Ecological theory predicts a pulse disturbance results in loss of soil organic carbon and short-term respiration losses that exceed recovery of productivity in many ecosystems. However, fundamental ...uncertainties remain in our understanding of ecosystem recovery where spatiotemporal variation in structure and function are not adequately represented in conceptual models. Here we show that wildfire in sagebrush shrublands results in multiscale responses that vary with ecosystem properties, landscape position, and their interactions. Consistent with ecological theory, soil pH increased and soil organic carbon (SOC) decreased following fire. In contrast, SOC responses were slope aspect and shrub-microsite dependent, with a larger proportional decrease under previous shrubs on north-facing aspects compared to south-facing ones. In addition, respiratory losses from burned aspects were not significantly different than losses from unburned aspects. We also documented the novel formation of soil inorganic carbon (SIC) with wildfire that differed significantly with aspect and microsite scale. Whereas pH and SIC recovered within 37 months post-fire, SOC stocks remained reduced, especially on north-facing aspects. Spatially, SIC formation was paired with reduced respiration losses, presumably lower partial pressure of carbon dioxide (pCO
), and increased calcium availability, consistent with geochemical models of carbonate formation. Our findings highlight the formation of SIC after fire as a novel short-term sink of carbon in non-forested shrubland ecosystems. Resiliency in sagebrush shrublands may be more complex and integrated across ecosystem to landscape scales than predicted based on current theory.
Policy interest in socio‐ecological systems has driven attempts to define and map socio‐ecological zones (SEZs), that is, spatial regions, distinguishable by their conjoined social and ...bio‐geo‐physical characteristics. The state of Idaho, USA, has a strong need for SEZ designations because of potential conflicts between rapidly increasing and impactful human populations, and proximal natural ecosystems. Our Idaho SEZs address analytical shortcomings in previously published SEZs by: (1) considering potential biases of clustering methods, (2) cross‐validating SEZ classifications, (3) measuring the relative importance of bio‐geo‐physical and social system predictors, and (4) considering spatial autocorrelation. We obtained authoritative bio‐geo‐physical and social system datasets for Idaho, aggregated into 5‐km grids = 25 km2, and decomposed these using principal components analyses (PCAs). PCA scores were classified using two clustering techniques commonly used in SEZ mapping: hierarchical clustering with Ward's linkage, and k‐means analysis. Classification evaluators indicated that eight‐ and five‐cluster solutions were optimal for the bio‐geo‐physical and social datasets for Ward's linkage, resulting in 31 SEZ composite types, and six‐ and five‐cluster solutions were optimal for k‐means analysis, resulting in 24 SEZ composite types. Ward's and k‐means solutions were similar for bio‐geo‐physical and social classifications with similar numbers of clusters. Further, both classifiers identified the same dominant SEZ composites. For rarer SEZs, however, classification methods strongly affected SEZ classifications, potentially altering land management perspectives. Our SEZs identify several critical regions of social–ecological overlap. These include suburban interface types and a high desert transition zone. Based on multinomial generalized linear models, bio‐geo‐physical information explained more variation in SEZs than social system data, after controlling for spatial autocorrelation, under both Ward's and k‐means approaches. Agreement (cross‐validation) levels were high for multinomial models with bio‐geo‐physical and social predictors for both Ward's and k‐means SEZs. A consideration of historical drivers, including indigenous social systems, and current trajectories of land and resource management in Idaho, indicates a strong need for rigorous SEZ designations to guide development and conservation in the region. Our analytical framework can be broadly applied in SES research and applied in other regions, when categorical responses—including cluster designations—have a spatial component.
