Diet and trophic position of two mackerel species in the archipelago of Madeira,Portugal

The Atlantic chub mackerel Scomber colias and the blue jack mackerel Trachurus picturatus are two abundant species in the Macaronesia region which includes the archipelago of Madeira, Portugal. Both are key species in the trophic web, being important prey for several local top predators, such as seabirds and marine mammals. Nonetheless, little is known about their feeding ecology in oceanic environments. In this study, the authors describe the seasonal variation in the diet of S. colias and T. picturatus in the oceanic region of Madeira throughout a year. Visual inspection of stomach contents revealed that S. colias fed on a broader range of prey groups than T. picturatus, but for both species, zooplankton (particularly calanoid copepods) and fish were the most important food items. The diet of S. colias included a higher proportion of fish, namely Atlantic saury Scomberesox saurus and S. colias, than that of T. picturatus, that included mostly the longspine snipefish Macroramphosus scolopax. T. picturatus consumed a higher proportion of decapods and other copepods. Seasonal variation was found in the diet of both species, with zooplanktonic species being more important in colder months (February to April) for S. colias and during warm months (May to October) for T. picturatus. Their diet in other seasons was dominated by fish. Although they consume similar prey, carbon and nitrogen stable isotope analysis of muscle of S. colias and T. picturatus showed little overlap in their diets, and T. picturatus showed higher δ¹⁵N and a narrower isotopic niche.     

Sixteen hundred years of increasing tree cover prior to modern deforestation in Southern Amazon and Central Brazilian savannas

Tropical ecosystems are under increasing pressure from land‐use change and deforestation. Changes in tropical forest cover are expected to affect carbon and water cycling with important implications for climatic stability at global scales. A major roadblock for predicting how tropical deforestation affects climate is the lack of baseline conditions (i.e., prior to human disturbance) of forest–savanna dynamics. To address this limitation, we developed a long‐term analysis of forest and savanna distribution across the Amazon–Cerrado transition of central Brazil. We used soil organic carbon isotope ratios as a proxy for changes in woody vegetation cover over time in response to fluctuations in precipitation inferred from speleothem oxygen and strontium stable isotope records. Based on stable isotope signatures and radiocarbon activity of organic matter in soil profiles, we quantified the magnitude and direction of changes in forest and savanna ecosystem cover. Using changes in tree cover measured in 83 different locations for forests and savannas, we developed interpolation maps to assess the coherence of regional changes in vegetation. Our analysis reveals a broad pattern of woody vegetation expansion into savannas and densification within forests and savannas for at least the past ~1,600 years. The rates of vegetation change varied significantly among sampling locations possibly due to variation in local environmental factors that constrain primary productivity. The few instances in which tree cover declined (7.7% of all sampled profiles) were associated with savannas under dry conditions. Our results suggest a regional increase in moisture and expansion of woody vegetation prior to modern deforestation, which could help inform conservation and management efforts for climate change mitigation. We discuss the possible mechanisms driving forest expansion and densification of savannas directly (i.e., increasing precipitation) and indirectly (e.g., decreasing disturbance) and suggest future research directions that have the potential to improve climate and ecosystem models.     

The dendroclimatic value of oak stable isotopes

Tree-ring stable oxygen and carbon isotope ratios (δ¹⁸O and δ¹³C) are an important archive for climate reconstructions. However, it remains unclear whether the polyvinyl acetate emulsion, often used for the preservation and fixation of wood samples, influences δ¹⁸O and δ¹³C signals. Further uncertainties are associated with the possible effects of geographical origin and cambial age of historical samples. Here, we present annually-resolved and absolutely-dated δ¹⁸O and δ¹³C measurements of 21 living oaks (Quercus robur and Q. petraea) from the Czech Republic. We find that the δ¹⁸O and δ¹³C signals in the extracted alpha-cellulose are not affected by polyvinyl acetate treatment. Covering the entire 20^th century and reaching until 2018 CE, our dataset reveals spatial and temporal coherency within and between the individual δ¹⁸O and δ¹³C chronologies of different oak species, sample locations, and tree ages. Highly significant (p < 0.01) Pearson’s correlation coefficients of the site-specific δ¹³C and δ¹⁸O chronologies range from 0.48–0.77 and 0.36–0.56, respectively. The isotopic inter-series correlations of Q. robur and Q. petraea from the same site are 0.75 and 0.43 for the mean δ¹³C and δ¹⁸O values, respectively. Significant (p < 0.01) correlations of 0.49 and 0.84 are found for δ¹³C and δ¹⁸O, respectively, when all measurements from all sampling locations and tree ages are included. Our study shows that non-pooled oak δ¹⁸O and δ¹³C measurements from both species, different locations, and diverse tree ages can be combined into robust isotopic chronologies for climate reconstructions.     

