Festuca Ovina Research Articles

Drought Response of Fine Fescue Mixtures Maintained as a Golf Course Fairway

Fine fescues (Festuca spp.) may provide acceptable turf quality and playability on golf course fairways with lower irrigation inputs. Information on fine fescue fairways is limited and these species are not widely used as fairway turfgrass in the United States. The objective of this project was to evaluate the green cover of fine fescue species as fairway turfgrass under an acute drought and access their ability to recover. Twenty‐five mixtures were developed with a simplex‐centroid design using ‘Treazure II’ Chewings fescue [Festuca rubra ssp. commutata (Thuill.) Nyman], ‘Beacon’ hard fescue [Festuca trachyphylla (Hack.) Krajina], ‘Navigator II’ strong creeping red fescue (Festuca rubra ssp. rubra Gaudin), ‘Shoreline’ slender creeping red fescue [Festuca rubra ssp. litoralis (G.F.W. Meyer) Auquier], and ‘Quatro’ sheep fescue (Festuca ovina L.). Experiments were seeded in fall 2014 at both St. Paul, MN, and Madison, WI. After 10 mo of establishment, rainout shelters were used to employ a 60‐d drought on each trial during summer 2015. Plots were not trafficked. Data collected included percentage green cover as determined by digital image analysis. Analysis of variance indicated significant differences in mixture treatments, but means separation with Fisher's protected LSD showed that many monocultures performed generally similar to seed mixtures. A marginal effects summary revealed no differences among individual species, with one exception. Sheep fescue and slender creeping red fescue, when in the same mixture, had a negative interaction effect for recovery after drought. This interaction was significantly lower than the all five species coefficients included in the model, based on a 90% confidence interval. Overall, this study found that fine fescues are able to survive a 60‐d drought period under North Central US summer conditions.

The diploid Festuca ovina subsp. ovina (Poaceae) confirmed cytologically for Ireland

Two subspecies of Festuca ovina L. (Sheep's-fescue) (Poaceae) are known to occur in Ireland, namely subsp. hirtula (Hack. ex Travis) M.J. Wilk. and subsp. ophioliticola (Kerguelen) M.J. Wilk. Festu...

Differential Physiological Responses and Genetic Variations in Fine Fescue Species for Heat and Drought Stress

Summer decline is typically characterized by heat and drought stress and is a major concern for fine fescue species (Festuca). The objectives of this study were to examine whether heat or drought stress is more detrimental, and to determine the genotypic variations in heat and drought tolerance for fine fescues. A total of 26 cultivars, including seven hard fescues (Festuca trachyphylla), eight chewings fescues (Festuca rubra ssp. commutate), seven strong creeping red fescues (Festuca rubra ssp. rubra), two sheep fescues (Festuca ovina ssp. hirtula), and two slender creeping red fescues (Festuca rubra ssp. littoralis) were subjected to prolonged heat or drought stress in growth chambers. Several physiological parameters, including turf quality (TQ), electrolyte leakage (EL), photochemical efficiency (Fv/Fm) chlorophyll content (Chl), and relative water content (RWC) were measured in plants exposed to heat or drought stress. The results indicated that heat stress was more detrimental than drought stress for fine fescue species. Based on TQ and major physiological parameters (EL and Fv/Fm) under heat stress, several cultivars with good heat tolerance were selected, including ‘Blue Ray’, ‘Spartan II’, ‘MN-HD1’, ‘Shoreline’, ‘Navigator II’, ‘Azure’, ‘Beacon’, ‘Aurora Gold’, ‘Reliant IV’, ‘Marco Polo’, ‘Garnet’, ‘Wendy Jean’, ‘Razor’, and ‘Cindy Lou’. Based on TQ and major physiological parameters (EL, RWC, and Fv/Fm) under drought stress, several cultivars with good drought tolerance were selected, including ‘Spartan II’, ‘MN-HD1’, ‘Reliant IV’, ‘Garnet’, ‘Azure’, and ‘Aurora Gold’. These cultivars could be used in hot, dry, or both environments and as breeding germplasm for developing heat tolerance, drought tolerance, or both.

