ALBERT

Description: This paper evaluates the suitability of the ECOSSE model to estimate soil greenhouse gas fluxes from short rotation coppice willow (SRC-Willow), short rotation forestry (SRF-Scots Pine) and Miscanthus after land-use change from conventional systems (grassland and arable). We simulate heterotrophic respiration (R h ), nitrous oxide (N 2 O) and methane (CH 4 ) fluxes at four paired sites in the UK, and compare them to estimates of R h derived from the ecosystem respiration estimated from eddy covariance (EC) and R h estimated from chamber (IRGA) measurements, as well as direct measurements of N 2 O and CH 4 fluxes. Significant association between modelled and EC-derived R h was found under Miscanthus , with correlation coefficient ( r ) ranging between 0.54 and 0.70. Association between IRGA-derived R h and modelled outputs was statistically significant at the Aberystwyth site ( r = 0.64) but not significant at the Lincolnshire site ( r = 0.29). At all SRC-Willow sites, significant association was found between modelled and measurement-derived R h (0.44 ≤ r ≤ 0.77); significant error was found only for the EC-derived R h at the Lincolnshire site. Significant association and no significant error were also found for SRF-Scots Pine and perennial grass. For the arable fields, the modelled CO 2 correlated well just with the IRGA-derived R h at one site ( r = 0.75). No bias in the model was found at any site, regardless of the measurement type used for the model evaluation. Across all land-uses, fluxes of CH 4 and N 2 O were shown to represent a small proportion of the total greenhouse gas balance; these fluxes have been modelled adequately on a monthly time-step. This study provides confidence in using ECOSSE for predicting the impacts of future land-use on greenhouse gas balance, at site level as well as at national level. This article is protected by copyright. All rights reserved.

Description: Calcific aortic vascular and valvular disease (CAVD) is associated with hyperlipidemia, the effects of which occur through chronic inflammation. Evidence suggests that inhibitory small mothers against decapentaplegic (I-Smads; Smad6 and 7) regulate valve embryogenesis and may serve as a mitigating factor in CAVD. However, whether I-Smads regulate inflammation-induced calcific vasculopathy is not clear. Therefore, we investigated the role of I-Smads in atherosclerotic calcification. Results showed that expression of Smad6, but not Smad7, was reduced in aortic and valve tissues of hyperlipidemic compared with normolipemic mice, while expression of tumor necrosis factor alpha (TNF-a) was upregulated. To test whether the effects are in response to inflammatory cytokines, we isolated murine aortic valve leaflets and cultured valvular interstitial cells (mVIC) from the normolipemic mice. By immunochemistry, mVICs were strongly positive for vimentin, weakly positive for smooth muscle alpha actin, and negative for an endothelial cell marker. TNF-a upregulated alkaline phosphatase (ALP) activity and matrix mineralization in mVICs. By gene expression analysis, TNF-a significantly upregulated bone morphogenetic protein 2 (BMP-2) expression while downregulating Smad6 expression. Smad7 expression was not significantly affected. To further test the role of Smad6 on TNF-a-induced valvular cell calcification, we knocked down Smad6 expression using lentiviral transfection. In cells transfected with Smad6 shRNA, TNF-a further augmented ALP activity, expression of BMP-2, Wnt- and redox-regulated genes, and matrix mineralization compared with the control cells. These findings suggest that TNF-a induces valvular and vascular cell calcification, in part, by specifically reducing the expression of a BMP-2 signaling inhibitor, Smad6. This article is protected by copyright. All rights reserved

Description: Introgressive hybridization between native and introduced species is a growing conservation concern. For native cutthroat trout and introduced rainbow trout in western North America, this process is thought to lead to the formation of hybrid swarms and the loss of monophyletic evolutionary lineages. Previous studies of this phenomenon, however, indicated that hybrid swarms were rare except when native and introduced forms of cutthroat trout co-occurred. We used a panel of 86 diagnostic, single nucleotide polymorphisms to evaluate the genetic composition of 3865 fish captured in 188 locations on 129 streams distributed across western Montana and northern Idaho. Although introgression was common and only 37% of the sites were occupied solely by parental westslope cutthroat trout, levels of hybridization were generally low. Of the 188 sites sampled, 73% contained ≤5% rainbow trout alleles and 58% had ≤1% rainbow trout alleles. Overall, 72% of specimens were nonadmixed westslope cutthroat trout, and an additional 3.5% were nonadmixed rainbow trout. Samples from seven sites met our criteria for hybrid swarms, that is, an absence of nonadmixed individuals and a random distribution of alleles within the sample; most (6/7) were associated with introgression by Yellowstone cutthroat trout. In streams with multiple sites, upstream locations exhibited less introgression than downstream locations. We conclude that although the widespread introduction of nonnative trout within the historical range of westslope cutthroat trout has increased the incidence of introgression, sites containing nonadmixed populations of this taxon are common and broadly distributed. Hybridization between westslope cutthroat trout and Yellowstone cutthroat trout was analyzed using a panel of 86 diagnostic, single nucleotide polymorphisms to evaluate the genetic composition of 3865 fish captured in 188 locations on 129 streams distributed across western Montana and northern Idaho. Nonintrogressed fish dominated the sample. Widespread introduction of nonnative trout within the historical range of westslope cutthroat trout has increased the incidence of introgression, but sites containing nonadmixed populations are common and broadly distributed.

