Larval habitat preferences of a threatened butterfly species in heavy-metal grasslands

Understanding the factors that determine habitat quality is of vital importance in ensuring appropriate habitat management. Here we used the Niobe fritillary (Argynnis niobe) as a study system to analyse the larval habitat preferences in a small network of heavy-metal grasslands in western Germany. The data were compared with the results of a previous study in coastal dune grasslands of the German North Sea. Based on this knowledge, we give management recommendations for the conservation of this threatened species. The key factors for the survival of A. niobe in heavy-metal grasslands were (i) open vegetation with a warm microclimate and (ii) sufficient host plants for the larvae. This reflects similar results from the previous study in coastal grey dune grasslands. However, in the heavy-metal grasslands, physiological stress generally slows down succession and favours the fritillary’s host plant, the metallophyte Viola calaminaria. As a result, the cover of the host plant was nearly twice as high in heavy-metal grasslands compared to the dune grasslands. Heavy-metal grasslands are of great significance for the conservation of A. niobe and overall butterfly diversity. Usually, the speed of succession in heavy-metal grasslands is slow and, hence, sites with high heavy-metal concentrations are characterised by relatively stable plant composition and vegetation structure. However, on soils with low heavy-metal content a loss of habitats of A. niobe and associated species of conservation concern may occur without management. On those sites sheep grazing seems to be an appropriate way to keep the habitats open and rich in violets.     

When Invasive Species have Benefits as well as Costs: Managing <Emphasis Type="Italic">Carex kobomugi</Emphasis> (Asiatic sand sedge) in New Jersey’s Coastal Dunes

Asiatic sand sedge, Carex kobomugi,was accidentally introduced into North America approximately a century ago and is now widespread along the Northeast coast of the USA. This paper documents the rapid spread rate of this species in two New Jersey coastal parks. Also documented are declines in native plant densities, species richness and diversity in invaded areas. Although C. kobomugi expansion is having negative ecological impacts, the species is a potentially important dune stabilizer, so its control or removal demands special care. A removal program was initiated in 1999, using carefully directed applications of Roundup^®, which was designed such that it would spare non-target plants, leaving them in place to hold the dunes. We show that this approach reduced, but did not eliminate, C. kobomugi, even after repeated herbicide application. Native plant stem densities, species richness and species diversity in treated and untreated stands were similar, suggesting that this application technique did effectively spare non-target plants. However, effective eradication of C. kobomugi would probably require more frequent and aggressive broadband herbicide application, precluding beneficial effects of localized treatment (both ecological and increased dune stability due to spared plants).     

Understanding the influence of urbanization on invasibility: <Emphasis Type="Italic">Carpobrotus edulis</Emphasis> as an exemplar

Coastal dune areas are valuable ecosystems, generally impacted by habitat destruction and invasive alien species. In this study, we assessed how human disturbance and invasion by Carpobrotus edulis impact the soils and the establishment of native flora in the north-western coastal regions of Spain. We compared soil characteristics (pH, conductivity, water content, nutrients and enzymatic activities) and native plant as well as C. edulis fitness correlates (germination and early growth) between uninvaded and invaded soils from urban and natural coastal dune areas. We found that human disturbance impacts coastal soils by increasing organic matter and water content, modifying soil nutrients and cycles, and reducing the pH in urban soils. The presence of invasive C. edulis further increases these impacts. These changes in soil characteristics allow for the establishment of the native, but ruderal, Scolymus hispanicus and non-native C. edulis, both of which are not adapted to the typically limiting conditions of coastal dunes. In some instances, the coastal dune endemic, Malcolmia littorea, showed no fitness effects in response to urbanization or the presence of C. edulis. These results suggest that human disturbed coastal areas might be more easily invaded than natural areas. More broadly, our findings of differential responses of different native species to disturbance and invasion, illustrate the need for multi-taxon approaches when assessing the impacts of invasive species.     

