bluuebunny/crossref_metadata_2025 huggingface dataset:
Holocene vegetation and climate changes in the central Mediterranean inferred from a high-resolution marine pollen record (Adriatic Sea)
Authors: Combourieu-Nebout N. , Peyron O. , Bout-Roumazeilles V. , Goring S. , Dormoy I. , Joannin S. , Sadori L. , Siani G. , Magny M.
Published: September 2013

Abstract. The high-resolution multiproxy study of the Adriatic marine core MD 90-917 provides new insights to reconstruct vegetation and regional climate changes over the southcentral Mediterranean during the Younger Dryas (YD) and Holocene. Pollen records show the rapid forest colonization of the Italian and Balkan borderlands and the gradual installation of the Mediterranean association during the Holocene. Quantitative estimates based on pollen data provide Holocene precipitations and temperatures in the Adriatic Sea using a multi-method approach. Clay mineral ratios from the same core reflect the relative contributions of riverine (illite and smectite) and eolian (kaolinite) contributions to the site, and thus act as an additional proxy with which to evaluate precipitation changes in the Holocene. Vegetation climate reconstructions show the response to the Preboreal oscillation (PBO), most likely driven by changes in temperature and seasonal precipitation, which is linked to increasing river inputs from Adriatic rivers recorded by increase in clay mineral contribution to marine sediments. Pollen-inferred temperature declines during the early–mid Holocene, then increases during the mid–late Holocene, similar to southwestern Mediterranean climatic patterns during the Holocene. Several short vegetation and climatic events appear in the record, indicating the sensitivity of vegetation in the region to millennial-scale variability. Reconstructed summer precipitation shows a regional maximum (170–200 mm) between 8000 and 7000 similar to the general pattern across southern Europe. Two important shifts in vegetation occur at 7700 cal yr BP (calendar years before present) and between 7500 and 7000 cal yr BP and are correlated with increased river inputs around the Adriatic Basin respectively from the northern (7700 event) and from the central Adriatic borderlands (7500–7000 event). During the mid-Holocene, the wet summers lead to permanent moisture all year resulting in a homogeneous seasonal precipitation regime. After 6000 cal yr BP, summer precipitation decreases towards present-day values while winter precipitation rises regularly showing the setting up of Mediterranean climate conditions. Multiproxy evidence from core MD 90-917 provides a deeper understanding of the role of precipitation and particularly the seasonality of precipitation in mediating vegetation change in the central Mediterranean during the Holocene.
Climate response to imposed solar radiation reductions in high latitudes
Authors: MacCracken M. C. , Shin H.-J. , Caldeira K. , Ban-Weiss G. A.
Published: September 2013

Abstract. With human-induced climate change leading to amplified warming in high latitudes, mitigation alone is unlikely to be rapid enough to prevent significant, even irreversible, impacts. Model simulations in which solar insolation was arbitrarily reduced poleward of 51, 61, or 71° latitude in one or both hemispheres not only cooled those regions, but also drew energy from lower latitudes, exerting a cooling influence over much of the particular hemisphere in which the reduction was imposed. The simulations, conducted using the National Center for Atmospheric Research's CAM3.1 atmospheric model coupled to a slab ocean, indicated that high-latitude reductions in absorbed solar radiation have a significantly larger cooling influence than solar reductions of equivalent magnitude spread evenly over the Earth. This amplified influence occurred primarily because concentrated high-latitude reductions in solar radiation led to increased sea ice fraction and surface albedo, thereby amplifying the energy deficit at the top of the atmosphere as compared to the response for an equivalent reduction in solar radiation spread evenly over the globe. Reductions in incoming solar radiation in one polar region (either north or south) resulted in increased poleward energy transport during that hemisphere's cold season and shifted the Inter-Tropical Convergence Zone (ITCZ) away from that pole, whereas comparable solar reductions in both polar regions resulted in increased poleward energy transport, but tended to leave the ITCZ approximately in place. Together, these results suggest that, until emissions reductions are sufficient to limit the warming influence of increasing greenhouse gas concentrations, polar reductions in solar radiation, if they could be efficiently and effectively implemented, warrant further research as an approach to moderating the early stages of both high-latitude and global warming.
Seismic visibility of a deep subduction channel: insights from numerical simulation of high-frequency seismic waves emitted from intermediate depth earthquakes
Authors: Friederich W. , Lambrecht L. , Stöckhert B. , Wassmann S. , Moos C.
Published: September 2013