Genetic Structure and Eco-Geographical Differentiation of Wild Sheep Fescue (Festuca ovina L.) in Xinjiang, Northwest China.

Glaciation and mountain orogeny have generated new ecologic opportunities for plants, favoring an increase in the speciation rate. Moreover, they also act as corridors or barriers for plant lineages and populations. High genetic diversity ensures that species are able to survive and adapt. Gene flow is one of the most important determinants of the genetic diversity and structure of out-crossed species, and it is easily affected by biotic and abiotic factors. The aim of this study was to characterize the genetic diversity and structure of an alpine species, Festuca ovina L., in Xinjiang, China. A total of 100 individuals from 10 populations were analyzed using six amplified fragment length polymorphism (AFLP) primer pairs. A total of 583 clear bands were generated, of which 392 were polymorphic; thus, the percentage of polymorphic bands (PPB) was 67.24%. The total and average genetic diversities were 0.2722 and 0.2006 (0.1686–0.2225), respectively. The unweighted group method with arithmetic mean (UPGMA) tree, principal coordinates analysis (PCoA) and Structure analyses revealed that these populations or individuals could be clustered into two groups. The analysis of molecular variance analysis (AMOVA) suggested that most of the genetic variance existed within a population, and the genetic differentiation (Fst) among populations was 20.71%. The Shannon differentiation coefficient (G’st) among populations was 0.2350. Limited gene flow (Nm = 0.9571) was detected across all sampling sites. The Fst and Nm presented at different levels under the genetic barriers due to fragmentation. The population genetic diversity was significant relative to environmental factors such as temperature, altitude and precipitation.

Biotic interactions in a Mediterranean oak forest: role of allelopathy along phenological development of woody species

Plant–plant chemical interactions in forests can have a strong impact on the biodiversity and dynamics of these ecosystems, particularly in Mediterranean forests where plants exhibit a high secondary metabolite diversity. Allelopathic interactions in Mediterranean ecosystems have been mostly studied in the first stages of ecosystem dynamics, shrublands and pine forests, but little is known about these interactions in mature oak forests. In this study, the allelopathic effect of three main woody species of downy oak forests (Quercus pubescens, Acer monspessu-lanum and Cotinus coggygria) on germination and growth of two herbaceous species (Festuca ovina and Linum per-enne) was tested through aqueous extracts obtained from different leaf phenological stages (green, senescent and litter). The germination velocity of the two target species was inhibited by the aqueous extracts of senescent leaves from all the woody species. The growth of F. ovina seedlings was affected by aqueous extracts of green leaves of all the woody species, while the growth of L. perenne was only affected by aqueous extracts of green leaves of A. monspessulanum. This shows that (i) allelochemicals released by leaf leachates of the dominant woody species could control the dynamic of the herbaceous species, and then their potential competition with trees and (ii) allelo-pathic effects of woody species are related to their phenological stage and seem consistent with the development stage of target species.

Mobilization of cadmium from Festuca ovina roots and its simultaneous immobilization by soil in a root-soil-extractant system (in vitro test)

ABSTRACTMobilization of cadmium accumulated in Festuca ovina L. roots and simultaneous immobilization of this metal by soil were studied in three chambers connected into one system containing: (1) roots in an extractant solution, (2) soil in an extractant solution, and (3) extractant solution alone. Six extractants sterilized by filtration were used: 0.1 M NaNO3 (NA), 0.1 mM desferrioxamine B (NA + DFOB) and 1 mM citric acid (NA + CA) in NA, and a water extract of soil (SE) supplemented with the same compounds. SE mobilized 53% of the Cd introduced to the system with roots. The addition of DFOB or CA to SE increased Cd extraction from roots by 17%, while the same compounds introduced to NA did not change mobilization of Cd (60% efficiency). Regardless of the extractant used, mobilization of Cd from roots was about 25% lower when extraction was done in a control system without soil. The metal released from roots was gradually immobilized by the soils loaded into all systems during a 4-day incubation. Sequential extractions of Cd from the soils showed that the metal released from roots with NA was stabilized mainly by soil Mn and Fe oxides, while that released with SE was stabilized by soil organic matter.