<Emphasis Type="Italic">Pinus contorta</Emphasis> invasion into treeless steppe reduces species richness and alters species traits of the local community

Pinus contorta, one of the most invasive tree species in the world, has been proposed as a model species for improving our understanding of invasion ecology. In this study, we assessed the impact of P. contorta invasions on the species richness, diversity and species traits of a resident treeless steppe community. In a Pinus contorta invasion gradient (Patagonia, Chile), we surveyed vegetation from high canopy closure pine invasion to treeless steppe, and computed species richness, diversity and Sørensen similarity indexes. For all species, we determined functional trait values from the literature, data bases, and personal observations. Species richness and diversity were related to canopy cover (a proxy for invasion intensity) using generalized linear mixed-effects models. Changes in species traits due to canopy cover were analyzed using RLQ ordination analysis and the fourth-corner analysis. We found that Pinus contorta canopy cover significantly reduced the number of native species by 70 %, implying a strong effect on species exclusion. A few native species, however, prevail in the novel conditions (e.g. Baccharis magellanica, Acaena integerrima). Species traits changed significantly with increasing pine canopy cover, where P. contorta promoted the existence of traits related to shade-tolerance and conservative reproductive strategies. We conclude that the negative impacts of Pinus contorta into the treeless steppe, including a reduction in the number of species and the shifting to traits adapted to tolerate shade and associated with conservative reproductive strategies, can have severe implications for the conservation of biodiversity and ecosystem functioning where it invades.     

The maritime species of Abronia (Nyctaginaceae)

An analysis of the variation patterns in the three Pacific Coast maritime species ofAbronia (Nyctaginaceae) based on 95 population studies, is presented in the form of scatter diagrams. The relationship of this group of species to other members of the genus, such asA. gracilis Benth., is considered. Despite widespread evidence of hybridization and introgression, the three maritime species (A. latifolia Eschsch.,A. maritima Nutt. ex S. Wats., andA. umbellata Lam.) maintain their distinctness. Most of the taxonomic segregants in this group have been based on what appear to be hybrid or introgressed individuals, many of which closely resemble members of a series of artificial hybrids made in the greenhouse. The chromosome number of all three species is estimated as 2n = ca. 46. The species are shown to differ markedly in ecological preference:A. latifolia competing successfully on stable areas of dunes from Vancouver Island, British Columbia, to Santa Barbara Co., California;A. maritima being the major foredune former along the strand from San Luis Obispo Co., California, south to Nayarit, Mexico; andA. umbellata occurring on more stable dunes from San Luis Obispo to San Diego Co., California, and sporadically north and south of this area. The latter species is pollinated chiefly by nocturnal insects and is fragrant in the evening, whereas the other two have diurnal flowers. One widespread and two rarer, more northern subspecies ofA. umbellata are recognized in the taxonomic revision, while the other two species are not subdivided taxonomically.     

Aphid herbivory as a potential driver of primary succession in coastal dunes

Herbivory is a major factor affecting both the performance and the fitness of the species composing a plant community and, ultimately, conditioning its temporal and spatial dynamics. Coastal dunes are a typical example of primary succession where different biotic and abiotic factors determine plant species occurrence; however, the effect of insect herbivory herein has remained little explored. To address this matter, we combined an observational study along a successional gradient with a green-house experiment to determine the occurrence and the impact of plant–aphid interactions. We focused on the species Schizaphis rufula, a widespread and abundant aphid associated with dune grasses in early stages of primary succession in Europe. Firstly, we studied aphid infestation rates on the dune grass Ammophila arenaria along a succession gradient in three locations of the North Sea coast to address the relationship between plant community composition and aphid occurrence; secondly, we tested the effect of aphid herbivory on a set of dune species typical for the different stages of succession. We found that the degree of aphid infestation was inversely correlated with the degree of dune fixation. The results of the experiment showed that aphid multiplication was significantly higher and its effect more pronounced on two early successional grass species, i.e. A. arenaria and Leymus arenarius. Here aphid multiplication resulted in a severe decrease in plant biomass; in late successional grass species, there was limited multiplication and no effect on biomass. The results of the field survey and the green-house experiment indicate that aphids show a clear preference for plants from early successional stages and, moreover, they have a greater impact on these plant species. All this supports the hypothesis of aphid herbivory as a driving factor of primary succession in coastal dunes.     

