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Grasslands can be a complex mixture of plant species. A method is described to allow the identification of both roots and shoots of five different grass species, thus permitting greater knowledge about whole plant allocation and competition in mixed pastures. The five species were Lolium perenne, Festuca ovina, Festuca rubra, Poa trivialis and Agrostis capillaris. N-alkanes with odd-numbers of carbon atoms in the chains predominate in plants and in the five grass species studied, concentrations of alkanes of chain length of C29, C31 and C33 were highest. Average concentrations of C27-C33 alkanes in shoots and roots were 187 and 11 mg kg−1, respectively. This wide range of values required considerable modifications to the method of analysis, including expressing concentrations on an organic matter basis and scaling-down the procedure. The n-alkane concentrations in roots are different from those in shoots and therefore values from shoots cannot be used to predict the composition in roots. Using a canonical variate analysis, all five grass species could be separated using concentrations of C26, C31 and C33 values in the roots. The greatest difference occurred between A. capillaris and the others, whereas discrimination was least between the two Festuca species. Defoliation had contrasting effects on the concentration of a few n-alkanes, but not in the n-alkanes used to discriminate between grass species. Alkane analysis shows great potential as a method to quantify the species composition of the root biomass beneath mixed pasture species.

The effects of grazing by cattle and horses on vegetation development were studied in the well-drained bor- der zone of the Oostvaardersplassen nature reserve, a man- aged eutrophic wetland in the young Zuidelijk Flevoland polder in The Netherlands. At the start of the study period, 12 yr after the area was enclosed by dykes, the vegetation was dominated by Phragmites australis and tall herbs, particularly Cirsium arvense. Over the next 8 yr, different plant communities developed under differ- ent grazing regimes. In all communities, C. arvense was gradually replaced by Urtica dioica, and stands dominated by these two species expanded at the expense of P. australis. The shrub Sambucus nigra invaded the stands of C. arvense and U. dioica. Grazing affected the rate of these developments and the degree to which the grass Poa trivialis became dominant. When cattle were enclosed at a relatively high stocking rate in an area of Phragmites australis and tall herbaceous vegetation during summer, P. trivialis became dominant within 4 yr. The introduction of herbivores led to a faster spread of S. nigra, which contains cyanogenic glycosides which only ruminants can detoxify. Horses, as hind-gut fermenters, did not feed on S. nigra. Grazing pressure and herbivore species, therefore, are two important variables that can be used to manage the develop- ment of Phragmites- and shrub vegetation: the greater the grazing pressure by cattle or horses the greater the area domi- nated by grasses, and a relatively high grazing pressure by cattle will retard S. nigra expansion.

Two field studies, a seeded study and a golf course study, were conducted to compare competition among creeping bentgrass, annual bluegrass, and roughstalk bluegrass when subjected to common weed control practices and foliar applications of iron and magnesium. A research site was selected for the seeded study and divided into 10 whole plots receiving irrigation at either 50 or 100% evapotranspiration deficit. Each whole plot was further divided into subplots receiving one of seven treatments: bensulide, ethofumesate, trinexapac-ethyl, foliar Mg, foliar Fe, foliar Mg plus foliar Fe, and control. The site was seeded to a mixture of creeping bentgrass, annual bluegrass, and roughstalk bluegrass in September 1995, and treatments began in March 1996. Annual bluegrass was reduced 29% in plots treated with foliar Fe and 65% in plots treated with foliar Fe plus foliar Mg. Roughstalk bluegrass was significantly reduced in seeded plots treated with foliar iron (50%), plant growth regulator (75%), and foliar iron plus foliar magnesium (100%). Annual bluegrass and roughstalk bluegrass proportions were not affected by irrigation regime. In a second study, the most effective treatment, foliar magnesium plus foliar iron, was tested on a working golf course fairway and on a practice putting green beginning April 1997 and ending November 1997. Treatments on the golf course fairway and practice putting green were ineffective due to the established, perennial nature of the annual bluegrass biotypes on these sites. Further research is required to improve the efficacy of nutritional treatments on these perennials.

1. Experimental grassland communities (turves) were exposed to elevated (60 Pa) and ambient (35 Pa) CO2 partial pressures (pCO2) in a Free-Air Carbon Dioxide Enrichment (FACE) experiment between 30 March 1995 and 4 July 1996. The vegetation was cut once during the experiment prior to the final harvest (harvest 2). 2. No significant treatment effects on total plant biomass at the whole turf level were detected, although biomass was typically about 25% higher under fumigation in year 1 and about 15% higher in year 2. 3. Biomass for two of the six sown species was significantly higher at harvest 2 than at harvest 1. There were no significant differences between individual species’ biomass under the two CO2 treatments at either harvest 1 or 2 or in terms of overall cumulative biomass. However, in four of the five sown species in both years biomass tended to be higher in the fumigated than in the control rings (Cerastium holosteiodes, Phleum pratense, Plantago lanceolata and Poa trivialis). In contrast, Lolium perenne showed increased biomass under the control treatment relative to the fumigated treatment in both years. Owing to the high variance both within and between rings for each of the two treatments the statistical power of most, but not all, of the analyses carried out was poor. 4. The relative proportions of each species in the turves under fumigated and control treatments was broadly similar after the first summer, with differences in the second year being mainly owing to the negative response of L. perenne to CO2 fumigation.