Contrasting patterns of nucleotide polymorphism suggest different selective regimes within different parts of the PgiC1 gene in Festuca ovina L.

BackgroundPhosphoglucose isomerase (PGI, EC 5.3.1.9) is an essential metabolic enzyme in all eukaryotes. An earlier study of the PgiC1 gene, which encodes cytosolic PGI in the grass Festuca ovina L., revealed a marked difference in the levels of nucleotide polymorphism between the 5’ and 3’ portions of the gene.MethodsIn the present study, we characterized the sequence polymorphism in F. ovina PgiC1 in more detail and examined possible explanations for the non-uniform pattern of nucleotide polymorphism across the gene.ResultsOur study confirms that the two portions of the PgiC1 gene show substantially different levels of DNA polymorphism and also suggests that the peptide encoded by the 3’ portion of PgiC1 is functionally and structurally more important than that encoded by the 5’ portion. Although there was some evidence of purifying selection (dN/dS test) on the 5’ portion of the gene, the signature of purifying selection was considerably stronger on the 3’ portion of the gene (dN/dS and McDonald–Kreitman tests). Several tests support the action of balancing selection within the 5’ portion of the gene. Wall’s B and Q tests were significant only for the 5’ portion of the gene. There were also marked peaks of nucleotide diversity, Tajima’s D and the dN/dS ratio at or around a PgiC1 codon site (within the 5’ portion of the gene) that a previous study had suggested was subject to positive diversifying selection.ConclusionsOur results suggest that the two portions of the gene have been subject to different selective regimes. Purifying selection appears to have been the main force contributing to the relatively low level of polymorphism within the 3’ portion of the sequence. In contrast, it is possible that balancing selection has contributed to the maintenance of the polymorphism within the 5’ portion of the gene.

Designing seed mixtures for restoration on alpine soils: who should your neighbours be?

AbstractQuestions(1) When alpine vegetation is actively restored by seeding, how is vegetation cover influenced by seeding treatments and soil conditions? (2) How does the cover of species differ when they are seeded in a mixture and how is their response influenced by soil conditions? (3) Do individual species perform better or worse in a mixture than when sown separately?LocationHjerkinn, Dovrefjell, Norway.MethodsIn a factorial, randomized field experiment, we recorded the percentage cover of Festuca ovina, Luzula multiflora subsp. frigida and Poa alpina seeded in four different soil types for 3 yr after seeding. We seeded the three species separately and in a mixture in organic topsoil, peat soil, mineral fine soil and mineral coarse soil. We also recorded seedling emergence in a greenhouse experiment, using the same seeding treatments.ResultsIn the field experiment, vegetation cover established fastest when F. ovina was sown in monoculture, followed by the seed mixture. After 3 yr, mean cover of F. ovina was 1.4 times higher than mean P. alpina cover and more than three times higher than mean L. multiflora cover for single species treatments, and four (P. alpina) and 15 (L. multiflora) times higher when the species were seeded together. L. multiflora germinated slowly in the greenhouse experiment, which could partly explain its poor field performance. In the field experiment, establishment was faster in organic soils than mineral soils for all seeding treatments. The largest difference between F. ovina and L. multiflora performance in the mixture treatment was found in the organic soil types, where overall cover was larger than in the mineral soils. In the organic soils, F. ovina was slightly facilitated in the mixture treatment, while the opposite was found for L. multiflora.ConclusionWhen the restoration goal is to quickly establish a vegetation cover, seeding monocultures of rapidly establishing species may be more effective than seeding mixtures, even in alpine sites, where interspecific facilitation may prevail.