Management affects the pollinator abundance but not the reproductive success of butterfly orchids

Management of semi-natural grasslands should be based on the requirements of plants as well as their pollinators since conditions beneficial for plants are not necessarily beneficial for their pollinators and vice versa. The factors affecting the reproductive success (fruit set) of Platanthera bifolia and Platanthera chlorantha and their pollinators in agricultural landscape and woodlands were studied. In the years 2014–2016, we observed and caught moths during the flowering period of Platanthera species (late June–mid July) in four pure P. bifolia, five pure P. chlorantha and nine mixed populations under management or no management in Estonia. We determined pollinator species richness, pollinator abundance, fruit set and visibility of Platanthera plants in each population. We found that pollinator assemblages of P. bifolia and P. chlorantha did not differ between managed and unmanaged sites. Pollinator abundance had an effect on the fruit set of P. bifolia but not on that of P. chlorantha. Presence or absence of management, visibility of plants and rarefied pollinator species richness did not affect the fruit set of either plant species. Pollinator abundance was significantly higher in unmanaged populations of both plant species but rarefied pollinator species richness was higher only in unmanaged populations of P. chlorantha. Based on our findings the recommendations for management of semi-natural grasslands are to promote larger landscape diversity for the benefit of moth abundance by leaving unmanaged patches in different parts of a grassland in different years and rotational and post-fruiting management for higher reproductive success of orchids.     

A new <Emphasis Type="Italic">Gephyraulus</Emphasis> species (Diptera: Cecidomyiidae) inducing flower bud galls on the European sea rocket <Emphasis Type="Italic">Cakile maritima</Emphasis> Scop. (Brassicaceae)

The European sea rocket Cakile maritima Scop. (Brassicaceae) is a common herb growing on sandy coastlines worldwide and is considered a useful plant because of its medicinal importance, its edibility, and potential as an oilseed crop. However, C. maritima is an invasive plant over a wide range, e.g., eastern South America, North America, northern Iran, Australia and New Zealand, and has a limited number of associated herbivorous insects. During investigations on gall midges (Diptera: Cecidomyiidae) in Egypt, we found a gall midge inducing flower bud galls on C. maritima and preventing fruit production, which suggested that this gall midge is a potential pest of this plant. In this paper, we describe this gall midge species, Gephyraulus zewaili Elsayed and Tokuda sp. nov., as new to science by comparing its morphology with that of close congeners. Partial sequence data of the mitochondrial DNA cytochrome oxidase subunit I gene are also provided.     

Spatial patterns of shrub encroachment in neighbouring grassland communities in the Pyrenees: floristic composition heterogeneity drives shrub proliferation rates

We studied the role of floristic composition and associational resistance in shrub dynamics by comparing spatial patterns of shrub cover after prescribed burning in neighbouring grassland communities with different palatability. The study focused on the shrub Cytisus balansae ssp. europaeus (G. López and Jarvis) Muñoz Garmendia. Seven two-dimensional transects (20 × 0.5 m) were established to monitor shrub cover for at least 10 years after prescribed burning. Shrub cover and spatial patterns were assessed in each transect. Floristic similarity between transects and Cytisus associations with different species were estimated. Over an entire transect, shrub cover and shrub scale of pattern and patch size were lowest in the unpalatable Festuca eskia grasslands and highest in F. paniculata grasslands. At short distances, we found negative associations between Cytisus and most of the grasses, except for F. nigrescens and Agrostis capillaris, which showed positive associations with Cytisus. Thus, the effects of associational resistance on shrub encroachment were not as marked as expected, F. eskia grasslands showing the lowest shrub encroachment rates after fire. By contrast, Cytisus was positively associated with the most palatable grasses in the site, namely F. nigrescens and A. capillaris. We conclude that differences in floristic composition drive shrub encroachment rates in these spatially heterogeneous communities.     