A hillside with abandoned, wooded hay meadows in Leikanger in Sogn og Fjordane county, Western Norway, was investigated in 1992–1995. A management regime combining restoration (topping) of old pollarded trees, scything and removal of hay was reintroduced in the area. The availability of light, hydrological conditions and the nutrient content of the soil were the most important factors determining development of hay meadow vegetation to forest vegetation. Indicators of shaded conditions included Valeriana sambucifolia and Oxalis acetosella, while Anthriscus sylvestris was indicator of light conditions. Species such as Campanula rotundifolia, Pimpinella saxifraga, Plantago lanceolata, Lychnis viscaria and Hieracium pilosella, which were recorded mostly on dry ridges, were regarded as “relict” species, more common formerly when the area was managed in a traditional way. The cover of tall grasses and herbs, such as Dactylis glomerata, Poa trivialis and Anthriscus sylvestris, increased the first two years after restoration. This indicates an increase in available nutrients, probably a “pioneer clearing fertilization” due to the introduced pollarding. Restoration and management resulted in drier, more homogenous ecological conditions and reduced the differences in local climate between formerly open meadows and more wooded areas in the restored area. However, most of the vegetation seemed to be quite stable during the study period. One class, however, comprised releves from several unstable plots of the experimental site. The frequency of some light-demanding species increased in the experimental site, while the frequency of Oxalis acetosella and Epilobium montanum increased in the control site.

Summary The composition of Monks Wood, a 157 ha nature reserve in eastern England, in 1964–66 was compared with that in 1996 using data from 36 temporary sample plots distributed systematically across the wood and from a 70 × 35 m permanent sample plot. The overall composition of the wood changed little, but declines in the abundance of Betula pendula, and locally of other species such as Populus tremula had occurred. Both the density of tree stems and of shrub stools declined significantly between 1966 and 1996: for trees from 1469 to 611 stems per hectare, for shrubs from 235 to 177 stools per hectare. Stem basal area also increased. There were substantial changes in the ground flora: reductions in frequency of Mercurialis perennis, increases in Brachypodium sylvaticum, Carex pendula, Glechoma hederacea, Poa trivialis and Urtica dioica. The changes in the tree and shrub layer appear to be mainly a consequence of ‘internal’ factors, stand growth and self-thinning. The ground flora changes reflect a new ‘...

Premergence (PRE) herbicides were applied to a bermudagrass golf green overseeded with 'Laser' roughstalk bluegrass during 1995 and 1996 to determine their effects on roughstalk bluegrass injury and on the transition from a mixed cool- and warm-season grass back to the permanent bermudagrass. Roughstalk bluegrass tolerated single March applications of trifluralin plus benefin at 2.2 kg/ha, pendimethalin at 3.4 kg/ha, dithiopyr at 0.6 kg/ha, prodiamine at 0.8 kg/ha, bensulide plus oxadiazon at 8.4 kg/ha, and bensulide at 11.2 kg/ha. A single March application of oxadiazon plus benefin at 3.4 kg/ha severely injured (35%) the overseeded turf in 1 yr, but not when 1.7 kg/ha was applied in March and repeated in May. One-half recommended rates of oxadiazon and bensulide plus oxadiazon applied in March did not cause any undesirable injury, but when repeated in May, mod- erate to severe injury (28 to 33%) occurred in June. Oryzalin at ' 1.1 kg/ha, benefin plus oryzalin at ? 1.1 kg/ha, and oxyfluorfen plus oryzalin at ' 1.7 kg/ha severely injured (' 35%) roughstalk bluegrass. The rate of transition of mixed roughstalk bluegrass and bermudagrass back to permanent bermudagrass was not affected by any of the PRE herbicides except when oryzalin was applied alone or in combination with benefin or oxyfluorfen. Nomenclature: Benefin, N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine; bensulide, 0,0- bis(I-methylethyl) S-(2-((phenylsulfonyl)amino)ethyl)phosphorodithioate; dithiopyr, S,S-dimethyl 2-(di- fluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate; oryzalin, 4-(dipropy- lamino)-3,5-dinitrobenzenesulfonamide; oxadiazon, 3-(2,4-dichloro-5-(1-methylethoxy)phenyl)-5-(1,1-di- methylethyl)-1,3,4-oxadiazol-2-(3H)-one; oxyfluorfen, 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoro- methyl)benzene; pendimethalin, N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine; prodiamine, 2,4-dinitro-A'3,N3-dipropyl-6-(trifluoromethyl)-1,3-benzenediamine; trifluralin, 2,6-dinitro-N, N-dipropyl- 4-(trifluoromethyl)benzenamine; roughstalk bluegrass, Poa trivialis L. #3 POATR 'Laser'; bermudagrass, Cynodon transvaalensis Burtt-Davey # CYNTR X C. dactylon (L.) Pers. # CYNDA 'Tifway.' Additional index words: POATR, CYNTR, CYNDA. Abbreviations: AS, aqueous suspension; EC, emulsifiable concentrate; Fb, followed by; FC, flowable concentrate; G, granule; PRE, preemergence; WDG, water dispersible granule.

Polyamines are thought to play a role in the control of inherent or environmentally-induced growth rates of plants. To test this contention, we grew plants of four grass species, the inherently fast-growing Poa annua L. and Poa trivialis L. and the inherently slow-growing Poa compressa L. and Poa pratensis (L.) Schreb., at three levels of nitrate supply. Firstly, plants were compared when grown with free access to nitrate, allowing the plants to grow at their maximum relative growth rate (RGRmax). Secondly, we compared the plants when grown with relative nitrate addition rates of 100 and 50 mmol N (mol N)−1 day−1 (RAR100 and RAR50, respectively).

