Reduced Species Richness Research Articles

Rural agricultural regions and sustainable development: a case study of the Allgäu region in Germany

Since the United Nations Conference on Environment and Development in 1992 in Rio de Janeiro, sustainable development became an important issue. Sustainable development often focuses on a single sector or parameter such as tourism, energy supply, water management, different aspects of nature conservation, or economy. In this paper, we provide a comprehensive picture of the development of a region since the Middle Ages and discuss whether this development can be evaluated as socially, economically and ecologically sustainable. We carried out a combined qualitative–quantitative assessment where we use quantitative data and indicators when available, as well as literature sources and expert knowledge from the region for a qualitative assessment. We judge that generally a sustainable development in the Allgau region can be found, although also some critical points and contentious issues exist. An overall good economic and income situation for most people, the good ecological conditions and rich biodiversity, the relatively well-established social structure, as well as the identity of the people with the region and comparatively low social discrepancy, can be positively stated. In contrast, different actual and future threats exist such as new or planned infrastructure, increasing traffic or tourism activities in certain areas that degrade habitats and reduce species richness, intensification of agriculture in certain areas, but also abandonment of agriculture in other areas, loss of traditions and customs, and declining numbers of smallholders. The objective for the region would be to minimise these negative impacts and reinforce positive trends to assure the sustainable development of the Allgau.

Comparison of Fish Communities at Random and Nonrandom Locations in a Sand‐Bed River

AbstractSurveys based on nonrandom site selection, or convenience samples, are often a necessary part of large‐scale monitoring programs to help minimize costs. The reliability of convenience samples to inform managers about distributions or population status of imperiled species is questionable, however, because the samples may not be representative of the whole population. We compared fish community data from 20 nonrandom, long‐term monitoring sites for Rio Grande Silvery Minnow Hybognathus amarus with those from 20 randomly chosen samples collected during two surveys (one in summer, one in autumn) in the Rio Grande, New Mexico. We compared the species richness, community composition, and the catch per unit effort (CPUE). Fish species compositions, which were similar between both sets of summer and autumn surveys, were nearly identical in the autumn surveys. Similarly, we found consistent Rio Grande Silvery Minnow CPUE between surveys; summer random surveys estimated 0.32 fish/100 m2 sampled, whereas summer nonrandom surveys estimated 0.37 fish/100 m2 sampled. In autumn, both surveys showed a marked decline in Rio Grande Silvery Minnow; random surveys found 0.08 fish/100 m2 sampled (95% confidence interval 0.04–0.18), whereas the nonrandom surveys failed to collect any Rio Grande Silvery Minnow. Both surveys showed a reduction in species richness between summer and autumn with a corresponding increase in dominance by Red Shiner Cyprinella lutrensis and a decline in Rio Grande Silvery Minnow. We failed to find any meaningful differences in either fish community or Rio Grande Silvery Minnow CPUE between random and nonrandom sites, suggesting that the long‐term, nonrandom locations currently used to monitor the Rio Grande Silvery Minnow population are representative of the middle Rio Grande. We believe our results are applicable to many monitoring programs in systems with a homogeneous distribution of mesohabitats; nonetheless, we recommend that managers assess potential bias in monitoring programs based on convenience samples.

Wetland Conservation in the Gulf of Mexico: The Example of the Salt Marsh Morning Glory, Ipomoea sagittata

Global climate change will have major effects on wetlands, ecosystems with elevated biodiversity and of enormous economic importance. Using ecological niche modeling and genetic data from three plastid DNA markers sequenced from 96 plants, we studied the salt marsh morning glory, Ipomoea sagittata, to understand the impact that future global warming and increasing sea level may have on aquatic plant conservation, distribution and genetic connectivity on the Gulf of Mexico. Data suggest that genetic variation is low and lacks structure; probable causes include high gene flow, clonal reproduction or use of ineffective molecular markers. Global warming models for its potential distribution in the year 2080 predict a loss of suitable habitat in its northern inland distribution (Cuatro Cienegas Basin), while its coastal and southern habitats increase. Genetic connectivity decreases along the coast owing to a rise in sea level (Yucatan, Laguna Madre Basin, Usumacinta Basin). Three zones are identified, each requiring a different conservation strategy: 1) A saltwater intrusion zone where most protected areas are; 2) A stability zone which may offer optimal conditions for the creation of protected areas; 3) A zone of range expansion that may cause ecological instability, reducing species richness and promoting colonization by opportunistic species.

