bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scale‐dependent effects of landscape composition and configuration on natural enemy diversity, crop herbivory, and yields
Authors: Martin Emily A. , Seo Bumsuk , Park Chan‐Ryul , Reineking Björn , Steffan‐Dewenter Ingolf 
Published: May 2016

Abstract(1) Land‐use intensification in agricultural landscapes has led to changes in the way habitats and resources are distributed in space. Pests and their natural enemies are influenced by these changes, and by the farming intensity of crop fields. However, it is unknown whether the composition of landscapes (amount and diversity of land cover types) or their configuration (spatial arrangement of cover types) are more important for natural enemy diversity, and how they impact crop damage and yields. In addition, effects of interactions between local farming practices (organic vs. conventional) and landscape variables are unclear. (2) Here, we make use of a data set where landscape composition and configuration were uncorrelated across multiple spatial scales. Natural enemies, crop damage, and yields were sampled in 35 organic and conventional crop fields. Out of seven broad natural enemy taxa, five were positively affected by a complex landscape configuration. In contrast, only carabids were positively affected by the amount of seminatural habitat around fields. Increasing diversity of land cover types had positive effects on some, but negative effects on other taxa. Effect sizes varied among taxa but increased with increasing spatial scale, defined by circular areas of increasing radius around fields. (3) The diversity of aerial, but not of ground‐dwelling enemies was higher in fields under organic than conventional management. Interactions of local and landscape variables were important for birds, but not other enemies. Bird richness was higher in organic fields in simple landscapes, but not in landscapes with complex configuration or high land cover diversity. (4) Crop damage decreased with landscape diversity, but increased in conventional fields with complex configuration. Yields increased with both parameters in conventional fields only, and were higher on average in organic compared to conventional fields. Enemy diversity was positively related to crop damage, indicating positive density‐dependence of enemies on pests. However, the diversity of aerial enemies was also positively related to yields. (5) Our results suggest that the effectiveness of agri‐environmental schemes for managing natural enemy diversity, crop damage and yields could be enhanced by optimizing the effects of distinct landscape parameters, particularly landscape configuration and diversity, across scales.
Consequences for conservation: population density and genetic effects on reproduction of an endangered lagomorph
Authors: DeMay Stephanie M. , Becker Penny A. , Waits Lisette P. , Johnson Timothy R. , Rachlow Janet L. 
Published: May 2016

AbstractUnderstanding reproduction and mating systems is important for managers tasked with conserving vulnerable species. Genetic tools allow biologists to investigate reproduction and mating systems with high resolution and are particularly useful for species that are otherwise difficult to study in their natural environments. We conducted parentage analyses using 19 nuclear DNA microsatellite loci to assess the influence of population density, genetic diversity, and ancestry on reproduction, and to examine the mating system of pygmy rabbits (Brachylagus idahoensis) bred in large naturalized enclosures for the reintroduction and recovery of the endangered distinct population in central Washington, USA. Reproductive output for females and males decreased as population density and individual homozygosity increased. We identified an interaction indicating that male reproductive output decreased as genetic diversity declined at high population densities, but there was no effect at low densities. Males with high amounts (>50%) of Washington ancestry had higher reproductive output than the other ancestry groups, while reproductive output was decreased for males with high northern Utah/Wyoming ancestry and females with high Oregon/Nevada ancestry. Females and males bred with an average of 3.8 and 3.6 mates per year, respectively, and we found no evidence of positive or negative assortative mating with regards to ancestry. Multiple paternity was confirmed in 81% of litters, and we report the first documented cases of juvenile breeding by pygmy rabbits. This study demonstrates how variation in population density, genetic diversity, and ancestry impact fitness for an endangered species being bred for conservation. Our results advance understanding of basic life history characteristics for a cryptic species that is difficult to study in the wild and provide lessons for managing populations of vulnerable species in captive and free‐ranging populations.
In‐Season and Carry‐Over Effects of Cover Crops on Productivity and Weed Suppression
Authors: Hodgdon Elisabeth A. , Warren Nicholas D. , Smith Richard G. , Sideman Rebecca G. 
Published: May 2016