Previous experiments have shown that the anatomy and chemical composition of leaves of inherently fast- and slow-growing grass species, grown at non-limiting nitrogen supply, differ systematically. The present experiment was carried out to investigate whether these differences persist when the plants are grown at an intermediate or a very low nitrogen supply. To this end, the inherently fast-growing Poa annua L. and Poa trivialis L., and the inherently slow-growing Poa compressa L. and Poa pratensis (L.) Schreb. were grown hydroponically at three levels of nitrate supply: at optimum (RGR max ) and at relative addition rates of 100 and 50 mmol N (mol N) -1 d -1 (RAR 100 and RAR 50 ), respectively. As expected, at the lowest N supply, the potentially fast-growing species grew at the same rate as the inherently slow-growing ones. Similarly, the differences in leaf area ratio (LAR, leaf area:total dry mass), specific leaf area (SLA, leaf area:leaf dry mass) and leaf mass ratio (LMR, leaf dry mass:total dry mass) disappeared. Under optimal conditions, the fast-growing species differed from the slow-growing ones in that they had a higher N concentration. There were no significant differences in C concentration. With decreasing N supply, the total N concentration decreased and the differences between the species disappeared. The total C concentration increased for the fast-growing species and decreased for the slow-growing ones, i.e. the small, but insignificant, difference in C concentration between the species at RGR max increased with decreasing N supply. The chemical composition of the leaves at low N supply, analysed in more detail by pyrolysis-mass spectrometry, showed an increase in the relative amounts of guaiacyl lignin, cellulose and hemicellulose, whereas those of syringyl lignin and protein decreased. The anatomy and morphology of the leaves of the four grass species differing in RGR max were analysed by image-processing analysis. The proportion of the total volume occupied by mesophyll plus intercellular spaces and epidermis did not correlate with the amount of leaf mass per unit leaf area (specific leaf mass, SLM) at different N supply. The higher SLM at low N supply was caused partly by a high proportion of non-veinal sclerenchymatic cells per cross-section and partly by the smaller volume of epidermal cells. We conclude that the decrease in relative growth rate (and increase in SLM) at decreasing N supply is partly due to chemical and anatomical changes. The differences between the fast- and slow-growing grass species at an optimum nutrient supply diminished when plants were growing at a limiting nitrogen supply.

Grassland ecosystems worldwide not only provide many important ecosystem services but they also function as a major source of the greenhouse gas nitrous oxide (N2O), especially in response to nitrogen deposition by grazing animals. To explore the role of plants as mediators of these emissions, we tested whether and how N2O emissions are dependent on grass species richness and/or specific grass species composition in the absence and presence of urine deposition. We hypothesized that: (i) N2O emissions relate negatively to plant productivity; (ii) four-species mixtures have lower emissions than monocultures (as they are expected to be more productive); (iii) emissions are lowest in combinations of species with diverging root morphology and high root biomass; and (iv) the identity of the key species that reduce N2O emissions is dependent on urine deposition. We established monocultures and two- and four-species mixtures of common grass species with diverging functional traits: Lolium perenne L. (Lp), Festuca arundinacea Schreb. (Fa), Phleum pratense L. (Php) and Poa trivialis L. (Pt), and quantified N2O emissions for 42 days. We found no relation between plant species richness and N2O emissions. However, N2O emissions were significantly reduced in specific plant species combinations. In the absence of urine, plant communities of Fa+Php acted as a sink for N2O, whereas the monocultures of these species constituted a N2O source. With urine application Lp+Pt plant communities reduced (P

""In this study, we analyzed the relationship between buried archaeological remains (masonries, pavements, and ancient ruins) and spontaneous vegetation. growing above them. We carried out several. vegetation surveys in the Domitian’s Stadium at the. archaeological site of the Palatine (Rome). Vegetation. data were collected using the Braun-Blanquet approach. and elaborated using statistical analyses (cluster. analysis) to assess the similarity among surveys.. Structural, chorological, and ecological features of the. plant communities were analyzed. Results showed that. the vegetation responds significantly to the presence. of sub-emerging ancient remains. The plant bioindication of this phenomenon occurs through the following floristic-vegetation variations: phenological alterations. in single individuals (reduction in height, displacement of flowering\\\/fruiting period), increase of annual species. and decrease of perennial ones, decrease of total. plant coverage, reduction of maturity level of the vegetation which remains blocked at a pioneer evolutive. stage. The presence of sub-surfacing ruins manifests. itself through the dominant occurrence of xerophilous. and not-nitrophilous species (e.g., Hypochaeris achyrophorus L., Aira elegantissima Schur, Trifolium scabrum L. ssp. scabrum, Trifolium stellatum L., Plantago lagopus L., Medicago minima (L.) L., and Catapodium rigidum (L.) C.E. Hubb. ex Dony ssp. rigidum) and in a rarefaction of more mesophilous and nitrophilous. species (e.g., Plantago lanceolata L., Trifolium pratense L. ssp. pratense, Trifolium repens L. ssp. repens, and Poa trivialis L.). Therefore, the vegetation can be used as bioindicator for the detection of buried ruins,. contributing in the archaeological prospection for a general, fast, and inexpensive interpretation of the underground.""

This study investigates the nitrogen economy of six altitudinally contrasting Poa species which differ in their relative growth rate (R). Two alpine (Poa fawcettiae and P. costiniana), one sub-alpine (P. alpina)and three temperate lowland species (P. pratensis, P. campressa and P. trivialis) were grown hydroponically under identical conditions in a growth room. The low R exhibited by the alpine species was associated with lower plant organic nitrogen concentration (np) and lower nitrogen productivity (Πp, amount of biomass accumulation per mol organic nitrogen and time). The differences in Πp between the alpine and lowland species did not appear to be due to differences in the carbon concentration or the proportion of total plant organic nitrogen allocated to the leaves, stems or roots. Variations in ΠP were also not due to variations in photosynthetic nitrogen use efficiency (ΨN, the rate of photosynthesis per unit organic leaf nitrogen) or shoot or root respiration rates per unit organic nitrogen (ΛSH and ΛR, respectively) per se. Rather, the lower Λp in the alpine species was probably due to a combination of small variations in several of the parameters (e.g. slightly lower ΨN, slightly higher ΛSH and ΛR, and slightly higher proportions of total plant organic nitrogen allocated to the roots). The alpine species exhibited lower organic acid and mineral concentrations. However, no differences in whole-plant construction costs (grams of glucose needed to synthesize one gram of biomass) were observed between She alpine and lowland Poa species. The lack of sub-stantial differences in ΨN between the alpine and lowland species contrasts with the large differences in ΨN between slow- and fast-growing lowland species that have been reported in the literature. The reasons for the unusually high ΨN values exhibited by the alpine Poa species are discussed.