Abstract. Return flow in a deep subduction channel (DSC) has been proposed to explain rapid exhumation of high pressure-low temperature metamorphic rocks, entirely based on the fossil rock record. Supported by thermo-mechanical models, the DSC is envisioned as a thin layer on top of the subducted plate reaching down to minimum depths of about 150 km. We perform numerical simulations of high-frequency seismic wave propagation (1 to 6 Hz) to explore potential seismological evidence for the in-situ existence of a DSC. Motivated by field observations, for modeling purposes we assume a simple block-in-matrix structure with eclogitic blocks floating in a serpentinite matrix. Homogenization calculations for block-in-matrix structures demonstrate that effective seismic velocities in such composites are lower than in the surrounding oceanic crust and mantle, with nearly constant values along the entire length of the DSC. Synthetic seismograms for receivers at the surface computed for intermediate depth earthquakes in the subducted oceanic crust for models with and without DSC turn out to be markedly influenced by its presence or absence. In models with channel, P and S waveforms are dominated by delayed high-amplitude guided waves emanating from the waveguide formed by oceanic crust and DSC. Simulated patterns allow for definition of typical signatures and discrimination between models with and without DSC. These signatures stably recur in slightly modified form for earthquakes at different depths inside subducted oceanic crust. Comparison with available seismological data from intermediate depth earthquakes recorded in the forearc of the Hellenic subduction zone reveal similar multi-arrival patterns as observed in the synthetic seismograms for models with DSC. According to our results, observation of intermediate depth earthquakes along a profile across the forearc may allow to test the hypothesis of a DSC and to identify situations where such processes could be active today.
The effect of acclimation to constant temperatures, pollution of food by heavy metals and short-term fasting on the metabolic activity of Glomeris balcanica (Diplopoda: Glomeridae)
Authors: Stamou G. P. , Karris G. , Tsiafouli M. A. , Papatheodorou E. M. , Argyropoulou M. D.
Published: September 2013

Abstract. Changing temperature regime has an important effect on the respiratory metabolism of Glomeris balcanica. A left skewing response of animals to increasing temperature is revealed and modeled. Acclimation from fluctuating to constant temperatures depresses metabolism through a three-step process. Short-term acclimation results in strongly depressed metabolism, mid-term acclimation induces metabolic recovery, whereas long-term acclimation results in an irreversible decline of metabolic activity. Heavy metal burdens of food do not affect the left skewing thermal response of animals, although they depress metabolic levels at the high temperature range, shorten tolerance ranges by shifting down the upper tolerance threshold, enlarge optimal temperature range (metabolic constancy) and stimulate the faster activation of the metabolic compensatory mechanism. Finally, no effect of short-term fasting on respiration was detected.
Environmental conservation and restoration ecology: two facets of the same problem
Authors: Urbanska K. M.
Published: September 2013

Abstract. Restoration ecology has often been regarded as a subordinate component of conservation biology and yet the two disciplines differ from each other. Conservation aims at staving off extinction, i.e. preserving ecological structures and services which still exist, however endangered they may be. On the other hand, the principal objective of restoration is re-building ecological structures and services that have been destroyed. The most distinct focus of conservation is on population response to exploitation, whereas restoration is principally concerned with over-exploited sites and landscapes in which communities/ecosystems are to be re-built. Conservation aims at preserving as many species as possible; on the other hand, the biodiversity approach in restoration may be addressed on three levels viz. 1) initial species diversity, 2) post-restoration increase of diversity via spontaneous species immigration, and 3) age-state diversity of developing plant cover. The conceptual framework in conservation biology differs from that in restoration ecology. The two basic paradigms used in conservation biology are 1) small-population paradigm and 2) declining-population paradigm, and one of its useful concepts is population viability assessment (PVA). The two principal paradigms used in restoration ecology are 1) nature-in-balance paradigm and 2) nature-in-flux paradigm. Interfaces between conservation and restoration may be recognized when e.g., recovery strategies for threatened species include habitat/ecosystem restoration, or when population processes in non-threatened species are studied to verify their usefulness as restoration material. Integration of species and ecosystem approaches is already recognizable in ecology. It is to be hoped that in future conservation and restoration become integrated components of ecosystem management, but for the time being they remain two different facets of the same problem which is the negative human impact upon environment.
Notes on the adaptation of some phytophagous and predacious mites to various ecological parameters in the Mediterranean countries
Authors: Ragusa S. , Tsolakis H.
Published: September 2013

Abstract. Notes on the adaptation to various habitats, climatic conditions, life-cycles, dispersion as well as on some morpho-physiological ones of the main phytophagous (Tetranychidae and Eriophyidae) and predaceous (Phytoseiidae) mites typical of the Mediterranean area are reported in the present paper.
Evolution of age specific dispersal: a general discussion from the standpoint of the invasion fitness concept
Authors: Johst K. , Brandl R.
Published: September 2013