Data necessary to evaluate cover crop multifunctionality are lacking, particularly for cool, short‐season cropping niches typical of northern New England. We quantified cover crop biomass, weed suppression, and carry‐over effects on subsequent crop and weed growth in 12 winter cover crop treatments {monocrops and mixtures of annual ryegrass [Lolium multiflorum Lam.], winter rye [Secale cereale L.], alfalfa [Medicago sativa L.], crimson clover [Trifolium incarnatum L.], white clover [T. repens L.], hairy vetch [Vicia villosa Roth], soybean [Glycine max (L.) Merr.], and forage radish [Raphanus sativus L.], and a weedy fallow [control] treatment}. The forage radish treatments (11 and 28 kg ha−1 seeding rates) were among the highest producers of fall cover crop biomass in all 4 site‐years. The forage radish treatments were also among the most weed‐suppressive in the fall, reducing weed biomass relative to the weedy fallow treatment by 89 to 97% in each of the 4 site‐years. In the spring, annual ryegrass was among the highest (ranging from 349–571 g m−2 across site‐years) and alfalfa was among the lowest (39–287 g m−2) biomass‐producing treatments in 3 out of 4 site‐years. Weed biomass in the spring was 73 to 99% lower in annual ryegrass, hairy vetch, and hairy vetch–winter rye mixture treatments than in the weedy fallow treatment. Biomass of the sorghum [Sorghum bicolor (L.) Moench]–sudangrass [S. sudanense (Piper) Stapf] phytometer was higher following white clover, hairy vetch, the hairy vetch–rye mixture, and both forage radish treatments compared to following annual ryegrass.Core Ideas

Cover crops differ in their ability to provide multiple ecosystem services.
This study quantified weed suppression services in 12 cover crop treatments.
Weed suppression in fall, spring, and a subsequent phytometer differed among the treatments.
Phytometer biomass was higher following forage radish and several legume cover crops compared to annual ryegrass.
Cover crop multi‐functionality and tradeoffs were assessed with spider plots.
Wheat Yield Gap in the Pampas: Modeling the Impact of Environmental Factors
Authors: De Paepe Josefina L. , Álvarez Roberto 
Published: May 2016

As global grain demand is expected to keep on rising, productive but underachieving regions like the Argentine Pampas play a key role. Reduction of yield gaps in these regions would allow an increase in global food production. The objectives were to model the spatial patterns of the wheat (Triticum aestivum L.) yield gap in the Pampas and relate it to environmental factors. The study comprised an area of approximately 45 Mha during a 40‐yr interval. Attainable yield was estimated by a stochastic frontier production function adjusted on statistical data generated at county scale. Yield gap was calculated for each combination of climate and soil variables as the difference between attainable yield and the average yield estimated using an artificial neural network (ANN) model. Yield gap was then modeled by another ANN using as inputs climate and soil factors. Average yield gap was 865 kg ha−1 (25% of average attainable yield), ranging from 740 kg ha−1 (26%) in humid environments to 1140 kg ha−1 (42%) under semiarid ones during the last 5 yr. Yield gap could be adequately modeled with an ANN (R2 = 0.745, RMSE = 144 kg ha−1). The model showed that soil factors deeply impacted yield gap and minimum values were obtained in soils with medium to high organic C contents and available water storage capacity. Yield gap and a soil productivity index developed locally were negatively correlated. The methodology developed for yield gap analysis can be used for other crops and regions.Core Ideas

Yield gap calculation combined two modeled yield levels, applying a frontier production function and an artificial neural network.
Climate partially defined yield gaps; in semiarid environments these were largest.
Soil properties explained 50% of yield gap variability at regional scale.
Soil organic carbon and available water holding capacity interacted positively defining a minimum yield gap.
Yield gap reducing efforts should be focused in low productivity soils.
Trace Elements in Dominant Species of the Fenghe River, China: Their Relations to Environmental Factors
Authors: Yang Yang , Zhou Zhengchao , Bai Yanying , Jiao Wentao , Chen Weiping 
Published: May 2016