Effects of habitat loss on taxonomic and phylogenetic diversity of understory Rubiaceae in Atlantic forest landscapes

Habitat loss has been long recognized as a major driver of the current species extinction crisis, but to date few studies have estimated deforestation thresholds above which biodiversity negatively respond to the changes in landscape configuration. In this study, we used a very representative understory plant family (Rubiaceae) to evaluate the effects of forest cover reduction in the landscape on taxonomic and phylogenetic alpha and beta diversity, species originality, and composition. We selected nine Atlantic forest sites in southern Bahia, Brazil, immersed in landscapes ranging from 9% to 71% of remaining forest cover. We established a 50×100m plot in each site and identified all the Rubiaceae individuals. Forest cover reduction at the landscape scale is strongly and negatively related to the number of individuals, species, and genera of Rubiaceae. Our model predicts that every 10% decreasing in landscape forest cover results in the loss of about three species and 74 individuals of understory Rubiaceae. Canopy openness at the plot level increased linearly with the decrease of forest cover in the landscape. A trend of linear decrease of the phylogenetic diversity with the loss of forest cover was also observed, increasing the co-occurrence of close relatives in more deforested landscapes. Furthermore, we found a reduction in the presence of species with higher values of originality along the gradient of forest cover, as a consequence of species richness reduction. Regardless of the geographical distances, areas with similar values of forest cover were different in composition (β-diversity) and phylogenetic relationship (phylogenetic β-diversity), indicating that even highly deforested landscapes contribute to the regional diversity. We concluded that less forested areas are losing species richness and diversity, and as a consequence species originality, and presenting a general trend of phylogenetic impoverishment at the landscape scale. However, regional conservation initiatives should take all landscapes into account, because they all contribute to taxonomic and phylogenetic beta diversity, to ensure the long-term protection of the irreplaceable evolutionary history of Rubiaceae and the numerous organisms it supports.

Species richness loss after nutrient addition as affected by N:C ratios and phytohormone GA3contents in an alpine meadow community

Aims From the light-competition hypothesis, competition for light is asymmetric and the observed increases in plant-size variability with increasingly denser canopies are primarily due to competition for light. Greater plant height provides pre-emptive access to light and produces increased height differences among species. The question is what produces these differences in plant height or height growth response among species in response to fertilization. Methods In 2009, a field experiment of N, P and N + P enrichments at three levels each was initiated in an alpine meadow on the northeast Qinghai- Tibet Plateau. Effects of fertilization on species richness, aboveground net primary production (ANPP), relative light intensity and plant height of different plant functional groups were determined. Festuca ovina (grass), Kobresia humilis (sedge), Oxytropis ochrocephala (legume), Taraxacum lugubre (rosette forb) and Geranium pylzowianum (upright forb) were selected as exemplars of each of the indicated functional groups. The N: C ratios in aboveground biomass, gibberellic acid (GA3) concentrations in leaves, plant heights and height relative growth rate (RGR) of these exemplar species were analyzed in detail. Important Findings Species richness of grasses significantly increased with increasing N + P levels. Species richness of legumes and upright forbs decreased after N and N + P additions. P addition had no significant effect on species richness. The effects of N + P addition on species richness and ANPP were consistently stronger than those of the single N or P fertilization. Reductions in species richness caused by nutrient addition paralleled the increases in ANPP and decreases in light intensity under the canopies, indicating indirect effect of nutrient addition on species richness via ANPP-induced light competition. The exemplar species that responded most positively to fertilization in height and RGR also displayed stronger increases in their GA3 content and N:C ratios. GA3 concentrations and N: C ratios were positively correlated with height RGR when the data were pooled for all species. The tallest and the fastest-growing grass, F. ovina, had the largest increase in N: C ratios and the highest leaf GA3 concentrations after nutrient addition. These results indicated that differential responses of GA3 concentrations and N: C ratios to fertilization were related to the inequality in plant heights among species.