Habitat partitioning in juvenile fishes associated with three vegetation types in selected warm temperate estuaries,South Africa

Three common vegetation types were studied to assess habitat partitioning in juvenile fishes in select warm temperate estuaries of South Africa. Vegetated habitat types are known as productive and important areas for predator avoidance and feeding and are often preferred by juvenile fishes. Habitat partitioning is not well understood, with previous studies mostly focusing on seagrass (Zostera capensis). This study aimed to assess three common vegetated fish nursery areas in estuaries to aid conservation planning. Fishes were collected by means of double-winged, six-hooped fyke nets, 1 mm mesh size secured in placed on the nocturnal flood tide at each inundated vegetation type (Phragmites australis, Zostera capensis, Spartina maritima) and at an adjacent unvegetated site for three consecutive months in 2014 and 2015 during the summer recruitment period for juvenile fishes. Higher catches were frequently recorded in vegetated areas for solely estuarine and marine estuarine dependent species. In general, the previously unstudied reed, P. australis showed the highest species richness and abundance of juvenile fishes overall, followed by, Z. capensis and the intertidal salt marsh species, S. maritima. Results from this study supports international trends on the value of vegetated areas as refugia for young fishes in estuaries.     

Native and exotic foundation grasses differ in traits and responses to belowground tri-trophic interactions

A plant’s growth and fitness are influenced by species interactions, including those belowground. In primary successional systems, belowground organisms are known to have particularly important control over plant growth. Exotic plant invasions in these and other habitats may in part be explained by altered associations with belowground organisms compared to native plants. We investigated the growth responses of two foundation grasses on Great Lakes sand dunes, the native grass Ammophila breviligulata and the exotic grass Leymus arenarius, to two groups of soil organisms with important roles in dune succession: arbuscular mycorrhizal fungi (AMF) and plant-parasitic nematodes (PPN). We manipulated the presence/absence of two generalist belowground species known to occur in Great Lakes dunes, Rhizophagus intraradices (AMF) and Pratylenchus penetrans (PPN) in a factorial greenhouse experiment and assessed the biomass production and root architectural traits of the plants. There were clear differences in growth and above- and belowground architecture between Ammophila and Leymus, with Leymus plants being bigger, taller, and having longer roots than Ammophila. Inoculation with Rhizophagus increased above- and belowground biomass production by ~32% for both plant species. Inoculation with Pratylenchus decreased aboveground biomass production by ~36% for both plant species. However belowground, the exotic Leymus was significantly more resistant to PPN than the native Ammophila, and gained more benefits from AMF in belowground tri-trophic interactions than Ammophila. Overall, our results indicate that differences in plant architecture coupled with altered belowground interactions with AMF and PPN have the potential to promote exotic plant invasion.     

Light absorption and scattering by cell suspensions of some cyanobacteria and microalgae

Absorption spectra of cyanobacteria (Anacystis nidulans, Anabaena variabilis, and Chlorogloeopsis fritschii), red (Cyanidium caldarum and Porphyridium cruentum), green (Dunaliella maritima and Dunaliella salina) and diatom (Thalassiosira weisflogii) alga cell suspensions are presented; the spectra were obtained by using an approach developed earlier to compensate for scattering [1, 2]. In all species, the shapes of the absorption spectra were independent of the cell concentration. For Th. weisflogii and D. maritima, the analysis of selective and nonselective scattering was carried out. The effect of mechanical cell disruption on optical properties (absorption, scattering, and “package” effect) on D. maritima was studied. The character and dynamics of optical changes in D. salina under the influence of sodium chloride were followed.     