Chemical stabilization of microbial-derived products such as extracellular enzymes (EE) onto mineral surfaces has gained attention as a possibly important mechanism leading to the persistence of soil ...organic carbon (SOC). While the controls on EE activities and their stabilization in the surface soil are reasonably well-understood, how these activities change with soil depth and possibly diverge from those at the soil surface due to distinct physical, chemical, and biotic conditions remains unclear. We assessed EE activity to a depth of 1 m (10 cm increments) in 19 soil profiles across the Critical Zone Observatory Network, which represents a wide range of climates, soil orders, and vegetation types. For all EEs, activities per mass of soil correlated positively with microbial biomass (MB) and SOC, and all three of these variables decreased logarithmically with depth (p < 0.05). Across all sites, over half of the potential EE activities per mass soil consistently occurred below 20 cm for all measured EEs. Activities per unit MB or SOC were substantially higher at depth (soils below 20 cm accounted for 80% of whole-profile EE activity), suggesting an accumulation of stabilized (i.e. mineral sorbed) EEs in subsoil horizons. The pronounced enzyme stabilization in subsurface horizons was corroborated by mixed-effects models that showed a significant, positive relationship between clay concentration and MB-normalized EE activities in the subsoil. Furthermore, the negative relationships between soil C, N, and P and C-, N-, and P-acquiring EEs found in the surface soil decoupled below 20 cm, which could have also been caused by EE stabilization. This finding suggests that EEs may not reflect soil nutrient availabilities deeper in the soil profile. Taken together, our results suggest that deeper soil horizons hold a significant reservoir of EEs, and that the controls of subsoil EEs differ from their surface soil counterparts.
We report the case of a 64-year-old woman with systemic lupus erythematosus (SLE) and recurrent bilateral stress fractures of the calcaneus due to long-term methotrexate (MTX) use. A detailed ...skeletal assessment pointed to osteoporomalacia with pronounced trabecular thinning and increased bone resorption. After years of unsuccessful treatment with bisphosphonates, a combined bone-specific denosumab-teriparatide treatment was initiated, and additional belimumab treatment was started to avoid intermittent steroid usage. As these measures did not lead to a significant improvement of the bone situation, MTX was eventually discontinued. This was followed by a rapid clinical improvement. In a follow-up MRI scan after 18 months, the stress fractures had almost disappeared. Furthermore, the bone density and microarchitecture markedly improved. In conclusion, this case demonstrates that MTX discontinuation/replacement in combination with an individualized and state-of-the-art bone-specific therapy is effective in SLE patients with stress fractures after long-term MTX use.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A changing climate has the potential to mobilize soil carbon, shifting seasonally snow-covered, forested ecosystems from carbon sinks to sources. To determine the sensitivity of soil carbon fluxes to ...changes in temperature and moisture, we quantified seasonal and spatial variability of soil carbon dioxide (CO₂) fluxes (N = 746) and dissolved organic carbon (DOC) in leachate (N = 260) in high-elevation, mixed conifer forests in Arizona and New Mexico. All sites have cold winters, warm summers, and bimodal soil moisture patterns associated with snowmelt and summer monsoon rainfall. We employed a state factor approach, quantifying how distal controls (parent material, regional climate, topography) interacted with proximal variability in soil temperature (−3 to 26 °C) and moisture (2–76 %) to influence carbon effluxes. Carbon loss was dominated by CO₂flux (250–1220 g C m⁻² year⁻¹) rather than leached DOC (7.0–9.4 g C m⁻² year⁻¹). Significant differences in mean growing season CO₂flux were associated with parent material and aspect; differences appear to be mediated by how these distal controls influence primarily moisture and secondarily temperature. Across all sites, a multiple linear regression model (MLR) relying on moisture and temperature best described growing season CO₂fluxes (r² = 0.63, p < 0.001). During winter, the MLR describing soil CO₂flux (r² = 0.98, p < 0.001) relied on distal factors including snow cover, clay content, and bulk carbon, all factors that influence liquid water content. Our findings highlight the importance of state factors in controlling soil respiration primarily through influencing spatial and temporal heterogeneity in soil moisture.