Assessing chilling and drought tolerance of different plant genera on extensive green roofs in an arid climate region in Iran

The harsh and stressful growing environment of extensive green roofs especially in arid environments allows a limited range of plant species to survive. Therefore, achieving plantings to survive in such conditions is a significant challenge. This paper describes an experiment investigating plant selections for extensive green roofs based on chilling (cold season) and drought (warm season) conditions of Iran. Nine species were selected from the three major taxonomic and functional plant groups that are commonly used on extensive green roofs including grasses, groundcovers and sedums. The species namely Agropyron cristatum, Festuca aurundinacea, Festuca ovina, Potentila sp., Frankinia thymifolia, Vinca minor, Sedum acre, Sedum spurinum, Carpobrotus edulis were imposed to natural chilling in autumn and winter using a randomized complete block design. For spring and summer, irrigation regimes at levels (48, 72 and 96 h intervals) in a factorial experiment based on a randomized complete block design with four replications were applied. The results showed that Agropyron cristatum, Frankinia thymifolia and Carpobrotus edulis were the best plants from each class. Carpobrotus edulis was the best choice for cold and warm seasons and this was followed by Frankinia thymifolia and Potentila sp. Vinca minor performed well in the cold seasons and Sedum spurinum appeared to be excellent in the warm seasons. The plants of the experiment showed significantly different appearances in different watering regimes. Little differences in drought tolerances were observed among the forbs and grasses, which must be watered during warm seasons. However, the succulents responded very well to the drought and low watering regimes. Overall, succulents and groundcovers were considered more appropriate for application in warm and cold seasons, respectively. According to the findings, drought and cold weather conditions cannot be a major obstacle for developing extensive green roofs in Iran if considerations are made on selecting its plant species.

The impacts of different management practices on botanical composition, quality, colour and growth of urban lawns

Mulching has increasingly become a standard method used in maintaining low-input lawns. This can be attributed to cost-savings, as these maintenance systems do not require loading and hauling of grass clippings. It is also possible to reduce the amount of nitrogen (N) fertilization and thus save on fertilizer costs. The effects of mowing management and rate of nitrogen fertilization on quality and growth of urban lawns were studied in a field trial during 2007–2012 on lawns newly sown in autumn 2006 and consisting of a grass–legume mixture (Lolium perenne 25%, Poa pratensis 25%, Festuca rubra 30%, Festuca ovina 5%, Anthoxanthum odoratum 5%, Cynosurus cristatus 5%, Trifolium repens 3%, Lotus corniculatus 2%). Nitrogen was used at three application levels: 0, 50 and 100kg of N ha−1year−1. Swards were cut to a height of 40mm five times annually and mulched to the same height. Mulching significantly affected the botanical composition of lawns, wherein a decrease in the portion of legumes (from 32% to 19.1%) was observed. The returned grass matter supported a significant increase in the grass component in the lawns (from 57.8% to 69.7% of total). When the clippings were returned, quality remained the same. Returned clippings had a positive impact on colour and increased the height of cut swards significantly. Application of nitrogen decreased the share of legumes, supported the grass component, statistically increased quality, improved colour, and increased sward height. The results show that returning grass clippings through mulching is beneficial. In any case, it is necessary to apply at least a basal amount of mineral fertilizer in order to preserve the quality of urban lawns over the long term.