The results are reported from an experiment on the effects of cutting date (14 June, 21 July and I September), fertilizer application (none or 80 kg ha−1 N plus 40 kg ha−1 P and K) and grazing treatments (none, autumn or autumn plus spring) on the vegetation of an upland mesotrophic grassland in Upper Teesdale. northern England, UK. Effects on plant species number and cover are reported for 4 years (1989–93) of treatment. Effects on ‘species -attributes’ are given for the fourth year. The cessation of grazing combined with the use of fertilizer progressively reduced species number by about 25%. Under traditional management (no fertilizer, cutting date on 21 July, autumn and spring grazing) the species number and cover remained relatively static over the 4 years. Comparison between treatments in the fourth year showed a reduction in species number under the fertilizer application, cutting date on 1 September and no-grazing treatments. Fertilizer use together with cutting date on 1 September particularly lowered species number and cover. Analysis of variance was used to assess the effect of treatment on species that occurred frequently in the sward. A cutting date of 1 September favoured Agrostis capillaris. Alopecurus pratensis, Poa trivialis, Phleum pratense and Trisetum flavescens, The absence of grazing favoured Dactylis glomerata and Holcus lanatus. The use of fertilizer particularly favoured A. pratensis and H. lanatus. Ordination methods were used to assess the effect of treatment on the less frequent species. These were primarily associated with the treatment combination that matched ‘traditional’ management. Deviations from this ‘traditional’ regime acted separately, rather than in combination, and favoured different grass species. Traditional management was associated with ruderal, stress-tolerant ruderal and competitive ruderal strategists and with longer seed germination times, heavier seeds, some of which needed scarifying or chilling to break dormancy, and transient seed banks that germinated in the autumn. The original sward was an Anthoxanthum odora-turn-Geranium sylvatirum grassland, Briza media subcommunity (MG3b). After 4 years, Festuca ovina-Agrostis capillaris-Galium saxatile grassland, Holcus lanatus-Trifolium repens subcom-munity (U4b) and Lolium perenne-Alopecurus pratensis-Festuca pratensis grassland (MG7c) were found in many of the fertilized and late-cutting treatments.

Fifty-eight quantitative and qualitative exomorphological characters were recorded on 48 herbarium specimens belonging to rhizomatous species belonging to the genusPoa. These were treated as OTUs and analysed, together with the data from caespitose species treated in a previous paper, using cluster analysis, principal component analyses and stepwise discriminant analyses. The following hypotheses are proposed and discussed. (1) There is no evidence supporting the hypothesis that growth habit characterizes supraspecific entities. (2)P. trivialis, P. secunda, P. subenervisand probablyP. compressaseem to be well defined species; those remaining are not discriminated through phenetic analysis. (3) There are no phenetic gaps between the rhizomatous species included in theP. oligeria–P. yaganica–P. chrysanthacomplex and the caespitoseP. hachadoensis; it is not clear that this single character supports its segregation. (4) The obscurity of the pattern of the species related toP. pratensis–P. nemoralisis probably explained by the capability ofP. pratensisto introgress with taxonomically distant species and by the possibility of seasonal intraindividual variation of some characters. (5) The geographical origin of some species postulated as introduced seems to be doubtful.

Planting sod beneath peach trees (Prunus persica) to control excessive vegetative growth was evaluated from 1987 to 1993 in three field studies. Peach trees were established and maintained in 2.5-m-wide vegetation-free strips for 3 years, and then sod was planted beneath the trees and maintained for 5 to 7 years. Reducing the vegetation-free area beneath established peach trees to a 30- or 60-cm-wide herbicide strip with three grass species (Festuca arundinacae, Festuca rubra, Poa trivialis), reduced total pruning weight/tree in 5 of 16 study-years and weight of canopy suckers in 6 of 7 study-years, while increasing light penetration into the canopy. Fruit yield was reduced by planting sod beneath peach trees in 5 of 18 study-years; however, yield efficiency of total fruit and large fruit (kg yield/cm2 trunk area) were not reduced in one study and in only 1 year in the other two studies. Planting sod beneath peach trees increased available soil water content in all years, and yield efficiency based on evapotranspiration (kg yield/cm soil water use plus precipitation) was the same or greater for trees with sod compared to the 2.5-m-wide herbicide strip. Planting sod beneath peach trees has the potential to increase light penetration into the canopy and may be appropriate for high-density peach production systems where small, efficient trees are needed.

SUMMARYThe concentration of nitrogen (N) within the emerging, youngest fully expanded and the youngest dead leaf laminae were examined in the grassesLolium perenne, Agrostis stolonifera, Holcus lanatusandPoa trivialisin Devon, UK, in 1986 and 1987. Lamina growth, appearance interval and lamina utilization were also examined in each species. Marked tillers were measuredin situover 14–21 day periods in a continuously grazed permanent pasture under steady state management on plots receiving either zero (ON) or 400 kg nitrogen (400N) fertilizer/ha per annum. The concentration of N tended to be greatest in the distal half and least in the basal part of each lamina in each species. Total mass showed an opposite trend due in part to the shape of the lamina. Less than 40 % of the lamina N was lost through grazing either in the ON or 400N plots in the four species, except once inH. lanatuswhen more was lost. In absolute terms, becauseL. perenneandH. lanatusmaintained larger and longer laminae than eitherA. stoloniferaorP. trivialis, they lost more N through grazing. The four grass species recycled N from the senescing lamina with the same apparent efficiency; this meant that differences in lamina N concentration and carbon: nitrogen ratios were present in the dead laminae of the four species.L. perenneachieved the highest tissue growth rate per unit of N in the lamina in the ON plot, not only in comparison with the three other grasses but also compared with the 400N plot. This high N-use efficiency inL. perennewas not translated into an ability to either expand or maintain its population in the ON plot.L. perennehad a lower leaf appearance rate than the other species in both the 400N and ON plots, but this inherent characteristic of the species was particularly pronounced in the ON plot. A slower leaf appearance rate would limit the potential tillering capacity ofL. perennecompared with the other species. A reduced tillering capacity, exacerbated by N deficiency, was probably the principal factor limiting the ability ofL. perenneto exploit available niches in the ON pasture.