Water and natural gas samples were collected from coalbed methane wells and a surface coal mine in the Powder River Basin (PRB) and analyzed for solute chemistry, isotopes, and gas composition to ...test hypotheses about the timing and source of recharge, importance of nutrient influx, and extent of microbial methanogenesis in coalbeds. Recharge to the Wyodak–Anderson coal zone in the central portions of the PRB appears to be from the southern basin margin based on δ
18O–H
2O values and hydraulic gradients. Coal zones along the eastern margin, near the coal outcrop, represent mixing between surface water and deeper circulating groundwater. Coalbeds along the northwestern basin margin may contain high elevation recharge from the Bighorn Mountains, with flow patterns likely affected by local faults. Detectable
14C (0.39 to 4.13
pmC) in coal waters throughout the PRB indicates they were recharged <
50,000
BP. Correlation of δD–CH
4 and δD–H
2O values suggests that methane has accumulated since the Late Pleistocene. Nutrient concentrations (C, N and P species) are low throughout the PRB and do not correlate to groundwater flowpaths or methanogenic pathways; nutrients may be sourced from in-situ leaching of coals. Carbon isotope values of CH
4 and CO
2 likely indicate the extent of methanogenesis (i.e. early versus late stage), rather than the dominant metabolic pathway (i.e. acetate fermentation versus CO
2 reduction). Coal gasses from the northwestern margin of the basin are isotopically depleted and suggest “early stage” methanogenesis, where the reactant carbon reservoir has not been significantly fractionated due to relatively rapid groundwater flow. Coal gasses from the central basin and southeastern margin are isotopically enriched and suggest “late stage” methanogenesis where the reactant carbon reservoir has been significantly depleted likely due to longer groundwater residence times.
Display omitted
► Carbon isotopes of CH
4 and CO
2 reflect early versus late stage methanogenesis. ► Metabolic pathways of methanogenesis are not related to nutrient concentrations. ► Oxygen and H isotopes of coal waters indicate regional groundwater flowpaths. ► Coal waters throughout the Powder River Basin are likely <
50,000
years old.
Abstract Background Since sorafenib has shown activity in different tumour types and gemcitabine regimens improved the outcome for biliary tract cancer (BTC) patients, we evaluated first-line ...gemcitabine plus sorafenib in a double-blind phase II study. Patients and methods 102 unresectable or metastatic BTC patients with histologically proven adenocarcinoma of gallbladder or intrahepatic bile ducts, Eastern Cooperative Oncology Group (ECOG) 0–2 were randomised to gemcitabine (1000 mg/m2 once weekly, first 7-weeks + 1-week rest followed by once 3-weeks + 1-week rest) plus sorafenib (400 mg twice daily) or placebo. Treatment continued until progression or unacceptable toxicity. Tumour samples were prospectively stained for sorafenib targets and potential biomarkers. Serum samples (first two cycles) were measured for vascular endothelial growth factors (VEGFs), vascular endothelial growth factor receptor 2 (VEGFR-2) and stromal cell-derived factor 1 (SDF1)α by enzyme-linked immunosorbent assay (ELISA). Results Gemcitabine plus sorafenib was generally well tolerated. Four and three patients achieved partial responses in the sorafenib and placebo groups, respectively. There was no difference in the primary end-point, median progression-free survival (PFS) for gemcitabine plus sorafenib versus gemcitabine plus placebo (3.0 versus 4.9 months, P = 0.859), and no difference for median overall survival (OS) (8.4 versus 11.2 months, P = 0.775). Patients with liver metastasis after resection of primary BTC survived longer with sorafenib ( P = 0.019) compared to placebo. Patients who developed hand-foot syndrome (HFS) showed longer PFS and OS than patients without HFS. Two sorafenib targets, VEGFR-2 and c-kit, were not expressed in BTC samples. VEGFR-3 and Hif1α were associated with lymph node metastases and T stage. Absence of PDGFRβ expression correlated with longer PFS. Conclusion The addition of sorafenib to gemcitabine did not demonstrate improved efficacy in advanced BTC patients. Biomarker subgroup analysis suggested that some patients might benefit from combined treatment.