Abstract. The age of dispersers is one of the important factors influencing the ecology and evolution of dispersal. Explanations in textbooks assume special social or genetic advantages to predict the dispersing age class. However, recent theoretical results suggest that age specific dispersal can evolve even without special advantages for the dispersing age class. Here we discuss and interpret these results on the basis of the invasion fitness concept and show with general arguments that the evolution of age specific dispersal is possible for purely demographic reasons. This furthers our general understanding of the evolution of age specific dispersal.
Fine-scale patterns of vegetation assembly in the monitoring of changes in coastal sand-dune landscapes
Authors: Honrado J. , Vicente J. , Lomba A. , Alves P. , Macedo J. A. , Henriques R. , Granja H. , Caldas F. B.
Published: September 2013

Abstract. Understanding dune ecosystem responses to multi-scale environmental changes can provide the framework for reliable forecasts and cost-efficient protocols for detecting shifts in prevailing coastal dynamics. Based on the hypothesis that stress and disturbance interact as primary community controls in coastal dunes, we studied the fine-scale floristic assembly of foredune vegetation, in its relation to topography, along regional and local environmental gradients in the 200 km long coastline of northern Portugal, encompassing a major biogeographic transition in western Europe. Thirty topographic profiles perpendicular to the shoreline were recorded at ten sites along the regional climate gradient, and vegetation was sampled by recording the frequency of plant species along those profiles. Quantitative topographic attributes of vegetated dune profiles (e.g. length or height) exhibited wide variations relatable to differences in prevailing coastal dynamics. Metrics of taxonomic diversity (e.g. total species richness and its additive beta component) and of the functional composition of vegetation were highly correlated to attributes of dune topography. Under transgressive dynamics, vegetation profiles have fewer species, increased dominance, lower turnover rates, and lower total vegetation cover. These changes may drive a decrease in structural and functional diversity, with important consequences for resistance, resilience and other ecosystem properties. Moreover, differences in both vegetation assembly (in meta-stable dunes) and response to increased disturbance (in eroding dunes) between distinct biogeographic contexts highlight a possible decline in facilitation efficiency under extreme physical stress (i.e. under Mediterranean climate) and support the significance of functional approaches in the study of local ecosystem responses to disturbance along regional gradients. Our results strongly suggest that assessing fine-scale community assembly can provide insights on the relation between dune vegetation, environmental filters and ecosystem processes. A combination of cost-efficient indicators from dune topography and vegetation is thus suggested as a promising approach to survey, forecast and monitor changes in coastal dune ecosystems.
Post-fire management and recovery of a pine forest in Greece
Authors: Spanos I. , Raftoyannis Y. , Platis P. , Xanthopoulou E.
Published: September 2013

Abstract. The effects of management after fire in Pinus halepensis forests were assessed in northern Greece. Seeding, logging and building of log barriers were applied in burned sites and compared to a control site. Two years after treatment application, 70–80% of the ground in all sites was covered with vegetation. Seeding with herbaceous plants did not increase plant cover. Logging and building of log barriers negatively affected herbaceous species but increased woody species. During the first spring after fire, the highest numbers of P. halepensis seedlings were observed in the control site and the lowest number in the logged site. Logging and log barrier building had a negative effect on pine regeneration compared to control and seeding treatments. Woody plant composition was similar in control and seeding sites, with dominance of P. halepensis and Cistus species. A different pattern was observed in the logging and log-barrier sites with a low number of seeders and a high number of resprouter species.
Structural analysis of mixed stands coming from natural regeneration and plantations after fire
Authors: Tsitsoni T. , Tsakaldimi M. , Simeliadou E. , Fouska M.
Published: September 2013

Abstract. We analyzed the structure and growth of naturally regenerated stands of Pinus brutia that mixed with planted broad-leaved and conifer species, 12 years after wildfire and examined the degree of species mix. Field data on stand structure of P. brutia forest were taken in spring 2009 on northern and southern aspects differing in regeneration conditions. Sixteen sample plots were selected and all individuals and their attributes measured. The results showed that in northern aspects the forest is composed of P. brutia in the over-storey and Quercus pubescens and Cupressus sempervirens in the under-storey, while in southern aspects the forest was mainly composed by P. brutia (81%). Stem diameter distribution of P. brutia in both aspects followed almost a normal pattern. All P. brutia individuals were characterized by vigorous growth and good to normal stem quality. Aspect did not statistically affect structural characteristics of P. brutia trees and saplings. However, on the northern aspect stem diameter, height, crown length and basal area of P. brutia were greater than in the southern aspect. Aspect significantly affected structural characteristics of Q. pubescens.
A systematic review of the recent ecological literature on cushion plants: champions of plant facilitation
Authors: Reid A. M. , Lamarque L. J. , Lortie C. J.
Published: September 2013