Native plants for roadside revegetation in Idaho

Establishing perennial plant communities on roadsides is a proactive approach to sustainable road management. The environmental and economic benefits of increasing desirable roadside vegetation include improving slope stabilization, soil conservation, and roadway safety while reducing erosion, maintenance costs, and invasive plants. This study evaluated the success of roadside revegetation on 16 sites in Idaho and on one site in adjacent southwest Montana. Study sites represent a diversity of climatic, topographic, and edaphic conditions in order to provide a variety of examples of roadside revegetation projects in 6 different ecoregions of Idaho. We measured all species’ canopy cover, including noxious weeds and other invasive plants. Of the seeded grass species, 21 of 27 established. Bluebunch wheatgrass ( Pseudoroegneria spicata (Pursh)A. Love [Poaceae]) and Idaho fescue ( Festuca idahoensis Elmer [Poaceae]) were the best-performing native grasses. Seeded grass species that consistently established but had a low mean canopy cover (2–5%) included sheep fescue ( Festuca ovina L.), western wheatgrass ( Pascopyrum smithii (Rydb.) A. Love [Poaceae]), and basin wildrye ( Leymus cinereus (Scribn. & Merr.) A. Love [Poaceae]). Seeded forbs and shrub species had low establishment success and low mean percent canopy cover. For example, no seeded forb species had more than 1% mean canopy cover and greater than 50% establishment when present in the seed mix. Seed mixes of 10 or fewer species resulted in ≥ 50% of the species establishing. Idaho noxious weeds were present in less than half of the sites (47%). Cheatgrass ( Bromus tectorum L. [Poaceae]), an invasive annual grass, occurred in 82% of the sites. These results provide species selection recommendations based on ecoregion for use in roadside revegetation projects in Idaho and portions of western Montana.

Dynamics of the density of lawn grass and herbage on loamy and sandy soils

Conducted research on the dynamics of the density of single-species and mixed grass crops on sod-podzolic soils of the Ryazan region. The estimation of the density of turf grass stands in the years 2012-2014 studies found that the highest density had a single-species crops: Kentucky bluegrass, red fescue, bent grass selenobrachys, and among mixed crops - a three-component grass mixture (red fescue, Kentucky bluegrass, bent grass selenobrachys) and four-component mixture (selenobrachys bent grass, red fescue, Kentucky bluegrass, red fescue). The lowest density of planting was installed at the perennial ryegrass in the second and third years and three-component grass mixture (red fescue, sheep's fescue, perennial ryegrass) in the third year of life of grass. The trend of higher density turf grass stands revealed in experiment 1 for loamy soils compared to sandy loam.

Effect of calcium on reducing salt stress in seed germination and early growth stage of Festuca ovina L.

Effect of calcium on reducing salt stress in seed germination and early growth stage of Festuca ovina L.

Can goats disperse seeds of herbaceous pasture plants in Mediterranean grasslands?

In the Mediterranean region, endozoochorous seed dispersal is a potential alternative for the recovery of degraded or abandoned grasslands and shrublands. The objectives of this study were to quantify the number of seeds that pass through the goat gut and to determine whether this process affects seed germination in six common herbaceous species of the Mediterranean area (Ornithopus compressus L., Biserrula pelecinus L., Medicago polymorpha L., Melilotus officinalis L. Pall, Festuca ovina L. and Dactylis glomerata L). We also examined whether the inclusion of the seeds in dung affected seed germination and seedling establishment and growth. The highest seed recovery rate was obtained 24–72h after ingestion. The amount of retrieved seeds varied among species and was generally low, with significant differences among some leguminous and grass species. With the exception of M. officinalis, the quantity of retrieved legume seeds (1.5–6.8%) was greater than that of the grass seeds (0.9–1.1%). A significant relationship was found between recovery of the seeds and their hardness and volume. In all species, the recovered seeds presented significantly lower germinability than seeds that had not been consumed. In general, all recovered legume seeds showed higher average germination rate values (18–50%) compared to recovered grass seeds (0–14%). Seedling emergence was lower in intact than in crumbled dung pellets and, in most cases, the values of both of these were lower than that of unconsumed (control) seeds. No seedling emergence was recorded for seeds of B. pelecinus and O. compressus contained in intact or crumbled faeces at all sampling times. While the percentages of recovery and subsequent emergence found in this study are low in absolute terms, we can conclude that a significant number of seeds may become established from the dung and could be a potential alternative for the recovery of degraded or abandoned grazing areas.