This note reports on the additions of nine native and five non-native species to the known vascular plant flora of the Pinaleno Mountains. Poa trivialis is reported as new to the state; the collections of Stellaria umbellata and Juncus mertensianus are range extensions from northern Arizona.

The paper is to present the trends of typical species of meadow habitats to colonize the frontier habitats. The area of research is the fly-ash landfills in the power plant EDF Torun SA in Torun. Several times, during the year mix of fly-ashes and slug, resulting from the combustion of coal, is transported by pipeline and this is mixed with water. Floristic research was conducted twice: in 2013 and 2015 year. Within an area of about 7 hectares 84 species of vascular plants (43 species in 2013 and 61 in 2015) were inventoried including 14 characteristic species of meadows. The presence of these species disturbed strong evidence of a wide ecological range and adaptations to survive adverse conditions of habitats. The results demonstrate that meadow species as Festuca arundinacea , Festuca rubra , Lolium perenne , Poa annua, Rumex acetosa and Taraxacum officinale, Poa trivialis and Viccia cracca can be helpful in restoration of fly-ash landfills.

Summary The competitive ability of Festuca rubra L., Hoicus lanatus L. and Poa trivialis L. when grown from seed, in monoculture and in 1:1 additive mixtures with Bromus sterilis L. was studied. B. sterilis was more aggressive when grown in additive mixtures with F. rubra than P. trivialis or H. lanatus. H. lanatus was less dominated by B. sterilis at the second harvest; visual observations suggested that this dichotomy was due to its slower initial growth rate, and its subsequent dense vegetative growth habit. There was no statistically significant difference between the Relative Yield Total (RYT) of B. sterilis in additive mixtures with F. rubra, H. lanatus or P. trivialis, indicating that they were competing for the same resources. B. sterilis produced significantly more reproductive tillers and seeds as a result of nitrogen application, and such production was accentuated in the absence of interspecific competition. The implications of sown grass strips for field margin management are discussed.

A trial carried out in a greenhouse over a two-year period is discussed. The effects on 137 Cs concentration in plants, roots and soil have been investigated versus the grassland species composition (legume, grass and mixture) and eight combinations of mineral fertilizers (NPK). The results indicate: (a) the effect of K fertilizer in reducing 137 Cs plant absorption; (b) the effect of N fertilizer in favouring grass growth and radiocaesium absorption; (c) for all fertilizer combinations, a higher 137 Cs storage in the root system of the legumes and a lower 137 Cs absorption in the plants.

Annual bluegrass (Poa annua L.) continues to be a problem in bermudagrass golf greens overseeded with roughstalk bluegrass (Poa trivialis L. `Sabre) due to weed encroachment from adjacent fairways, lack of selective herbicide options, and weed diversity. A 2-year study was conducted on an overseeded `Tifgreen bermudagrass putting green to evaluate effects of herbicide treatments on overseeding and annual bluegrass control. Excellent annual bluegrass control (≥90%) and acceptable turfgrass cover (§70%) was achieved with oxadiazon at 2.2 kg·ha-1 a.i. applied 60 days before overseeding (DBO). Fenarimol (AS) at 4.1 kg·ha-1 a.i. (30 + 15 DBO) followed by 1.4 kg·ha-1 a.i. 60 days after overseeding (DAO) and dithiopyr at 0.6 kg·ha-1 a.i. (60 DBO + 120 DAO) also provided acceptable results. Dithiopyr at 0.4 kg·ha-1 a.i. (30 DBO + 120 DAO), dithiopyr at 0.3 kg·ha-1 a.i. (30 DBO + 30 + 120 DAO), and fenarimol (G) at 2.0 kg·ha-1 a.i. (45 + 30 DBO) followed by 0.8 kg·ha-1 a.i. 60 DAO provided inconsistent annual bluegrass control (55% to 75% in 1999 and 87% to 95% in 2000), but offered acceptable turfgrass cover (§70%) each year. The remaining treatments were generally ineffective and provided -1 a.i. provides an excellent option for annual bluegrass control in overseeded bermudagrass putting greens.

Despite concentrated conservation efforts and targeted agri-environmental schemes, breeding wader species have declined in most western European countries during recent decades. Assuming that wader species aggregate in relation to physical and biological features of their breeding habitats, this study aimed to identify botanical and environmental indicators that can be used to identify sites and management regimes to enhance breeding potential for the Black-tailed Godwit Limosa limosa as a focal species. We selected 36 fields (mean 7.1 ha) with and without this species in grazed lowland grasslands in the Danish Wadden Sea area. Bird numbers observed during 2007 and 2008 were analysed in relation to environmental and management variables together with presence/absence of plant species in the main body of the fields, the field silt trenches and field edges. Black-tailed Godwits preferred unfertilized fields with a short growth plant community that included the presence of moss-carpet. The plant indicator species for fields with Black-tailed Godwit were besides Bryopsida (moss sp.) also Trifolium pratense var. maritimum (maritime red clover), Poa trivialis (rough meadowgrass), Plantago major (greater plantain) and Veronica serpyllifolia (thyme-leaved speedwell).

summary Plants of Agrostis castellana, Festuca rubra, Lolium perenne and Poa trivials were grown in sand culture and supplied with a complete nutrient solution containing either 0.5 or 1.5 mol m−3 NH4NO3. Plants were clipped weekly to a height of 4 cm. At the time of the ninth clipping (day Q) the nutrient solution was replaced by one in which all nitrogen (N) was enriched with 15N to 5 atom %, but otherwise identical. Weekly destructive harvests were taken from day 0 to day 35. whilst unharvested plants continued to receive the weekly clipping. The 15N-labelling allowed discrimination between remobilization within the plant from current root uptake in supplying N for laminae regrowth. For all four species a poor N supply reduced both N uptake by roots and the potential N available for remobilization, as welt as allocation of both these sources to laminae regrowth. Overall the N supply derived from root uptake was reduced by a greater extent, and the proportion of N in laminae regrowth derived from remobilization increased with low N supply. The rate of remobilization of the N which was accessible was slower with a reduced supply of N. The species order for increasing proportion of N for laminae regrowth being derived from remobilization was L. perenne < P. trivialis < A. castellana < F. rubra irrespective of N supply.