Abstract. Cushion-forming plant species are found in alpine and polar environments around the world. They modify the microclimate, thereby facilitating other plant species. Similar to the effectiveness of shrubs as a means to study facilitation in arid and semi-arid environments, we explore the potential for cushion plant species to expand the generality of research on this contemporary ecological interaction. A systematic review was conducted to determine the number of publications and citation frequency on relevant ecological topics whilst using shrub literature as a baseline to assess relative importance of cushions as a focal point for future ecological research. Although there are forty times more shrub articles, mean citations per paper is comparable between cushion and shrub literature. Furthermore, the scope of ecological research topics studied using cushions is broad including facilitation, competition, environmental gradients, life history, genetics, reproduction, community, ecosystem and evolution. The preliminary ecological evidence to date also strongly suggests that cushion plants can be keystone species in their ecosystems. Hence, ecological research on net interactions including facilitation and patterns of diversity can be successfully examined using cushion plants, and this is particularly timely given expectations associated with a changing climate in these regions.
Slow and fast development in ladybirds: occurrence, effects and significance
Authors: Mishra G. ,   Omkar
Published: September 2013

Abstract. Developmental and growth rates are known to vary in response to genetic, developmental, physiological and environmental factors. However, developmental variations that exist within a cohort under any constant rearing condition are not so well investigated. A few such prominent polymorphisms have been studied, but not the subtle ones. The current study investigates the presence of such varying rates of development, slow and fast, in a cohort reared under constant conditions in two ladybirds, Cheilomenes sexmaculata and Propylea dissecta. Our results reveal slow and fast developers in the cohorts of each species and the ratio of slow and fast developers was similar. Slow developers showed a female biased sex ratio. The two developmental variants differed significantly in juvenile duration only in the first instar and the pupal stage, though variations in developmental time were observed in all stages. Fecundity was higher in slow developers, but developmental rates did not affect egg viability. The similar ratio in both ladybirds indicates it to be a result of either presence of a constant ratio across species or an effect of the similar rearing environment.
A perspective on the importance of within-tree variation in mortality risk for a leaf-mining insect
Authors: Low C. , Hanley D.
Published: September 2013

Abstract. Within-tree variation in abiotic conditions can create a mosaic of fitness gradients for herbivorous insects. To explore these effects, we quantified the patterns of mortality of the solitary oak leafminer, Cameraria hamadryadella (Lepidoptera: Gracillariidae), which lives within leaves of white oak, Quercus alba. We found differential patterns of survival and larval feeding rate within the tree and in association with several abiotic factors: light levels, leaf nitrogen content, and canopy height. We suggest that the leaf scale microhabitat conditions are fundamental to plant-herbivore-enemy interactions because of the differential fitness effects on herbivores. Such effects would be missed by studies that average effects by whole plants. Our study population of C. hamadryadella is located within the Orland E. White State Arboretum of Virginia in Boyce, Virginia, USA.
Macro-habitat preferences by the African manatee and crocodiles – ecological and conservation implications
Authors: Luiselli L. , Akani G. C. , Ebere N. , Angelici F. M. , Amori G. , Politano E.
Published: September 2013

Abstract. African manatees (Trichechus senegalensis) and crocodiles are threatened species in parts of their range. In West Africa, crocodiles may constitute the main predators for manatees apart from humans. Here, we explore the macro-habitat selection of manatees and two species of crocodiles (West African crocodiles Crocodylus suchus and dwarf crocodile Osteolaemus tetraspis) in the Niger Delta (Nigeria), testing the hypotheses that (i) manatees may avoid crocodiles in order to minimize risks of predation, and (ii) the two crocodile species do compete. The study was carried out between 1994 and 2010 with a suite of different field techniques. We observed that the main macro-habitat types were freshwater rivers and coastal lagoons for manatees, mangroves for West African crocodiles, and rivers and creeks for dwarf crocodiles, with (i) the three species differing significantly in terms of their macro-habitat type selection, and (ii) significant seasonal influence on habitat selection of each species. Null models for niche overlap showed a significantly lower overlap in macro-habitat type use between manatee and crocodiles, whereas the two crocodiles were relatively similar. Null model analyses did not indicate any competitive interactions between crocodiles. On the other hand, manatees avoided macro-habitats where crocodiles, and especially West African crocodiles, are abundant.
Biomass explains the intensity of facilitative – not competitive – interactions: three intraspecific tests with annuals
Authors: Ariza C. , Tielbörger K.
Published: September 2013