The distribution of trace elements (TEs) in water, sediment, riparian soil and dominant plants was investigated in the Fenghe River, Northwestern China. The Fenghe River ecosystem was polluted with Cd, Cr, Hg and Pb. There was a high pollution risk in the midstream and downstream regions and the risk level for Cd was much higher than that of the other elements. The average values of bioconcentration coefficient for Cd and Zn were 2.21 and 1.75, respectively, indicating a large accumulation of Cd and Zn in the studied species. With broad ecological amplitudes, Portulaca oleracea L., Artemisia argyi Levl. et Vant., Phragmites communis Trin., and Polygonum hydropiper L. had the greatest TE concentrations in aboveground and belowground biomass of the studied species and were potential biomonitors or phytoremediators for the study area. Multivariate techniques including cluster analysis, correlation analysis, principal component analysis, and canonical correspondence analysis were used to analyze the relations between TE concentrations in plants and various environmental factors. The soil element concentration is the main factor determining the accumulation of TEs in plants. The co‐release behavior of common pollutants and TEs drove the accumulation of Hg, Cd, and As in the studied plants. Significant enrichment of some elements in the Fenghe River has led to a decline in the biodiversity of plants.Core Ideas
Trace elements posed high ecological risk in the Fenghe River system.
Four native species could be used for phytoremediation.
Dissolved NH3–N, NO3–N, TN, and TP drove elemental uptake by plants.
Soil elements and soil pH had major effect on plants uptake of elements.
Plant diversity was sensitive to the high level trace elements in the water habitats.
Illinois River Nitrate‐Nitrogen Concentrations and Loads: Long‐term Variation and Association with Watershed Nitrogen Inputs
Authors: McIsaac Gregory F. , David Mark B. , Gertner George Z. 
Published: May 2016

The Illinois River is a major contributor of nitrate‐N to the Mississippi River and the Gulf of Mexico, where nitrate is a leading cause of summertime benthic hypoxia. Corn–soybean production on tile‐drained land is a leading source of nitrate‐N in this river system, in addition to municipal wastewater discharge. We calculated annual nitrate‐N loads in the Illinois River at Valley City from 1976 to 2014 by linear interpolation. Although there was not a significant trend in annual loads during the entire study period, there was a significant downward trend in flow‐weighted nitrate‐N concentration after 1990 despite high concentrations in 2013 after the 2012 drought. Multivariate regression analysis revealed a statistically significant association between annual flow‐weighted nitrate‐N concentration and cumulative residual agricultural N inputs to the watershed during a 6‐yr window. This suggests that declines in flow‐weighted nitrate‐N concentration may reflect increasing N use efficiency in agriculture and a depletion of legacy N stored in the watershed. The watershed appears to have transitioned from a state of stationarity in nitrate concentration to nonstationarity. The average annual nitrate‐N load at Valley City from 2010 to 2014 was 10% less than the 1980–1996 average load, indicating recent progress toward Illinois’ nutrient loss reduction milestone of 15% reduction by 2025 and ultimate target of 45% reduction.Core Ideas
Downward trend in annual flow‐weighted nitrate‐N concentrations since 1990.
Nitrate‐N concentrations correlated with residual agricultural N during the previous 6 yr.
Nitrate‐N concentrations correlated with current year Chicago wastewater discharge.
Nitrate‐N load highly variable due to variation in precipitation and water discharge.
Average nitrate‐N load during 2010–2014 was 10% less than the 1980–1996 baseline period.
Riverine Response of Sulfate to Declining Atmospheric Sulfur Deposition in Agricultural Watersheds
Authors: David Mark B. , Gentry Lowell E. , Mitchell Corey A. 
Published: May 2016