A lonely dot on the map: Exploring the climate signal in tree-ring density and stable isotopes of clanwilliam cedar,South Africa

Clanwilliam cedar (Widdringtonia cedarbergensis; WICE), a long-lived conifer with distinct tree rings in Cape Province, South Africa, has potential to provide a unique high-resolution climate proxy for southern Africa. However, the climate signal in WICE tree-ring width (TRW) is weak and the dendroclimatic potential of other WICE tree-ring parameters therefore needs to be explored. Here, we investigate the climatic signal in various tree-ring parameters, including TRW, Minimum Density (MND), Maximum Latewood Density (MXD), Maximum Latewood Blue Intensity (MXBI), and stable carbon and oxygen isotopes (δ¹⁸O and δ¹³C) measured in WICE samples collected in 1978. MND was negatively influenced by early spring (October-November) precipitation whereas TRW was positively influenced by spring November-December precipitation. MXD was negatively influenced by autumn (April-May) temperature whereas MXBI was not influenced by temperature. Both MXD and MXBI were negatively influenced by January-March and January-May precipitation respectively. We did not find a significant climate signal in either of the stable isotope time series, which were measured on a limited number of samples. WICE can live to be at least 356 years old and the current TRW chronology extends back to 1564 CE. The development of full-length chronologies of alternative tree-ring parameters, particularly MND, would allow for an annually resolved, multi-century spring precipitation reconstruction for this region in southern Africa, where vulnerability to future climate change is high.     

Long‐term changes in forest carbon under temperature and nitrogen amendments in a temperate northern hardwood forest

Currently, forests in the northeastern United States are net sinks of atmospheric carbon. Under future climate change scenarios, the combined effects of climate change and nitrogen deposition on soil decomposition, aboveground processes, and the forest carbon balance remain unclear. We applied carbon stock, flux, and isotope data from field studies at the Harvard forest, Massachusetts, to the ForCent model, which integrates above‐ and belowground processes. The model was able to represent decadal‐scale measurements in soil C stocks, mean residence times, fluxes, and responses to a warming and N addition experiment. The calibrated model then simulated the longer term impacts of warming and N deposition on the distribution of forest carbon stocks. For simulation to 2030, soil warming resulted in a loss of soil organic matter (SOM), decreased allocation to belowground biomass, and gain of aboveground carbon, primarily in large wood, with an overall small gain in total system carbon. Simulated nitrogen addition resulted in a small increase in belowground carbon pools, but a large increase in aboveground large wood pools, resulting in a substantial increase in total system carbon. Combined warming and nitrogen addition simulations showed a net gain in total system carbon, predominately in the aboveground carbon pools, but offset somewhat by losses in SOM. Hence, the impact of continuation of anthropogenic N deposition on the hardwood forests of the northeastern United States may exceed the impact of warming in terms of total ecosystem carbon stocks. However, it should be cautioned that these simulations do not include some climate‐related processes, different responses from changing tree species composition. Despite uncertainties, this effort is among the first to use decadal‐scale observations of soil carbon dynamics and results of multifactor manipulations to calibrate a model that can project integrated aboveground and belowground responses to nitrogen and climate changes for subsequent decades.     

No cumulative effect of 10 years of elevated [CO2] on perennial plant biomass components in the Mojave Desert