The widespread and overlooked replacement of <Emphasis Type="Italic">Spartina maritima</Emphasis> by non-indigenous <Emphasis Type="Italic">S. anglica</Emphasis> and <Emphasis Type="Italic">S. townsendii</Emphasis> in north-western Adriatic saltmarshes

Non-native Spartina spp. have invaded many coastal saltmarshes worldwide. Introduced Spartina may cause problems like displacement of native vegetation and hybridisation with native species, leading to changes to relevant ecosystem services and saltmarsh geomorphology. Here we report the extensive and so far overlooked replacement of the native Spartina maritima by non-native S. anglica and S. townsendii along 400 km of the coast of the north-western Adriatic Sea (Mediterranean Sea). We analysed the distribution of both native and non-native Spartina spp. along the six main saltmarsh areas in the region, and produced maps of their presence by using a combination of genetic tools, morphological analysis and geotagged photographs, complemented with field observations. We also reviewed historical herbaria from the region to explore when the first non-native introductions could have occured. We found that S. anglica and S. townsendii are unexpectedly widespread, having established along the whole study region, in one lagoon totally replacing the local native species. Its introduction happened virtually unnoticed, and misidentified herbarium specimens date back as early as 1987. We discuss the ecological implications of this overlooked extensive replacement, and the need for a comprehensive assessment of the status of the saltmarshes in this region, both to protect the few remaining patches of the native S. maritima and control the spread of the non-native species across the Mediterranean Sea.     

Spatiotemporal variation of Diptera changes how we evaluate High Nature Value (HNV) wet grasslands

Proposed strategies to protect biodiversity within agricultural systems are often based on botanical criteria with plant species richness generally considered the prime indicator of conservation potential. While wet grasslands dominated by rushes (Juncus spp.) are commonly considered to be of lesser ecological value than those which are more botanically diverse (e.g. Carex dominated wet grasslands), their value for invertebrates such as Diptera has not yet been fully explored. Data from two Diptera families (Sciomyzidae and Syrphidae) were examined at spatial, temporal and spatiotemporal scales to determine the contribution of two different (Juncus and Carex dominated) wet grassland habitats towards the maintenance of Diptera diversity. The two habitats were significantly different in terms of community structure for both families and temporal variation was a significant component of dipteran diversity. Spatiotemporal analysis showed that species turnover between habitats at different times made the most significant contribution to overall Diptera diversity. Temporal variation of both families suggests that the relative importance of each habitat type to overall diversity fluctuates depending on sampling period, with both habitats supporting diversity at different times. Our results indicate that lowland wet grasslands characterised by Juncus cover need to be recognised as ecologically important for the maintenance of dipteran diversity. We discuss the possible implications for the diversity of Diptera in wet grasslands if these commonly perceived marginal areas (both agriculturally and ecologically) are ignored in conservation strategies. The necessity of recognising spatiotemporal variation when evaluating habitats using invertebrates as indicators is also discussed.     

Ecophysiological response of native and invasive <Emphasis Type="Italic">Spartina</Emphasis> species to extreme temperature events in Mediterranean marshes

The recent IPCC WG2 5th Assessment Report (IPCC 2014), notes an increase in the frequency and duration of extreme climatic events, especially for the Mediterranean region. Together with climate change, the invasion of natural communities by non-indigenous species (NIS) constitutes a serious threat to biodiversity. One of these NIS is the American Spartina patens, now present in Western European marshes. The present study aims to understand the biochemical and photochemical responses of S. patens compared with S. maritima under extreme temperature events. Under normal and extreme heat conditions, S. patens had a higher photosynthetic efficiency (α), compared with cold wave events, where the native S. maritima was far more efficient. This reduced photosynthetic efficiency was mostly due to a decrease in the connectivity between photosystem II (PSII) antennae. This was accompanied by severe damage to the oxygen-evolving complex of PSII. On the other hand, S. patens oxygen evolving complexes (OECs) seem to be temperature insensitive. The light absorption capacity was maintained due to a higher net rate of reaction centre (RC) closure as a counteractive measure of the reduced number of RC, especially in S. maritima. The loss of connectivity between PSII antennae and damage in OECs under heat stress leads to a severe reduction in the maximum yield for photochemistry enhanced by the low probability of each absorbed quanta to produce electronic work. However, while S. maritima presents high energy losses under heat stress, S. patens developed efficient quenching mechanisms under thermal stress, through auroxanthin. In S. patens, cold wave-treated individuals also displayed a very active line of enzymatic defences for reactive oxygen species scavenging. In fact, only cold treated individuals of this species presented higher activities of anti-oxidant enzymes, revealing some degree of adaptation to this new environment. In contrast, in S. maritima the exposure to extreme heat periods led, in most cases, to a decrease in the enzymatic defences, leaving the cell prone to oxidative damage. In summary, S. patens appears to have a higher fitness for the incoming climatic scenarios, being more tolerant to heat stress, while S. maritima will have its photobiological fitness decreased. This will impose a shift in the salt marsh biodiversity, favouring the non-indigenous S. patens expansion.     