Research and analysis of the tensile strength quality of the sod in lawn grass stands during landscape design of collective farm enterprises

Studies on evaluating the tensile strength quality of the sod of single-specific and mixed lawn crops have been carried out on sod–podzolic soils in the Ryazan oblast. An evaluation is given for the tensile strength quality of sod in lawn herbage crops over the period of 3 study years. The highest sod tensile strength was recorded in single-specific crops, namely, in creeping red fescue, red fescue, Kentucky bluegrass, and stolon-forming bentgrass; among mixed crops, the highest sod tensile strength was found in the three-component (creeping red fescue, Kentucky bluegrass, and stolon-forming bentgrass) and four-component (stolon-forming bentgrass, red fescue, Kentucky bluegrass, and creeping red fescue) herbage mixture. The lowest tensile strength of the sod was recorded in perennial ryegrass and three-component mixtures (creeping red fescue, sheep fescue, and perennial ryegrass).

Ecosystem functions as indicators for heathland responses to nitrogen fertilisation

Anthropogenic deposition of reactive nitrogen (N) has increased during the 20th century, and is considered an important driver of shifts in ecosystem functions and biodiversity loss. The objective of the present study was to identify those ecosystem functions that best evidence a target ecosystem’s sensitivity to N deposition, taking coastal heathlands as an example. We conducted a three-year field experiment in heathlands of the island Fehmarn (Baltic Sea, North Germany), which currently are subject to a background deposition of 9kgNha−1 yr−1. We experimentally applied six levels of N fertilisation (application of 0, 2.5, 5, 10, 20, and 50kgNha−1 yr−1), and quantified the growth responses of different plant species of different life forms (dwarf shrubs, graminoids, bryophytes, lichens) as well as shifts in the C:N ratios of plant tissue and humus horizons. For an applicability of the experimental findings (in terms of heathland management and critical load assessment) fertilisation effects on response variables were visualised by calculating the treatment ‘effect sizes’. The current year’s shoot increment of the dominant dwarf shrub Calluna vulgaris proved to be the most sensitive indicator to N fertilisation. Shoot increment significantly responded to additions of ≥ 5kgNha−1 yr−1 already in the first year, whereas flower formation of Calluna vulgaris increased only in the high-N treatments. Similarly, tissue C:N ratios of vascular plants (Calluna vulgaris and the graminoids Carex arenaria and Festuca ovina agg.) only decreased in the highest N treatments (50 and 20kgNha−1 yr−1, respectively). In contrast, tissue C:N ratios of cryptogams responded more quickly and sensitively than vascular plants. For example, Cladonia spp. tissue C:N ratios responded to N additions ≥ 5kgNha−1 yr−1 in the second study year. After three years we observed an increase in cover of graminoids and a corresponding decrease of cryptogams at N fertilisation rates of ≥ 10kgNha−1 yr−1. Soil C:N ratios proved to be an inappropriate indicator for N fertilisation at least within our three-year study period. Although current critical N loads for heathlands (10−20kgNha−1 yr−1) were confirmed in our experiment, the immediate and highly sensitive response of the current year’s shoots of Calluna vulgaris suggests that at least some ecosystem functions (e.g. dwarf shrub growth) also might respond to low (i.e.<10kgNha−1 yr−1) but chronic inputs of N.

Influence of temperature and carbon sources on auxin biosynthesis by &lt;i&gt;Rhodococcus erythropolis&lt;/i&gt; strain and their phytostimulating activity in urbanozem soil

The aim of this research was to study the effect of temperature and carbon sources for synthesizing activity of Rhodococcus erythropolis VKM Ac-2017D strain on the mineral medium. Tryptophan at a concentration of 0,5 g/l was added as a precursor for indole-3-acetic acid (IAA) biosynthesis. Phytostimulating effect was shown in condition of soil experiment using lawn grass mixture (Festuca rubra 30%, Lolium perenne 30%, Poa pratensis 20%, Festuca rubra trichlorophylla 15%, Festuca ovina 5%). The strain of selected oil-degrading bacteria was able to produce IAA on both hydrocarbon and carbohydrates as carbon sources. The differences were found in the production of auxin that depended on temperature and types of C-substrate. When sucrose used as a carbon source the maximum in production of IAA was 34,3 g/ml at the temperature of 15C. When culturing microorganisms on hexadecane the highest concentration IAA (77,69 g/ml ) was achieved at 25C. The culture broth (supernatant) and native bacterial suspension had shown phytostimulating activity on the lawn grass (weight of plant biomass, germination) to compare to water and chemically synthesized IAA in condition of soil experiment.