Bermudagrass (Cynodon spp.) putting greens are overseeded with cool-season grasses in the fall to maintain a high-quality putting turf throughout the southern USA. Perennial ryegrass (Lolium perenne L.) has been the predominant grass used for overseeding until recently, when roughstalk (Poa trivialis L.) has been increasingly used for overseeding. Annual bluegrass (Poa annua L.) is a problem winter annual weed that infests most overseeded bermudagrass greens and the weed must be controlled with a herbicide to maintain a high-quality putting surface. Fenarimol [α(2-chlorophenyl)-α-(4-chlorophenyl)-5-pyrimidinemethanol] has preemergence herbicidal activity on annual bluegrass, but it may also reduce the germination and establishment of roughstalk bluegrass seedlings [...]

Large turves from a ryegrass/white clover based pasture were exposed to 350 or 700 μl l-1 CO2 for a period of 217 d in controlled environment rooms. The temperature was increased during the experiment from 10/4 °C day/night to 16/10 °C and finally to 22/16 °C. The turves were cut to a height of 2 cm at intervals and growth rates calculated from the regrowth. Growth rates over the duration of the experiment were 8% higher at elevated CO2; the difference between CO2 treatments being statistically significant only at the highest temperature. Species composition of the turves at 350 μl l-1 CO2 showed seasonal changes similar to those measured in the field. The effect of CO2 was to exaggerate the normal decline of ryegrass at warmer temperatures and increase the proportion of white clover. About 30% of the total growth rate was from other species (notably Bromus hordeaceus L. and Poa trivialis L.) and this fraction was similar between CO2 levels. Root mass was measured at the end of the experiment and was 50% higher at elevated CO2. The modest above-ground response to CO2 was a result of CO2 stimulation occurring only at the higher temperature. Because of the CO2 × temperature interaction, the effect of CO2 in temperate regions will be seasonal. When this is matched with seasonal growth patterns of herbage species, a complex response of pasture communities to CO2 is possible. In our case, white clover was growing most strongly during the period of greatest CO2 stimulation and consequently its growth was enhanced more than that of ryegrass; however, the cooler season growth of ryegrass gives it a temporal niche which is little affected by CO2 and this may be important for ryegrass stability if it is an inherently poor responder to CO2. The results indicate that for temperate species the effects of competition at elevated CO2 cannot be easily determined from experiments conducted at a single temperature.

The changing populations of weeds during 13 years of the Broadbalk continuous wheat experiment were analysed to investigate the extent of differences in shortterm variability of cover between species. The data were from two sections of the experiment where winter wheat was grown continuously under herbicide treatment for 13 and 6 years respectively. Logistic regressions were fitted to the data. Equisetum arvense showed significant long-term increases on both sections; long-term trends were also detected in the longer data run for Agrostis stolonifera, Cirsium arvensa, Poa trivialis, Ranunculus arvensis and Vicia sativa, and for Medicago lupulina on the shorter data run. Variation around long-term trends was low in the case of Equisetum, and, in the longer data run, for Cirsium and Tussilago farfara, and high for Poa spp. and Vicia. Cover values on the two sections were positively correlated for Alopecurus myosuroides, Equisetum, Poa annua and Tripleurospermum inodorum. There was a weak correlation between C-S-R strategy and short-term variability; the more competitive species displayed less variability than the ruderal species. Furthermore, species regenerating from persistent seed banks were more variable in the short term than those regenerating from short-lived seed or bud banks. This can be explained by differences in response to year-to-year variation in environmental conditions, those species with persistent seed banks being typically more sensitive to annual fluctuations in the environment than those without.

Pulmonary diseases such as recurrent airway obstruction have become a major concern in the horse industry. Airborne dust, including aeroallergens from forages, is suspected to be the main factor in its aetiology. Hypothesizing that grassland flora could affect hay hygienic quality, and therefore have implications for the respiratory health of horses, we compared five single-species hays (Trifolium repens, Lolium perenne, Alopecurus geniculatus, Poa trivialis and Holcus lanatus). Multi-species hay from Normandy, and different commercial forages (single-species haylage, multi-species haylage, Crau hay and hay from Swiss mixing), chosen to represent current horse forages, were also investigated. Dust, moulds, pollens and endotoxins were different among forage types, while mycotoxins were not detected in any of the forage types. Holcus lanatus hay was the dustiest among the single-species hays but also the least contaminated by moulds. A particular mould profile was associated with each plant species. The four commercial forages appeared to have a better hygienic quality than the multi-species hay. Among commercial forages, the single-species haylage was the least dusty but also the most contaminated by moulds. Overall the results suggest that the hygienic quality of equine forages could be improved by an appropriate choice of grassland species.