Effects of climate change on plant composition and diversity in the Gurbantünggüt Desert of northwestern China

Understanding changes in plant diversity is important with changing climate in desert ecosystems. We analyzed the changes in species richness and plant functional types in different landscape positions and species turnover between five sub-regions of the Gurbantünggüt Desert, China, from 2009 to 2013. We also analyzed how species density, richness, and plant functional types responded to annual precipitation, mean annual temperature, and the coefficient of variation (C _v) of both daily precipitation and monthly temperature, throughout this entire desert region. The results showed significant differences in the Shannon–Weiner, Evenness, and Gleason indices between the sub-regions over the 5-year study period. Species richness varied in the order of ephemeral plants > long-lived annual plants > perennial herbs > shrubs. Species richness in the lower and inter-dune area was higher than on the upper dune and on top of dunes. About 34.8 % of total species were influenced by climate change. The density of about 8.7 % of total species declined with increasing precipitation, especially the two dominant species, Haloxylon persicum and Haloxylon ammodendron. Plant richness increased significantly with increased precipitation. Ephemeral plant made the largest contribution to increasing plant diversity in the desert, while shrubs made the smallest. Ephemeral plants play an important role in maintaining plant community composition and function. In addition, species turnover declined with increasing precipitation. We suggest that differences in flora and different landscape positions in the dunes, specifically in shaping the heterogeneous microhabitats, are important reasons for the complex responses of species to climate change.     

Cover thresholds for impacts of an exotic grass on the structure and assembly of a wet prairie community

Potential impacts of an exotic grass, Hemarthria altissima, on restoration of wet prairie community structure (species richness and cover of indicator species) and assembly processes (temporal turnover rates of plant species) on the Kissimmee River floodplain in Central Florida, USA, were evaluated over a 12-year period before and after restoration of hydrologic regimes (2001), and implementation of herbicide treatments (2006–2007) to control its spread. Thresholds for impacts were derived from comparisons of sample sites with variable levels of H. altissima cover. Prior to herbicide treatments, cover of H. altissima exhibited a logistic increase over time, with peak colonization and expansion occurring during major flood events. Mean post-restoration cover of three native wet prairie indicator species (Polygonum punctatum, Panicum hemitomon, and Luziola fluitans) increased to 37.8 ± 3.4 % in plots in which H. altissima cover was <12 %, and did not exceed 15 % in any plots with H. altissima cover >30 %. Prior to and after herbicide treatments, these indicator species largely accounted for observed differences in wet prairie community structure (i.e., cover of wetland forbs and grasses) between heavily infested sites and plots with low or no cover of H. altissima. The cover threshold at which H. altissima began to have these community-level effects was 40–50 %, but lower species richness was found only where H. altissima cover was >80 %. Increasing cover of H. altissima led to a significant decline in temporal turnover rates of plant species (P < 0.001, r² = 0.10), but also was largely due to plots with very high (>75 %) cover of H. altissima. Mean temporal turnover rates of plant species increased significantly (P = 0.03) after herbicide treatments and subsequently were highest during an ensuing flood pulse. However, 2–3 years after herbicide treatments, regrowth of H. altissima reestablished high cover (mean = 59 ± 9.5 %) in over half of the treated plots. The ability of H. altissima to establish dominant cover in restored hydrologic conditions on the Kissimmee River floodplain, and documented regrowth following herbicide treatments, increase the potential for this exotic grass species to be a pervasive threat to successful reestablishment of wet prairie community structure and assembly processes.     