What's the meaning of local? Using molecular markers to define seed transfer zones for ecological restoration in Norway

According to the Norwegian Diversity Act, practitioners of restoration in Norway are instructed to use seed mixtures of local provenance. However, there are no guidelines for how local seed should be selected. In this study, we use genetic variation in a set of alpine species (Agrostis mertensii, Avenella flexuosa, Carex bigelowii, Festuca ovina, Poa alpina and Scorzoneroides autumnalis) to define seed transfer zones to reduce confusion about the definition of ‘local seeds’. The species selected for the study are common in all parts of Norway and suitable for commercial seed production. The sampling covered the entire alpine region (7–20 populations per species, 3–15 individuals per population). We characterised genetic diversity using amplified fragment length polymorphisms. We identified different spatial genetic diversity structures in the species, most likely related to differences in reproductive strategies, phylogeographic factors and geographic distribution. Based on results from all species, we suggest four general seed transfer zones for alpine Norway. This is likely more conservative than needed for all species, given that no species show more than two genetic groups. Even so, the approach is practical as four seed mixtures will serve the need for restoration of vegetation in alpine regions in Norway.

Warming alters competition for organic and inorganic nitrogen between co-existing grassland plant species

Grass species may acquire different forms of nitrogen (N) to reduce competition for the same resources. Climate change influences the availability of soil N and is therefore likely to cause shifts in N forms acquired by plants, thereby affecting their competitive interactions. We investigated the effects of warming on the uptake of different N forms and competitive interactions of Festuca ovina and Anthoxanthum odoratum in a pot experiment. The plants were grown either in monocultures or mixture, and at ambient or elevated temperature (+10 °C), and supplied with 13C and 15N isotopes to test for treatment effects on the relative uptake of ammonium, alanine or tri-alanine. Both grass species took up relatively more N supplied as ammonium than as alanine or tri-alanine when grown under ambient conditions in monoculture. In contrast, when grown in mixtures, F. ovina took up the three supplied N forms in equal amounts, whereas A. odoratum switched to tri-alanine as the main N form. Under warmed conditions, both species took up the N forms equally, irrespective of competition treatments. We have shown that grass species grown in mixture and under ambient conditions reduce competition by acquiring different N forms. Warming increased the availability of inorganic N in the soil and therefore deregulated the need for differential uptake of N forms.

Thirty years unmanaged green roofs: Ecological research and design implications

The variations in species composition and assemblage of unmanaged simple-intensive green roofs in Hannover, Germany, were investigated over a thirty year period, in order to assess the persistence of the initial seed mixture and to evaluate floristic changes. The roofs were greened in 1985 with soil-based turf rolls sown with a mixture of five grasses (Festuca rubra, Festuca ovina, Agrostis capillaris, Lolium perenne and Poa pratensis). Three sets of 120 phytosociological relevés, sampled in 1987, 1999 and 2014, have been compared to assess: (1) nestedness vs spatial turnover, (2) functional diversity and (3) the importance of vegetation dynamics on green roof performance and design. Results demonstrated that from 1987 to 1999 the species diversity increased and the species turnover prevailed over nestedness, due to the progressive niche occupation by new species. In contrast, from 1999 to 2014 species diversity remained steady, suggesting that nestedness prevailed over species turnover. The main driver of the observed functional changes was a shift towards relatively more thermoxeric conditions. In terms of plant life strategies, the competitive species sown on the roof gradually gave way to stress-tolerant and ruderal species, along with a progressive increase in species with shortdistance seed dispersal strategies. It is concluded that: (a) to create resilient green roofs, spontaneous colonisation should be accepted and considered as a design factor; and (b) regional plant communities could serve as a model for seed recruitment and installations.