New parameterizations for surface–atmosphere exchange of ammonia are presented for application in atmospheric transport models and compared with parameterizations of the literature. The new parameterizations are based on a combination of the results of three years of ammonia flux measurements over a grassland canopy (dominated by Lolium perenne and Poa trivialis) near Wageningen, the Netherlands and existing parameterizations from literature. First, a model for the surface–atmosphere exchange of ammonia that includes the concentration at the external leaf surface is derived and validated. Second, a parameterization for the stomatal compensation point (expressed as Γs, the ratio of [NH4+]/[H+] in the leaf apoplast) that accounts for the observed seasonal variation is derived from the measurements. The new, temperature-dependent Γs describes the observed seasonal behavior very well. It is noted, however, that senescence of plants and field management practices will also influence the seasonal variation of Γs on a shorter timescale. Finally, a relation that links Γs to the atmospheric pollution level of the location through the ‘long-term’ NH3 concentration in the air is proposed.

Formulations of fenoxaprop enriched in the R(+) isomer, HOE 46360-08H EW (described as an emulsifiable water-based formulation) and HOE 46360-05H EC (emulsifiable concentrate), were compared with the commercial racemate EC for control of roughstalk bluegrass and tolerance of perennial ryegrass and tall fescue grown for seed. The enriched EW and EC formulations were more than twice as active as the racemate per kg total fenoxaprop, despite enrichment to only 92 and 89% R(+) isomer purity, which should have increased activity by 1.84- and 1.78-fold, respectively. Increased activity was evident both as improved weed control and as decreased crop tolerance. Although the 3.69-fold increase in activity of HOE 46360 EW on roughstalk bluegrass relative to the racemate may be partly due to changes in the emulsion, the 3.06-fold increase in activity of HOE 46360 EC suggests that the S(-) isomer somehow interferes wih the activity of the R(+) isomer. Use of 280 g ai ha–1of the racemate could be replaced with 76 g ha–1of the EW or 92 g ha–1of the EC formulation of HOE 46360 for equivalent roughstalk bluegrass control, but with decreased crop tolerance in perennial ryegrass and tall fescue.

Lamina wettability, assessed using water droplet contact-angle and surface water-retention measurements on excised leaves, was examined in Lolium perenne cv. Melle, cv. Condesa and an indigenous population from an old pasture, Holcus lanatus, Poa trivialis and Agrostis stolonifera. The species fell into two significantly distinct categories, those with unwettable laminae, namely H. lanatus and A. stolonifera, and those with highly wettable laminae, P. trivialis and the three L. perenne populations. There was no significant difference between the L. perenne populations, which had the most wettable laminae overall. The possible implication of these differences in lamina wettability on animal production is discussed.

The productivity of ten grasses was measured under six cuts per annum for 3 years and three cuts for a fourth harvest year in comparison with a perennial ryegrass (Lolium perenne) control. The grasses were Yorkshire fog (Holcus lanatus), two red fescues (Festuca rubra), creeping bent (Agrostis stolonifera), bent (Agrostis castellana), bent (Agrostis capillaris), smooth meadow-grass (Poa pratensis), crested dogstail (Cynosurus cristatus), sweet vernal (Anthoxanthum odoratum) and timothy (Phleum bertolonii). Another grass sown, rough meadow-grass (Poa trivialis), did not persist after the first harvest year. Annual N rates were 0, 120, 240, 360 and 480 kg ha−1. Classified by DM production, the grasses grouped into: high (perennial ryegrass, Yorkshire fog and red fescue), intermediate (creeping bent, bent (A. castellana), crested dogstail and smooth meadow-grass) and low (bent (A. capillaris), sweet vernal and timothy. With frequent cutting, production ranking interacted with N rate: Yorkshire fog. red fescue and creeping bent were more productive than ryegrass at the 0 N and 120 N rates but not at higher N rates; crested dogstail and sweet vernal outperformed ryegrass at 0 N; ryegrass and smooth meadow-grass performed relatively better at moderate to high N. DM production of ryegrass was matched or exceeded by some of the other grasses during different parts of the season particularly at low N rates. Notable features from the 3-cut regime were the outstanding DM production of Yorkshire fog at all N rates and the poor production of bent (A. capillaris) and crested dogstail. High DM response to applied N in both cutting regimes was given by perennial ryegrass. smooth meadow-grass, red fescue cv. Boreal, timothy, crested dogstail and Yorkshire fog. N concentrations were highest in less productive grasses such as the bents and lowest in highly productive ryegrass and Yorkshire fog. Ryegrass was superior in digestibility to the other grasses, but especially to the red fescues, bents and smooth meadow-grass. The other grasses, especially Yorkshire fog and bent (A. capillaris) were superior to ryegrass in P, K and Mg concentrations, but not Ca. It is concluded that the annual and/or seasonal production of some of the secondary grasses at low to moderate N rates, e.g. the performance of Yorkshire fog and red fescue, warrant a reconsideration of their poor reputation, particularly within the context of increasing grassland extensification. Breeding to improve selected characteristics, such as digestibility in red fescue, seems justified. Assessment of the grazing and ensiling qualities of secondary grasses require further study.

We determined how differences in peach tree water use and shoot and root growth due to ground cover treatments are affected by tree response and soil conditions in the adjacent soil environment. Ground cover combi- nations of bare soil (BS), a killed K-31 tall fescue sod (KS), a living Poa trivialis sod (PT), and a living K-31 tall fescue sod (LS) were imposed on 50% of the soil surface in greenhouse studies. The ground cover on 50% of the soil surface influenced root and top growth of the peach trees (Prunus persica (L) Batsch), water use, and NO3-N levels in the opposing 50%, depending on the competitiveness of the cover crop (LS vs. PT and KS) and characteristics of the soil (BS vs. KS). Tree growth was allometrically related to root growth. Deciduous fruit trees grow and develop in heterogeneous soil environments. Orchard soil characteristics vary vertically due to natural soil morphogenesis and horizontally due to manage- ment practices, such as the conventional herbicide-strip tree row with a grassed middle and zones wetted by irrigation. Peach tree growth is sensitive to the proximity of sod (Welker and Glenn, 1985), the competitive ability of cover crops and grassed middles (Butler, 1986; Skroch and Shribbs, 1986), and the man- agement of the tree row strip (Hogue and Neilsen, 1987). The impact of management practices, such as drip irrigation and weed control, may extend into nontargeted areas of the soil environment. Our objective was to document how differences in peach tree water use and shoot and root growth due to ground- cover treatments are affected by tree response and soil condi- tions in the adjacent soil environment.