Description: The volcanic succession on Montserrat provides an opportunity to examine the magmatic evolution of island arc volcanism over a ∼2.5 Ma period, extending from the andesites of the Silver Hills center, to the currently active Soufrière Hills volcano (February 2010). Here we present high-precision double-spike Pb isotope data, combined with trace element and Sr-Nd isotope data throughout this period of Montserrat's volcanic evolution. We demonstrate that each volcanic center; South Soufrière Hills, Soufrière Hills, Centre Hills and Silver Hills, can be clearly discriminated using trace element and isotopic parameters. Variations in these parameters suggest there have been systematic and episodic changes in the subduction input. The SSH center, in particular, has a greater slab fluid signature, as indicated by low Ce/Pb, but less sediment addition than the other volcanic centers, which have higher Th/Ce. Pb isotope data from Montserrat fall along two trends, the Silver Hills, Centre Hills and Soufrière Hills lie on a general trend of the Lesser Antilles volcanics, whereas SSH volcanics define a separate trend. The Soufrière Hills and SSH volcanic centers were erupted at approximately the same time, but retain distinctive isotopic signatures, suggesting that the SSH magmas have a different source to the other volcanic centers. We hypothesize that this rapid magmatic source change is controlled by the regional transtensional regime, which allowed the SSH magma to be extracted from a shallower source. The Pb isotopes indicate an interplay between subduction derived components and a MORB-like mantle wedge influenced by a Galapagos plume-like source.

Description: We present laboratory measurements of biomass burning aerosol light scattering and absorption coefficients at 405, 532 and 781 nm and investigate their relationship with aerosol composition and fuel type. Aerosol composition measurements included non-refractory components measured by a high-resolution aerosol mass spectrometer (AMS), composition of refractory black carbon-containing particles by a soot particle aerosol mass spectrometer (SP-AMS) and refractory black carbon measured by a single particle soot photometer (SP2). All measurements were performed downstream of a thermal denuder system to probe the effects of non-refractory material on observed optical properties. The fires studied emitted aerosol with a wide range of optical properties with some producing more strongly light absorbing particles (single scattering albedo or SSA at 781 nm =0.4) with a weak wavelength dependence of absorption (absorption Ångström exponent or AAE =1-2) and others producing weakly light absorbing particles (SSA at 781 nm ~1) with strong wavelength dependence of absorption (AAE ~7). Removal of non-refractory material from the particles by the thermal denuder system led to substantial (20-80%) decreases in light absorption coefficients, particularly at shorter wavelengths, reflecting the removal of light absorbing material that had enhanced BC absorption in internally-mixed untreated samples. Observed enhancements of absorption by all mechanisms were at least factors of 1.2-1.5 at 532 nm and 781 nm as determined from the heated samples. A mass absorption cross-section based approach indicated larger enhancements, particularly at shorter wavelengths.

Description: Invasive hybridization, in which an introduced species may introgressively hybridize with a native taxon and threaten its persistence, is prominently featured in the conservation literature. One of the most frequently cited examples of this phenomenon involves interactions between native westslope cutthroat trout Oncorhynchus clarkii lewisi and introduced rainbow trout O. mykiss in a portion of the U.S. Northern Rocky Mountains (Allendorf & Leary, 1988). This article is protected by copyright. All rights reserved.

Description: In nutrient limited conditions, phytoplankton growth at fronts is enhanced by winds, which drive upward nutrient fluxes via enhanced turbulent mixing and upwelling. Hence, depth-integrated phytoplankton biomass can be ten times greater at isolated fronts. Using theory and two-dimensional simulations with a coupled physical-biogeochemical ocean model, this paper builds conceptual understanding of the physical processes driving upward nutrient fluxes at fronts forced by unsteady winds with timescales of 4-16 days. The largest vertical nutrient fluxes occur when the surface mixing layer penetrates the nutricline, which fuels phytoplankton in the mixed layer. At a front, mixed layer deepening depends on the magnitude and direction of the wind stress, cross-front variations in buoyancy and velocity at the surface, and potential vorticity at the base of the mixed layer, which itself depends on past wind events. Consequently, mixing layers are deeper and more intermittent in time at fronts than outside fronts. Moreover, mixing can decouple in time from the wind stress, even without other sources of physical variability. Wind-driven upwelling also enhances depth-integrated phytoplankton biomass at fronts; when the mixed layer remains shallower than the nutricline, this results in enhanced subsurface phytoplankton. Oscillatory along-front winds induce both oscillatory and mean upwelling. The mean effect of oscillatory vertical motion is to transiently increase subsurface phytoplankton over days to weeks, whereas slower mean upwelling sustains this increase over weeks to months. Taken together, these results emphasize that wind-driven phytoplankton growth is both spatially and temporally intermittent and depends on a diverse combination of physical processes.