Territorial dynamics and boundary effects in a protected area of the Central Iberian Peninsula

We analysed the main changes in land use over a 21 year period within the perimeter of a Protected Natural Area (PNA) and outside this perimeter. The area is characterised by its Mediterranean mid-mountain landscape and its piedmont, which extends almost as far as the city of Madrid. We employed cartography of land use and plant formation from 1980 and 2001. We identified land uses and their changes in this time period in order to determine the principal territorial dynamics (scrub encroachment, urban development, forest encroachment, new pastures and new crops). Subsequently, we performed a comparative analysis between the changes inside and those outside the protected area. The results show that there is a boundary effect between the protected area and the surrounding zone, which is more notable in the areas where urban development has intensified. This kind of research serves to establish whether or not a PNA contributes to protecting and conserving natural resources as compared to what occurs in the unprotected surrounding area, which tends to be subjected to more aggressive dynamics.     

Structural-stratigraphic control on the Umitaka Spur gas hydrates of Joetsu Basin in the eastern margin of Japan Sea

Integrated geological, geochemical, and geophysical exploration since 2004 has identified massive accumulation of gas hydrate associated with active methane seeps on the Umitaka Spur, located in the Joetsu Basin on the eastern margin of Japan Sea. Umitaka Spur is an asymmetric anticline formed along an incipient subduction zone that extends throughout the western side of the Japanese island-arc system. Seismic surveys recognized chimney structures that seem strongly controlled by a complex anticlinal axial fault system, and exhibit high seismic amplitudes with apparent pull-up structures, probably due to massive and dense accumulation of gas hydrate. Bottom simulating reflectors are widely developed, in particular within gas chimneys and in the gently dipping eastern flank of the anticline, where debris can store gas hydrates that may represent a potential natural gas resource. The axial fault system, the shape of the anticline, and the carrier beds induce thermogenic gas migration to the top of the structure, and supply gas to the gas hydrate stability zone. Gas reaching the seafloor produces strong seepages and giant plumes in the sea water column.     

Seasonal variability in somatic and reproductive investment of the bivalve Scrobicularia plana (da Costa, 1778) along a latitudinal gradient

Monthly investment in soma and gonads in the bivalve Scrobicularia plana is described for three populations along its distributional range: Minho estuary, Portugal; Westerschelde estuary, The Netherlands and Buvika estuary, Norway. Seasonal cycles in body mass (BMI), somatic mass (SMI) and gonadal mass (GMI) indices were observed for all populations. In Portugal, BMI and SMI peaked in mid-autumn, while in The Netherlands both indices were at their highest in mid-spring. Norway showed a different pattern with two distinct peaks: one in mid-autumn and a second peak in spring. GMI reached maximum values in July in Portugal and Netherlands and in June in Norway. Overall, mean BMI and SMI were lower in Portugal while mean GMI was lower in Norway. The spawning period lasted the whole summer in Portugal, but was shorter (only two months) in The Netherlands and Norway. The reproductive investment in The Netherlands was significantly higher than in Portugal and Norway, with the lowest values being observed in Norway. Differences in annual cycles between populations were attributed to environmental factors, namely temperature and food availability. Temperature seems important in shaping the reproductive pattern with more northern populations showing shorter reproductive periods starting later in the year, and a lower reproductive output. In addition, winter water temperatures can explain the lower mean body and somatic mass values observed in Portugal. Food availability influenced the physiological performance of the species with peaks in somatic mass coinciding with phytoplankton blooms. This relation between physiological performance and environmental factors influences S. plana distribution, densities and even survival, with natural consequences on its commercial importance.     

Impact of mega-scale sand extraction on tidal dynamics in semi-enclosed basins: An idealized model study with application to the Southern North Sea

Long-term considerations of repeated and increasing sand extraction on the Netherlands Continental Shelf (North Sea) may lead to the creation of a mega-scale extraction trench in front of the Dutch coast (length hundreds of km, width over 10 km, depth several m). We investigate the impact of such a huge topographic intervention on tidal dynamics, which is a key aspect in hydrodynamics, and indirectly also affecting morphodynamics and ecology.     

Trust relationships between fishers and government: New challenges for the co-management arrangements in the Dutch flatfish industry

Until the 1990s fisheries were largely managed by the state. Since then, Dutch government and the sector increasingly recognized that a fishing industry cannot be managed effectively without the cooperation and participation of fishers to formulate policy and to implement and enforce laws and regulations. As a result, in the nineties, the existing neo-corporatist arrangement was replaced by a co-management system in the Dutch flatfish fishery. Co-management is often seen as leading to greater procedural legitimacy and subsequently compliance. However, constructing an effective co-management arrangement is not only a matter of building institutions but also a matter of building trust relations between the government and industry. Institutional arrangements such as co-management can contribute to these trust building processes; however, a too strong reliance on institutional arrangements can lead to distrust when new challenges are being faced and institutional arrangements fail to adapt to these changes.     

Molluskan species richness and endemism on New Caledonian seamounts: Are they enhanced compared to adjacent slopes?