Between‐species facilitation by male fig wasps in shared figs

1. Facilitation is recorded from diverse plant–insect interactions, including pollination and herbivory.2. The significance of facilitation resulting from the behavior of males of multiple fig wasp species inside figs was investigated. Female fig wasps emerge from natal figs via exit holes dug by males, especially male pollinators. When no males are present, the females struggle to escape and may die.3. Ficus microcarpa L. is a widely‐established invasive fig tree from Southeast Asia. Its pollinator is absent in South Africa, so the tree cannot reproduce, but two Asian non‐pollinating fig wasps (NPFW) Walkerella microcarpae and Odontofroggatia galili occupy its figs. Abundance patterns of the two NPFW and the proportion of male‐free figs in South Africa, Spain (where the pollinator is introduced), and in China, where the native fig wasp community is diverse, were compared to determine the consequences of reduced species richness for insect survival.4. Female fig wasps in male‐free figs were found to be trapped, and small clutch sizes contributed to the absence of males in both species. The presence of pollinators in Spain allowed most NPFW to develop in figs containing males. Far more male‐free figs were present in South Africa, elevating mortality rates among female NPFW. Facilitation of female release by males of other NPFW species nonetheless benefitted the rarer species.5. Selection pressures in South Africa currently favour greater aggregation of NPFW offspring and/or less female biased sex ratios.

Local and landscape management drive trait-mediated biodiversity of nine taxa on small grassland fragments

Aim Biodiversity across the globe is heavily eroded by intensified management at local and landscape scales. Species communities of calcareous grasslands, which are among Europe's most diverse habitats, are severely threatened by the cessation of appropriate traditional management, loss of habitat connectivity and simplification of the surrounding landscape. However, our understanding of these often interrelated factors remains limited, in particular for trait-mediated responses across taxa. Here, we test the independent effects of local management (grazing, mowing and abandonment), habitat connectivity (measured by a connectivity index) and landscape complexity (indicated by the percentage of arable land) on nine taxa: plants, butterflies, bees, grasshoppers, hoverflies, spiders, true bugs, rove beetles and leafhoppers on small semi-natural calcareous grassland remnants (< 1 ha). Location Central Germany. Methods We use a joint analysis across taxa to identify general and trait-mediated responses (body size and Red List status) in species richness, abundance and community composition. Results We identified three key drivers of local diversity patterns: First, an increasing proportion of arable land from 10% to 80% led to a 29% loss of overall species richness. Second, despite differences between taxa, increasing habitat connectivity generally enhanced species richness. Connectivity effects were more accentuated in the large species per taxon, which can be expected to be good dispersers. Finally, grazing reduced species richness and abundance much more than annual mowing or short-term abandonment (5–15 years), in particular for red-listed species. We attribute this to plant resource removal through overgrazing and trampling. Main conclusions For the conservation management of small calcareous grasslands, we advocate an alternating strategy of mowing or lenient grazing and short-term abandonment, prioritizing connected fragments surrounded by diverse landscapes. Despite taxon-specific responses, our study across nine taxa demonstrates universal, trait-mediated effects of management, landscape complexity and connectivity on local biodiversity in fragmented communities.