The influx of atmospheric nitrogen to soils and surfaces in arid environments is of growing concern due to increased N emissions and N usage associated with urbanization. Atmospheric nitrogen inputs ...to the critical zone can occur as wet (rain or snow) or dry (dust or aerosols) deposition, and can lead to eutrophication, soil acidification, and groundwater contamination through leaching of excess nitrate. The objective of this research was to use the δ¹⁵N, δ¹⁸O, and Δ¹⁷O values of atmospheric nitrate (NO₃ ⁻) (precipitation and aerosols) and NO₃ ⁻ in runoff to assess the importance of N deposition and turnover in semi-arid urban watersheds. Data show that the fractions of atmospheric NO₃ ⁻ exported from all the urban catchments, throughout the study period, were substantially higher than in nearly all other ecosystems studied with mean atmospheric contributions of 38% (min 0% and max 82%). These results suggest that catchment and stream channel imperviousness enhance atmospheric NO₃ ⁻ export due to inefficient N cycling and retention. In contrast, catchment and stream channel perviousness allow for enhanced N processing and therefore reduced atmospheric NO₃ ⁻ export. Overall high fractions of atmospheric NO₃ ⁻ were primarily attributed to slow N turn over in arid/semi-arid ecosystems. A relatively high fraction of nitrification NO₃ ⁻ (~30%) was found in runoff from a nearly completely impervious watershed (91%). This was attributed to nitrification of atmospheric NH₄ ⁺ in dry-deposited dust, suggesting that N nitrifiers have adapted to urban micro niches. Gross nitrification rates based on NO₃ ⁻ Δ¹⁷O values ranged from a low 3.04 ± 2 kg NO₃-N km⁻² day⁻¹ in highly impervious catchments to a high of 10.15 ± 1 kg NO₃-N km⁻² day⁻¹ in the low density urban catchment. These low gross nitrification rates were attributed to low soil C:N ratios that control gross autotrophic nitrification by regulating gross NH₄ ⁺ production rates.
Background
Hepatitis C virus (HCV) infection is associated with a particularly poor outcome after liver transplantation. In December 2014, sofosbuvir/ledipasvir (SOF/LDV) fixed‐dose combination (FDC) ...was approved for HCV genotype 1 and 4 in Europe. In orthotopic liver transplantation (OLT) recipients, the interferon‐free treatment of HCV re‐infection with novel direct‐acting antivirals has been demonstrated to be safe and effective in clinical trials, but real‐world data are missing. The aim of this study was to investigate the safety and efficacy of SOF/LDV FDC in OLT recipients in the real‐life setting.
Methods
All consecutive OLT patients started on SOF/LDV FDC for 12 or 24 weeks at the University Medical Center Hamburg‐Eppendorf and Medical School Hannover between October 2014 and August 2015 were retrospectively analyzed (n = 30). The primary efficacy endpoint was sustained virological response (SVR), i.e., absence of viremia 12 weeks after end of treatment (SVR 12). Liver function tests, creatinine, blood count, and HCV RNA (by polymerase chain reaction assay) were determined at each visit.
Results
SVR was achieved in 29/30 patients (96.67%) treated with SOF/LDV ± ribavirin (RBV) for 12 (n = 4) or 24 weeks (n = 25). Twenty‐five patients (86.2%) received RBV. However, in 15 of the 25 patients, RBV administration had to be discontinued because of severe anemia (57.7%). One RBV‐treated patient died of a myocardial infarction during antiviral therapy; this event was most likely not directly related to SOF/LDV. Aside from RBV‐associated anemia, no severe side effects of the antiviral regimen were observed.
Conclusion
Antiviral treatment with SOF/LDV is highly effective, safe, and well tolerated in OLT recipients. The addition of RBV often results in severe anemia, requiring dose reduction or discontinuation.
The sources and distribution of anthropogenic nitrogen (N), including N fertilization and N fixed during fossil-fuel combustion, are rapidly becoming globally distributed. Responses of terrestrial ...ecosystems to anthropogenic N inputs are likely to vary geographically. In the temperate zone, long-term N inputs can lead to increases in plant growth and also can result in over-enrichment with N, eventually leading to increased losses of N via solution leaching and trace-gas emissions, and in some cases, to changes in species composition and to ecosystem decline. However, not all ecosystems respond to N deposition similarly; their response depends on factors such as successional state, ecosystem type, N demand or retention capacity, land-use history, soils, topography, climate, and the rate, timing, and type of N deposition. We point to some of the conditions under which anthropogenic impacts can be significant, some of the factors that control variations in response, and some areas where uncertainty is large due to limited information.
PDF
