondents suggested that a child's weight is seen as a medical rather than dental issue. Most pediatric dentists provide interventions related to consumption of SSBs, perceiving the issue as integral to their care of children.