Plantations, not farmlands, cause biotic homogenisation of ground-active beetles in south-eastern Australia

Following landscape change, species invasions and extinctions may lead to biotic homogenisation, resulting in increased taxonomic and functional similarity between previously distinct biotas. Biotic homogenisation is more likely to occur in landscapes where the matrix contrasts strongly with native vegetation patches. To test this, we examined the distribution of ground-active beetles in a landscape of remnant Eucalyptus open woodland patches where large areas of lower contrast matrix (farmland) are being transformed to high-contrast pine plantations in south-eastern Australia. We sampled beetles from 30 sites including six replicates of five categories; (1) remnants adjacent to farmland, (2) remnants adjacent to plantation, (3) farmland, (4) plantation, and, (5) remnants between pine plantation and farmland. Community composition in the pine matrix was similar to native patches embedded in pine (ANOSIM, Global R=0.49, P<0.000), which we suggest is due to biotic homogenisation. Remnant patches with edges of both farmland and pine plantation did not represent an intermediate community composition between patches surrounded by either matrix type, but rather a unique habitat with unique species. Farmland supported the greatest number of individuals (F=9.049, df=25, P<0.000) and species (F=5.875, df=25, P=0.002), even compared to native remnant patches. Our results suggest that matrix transformations can reduce species richness and homogenise within-patch populations. This may increase the risk of species declines in fragmented landscapes where plantations are not only replacing native vegetation patches, but also other matrix types that may better support biodiversity. Our findings are particularly concerning given expanding plantation establishment worldwide.

Effects of Aminopyralid on California Annual Grassland Plant Communities

AbstractAminopyralid is the most commonly used herbicide for the control of yellow starthistle and other invasive thistles in annual grasslands of California. Although the effects of aminopyralid on native plant communities over a 2-yr period have been evaluated in prairies dominated by perennial species in the northern central states, similar evaluations have not been conducted in grassland communities of California, which are generally composed of a high diversity of native and nonnative annual species. In this study we monitored the effects of 53 and 123 g ae aminopyralid ha−1on individual species cover and species richness over three growing seasons in two locations on California annual grassland. Treated plots were compared to untreated plots in randomized complete-block designs. Results were largely consistent between the two trials. In the first season after treatment, both rates of aminopyralid reduced dicot cover significantly, particularly members of the Asteraceae and Fabaceae. Treated plots also showed reduced species richness. However, these differences were less pronounced in the second season after treatment, particularly at the low rate. By the third season after treatment in both sites, there were no longer any significant effects on cover or species richness at the low herbicide rate. On California annual grasslands, winter applications of low rates of aminopyralid have been shown to give excellent control of yellow starthistle, providing long-term benefits to grassland ecosystems. Results of the current study suggest that negative impacts of aminopyralid on the desirable native forb community are transitory.

Using species richness and functional traits predictions to constrain assemblage predictions from stacked species distribution models

AbstractAimModelling species distributions at the community level is required to make effective forecasts of global change impacts on diversity and ecosystem functioning. Community predictions may be achieved using macroecological properties of communities (macroecological models, MEM), or by stacking of individual species distribution models (stacked species distribution models, S‐SDMs). To obtain more realistic predictions of species assemblages, the SESAM (spatially explicit species assemblage modelling) framework suggests applying successive filters to the initial species source pool, by combining different modelling approaches and rules. Here we provide a first test of this framework in mountain grassland communities.LocationThe western Swiss Alps.MethodsTwo implementations of the SESAM framework were tested: a ‘probability ranking’ rule based on species richness predictions and rough probabilities from SDMs, and a ‘trait range’ rule that uses the predicted upper and lower bound of community‐level distribution of three different functional traits (vegetative height, specific leaf area, and seed mass) to constrain a pool of species from binary SDMs predictions.ResultsWe showed that all independent constraints contributed to reduce species richness overprediction. Only the ‘probability ranking’ rule allowed slight but significant improvements in the predictions of community composition.Main conclusionsWe tested various implementations of the SESAM framework by integrating macroecological constraints into S‐SDM predictions, and report one that is able to improve compositional predictions. We discuss possible improvements, such as further understanding the causality and precision of environmental predictors, using other assembly rules and testing other types of ecological or functional constraints.