Abstract. Despite efforts to discern the role of plant size in resource competition, the circumstances under which size-dependent plant-plant interactions occur are still unclear. The traditional assumption is that competition intensifies with increasing neighbour size. However, recent studies suggest that the size (biomass) dependence of competitive interactions is strongest at very low biomass levels and becomes negligible after a certain threshold neighbour biomass has been reached. We searched for the generality of such patterns for three common annual plant species in Israel. We monitored target and neighbour biomass along their entire lifecycle using an even-aged, intraspecific and intrapopulation competition screenhouse experiment under water-limited conditions. For all focal species, neighbour presence had a net negative effect on vegetative biomass at harvest. However, this was not explained by increasing neighbour biomass over time, as a consistent pattern of size-dependent facilitative, rather than competitive, interactions was observed at all life stages. We explain these observations in terms of co-occurring aboveground facilitation and dominant belowground competition for water. Since our findings are the first of their kind and contradict theoretical predictions of biomass dependence of net negative interactions, we advocate further experiments addressing size dependence in interactions among plants. In particular, theoretical models addressing size dependence of positive interactions must be developed.
The geography of high-value biodiversity areas for terrestrial vertebrates in Western Europe and their coverage by protected area networks
Authors: Assunção-Albuquerque M. J. T. , Rey Benayas J. M. , Albuquerque F. S. , Rodríguez M. Á.
Published: September 2013

Abstract. We identified high-value biodiversity areas (HVBAs) of terrestrial vertebrates according to a combined index of biodiversity (CBI) for each major taxon and a standardized biodiversity index (SBI) for all taxa in 2195 cells of 50 × 50 km in Western Europe to evaluate whether these areas are included in the current protected area networks. The World Database on Protected Areas (WDPA) and NATURA 2000 protected area network were used to assess the protected area cover in HVBAs. WDPA and NATURA 2000 were geographically quite complementary as WDPA is more densely represented in Central and Northern Europe and NATURA 2000 in the Mediterranean basin. A total of 729 cells were identified as HVBAs. From the total of these HVBA areas, NATURA 2000 network was present in more cells (660) than the WDPA network (584 cells). The sum of protected land percentages across all the HVBA cells was 28.8%. The identified HVBA cells according to the SBI included 603 or 78.2% of all vertebrate species in the study region, whereas the identified HVBA cells according to the SBI for individual taxa included 47 (90.4%) species of amphibians, 79 (74.5%) of reptiles, 417 (88.5%) of birds, and 130 (91.5%) of mammals. However, neither network was present in 7 or 3% of the identified HVBA cells. Thus, we recommend expanding protected areas in Europe to fill this gap and improve coverage of vertebrate species to strengthen biodiversity conservation.
Millipede and centipede (Myriapoda: Diplopoda, Chilopoda) assemblages in secondary succession: variance and abundance in Western German beech and coniferous forests as compared to fallow ground
Authors: Schreiner A. , Decker P. , Hannig K. , Schwerk A.
Published: September 2013

Abstract. Successional processes are an important element of commercial-forest ecosystems. They can be followed by studying the species composition of various animal groups, e.g. millipedes. Over the vegetation periods 2009 and 2010, we pitfall-trapped millipedes and centipedes (Myriapoda: Diplopoda, Chilopoda) on 21 Western German (North Rhine-Westphalian) deciduous and coniferous forest as well as fallow-ground sites of increasing age (1–165 yr) and determined them to the species and sex. Diplopoda (2009: 1659/2010: 3417 individuals) outnumbered the trapped Chilopoda (2009: 37/2010: 111 individuals) by far while the general catching results approximately doubled from 2009 to 2010. Indirect gradient analysis (CA) revealed that the influence of the habitat type on the formation of diplopod assemblages exceeded the influence of the successional stage. Although no clear trend in individual-count development over time occurred in most species detected, Julus scandinavius (Latzel, 1884) significantly increased in numbers with ageing of the deciduous (beech) forests. In conclusion, J. scandinavius may be a suitable bioindicator of deciduous-forest succession. More data are necessary to transfer our results into a mathematical function describing the course of increasing J. scandinavius abundance.
Effects of within-patch heterogeneity on connectivity in pond-breeding amphibians studied by means of an individual-based model
Authors: Pontoppidan M.-B. , Nachman G.
Published: September 2013

Abstract. The metapopulation framework presumes the habitat of a local population to be continuous and homogenous, and patch area is often used as a proxy for population size. Many populations of pond-breeding amphibians are assumed to follow metapopulation dynamics, and connectivity is mostly measured between breeding ponds. However, the habitat of pond-breeding amphibians is not only defined by the pond but, typically, consists of a breeding pond surrounded by clusters of disjoint summer-habitat patches interspersed with an agricultural/semi-urban matrix. We hypothesise that the internal structure of a habitat patch may change connectivity in two ways: (i) by affecting animal movements and thereby emigration and immigration probabilities; and (ii) by affecting habitat quality and population size. To test our hypotheses, we apply a spatially explicit individual-based model of Moor frog dispersal. We find that the realised connectivity depends on internal structure of both the target and the source patch as well as on how habitat quality is affected by patch structure. Although fragmentation is generally thought to have negative effects on connectivity, our results suggest that, depending on patch structure and habitat quality, positive effects on connectivity may occur.
How to decrease the negative effects of medium intensity disturbances on arthropod communities
Authors: Györffy G. , Körmöczi L.
Published: September 2013

