8000 years of vegetation history in the northern Iberian Peninsula inferred from the palaeoenvironmental study of the Zalama ombrotrophic bog (Basque‐Cantabrian Mountains,Spain)

This paper focuses on pollen, spores, non‐pollen palynomorphs (NPPs) and certain geochemical elements from the ombrotrophic blanket bog of Zalama (Basque‐Cantabrian Mountains, northern Iberian Peninsula), with the support of a robust chronology based on 17 AMS ¹⁴C dates. The main results related to the last 8000 years show that, during the early middle Holocene, pines and deciduous forests were the most extensive tree formations. At the beginning of the succession, pines reach 44%, showing regional presence, whereas after 7600 cal. a BP, deciduous forests were particularly abundant. From c. 6500 cal. a BP the pollen diagram constructed from our samples shows the first anthropogenic evidence, linked with the new economic practices related to the Neolithic of the Basque‐Cantabrian Mountains. From 3300 cal. a BP the expansion of Fagus sylvatica is particularly clear, and has since then become one of the dominant forest species in this region. We also discuss the Holocene evolution of other noteworthy plant communities in southwestern Europe, such as Taxus baccata, Juglans and shrublands.     

Pressure image assimilation for atmospheric motion estimation

The complexity of the laws of dynamics governing 3-D atmospheric flows associated with incomplete and noisy observations make the recovery of atmospheric dynamics from satellite image sequences very difficult. In this paper, we address the challenging problem of estimating physical sound and time-consistent horizontal motion fields at various atmospheric depths for a whole image sequence. Based on a vertical decomposition of the atmosphere, we propose a dynamically consistent atmospheric motion estimator relying on a multilayer dynamic model. This estimator is based on a weak constraint variational data assimilation scheme and is applied on noisy and incomplete pressure difference observations derived from satellite images. The dynamic model is a simplified vorticity-divergence form of a multilayer shallow-water model. Average horizontal motion fields are estimated for each layer. The performance of the proposed technique is assessed using synthetic examples and using real world meteorological satellite image sequences. In particular, it is shown that the estimator enables exploiting fine spatio-temporal image structures and succeeds in characterizing motion at small spatial scales.     

The effects of suspended sediment on brown trout (Salmo trutta) feeding and respiration after macrophyte control

Sediment resuspension during and after mechanical excavation of macrophytes may have a significant impact on resident fish populations. Unfortunately, little is known about the influence of this sediment on the respiratory performance and feeding abilities of fishes in New Zealand waterways. We examined the effects of suspended sediment (SS) concentrations previously observed after a large-scale macrophyte removal operation on oxygen consumption (MO₂) and feeding rates of brown trout (Salmo trutta). MO₂ at 0 mg L^?1, 150 mg L^?1, 300 mg L^?1, 450 mg L^?1 and 600 mg L^?1 of SS was measured using semi-closed respirometry. Feeding rates at the same SS concentrations were also measured using laboratory tank experiments. Results suggest that SS concentrations up to 600 mg L^?1 have no effect on MO₂. Conversely, feeding rates were significantly reduced at 450 mg L^?1 (22% reduction) and 600 mg L^?1 (31% reduction), indicating that sediment concentrations above 450 mg L^?1 may negatively affect brown trout populations.     

Introduction of geospatial perspective to the ecology of fish-habitat relationships in Indonesian coral reefs: A remote sensing approach

Coral reef ecosystems worldwide are now being harmed by various stresses accompanying the degradation of fish habitats and thus knowledge of fish-habitat relationships is urgently required. Because conventional research methods were not practical for this purpose due to the lack of a geospatial perspective, we attempted to develop a research method integrating visual fish observation with a seabed habitat map and to expand knowledge to a two-dimensional scale. WorldView-2 satellite imagery of Spermonde Archipelago, Indonesia obtained in September 2012 was analyzed and classified into four typical substrates: live coral, dead coral, seagrass and sand. Overall classification accuracy of this map was 81.3% and considered precise enough for subsequent analyses. Three sub-areas (CC: continuous coral reef, BC: boundary of coral reef and FC: few live coral zone) around reef slopes were extracted from the map. Visual transect surveys for several fish species were conducted within each sub-area in June 2013. As a result, Mean density (Ind. / 300 m²) of Chaetodon octofasciatus, known as an obligate feeder of corals, was significantly higher at BC than at the others (p < 0.05), implying that this species’ density is strongly influenced by spatial configuration of its habitat, like the “edge effect.” This indicates that future conservation procedures for coral reef fishes should consider not only coral cover but also its spatial configuration. The present study also indicates that the introduction of a geospatial perspective derived from remote sensing has great potential to progress conventional ecological studies on coral reef fishes.

     

Combining Robustness with Efficiency in?the?Estimation of the Variogram

In the present paper, we propose a new method for the estimation of the variogram, which combines robustness with efficiency under intrinsic stationary geostatistical processes. The method starts by using a robust estimator to obtain discrete estimates of the variogram and control atypical observations that may exist. When the number of points used in the fit of a model is the same as the number of parameters, ordinary least squares and generalized least squares are asymptotically equivalent. Therefore, the next step is to fit the variogram by ordinary least squares, using just a few discrete estimates. The procedure is then repeated several times with different subsets of points and this produces a sequence of variogram estimates. The final estimate is the median of the multiple estimates of the variogram parameters. The suggested estimator will be called multiple variograms estimator. This procedure assures a global robust estimator, which is more efficient than other robust proposals. Under the assumed dependence structure, we prove that the multiple variograms estimator is consistent and asymptotically normally distributed. A simulation study confirms that the new method has several advantages when compared with other current methods.     

10,000 years of climate control over carbon accumulation in an Iberian bog(southwestern Europe)

The northwest region of the Iberian Peninsula is home to a unique ecosystem of bogs,which are particularly sensitive to projected climate cha nge.In this context,the rate of carbon(C)accumulation in Chao de Veiga Mol.an intact raised bog,was analysed.Changes in the accumulation rate over the past10 millennia were determined in a peat core of 847 cm in depth,with a high mean rate of peat growth(11 yr cm^-1,0.09 cm yr^-1).An age-depth model was generated from 22 14C dates and fallout radionuclides.Chronological,stratigraphical and physico-chemical data confirmed the existence of a single cycle of peat formation throughout the Holocene and the formation of ombrotrophic peat 9500 years ago.The total mean C content was 50.2%,and over 10 millennia 583 kg C m^-2 accumulated at a mean rate of 35.3 g C m^-2 yr^-1,with a long-term(apparent)rate of carbon accumulation in the catotelm of59.9 g C m^-2 yr^-1.These values are much higher than reported for other Iberian peatlands and are amongst the highest documented for peatlands in the northern hemisphere.The dynamics of C accumulation and other measured parameters reveals important variations throughout the Holocene.They could be associated with the main climatic events described in the northern hemisphere and are highly consistent with models established for northern latitudes.The Chao de Veiga Mol raised bog is unique and of great potential value for carrying out high resolution palaeoenvironmental studies,especially in relation to regional and Iocal modulations in southern Europe.