Cushion plants can have a positive effect on diversity at high elevations in the Himalayan Hengduan Mountains

AbstractQuestionsWhat is the community‐level consequence of biotic processes, in particular the importance of facilitation, in determining patterns of diversity in alpine plant communities of the Himalayan Hengduan Mountains? Does facilitation intensity change with environmental severity, and are these changes due to environmental severity or nurse trait effects?LocationEleven alpine plant communities dominated by cushion plants in the Himalayan Hengduan Mountains, within the mountain system of south‐central China.MethodsWe determined plant species richness and abundance in habitats created by cushions and cushion‐free areas, and assessed the cushion effects on species richness and abundance with rarefaction curves and the relative interaction index, respectively. We examined the relationship between cushion effects on diversity and habitat severity and tested if changes in the net cushion effects along the severity gradient were due to a change in the performance of species without cushions (environmental severity effect) and/or with cushions (nurse trait‐mediated effect).ResultsThe presence of cushion plants increased species richness and abundance in most studied plant communities. The net facilitation effect of cushions increased with increasing habitat severity, an effect that could be attributed mainly to a reduction in species richness in cushion‐free areas with increasing severity. However, the changes in magnitude of facilitation of particular cushion species growing in high and low severity habitats could be attributed to both environmental severity and neighbour trait effects. Despite the overall positive effect of cushion plants on plant species richness, not all cushion species contributed to higher species richness. The deviation of individual cushion species from the general pattern of increasing facilitation with increasing severity indicated the species specificity of facilitation depends on the traits of nurse species.ConclusionThe presence of cushion plants generally increased species richness in alpine plant communities of the Himalayan Hengduan Mountains, with the importance of the cushion effect increasing with habitat severity due to a buffering effect by cushions of the negative effect of habitat severity on species richness observed in cushion‐free areas. This indicates the pivotal role of facilitative interactions among plant species in supporting high diversity in these severe environments.

Climate moderates release from nutrient limitation in natural annual plant communities

AbstractAimTo assess the combined influences of nutrient enrichment, invasive species and climate on assembly processes in natural annual plant communities.LocationSouth‐west Western Australia.MethodsA comprehensive survey of winter annual plant communities (more than a thousand communities sampled in total) was undertaken across a natural moisture availability gradient in phosphorus (P)‐limited York gum woodlands exposed to different levels of anthropogenic P enrichment. Three key functional traits (height, seed mass and specific leaf area) were measured incorporating intraspecific variation. Community richness, dominance of exotic species and trait distributions were investigated along local nutrient and regional climate gradients using hierarchical linear models. Results were assessed against expectations of moisture‐regulated release from nutrient limitation based on trade‐off theories and experimental findings of synergistic water and nutrient effects.ResultsConsistent with theoretical expectations, we identified significant interactions between local P levels and regional moisture availability for many of the response variables examined. Specifically, in communities exposed to both high P and high moisture we found: (1) reduced species richness, (2) high dominance of exotic species, (3) increases in community mean trait values and (4) strongly narrowing trait ranges. These results are consistent with competitive exclusion (via light competition). In naturally low‐P situations we also identified shifting trait distributions and narrowing ranges as moisture stress increased, a finding consistent with environmental filtering.Main conclusionIn this P‐ and water‐limited system, plant community responses to P enrichment are contingent on regional moisture availability in a non‐additive fashion. The most dramatic changes are seen under high‐P and high‐moisture conditions, i.e. where productivity is high and light has become a major limiting resource. By empirically validating theory, this study enhances our ability to predict ecological responses to multifaceted drivers of global change.