Sulfur received extensive study as an input to terrestrial ecosystems from acidic deposition during the 1980s. With declining S deposition inputs across the eastern United States, there have been many studies evaluating ecosystem response, with the exception of agricultural watersheds. We used long‐term (22 and 18 yr) sulfate concentration data from two rivers and recent (6 yr) data from a third river to better understand cycling and transport of S in agricultural, tile‐drained watersheds. Sulfate concentrations and yields steadily declined in the Embarras (from ∼10 to 6 mg S L−1) and Kaskaskia rivers (from 7 to 3.5 mg S L−1) during the sampling period, with an overall −23.1 and −12.8 kg S ha−1 yr−1 balance for the two watersheds. There was evidence of deep groundwater inputs of sulfate in the Salt Fork watershed, with a much smaller input to the Embarras and none to the Kaskaskia. Tiles in the watersheds had low sulfate concentrations (<10 mg S L−1), similar to the Kaskaskia River, unless the field had received some form of S fertilizer. A multiple regression model of runoff (cm) and S deposition explained much of the variation in Embarras River sulfate (R2 = 0.86 and 0.80 for concentrations and yields; n = 46). Although atmospheric deposition was much less than outputs (grain harvest + stream export of sulfate), riverine transport of sulfate reflected the decline in inputs. Watershed S balances suggest a small annual depletion of soil organic S pools, and S fertilization will likely be needed at some future date to maintain crop yields.Core Ideas
Riverine sulfate in agricultural watersheds responds to atmospheric deposition inputs.
Agricultural sulfur budgets suggest annual depletion of organic S pools.
Tile drains respond quickly to agricultural sulfate inputs.
Influence of Surface Crusting on Infiltration of a Loess Plateau Soil
Authors: Wang Jian , Watts Dexter B. , Meng Qinqian , Zhang Qingfeng , Way Thomas R. 
Published: May 2016

Core Ideas
Soil crusting and surface sealing often adversely affect agricultural yields.
A modified Green–Ampt model was evaluated for predicting infiltration of crusted soil.
The model provided a good estimate of soil crusting's influence on infiltration.
Crusting frequently occurs on farmland soil of the Loess Plateau in China and often adversely affects agricultural yields. Therefore, a study was conducted to evaluate the occurrence of soil crusting and its influence on infiltration in a Loess Plateau silt loam soil. Simulated rainfall events were conducted at two intensities (0.67 and 1.33 mm min−1) on four slopes (5, 9, 18, and 29%) under two soil conditions (crusted and uncrusted). Infiltration was evaluated as the difference between precipitation applied and water lost to runoff. A modified Green–Ampt model adjusted to account for soil crusting was also evaluated for predicting infiltration of crusted soil. Mean soil crust thickness was 3.33 and 3.94 mm under rainfall intensities of 0.67 and 1.33 mm min−1, respectively. Slope had no effect on crust formation. In all instances, cumulative infiltration was lower in crusted soil than in uncrusted soil. The time to runoff decreased from 17.98 min in uncrusted soil to 4.64 min in crusted soil under a rainfall intensity of 0.67 mm min−1. Time to runoff also decreased from 16.25 min in uncrusted soil to 4.54 min in crusted soil at a rainfall intensity of 1.33 mm min−1. The modified Green–Ampt model provided a good estimate of soil crusting's influence on infiltration (coefficient of determination range 0.85–0.97). This suggests that the Green–Ampt model could be used as a tool for predicting soil crusting's influence on infiltration and runoff from soils of the Loess Plateau.
Use of the modified frailty index to predict 30-day morbidity and mortality from spine surgery
Authors: Ali Rushna , Schwalb Jason M. , Nerenz David R. , Antoine Heath J. , Rubinfeld Ilan 
Published: May 2016

OBJECTIVE
Limited tools exist to stratify perioperative risk in patients undergoing spinal procedures. The modified frailty index (mFI) based on the Canadian Study of Health and Aging Frailty Index (CSHA-FI), constructed from standard demographic variables, has been applied to various other surgical populations for risk stratification. The authors hypothesized that it would be predictive of postoperative morbidity and mortality in patients undergoing spine surgery.