Abstract. One of the major goals in nature conservation practice is to optimise the timing or the method of treatments or both. We studied the response of the Auchenorrhyncha (Insecta: Homoptera) assemblage to annual mowing in three different locations along an elevation gradient of a mesic grassland. Several weeks after mowing, the total number of imagoes and larvae decreased considerably, and the relative abundance differences between populations at different elevations also decreased, reflecting the density dependent effect of this treatment. The rate of changes in species composition was greatest in the microhabitats with more comfortable microclimates, in the opposite direction of the alteration of abundance, perhaps interfering with the migration. By the next spring the fauna of the wettest habitat proved to be the most sensitive to mowing and the most different from the others. The overall similarity of the insect communities increased, i.e. the community-level biodiversity decreased due to homogenising effect of mowing. In a heteromorphous habitat, the variability of spatio-temporal dynamics of the populations makes it impossible to find either single optimal time or optimal rotation plan for treatment based on the habitat types. For this reason, we suggest mowing in stripes parallel to the elevation gradient, which would mean synchronous treatment of each microhabitat instead of randomly chosen patches, where the execution is problematic. It is easier to keep the ratio of treated to untreated areas at 50%. Stripes should be narrow enough to provide the possibility of migration to favourable habitat patches, and should not hinder mechanical mowing. Suggested width of stripes is 10–15 m for Auchenorrhyncha.
Seedling diversity and spatially related regenaration dynamics in holly woodlands and surrounding habitats
Authors: Arrieta S. , Suárez F.
Published: September 2013

Abstract. Spatial patterns of seedling distribution and diversity were analysed in small fragments of holly Ilex aquifolium L. woodlands and in their surrounding areas. Two sampling locations with similar structure were selected for this study: Oncala and Robregordo. They consist of nearly monospecific Ilex stands surrounded by grasslands with high scrub abundance. The seedling appearance of woody species was quantified from March to November 1998. Sampled areas were: 1) closed holly canopy; 2) open holly canopy or small forest gaps; 3) holly woodland edge; 4) surrounding grassland; 5) under isolated fleshy-fruited shrubs scattered over the grassland; 6) under dry-fruited shrubs and 7) the closest forest to the holly woodland. Additionally, a pine forest at a distance of 20 km from Oncala was sampled. In every area ten permanent 50 × 50 cm quadrats were fixed for monthly seedling control. The highest germination density occurs under the holly woodland, especially in closed canopy areas. Nevertheless, these closed woodlands neither maintain a great quantity of surviving seedlings nor a high diversity. Seedling density is considerable in canopy gaps, shrubs and forest edge, and these habitats have greater diversity values than understorey habitats. Fleshy-fruited shrubs maintain higher seedling densities and diversity than dry-fruited shrubs. Woody seedlings are rare over the grassland. The three non-holly forests studied have very similar seedling densities and diversity values, higher than those under closed-canopy holly. Regional differences are important for the numbers of seedlings surviving from previous years, which are scareer in Robregordo. However, little difference is observed in spatial patterns of seedling diversity between the two locations. We discuss a number of processes affecting seed rain density and differential mortality rates that could account for these spatial patterns, namely competition for light inside the woodlands, facilitation under nurse shrubs, or competition escape at the edge. Environmental factors such as moisture stress may play a role in regional differences.
Modelling the extinction risk of isolated populations of natterjack toad Bufo calamita
Authors: Stephan T. , Ulbrich K. , Grosse W.-R. , Meyer F.
Published: September 2013

Abstract. Many local populations of the natterjack toad Bufo calamita in Germany are endangered. Due to the fragmentation and destruction of natural habitats by man, toads have often been forced to switch to secondary habitats. The permanent existence of these habitats is uncertain. Habitat and area requirements have been investigated in various parts of Germany in recent years. Our study uses field observations from sites in Halle (Saxony-Anhalt) and List (Schleswig-Holstein) as a basis for analyses of the population dynamics under different environmental conditions. Deterministic trends of these populations are calculated with the help of a Leslie matrix consisting of average parameters for mortality and reproduction. For a more thorough analysis we use a stochastic simulation model in order to assess survival probabilities of local toad populations. This model also takes into account environmental fluctuations affecting mortality and reproduction. Using scenarios from different locations, a sensitivity analysis of the parameters indicates which management options are the most promising to preserve a population. Our results indicate that the mortality rates of juveniles and the availability of spawning ground have the greatest influence on a population’s survival. Consequently, habitat management should focus on these aspects. In addition, we investigate the risk of extinction for different reproductive strategies. Natterjack toad populations observed in the field actually follow a strategy with three breeding periods. We find that this strategy supports the survival of the population better than strategies with less periods, which are more likely to result in a complete breeding failure during one season.
Modeling population dynamics of solitary bees in relation to habitat quality
Authors: Ulbrich K. , Seidelmann K.
Published: September 2013