Effects of terrestrial–aquatic connectivity on an estuarine turtle

AbstractAimEstuaries world‐wide have been modified or fragmented due to human stressors in their terrestrial and aquatic components. Estuary fragmentation often results in reductions in species richness, diversity and connectivity. Effects of human modification on estuaries have been well studied, but less is known about how land use alters connectivity of the terrestrial–aquatic ecotone. We studied the relationship between terrestrial–aquatic connectivity and the distribution of an estuarine turtle, diamondback terrapin (Malaclemys terrapin).LocationChesapeake Bay, Virginia, USA.MethodsWe conducted diamondback terrapin surveys at 165 sites from late spring to mid‐summer in 2012 and 2013. We evaluated associations between terrapin occurrence, land use, salt marsh, shoreline armouring and crabbing intensity in concentric–circular neighbourhoods ranging from 0.27 to 2 km to cover daily and annual terrapin movements. We used occupancy modelling and model averaging to identify key terrestrial and aquatic variables explaining heterogeneity in terrapin occupancy. We evaluated the final model with an independent data set and identified occurrence thresholds for key variables.ResultsDiamondback terrapin occupy areas with ≥ 10% of marsh within a 750‐m neighbourhood, ≤ 17% armoured shoreline within a 1‐km neighbourhood, ≤ 20% of agriculture within a 500‐m neighbourhood, ≤ 33% low‐density housing within a 270‐m neighbourhood and ≤ 9 active crab pots within a 270‐m neighbourhood. Our model performed well when evaluated with an independent data set.Main conclusionsWe are the first to identify thresholds and quantify negative associations between the distribution of diamondback terrapin and alterations to terrestrial–aquatic connectivity from land development, shoreline armouring, and fishing activity. Because diamondback terrapin responses are reflective of changes in coastal habitats, especially marshes, terrapin occurrence can be used to direct wetlands conservation and restoration efforts.

Impacts of climate change on distributions and diversity of ungulates on the Tibetan Plateau.

Climate change has significant impacts on species' distributions and diversity patterns. Understanding range shifts and changes in richness gradients under climate change is crucial for conservation. The Tibetan Plateau, home to wild yak, chiru, and kiang, contains a biome with many endemic ungulates. It is highly sensitive to climate change and a region that merits particular attention with regard to the impacts of global climate change on its biomes. Maximum entropy approaches were used to estimate current and future potential distributions, in response to climate change, for 22 ungulate species. We used three general circulation (MK3, HADCM3, MIROC3_2-MED) and three emissions scenarios (Bl, A1B, A2) to derive estimated future measurements of 14 environmental variables over three time periods (2020, 2050, 2080), and then modeled species distributions using these predicted environmental measurements for each time period under two dispersal hypotheses (full and zero, respectively). This resulted in a total of 6160 prediction models. We found that these ungulates, on average, may lose 30-50% of their distributional areas, depending on the dispersal scenarios. In addition, 55-68% of the ungulate species were predicted to become locally endangered under the different dispersal assumptions, 23-32% to become locally critically endangered, and 4-7 endemic species to become globally endangered. Furthermore, ungulate species ranges may experience average poleward shifts of ~300 km. We also predict west-to-east reductions in species richness: southeastern mountainous areas currently have the highest species richness, but are predicted to face the greatest diversity losses, whereas the northern areas are predicted to see increasing numbers of ungulate species in the 21st century. Our study indicates much more severe range reductions of ungulates on the Tibetan Plateau than those anticipated elsewhere in the world, and species richness patterns will change dramatically with climate change. For conservation, we suggest (1) securing existing protected areas, and (2) establishing new nature reserves to counterbalance climate change impacts.