Elevated atmospheric CO₂ concentrations ([CO₂]) generally increase primary production of terrestrial ecosystems. Production responses to elevated [CO₂] may be particularly large in deserts, but information on their long‐term response is unknown. We evaluated the cumulative effects of elevated [CO₂] on primary production at the Nevada Desert FACE (free‐air carbon dioxide enrichment) Facility. Aboveground and belowground perennial plant biomass was harvested in an intact Mojave Desert ecosystem at the end of a 10‐year elevated [CO₂] experiment. We measured community standing biomass, biomass allocation, canopy cover, leaf area index (LAI), carbon and nitrogen content, and isotopic composition of plant tissues for five to eight dominant species. We provide the first long‐term results of elevated [CO₂] on biomass components of a desert ecosystem and offer information on understudied Mojave Desert species. In contrast to initial expectations, 10 years of elevated [CO₂] had no significant effect on standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground components. However, elevated [CO₂] increased short‐term responses, including leaf water‐use efficiency (WUE) as measured by carbon isotope discrimination and increased plot‐level LAI. Standing biomass, biomass allocation, canopy cover, and C : N ratios of above‐ and belowground pools significantly differed among dominant species, but responses to elevated [CO₂] did not vary among species, photosynthetic pathway (C₃ vs. C₄), or growth form (drought‐deciduous shrub vs. evergreen shrub vs. grass). Thus, even though previous and current results occasionally show increased leaf‐level photosynthetic rates, WUE, LAI, and plant growth under elevated [CO₂] during the 10‐year experiment, most responses were in wet years and did not lead to sustained increases in community biomass. We presume that the lack of sustained biomass responses to elevated [CO₂] is explained by inter‐annual differences in water availability. Therefore, the high frequency of low precipitation years may constrain cumulative biomass responses to elevated [CO₂] in desert environments.     

Expression Profile of Vascular Cell Adhesion Molecule-1 (CD106) in Inflammatory Foci using Rhenium-188 Labelled Monoclonal Antibody in Mice

Rhenium (Re)-188 is a generator (W-188/Re-188) produced high energy β-emitter suitable for radionuclide therapy (T_1/2 is 16.9 hrs and E_max 2.1 MeV (range 11 mm)). We have labelled monoclonal antibody (MAb) raised against vascular cell adhesion molecule-1 (VCAM-1) with Re-188 using glucoheptonate chelation technique and SnCl₂ as reducing agent. The labelling efficiency, free perrhenate and reduced Re were controlled with thin layer chromatography and the purification of Re-188-MoAbs was performed using gel filtration. Our results indicate that Re-188-labelled antibodies remain in vitro stable and the labelling purity is >90%. We also have applied these Re-188-MoAbs for detection of inflammatory disease in a mouse. The effective half-lives of organs of interest after an injection of Re-188-anti-VCAM1 were as follows: blood 5.2 hr, kidney 4.7 hr, and liver 9.6 hr. Re-188-anti-VCAM-1 was found to accumulate mainly in kidney and liver. One hour after the injection, the kidney contained in average as high as 12.5% and the liver 2.8 ID/g tissue. After 6 hr, the kidney contained 5.5% ID/g and the liver 2.6% ID/g. At 24 hr, the kidney uptake was 0.5% ID/g and the liver uptake 0.8 % ID/g, respectively. The inflamed foci, subcutaneous lesions in the footpad skin, were visualized using gamma camera. From the distribution data the upakes in the inflamed foci as follows: at 1 hr 2.18 (inflammation) and 1.72% ID/g (control), at 6 hr 1.42 (inflammation) and 0.85% ID/g (control), and at 24 hr 0.17 (inflammation) and 0.084% ID/g (control), respectively. Anti-VCAM-1 MAb showed better targeting as compared to control MoAbs in inflammation (caused by E. coli lipoplysaccaride). In conclusion, Re-188 is suitable for MAb labelling, and MAb against VCAM-1 may be used for detection of local inflammatory disease.     

Coupled plant traits adapted to wetting/drying cycles of substrates co-define niche multidimensionality

Theories attempting to explain species coexistence in plant communities have argued in favour of species' capacities to occupy a multidimensional niche with spatial, temporal and biotic axes. We used the concept of hydrological niche segregation to learn how ecological niches are structured both spatially and temporally and whether small scale humidity gradients between adjacent niches are the main factor explaining water partitioning among tree species in a highly water-limited semiarid forest ecosystem. By combining geophysical methods, isotopic ecology, plant ecophysiology and anatomical measurements, we show how coexisting pine and oak species share, use and temporally switch between diverse spatially distinct niches by employing a set of functionally coupled plant traits in response to changing environmental signals. We identified four geospatial niches that turned into nine, when considering the temporal dynamics of the wetting/drying cycles in the substrate and the particular plant species adaptations to garner, transfer, store and use water. Under water scarcity, pine and oak exhibited water use segregation from different niches, yet under maximum drought when oak trees crossed physiological thresholds, niche overlap occurred. The identification of niches and mechanistic understanding of when and how species use them will help unify theories of plant coexistence and competition.