Abstract. To understand associations between habitat, individual behaviour, and population development of solitary bees we developed an individual-based model. This model is based on field observations of Osmia rufa (L) (Apoideae: Megachilidae) and describes population dynamics of solitary bees. Model rules are focused on maternal investment, in particular on the female’s individual decisions about sex and size of progeny. In the present paper, we address the effect of habitat quality on population size and sex ratio. We examine how food availability and the risk of parasitism influence long-term population development. It can be shown how population properties result from individual maternal investment which is described as a functional response to fluctuations of environmental conditions. We found that habitat quality can be expressed in terms of cell construction time. This interface factor influences the rate of open cell parasitism as the risk for a brood cell to be parasitized is positively correlated with the time of its construction. Under conditions of scarce food and under resulting long provision times even low parasitism rates lead to a high extinction risk of the population, whereas in rich habitats probabilities of extinction are low even for high rates of parasitism. For a given level of food and parasitism there is an optimum time for cell construction which minimizes the extinction risk of the population. Model results demonstrate that under fluctuating environmental conditions, decreasing habitat quality leads to a decrease in population size but also to rapid shifts in sex ratio.
Geometrical consideration for evaluation of reserve design
Authors: Bogaert J. , Salvador-Van Eysenrod D. , Van Hecke P. , Impens I.
Published: September 2013

Abstract. The edge effect, generated by the interaction of patch and matrix, is preferably described by the interior-to-edge ratio of the patch. This ratio quantifies the extent of microclimatic changes at the boundary, and influences nature reserve design. As shown for elliptical and rectangular shapes, large and isodiametric patch designs are characterized by high interior-to-edge ratios. Different patch geometries can however lead to similar values of the ratio. A reference value, based upon the patch size, is therefore proposed to normalize the ratio to its maximum value, as observed for a perfectly isodiametric patch. The effect of patch geometry on the normalized ratio is discussed, as well as patch ranking based upon both the simple ratio and the normalized interior-to-edge ratio. An example is included using forest patches in the Belgian Campine region to illustrate the usefulness of the proposed index.
Irregular flowering patterns in terrestrial orchids: theories vs. empirical data
Authors: Kindlmann P. , Balounová Z.
Published: September 2013

Abstract. Empirical data on many species of terrestrial orchids suggest that their between-year flowering pattern is extremely irregular and unpredictable. A long search for the reason has hitherto proved inconclusive. Here we summarise and critically review the hypotheses that were put forward as explanations of this phenomenon: irregular flowering was attributed to costs associated with sexual reproduction, to herbivory, or to the chaotic behaviour of the system represented by difference equations describing growth of the vegetative and reproductive organs. None of these seems to explain fully the events of a transition from flowering one year to sterility or absence the next year. Data on the seasonal growth of leaves and inflorescence of two terrestrial orchid species, Epipactis albensis and Dactylorhiza fuchsii and our previous results are then used here to fill gaps in what has been published until now and to test alternative explanations of the irregular flowering patterns of orchids.
Canopy gap edge determination and the importance of gap edges for plant diversity
Authors: Salvador-Van Eysenrode D. , Kockelbergh F. , Bogaert J. , Impens I. , Van Hecke P.
Published: September 2013

Abstract. Canopy gaps, i.e. openings in the forest cover caused by the fall of structural elements, are considered to be important for the maintenance of diversity and for the forest cycle. A gap can be considered as a young forest patch in the forest matrix, composed of interior surrounded by an edge, both enclosed by a perimeter. Much of the attention has been focused on the gap interior. However, at gap edges the spectrum of regeneration opportunities for plants may be larger than in the interior. Although definitions of gap are still discussed, any definition can describe it in an acceptable way, if justified, but defining edges is complicated and appropriate descriptors should be used. A method to determine gap interior and edge, using light as a descriptor, is presented with an example of gaps from a beech forest (Fagus sylvatica) in Belgium. Also, the relevance and implications of gap edges for plant diversity and calculation of forest turnover is discussed.
Incorporating multiple ecological criteria in classical zero one selection algorithms
Authors: Memtsas D. P. , Dimitrakopoulos P. G. , Troumbis A. Y.
Published: September 2013

Abstract. Avifauna on Greek wetland sites is used as a model for the implementation of the Set Covering Problem in selecting nature reserves. Three site conservation values, which depend on species presence, are used as selection criteria. Their calculation is based upon species richness, species rarity and species-danger status. The conservation values must be inserted in the linear programming problem’s objective function by the form of weighting factors. Optimal solutions according to the three ecological criteria are produced. These solutions belong to the set of alternative optimal solutions of the basic Set Covering Problem with no other criterion taken into account except that of the whole species-list coverage. The set of alternative optimal solutions is generated by the explicit exclusion method. The relative value of goal programming and weighing up-criteria methods in producing a unique solution based on the three criteria simultaneously is assessed. Both methods coincide with the same alternative solution that is thus regarded as the final optimal one incorporating all the three ecological criteria.
Qualitative models to predict impacts of human interventions in a wetland ecosystem
Authors: Loiselle S. , Hull V. , Permingeat E. , Falucci M. , Rossi C.
Published: September 2013