Zoned selective coppice – A management system for graded forest edges

Graded forest edges with low shrubs at the periphery and increasingly higher shrubs and trees towards the interior are often considered ideal in urban and infrastructure environments. They provide high biodiversity, filter and shelter functions, aesthetic appeal and recreation values, while keeping potentially hazardous trees away from railways, houses, roads and power-lines. This short communication presents zoned selective coppice (ZSC) as a novel management system for developing and sustaining species-rich forest edges with graded profile. ZSC is based on threshold height decreasing stepwise from the inner through the middle to the outer edge zone, resulting in height and density gradients over the edge cross-section. Preliminary results from simulation and implementation of ZSC in a controlled trial in 14 unmanaged edge sections 20 years after planting showed that the trend towards abrupt edge profiles was reversed and the strong spatial regularity of the original planting reduced. Most edge sections approached complete spatial randomness after only one coppicing operation and woody species diversity increased, without reducing species richness. While these results are based on one management operation, the controlled trial enables future long-term monitoring of how edge profile and species diversity are affected by repeated ZSC operations.

A preliminary survey of the diversity of soil algae and cyanoprokaryotes on mafic and ultramafic substrates in South Africa

Despite a large body of work on the serpentine-substrate effect on vascular plants, little work has been undertaken to describe algal communities found on serpentine soils derived from peridotite and other ultramafic rocks. We report a preliminary study describing the occurrence of algae and cyanoprokaryotes on mafic and ultramafic substrates from South Africa. Results suggest that slope and aspect play a key role in species diversity and community composition and, although low pH, nutrients and metal content do not reduce species richness, these edaphic features also influence species composition. Further, typical soil genera such as Leptolyngbya, Microcoleus, Phormidium, Chlamydomonas, Chlorococcum and Hantzschia were found at most sites. Chroococcus sp., Scytonema ocellatum, Nostoc linckia, Chlorotetraedron sp., Hormotilopsis gelatinosa, Klebsormidium flaccidium, Pleurococcus sp. and Tetracystis elliptica were unique to one serpentine site. The preliminary survey provides directions for future research on the serpentine-substrate effect on algal and cyanoprokaryote diversity in South Africa.

Habitat urbanization and its effects on birds

By transforming landscapes, human activity creates new types of habitats with altered environmental characteristics that never existed before. As the process of habitat urbanization bears impact on more and more natural habitats, it is essential for us to understand the changes we bring forth in the ecological forces shaping urban animal communities. Birds are perhaps the most frequently studied model organisms by urban ecologists. It is a well known general pattern that urban avian communities have typically reduced species richness, while the density of a few successful species is often higher in cities than in adjacent more natural habitats. But it is less understood which mechanisms generate and uphold these community-level changes. In this review we discuss the most important components of the urban environment influencing birds’ physiology, behaviour or morphology, and compile several recent studies to illustrate their effects. To understand urban food webs we also review the results of bottom-up and top-down approach which suggest that altered food availability and predation may play key roles in forming recent urban bird communities. We encourage future research to focus more on experimental, manipulative studies, that would help us not just to realize general patterns but shed more light on the mechanisms, the underlying processes prompting changes in urban bird communities.

Does the recent pool of benthic foraminiferal tests in fjordic surface sediments reflect interannual environmental changes? The resolution limit of the foraminiferal record

Benthic foraminifera tests (living + dead) and conductivity, temperature and depth (CTD) records in Hornsund Fjord (SW Spitsbergen) were studied over five non-consecutive summer seasons during 2002–2011. The data indicated significant changes in the abundance of benthic foraminifera, species composition and the variability of hydrological and micro-environmental conditions in this fjord. The increased inflow of Atlantic Water (AW) resulted in higher foraminiferal biodiversity and a greater number of rare species; however, many of these were fragile and were thus poorly preserved in the sediment. Cold years significantly reduced species richness in the fjord centre, while more stable hydrological conditions with a predominance of opportunistic foraminifera were noted at the fjord head. Elphidium excavatum f. clavata and Cassidulina reniforme exhibited sensitivity to salinity changes and food supply. The dynamic foraminiferal response to hydrological changes led to the conclusion that the annual foraminiferal flux, compounded by the poor preservation of fragile individuals, significantly changed the spatial and interannual composition of the foraminiferal tests remaining in the sediment. Furthermore, only mature individuals are representative of yearlong or multi-year fjord conditions, since the juveniles that bloom during their maximum growth periods in spring can die out under poor summer and winter conditions. The findings of this study indicated that the upper 8 cm of the sediment in the intense depositional systems of the Svalbard fjords provide good representation of recently departed benthic foraminifera, because of their mobility in surface sediments and further sediment compaction. Hence, the corresponding 10- to 15-year resolution in palaeoceanographic investigations seems to be the most reliable.