Effect of vegetation cover on the abundance and diversity of ladybirds (Coccinellidae) assemblages in a peat bog

Predaceous ladybirds are important natural enemies of many insect pests in terrestrial ecosystems such as peatlands, which are habitats for specialized cold-adapted plants. Ladybird assemblages of pristine peat bogs have not yet been assessed. In total, 15 ladybird species were recorded in peat bog in Belarus by using entomological sweep net. The present study shows low diversity, evenness and species richness of ladybird assemblages. However, a small number of species were present in high numbers. These are Coccinella hieroglyphica, Chilocorus bipustulatus, Coccinulla qutuordecimpustulata and Hippodamia tredecimpunctata. Ladybird abundance was positively related to shrub cover and number of vascular plant species, and negatively related to herb cover. In terms of ladybird diversity, only shrub cover had a significant negative effect.     

Ecophysiological responses of native invasive woody <Emphasis Type="Italic">Juniperus virginiana</Emphasis> L. to resource availability and stand characteristics in the semiarid grasslands of the Nebraska Sandhills

Vegetation in grasslands is changing at an unprecedented rate. In the Nebraska Sandhills, this shift is attributed in part to encroachment of the woody species Juniperus virginiana. We investigated changes in resource availability and their feedback on seasonal trends in photosynthetic characteristics of J. virginiana trees scattered in open grasslands vs. a dense 57-year-old stand. Dense stand exhibited lower volumetric soil water content, NH₄ ⁺, NO₃ ^–, and δ¹³C, as well as foliage δ¹³C, δ¹⁵N, and N content, compared to grasslands. Water potential was higher in trees in grasslands compared to dense stand. J. virginiana in dense stand exhibited similar trends to trees in grasslands for net photosynthetic rate (P _N), stomatal conductance, transpiration, maximum photochemical efficiency of PSII, maximum carboxylation velocity, and maximum rate of electron transport. P _N peaked early summer and declined in the fall, with trees in open grasslands lagging behind those in dense stand. Plasticity of this species may place it at a competitive advantage in the Sandhills, further altering grasslands vegetation and ecosystem processes.     

Patterns and drivers of phytodiversity in steppe grasslands of Central Podolia (Ukraine)

We asked: (i) Which environmental factors determine the level of α-diversity at several scales and β-diversity in steppic grasslands? (ii) How do the effects of environmental factors on α- and β-diversity vary between the different taxonomic groups (vascular plants, bryophytes, lichens)? We sampled nested-plot series ranging from 0.0001 to 100 m² and additional 10-m² plots, covering different vegetation types and management regimes in steppes and semi-natural dry grasslands of Central Podolia (Ukraine). We recorded all terricolous taxa and used topographic, soil, land-use and climatic variables as predictors. Richness-environment relationships at different scales and across taxonomic groups were assessed with multimodel inference. We also fitted power-law species-area relationships, using the exponent (z value) as a measure of β-diversity. In general, the richness values in the study region were intermediate compared to those known from similar grasslands throughout the Palaearctic, but for 1 cm² we found seven species of vascular plants, a new world record. Heat index was the most important factor for vascular plants and bryophytes (negative relation), while lichen diversity depended mainly on stone and rock cover (positive). The explanatory power of climate-related variables increased with increasing grain size, while anthropogenic burning was the most important factor for richness patterns at the finest grain sizes (positive effect). The z values showed more variation at the finest grain sizes, but no significant differences in their mean between scales. The results highlight the importance of integrating scale into ecological analyses and nature conservation assessments in order to understand and manage biological diversity in steppe ecosystems.