Abstract. The large shallow wetlands that dominate much of the South American continent are rich in biodiversity and complexity. Many of these undamaged ecosystems are presently being examined for their potential economic utility, putting pressure on local authorities and the conservation community to find ways of correctly utilising the available natural resources without compromising the ecosystem functioning and overall integrity. Contrary to many northern hemisphere ecosystems, there have been little long term ecological studies of these systems, leading to a lack of quantitative data on which to construct ecological or resource use models. As a result, decision makers, even well meaning ones, have difficulty in determining if particular economic activities can potentially cause significant damage to the ecosystem and how one should go about monitoring the impacts of such activities. While the direct impact of many activities is often known, the secondary indirect impacts are usually less clear and can depend on local ecological conditions. The use of qualitative models is a helpful tool to highlight potential feedback mechanisms and secondary effects of management action on ecosystem integrity. The harvesting of a single, apparently abundant, species can have indirect secondary effects on key trophic and abiotic compartments. In this paper, loop model analysis is used to qualitatively examine secondary effects of potential economic activities in a large wetland area in northeast Argentina, the Esteros del Ibera. Based on interaction with local actors together with observed ecological information, loop models were constructed to reflect relationships between biotic and abiotic compartments. A series of analyses were made to study the effect of different economic scenarios on key ecosystem compartments. Important impacts on key biotic compartments (phytoplankton, zooplankton, ichthyofauna, aquatic macrophytes) and on the abiotic environment (nutrients and sediment resuspension) were observed through model analysis. These models results do not indicate a definite relationship between activity and a possible impact, but a potential impact that can be further studied and modelled. Likewise, the model is not intended to be an end in itself, but as a tool to help focus further ecological study, monitoring and modelling. In the real world of wetland management, it is not always possible to conduct extensive (and expensive) analysis of all the principal ecological compartments. In the same manner, the construction of larger and more complex models for resource management usually needs to be focused to those areas most likely to effect resource quality or ecosystem functioning. In this light, the development of qualitative models was considered as a first step to help researchers and decision makers focus their efforts (and economic resources) in an intensive ecological sampling programme and the construction of predictive models.
Analysis of adaptive foraging in an intraguild predation system
Authors: Okuyama T. , Ruyle R. L.
Published: September 2013

Abstract. An intraguild predation (IGP) system with adaptive foraging behavior was analyzed using a simple mathematical model. The main aim was to explore how the adaptive behavior affects species interactions as well as how such interactions derived from adaptive behavior affect community stability. The focal system contained top predators, intermediate predators, and basal prey. Intermediate predators exhibit antipredator behavior and balance costs (e.g. perceived predation risk) and benefits (e.g. resource intake) to determine their foraging effort. Density-dependent foraging behavior with the unique connectance of the IGP food web created unusual species interactions. Notably, increased prey density can transmit negative indirect effects to top predators while increased top predator density transmits positive indirect effects to prey population. The nature of these interactions is density-dependent. The results suggest that both IGP (as opposed to linear food chain) and adaptive foraging behaviors may strongly influence community dynamics due to emergent interactions among direct effects and indirect effects. Furthermore, the adaptive foraging of intermediate predators may stabilize the community as a whole.
Trends in the evolution of ecology: “Spain is different”
Authors: Cordero Rivera A.
Published: September 2013

Abstract. During the last fifty years ecology has matured as a scientific discipline. In this paper I analyse the temporal development of the paradigm based on physical systems (the ecosystem paradigm), and the evolutionary ecology paradigm. I first analyse the contents of 61 textbooks to calculate the relative importance of ecosystem and evolutionary ecology in the training of new generations of ecologists. Results indicate that the evolutionary approach is becoming more important since 1980, and now most textbooks dedicate 10–20% of their pages to evolutionary concepts. In a second analysis I searched the names of ecology departments in universities around the world, and found out conspicuous differences between USA, where 43% of addresses associate ecology and evolution or behaviour on the same department, and Europe, where only 10% of ecology departments also include a reference to evolution or behaviour in their name. In both analyses Spain seems to follow only the ecosystem paradigm, because Spanish textbooks dedicate almost no pages to evolutionary concepts, and there is not a single university department that includes ecology and evolution. A further bibliometric study confirmed that Spanish ecologists prefer to publish their research in general ecology journals, and are under-represented in evolutionary ecology journals. I discuss the importance of historical factors on the development of paradigms of ecology, and the special case of Spain, likely due to the influence of pioneers working in oceanography, limnology and geography.