Managing cattle grazing and overstorey cover for the conversion of pine monocultures into mixedMediterranean woodlands

AbstractQuestionA large proportion (70%) of coniferous forest area in Israel is used for livestock grazing. Recently, the possibility of managing these monospecific plantations to form mixed conifer–broad‐leaved woodlands via natural regeneration processes has been considered. In light of this we pose the question, how does the interaction of cattle grazing and overstorey thinning (hereafter, thinning) affect natural regeneration in east Mediterranean pine plantations?LocationMenashe region, Mediterranean Israel (rainfall = 600 mm·yr−1).MethodsThe experiment was carried out in a mature (50 yr)Pinus brutiaplantation. Ten plots (0.25 ha) were selected, representing thinned (five plots, ≈100 trees·ha−1, leaf area index,LAI≈3) and non‐thinned (five plots, ≈230 trees·ha−1,LAI≈6) forest patches. Paired 100‐m2subplots were positioned within each plot, one of which was fenced to exclude cattle grazing while the other remained available for grazing. Recruitment, growth and shoot water potential of pines and broad‐leaved tree species were measured after 10 yr of grazing exclusion.ResultsThe density of newly emerged (up to 3‐mo‐old) pine seedlings was decreased by thinning but not affected by grazing. However, pine sapling (established seedlings) density and height were increased by thinning and decreased by grazing. Sapling density of the dominant native oakQuercus ithaburensiswas reduced by both thinning and grazing. Thinning enhanced the growth ofQ. ithaburensissaplings while grazing restricted their height. Grazing and thinning had no significant effect on the total sapling density of broad‐leaved tree species, but grazing restricted their height and reduced species richness. Grazing reduced topsoil water content in non‐thinned plots but had no effect in the thinned plots. Grazing increased the water potential of pine seedlings while thinning reduced it. Both grazing and thinning had no effect on the water potential of maturePistacia lentiscusshrubs.ConclusionsNatural regeneration within east Mediterranean pine plantations is limited by both dense overstorey cover and cattle grazing. While grazing exclusion is necessary for the establishment and early growth of recruits, reintroduction of grazing at later phases may facilitate the development of young forests by controlling competition.

Environmental variation as a key process of co‐existence in flood‐meadows

AbstractQuestionHow does the species composition and functional structure of flood‐meadows change over time during a period with strong variations in flooding frequency and height?LocationFlood‐meadows at the northern Upper Rhine, Germany.MethodsFrom 1998 to 2004 annually, and again in 2008, species composition and above‐ground biomass were studied in 46 permanent plots located along a flooding gradient ranging from frequently flooded Magnocaricion to rarely flooded Arrhenaterion meadows. The plots were situated in the functional floodplain (natural) and in the fossil floodplain on the land side of high winter levees (anthropogenic altered). Temporal variation of the functional structure was analysed based on community‐weighted mean traits.ResultsProductivity and functional structure varied markedly over the study period and between the functional and fossil floodplain. During the study period two contrasting extreme events occurred: a summer flood in 1999 and a drought period after 2003. After the flood in 1999, species composition and functional structure of the studied flood‐meadows shifted towards the species composition of wetter sites. Flooding reduced species richness in the functional floodplain, but not in the fossil floodplain.ConclusionsFlood‐meadows in the Upper Rhine fully recover from extreme disturbance events within a time frame of less than 10 yr. Environmental fluctuations and disturbances, enabling the co‐existence of species with contrasting ecological requirements are a key factor for the preservation of plant biodiversity in flood‐meadows.