Seamounts were often considered as ‘hotspots of diversity’ and ‘centers of endemism’, but recently this opinion has been challenged. After 25 years of exploration and the work of numerous taxonomists, the Norfolk Ridge (Southwest Pacific) is probably one of the best-studied seamount chains worldwide. However, even in this intensively explored area, the richness and the geographic patterns of diversity are still poorly characterized. Among the benthic organisms, the post-mortem remains of mollusks can supplement live records to comprehensively document geographical distributions. Moreover, the accretionary growth of mollusk shells informs us about the life span of the pelagic larva. To compare diversity and level of endemism between the Norfolk Ridge seamounts and the continental slopes of New Caledonia we used species occurrence data drawn from (i) the taxonomic literature on mollusks and (ii) a raw dataset of mainly undescribed deep-sea species of the hyperdiverse Turridae. Patterns of endemism and species richness were analyzed through quantitative indices of endemism and species richness estimator metrics. To date, 403 gastropods and bivalves species have been recorded on the Norfolk Ridge seamounts. Of these, at least 38 species (∼10%) are potentially endemic to the seamounts and nearly all of 38 species have protoconchs indicating lecithotrophic larval development. Overall, our results suggest that estimates of species richness and endemism, when sampling effort is taken into account, were not significantly different between slopes and seamounts. By including in our analyses 347 undescribed morphospecies from the Norfolk Ridge, our results also demonstrate the influence of taxonomic bias on our estimates of species richness and endemism.     

A continental analysis of correlations between tree patterns in African savannas and human and environmental variables

This study analyses possible relationships between natural processes taking place in savannas and the tree patterns found in savannas. This can lead to new hypotheses about which processes are driving savanna physiognomy. To do so tree patterns were quantified for African savannas from historical aerial photographs applying frequently used landscape metrics. Also, additional data for these areas were collected to quantify the processes taking place at these locations. Correlations between tree pattern indices and explaining factors were analysed. We found a negative trend between tree cover and density of sheep and goats, but no relationship between tree cover and density of cattle, suggesting that small livestock have an effect on tree cover, but that larger livestock (or obligate grazers) do not. Also, a positive correlation between human population density and tree cover was found. Possible explanations for the found relations are discussed. Subsequent ways to analyse the latter correlation are discussed, and the potential of the presented historical database of aerial photographs is highlighted.     

Frequency and variability of missing tree rings along the stems of Pinus halepensis and Pinus pinea from a semiarid site in SE Spain

We studied the occurrence of missing rings (MR) around and along the stems of three Pinus halepensis and three Pinus pinea trees growing in a semiarid Mediterranean site in SE Spain. Tree-ring analyses were performed along 8 radii on stem discs taken at 1 m distances from the base to the top of the trees. The tree rings analysed showed that 19% were missing in P. halepensis and 10% in P. pinea. MR were recorded in 61% of P. halepensis and 24% of P. pinea in the years analysed. Dry conditions from January to May and high late winter to spring temperatures seem to be the main climatic elements promoting MR in both species. In our research into P. halepensis, the frequency of MR gradually decreased from the bottom upward, but no such pattern was observed in P. pinea. Most tree rings were missing only locally (LMR), indicating that wood formation occurred every year in at least some part of a tree, and the tree rings were often discontinuous around and along the stem. Since the frequency of LMR greatly varies around and along the stem, our results suggest that serial sectioning along the stem provides more information on wood formation and responses of trees to environment than studying the samples at breast height only. The disadvantage of the technique is that, as in our study case, research is based on a limited sample size, since it requires destructive sampling with tree felling, which is not usually possible or desirable on highly vulnerable semiarid forest ecosystems.     

Desertification in the Sahel: Towards better accounting for ecosystem dynamics in the interpretation of remote sensing images

To date, the interpretation of remote sensing images has not revealed wide-spread degradation of the vegetation in the Sahel. However, the interpretation of spectral information depends on a range of assumptions regarding the dynamics of the Sahelian vegetation as a function of rainfall variability and human management. Recent papers have presented diverging views on the vegetation dynamics of the Sahel and how these can be analysed with remote sensing images. We present a further analysis of the vegetation dynamics of semi-arid rangelands, in particular the Sahel, and the subsequent implications for the interpretation of remote sensing images. Specifically, the ecological processes driving the response of the Sahelian vegetation to rainfall variation are re-examined, and a regression analysis of NPP versus rainfall data is carried out. It is shown that the relation between the interannual variation in NPP and rainfall in the Sahel is non-linear and that this relation differs between sites with different average annual rainfall. It has been common practise in remote sensing studies for the Sahel to aggregate data from various Sahelian sites in order to obtain an average relation between rainfall, NPP and Rain Use Efficiency, and to assume these relations to be linear. This paper shows that this approach may lead to a bias in the interpretation of remote sensing images and that further work is required to clarify if wide-spread ecosystem degradation has occurred in the Sahel.     

Reproductive biology of Spondias tuberosa Arruda (Anacardiaceae), an endemic fructiferous species of the caatinga (dry forest), under different management conditions in northeastern Brazil

In areas under different management conditions (management units, MUs) located either on a slope or at the base of a slope and either in a plantation or in a pasture, we compared the flower and fruit production, floral visitors, visitation rates and pre-emergent reproductive success (PERS) of Spondias tuberosa (Anacardiaceae) in an area of dry forest in NE Brazil. Individuals in the plantation MU produced more flowers per inflorescence than those in other MUs, but there were no statistical differences in mean fruit set among MUs. The only difference in mean visitation rates was between the plantation (65.83 ± 38.49) and the slope sites (11.5 ± 12.8). We observed visits by 19 insect species, including bees (31.6%), butterflies (31.6%), wasps (26.3%) and flies (10.5%). A clustering analysis based on the number of visits showed that a) the plantation site is most different from the other MUs, b) the pasture and the site at the base of the slope are similar to the slope site, and c) the higher frequency of visits of pollinators in the plantation MU was responsible for these differences. Of the 19 species of insects visiting the flowers, 12 were considered pollinators. The pollinator similarity analysis indicated a clear separation between areas and suggested that human activity has resulted in the replacement of native pollinators by exotic species. However, these changes apparently have not affected the pre-emergent reproductive success of S. tuberosa. Our results show that plant reproductive biology in semi-arid ecosystems may be modified by human action and that changes in floral production and pollinator guilds are the most conspicuous effects. However, the traditional management performed by local people may not affect the reproductive success of plant species.