METHODS
The 2006–2010 National Surgical Quality Improvement Program (NSQIP) data set was accessed for patients undergoing spine surgeries based on Current Procedural Terminology (CPT) codes. Sixteen preoperative clinical NSQIP variables were matched to 11 CSHA-FI variables (changes in daily activities, gastrointestinal problems, respiratory problems, clouding or delirium, hypertension, coronary artery and peripheral vascular disease, congestive heart failure, and so on). The outcomes assessed were 30-day occurrences of adverse events. These were then summarized in groups: any infection, wound-related complication, Clavien IV complications (life-threatening, requiring ICU admission), and mortality.

RESULTS
A total of 18,294 patients were identified. In 8.1% of patients with an mFI of 0 there was at least one morbid complication, compared with 24.3% of patients with an mFI of ≥ 0.27 (p < 0.001). An mFI of 0 was associated with a mortality rate of 0.1%, compared with 2.3% for an mFI of ≥ 0.27 (p < 0.001). Patients with an mFI of 0 had a 1.7% rate of surgical site infections and a 0.8% rate of Clavien IV complications, whereas patients with an mFI of ≥ 0.27 had rates of 4.1% and 7.1% for surgical site infections and Clavien IV complications, respectively (p < 0.001 for both). Multivariate analysis showed that the preoperative mFI and American Society of Anesthesiologists classification of ≥ III had a significantly increased risk of leading to Clavien IV complications and death.

CONCLUSIONS
A higher mFI was associated with a higher risk of postoperative morbidity and mortality, providing an additional tool to improve perioperative risk stratification.
Cephalometric oropharynx and oral cavity analysis in Chiari malformation Type I: a retrospective case-control study
Authors: Urbizu Aintzane , Ferré Alex , Poca Maria-Antonia , Rovira Alex , Sahuquillo Juan , Martin Bryn A. , Macaya Alfons 
Published: May 2016

OBJECTIVETraditionally, Chiari malformation Type I has been related to downward herniation of the cerebellar tonsils as a consequence of an underdeveloped posterior cranial fossa. Although the common symptoms of Chiari malformation Type I are occipital headaches, cervical pain, dizziness, paresthesia, and sensory loss, patients often report symptoms related to pharyngeal dysfunction such as choking, regurgitation, dysphagia, aspiration, chronic cough, and sleep disorders. In addition, tracheal intubation is often difficult in these patients. The purpose of this study was to analyze the morphological features of the oropharynx and oral cavity in patients with Chiari malformation Type I to help identify underlying anatomical anomalies leading to these debilitating symptoms.METHODSSeventy-six adult patients with symptomatic Chiari malformation Type I with cerebellar tonsillar descent greater than 5 mm below the foramen magnum and a small posterior cranial fossa and 49 sex-matched controls were selected to perform a retrospective case-control MRI-based morphometric study in a tertiary hospital. Eleven linear and areal parameters of the oropharyngeal cavity on midsagittal T1-weighted MRI were measured and the average values between patients and control cohorts were compared. Correlations between variables showing or approaching statistical significance in these structures and posterior cranial fossa measurements related with the occipital bone were sought.RESULTSSignificant differences were detected for several oropharynx and oral cavity measures in the patient cohort, primarily involving the length and thickness of the soft palate (p = 9.5E-05 and p = 3.0E-03, respectively). A statistically significant (p < 0.01) moderate correlation between some of these variables and posterior cranial fossa parameters was observed.CONCLUSIONSThe existence of structural oropharyngeal and oral cavity anomalies in patients with Chiari malformation Type I was confirmed, which may contribute to the frequent occurrence of respiratory and deglutitory complications and sleep disorders in this syndrome.