1. Restoration of high plant species diversity to sites where it has been reduced by intensive grassland management requires identification of appropriate management regimes. Understanding the combinatorial effects of management on above-ground vegetation and below-ground microbial communities will inform management prescriptions on how best to increase plant diversity, restore rare vegetation types and achieve agri-environmental objectives. 2. Changes in vegetation and soil microbial community structure are described from the second phase of a 1990-2004 field trial that investigated the interacting effects of fertilizer and farmyard manure (FYM) treatments imposed after 1998, in the context of previous hay-cut date and seed-addition treatments. 3. Hay-cut date was the main factor influencing plant species composition in phase 1, whereas FYM was the dominant factor in phase 2. 4. Poa trivialis and Lolium perenne increased in abundance with FYM application, particularly in combination with mineral fertilizer, and particularly in 2002 after the 2001 foot and mouth epidemic. The lowest Ellenberg fertility scores were associated with absence of FYM and mineral fertilizer but with addition of seed. 5. The highest plant species diversity in phase 2 was associated with seed addition and the absence of mineral fertilizer, an effect that had probably persisted from phase 1. Progressive development of the target traditional meadow vegetation occurred through phase 2. 6. Fungal:bacterial (F:B) ratios, a measure of changes in the relative abundance of fungi and bacteria in the microbial community, generally increased from 1996 to 2004, and were particularly high in the seed-addition treatments and in the absence of fertilizer. Here the high F:B ratios were associated with species (including legumes) typical of traditionally managed mesotrophic grassland in northern England. 7. Synthesis and applications. These results demonstrate that biodiversity goals for upland meadows need to plan beyond the typical 5-10-year management agreement period of agri-environment schemes. Combination treatments, in which seed addition is vital, alongside appropriate fertilizer, FYM, hay-cut date and grazing regimes, are needed for grassland restoration. However, even after 14 years the most effective treatment combinations had still not restored the target species composition and diversity. The demonstrated change in soil microbial communities, linked to the growth of legumes, might be important to facilitate future increases in plant diversity.

Rhizome growth of Elymus repens (L.) Gould (couch grass) from single-node fragments on plots sown with six perennial grasses in a surrounding hexagonal mosaic was reduced by a factor of 10, compared with initially bare plots. The location of shoot complexes of E. repens after three seasons indicated that Arrhenatherum elatius and, to lesser extents, Agrostis stolonifera or Dactylis glomerata , prevented couch growth more than Holcus lanatus or Poa trivialis . Strips of sown grass at the edge of arable fields may therefore reduce the spread of couch grass into adjacent crops. Fertiliser application of 32 kg N ha −1 doubled the amount of couch rhizome. Mefluidide and paclobutrazol, plant growth regulators which might be used to manage sown grass, had minor effects on rhizome structure. D. glomerata did not spread from where it was sown and was largely uninvaded by other species.

Fenoxaprop applied between late winter and mid-spring selectively controlled roughstalk bluegrass in perennial ryegrass grown for seed in Oregon. Fenoxaprop applied after the arrival of warmer weather in late March had enhanced effectiveness against roughstalk bluegrass compared to earlier application. However, additional delay into April increased damage to perennial ryegrass. Optimum application date coincided with a 15to 18-cm perennial ryegrass canopy height. Mixed stands of seedling and established roughstalk bluegrass were more consistently controlled by 0.28 kg ai/ha fenoxaprop than by lower rates. Nomenclature: Fenoxaprop, (?)-2-[4-[(6-chloro-2-benzoxazolyl)oxy]phenoxy]propanoic acid; perennial ryegrass, Lolium perenne L. #3 LOLPE; roughstalk bluegrass, Poa trivialis L. # POATR. Additional index words: Seed production, seed certification.

Red fescue (Festuca rubra L.) cvs Reptans, Dawson and Ruby, perennial ryegrass (Lolium perenne L.) cvs Perma and Sprinter, crested dogstail (Cynosurus cristatus L.) cv. Southlands, smooth meadow-grass (Poa pratensis L.) cvs Parade and Arena, Yorkshire fog (Holcus lanatus L.) commercial types I and II, creeping bent (Agrostis stolonifera L.) cv. Penncross and rough meadow-grass (Poa trivialis L.) cvs Omega Otofte, Dasas and Sabre were each sown with white clover (Trifolium repens L.) cv. Donna and the productivity of the fourteen mixtures assessed under simulated grazing (six harvests per year) for 3 years. A single fertilizer-N rate (50 kg ha−1) in early spring was applied to all treatments each year. Over the 3 years, mean annual dry matter (DM) production of the swards ranged from 5·25 t ha−1 (creeping bent) to 8·71 t ha−1 (red fescue cv. Reptans), with the species ranking order of: red fescue > perennial ryegrass > crested dogstail > smooth meadow-grass > Yorkshire fog > creeping bent. Rough meadow-grass only persisted over the first harvest year. Mean annual organic matter digestibility (OMD) values of the swards ranged from 0·712 (creeping bent) to 0·782 (ryegrass cv. Sprinter). Mixtures with the lowest proportion of grass (crested dogstail and smooth meadow-grass) generally gave the highest proportions of white clover. The creeping bent mixture had exceptionally low production of both components. Red fescue, crested dogstail and smooth meadow-grass showed compatibility with clover and, therefore, have potential for use in grass/clover swards. Yorkshire fog had lower compatability with clover. Some breeding effort to improve selected characteristics of promising species, e.g. improvement of low OMD in red fescue, seems warranted.

Poa trivialis Linnaeus, Species Plantarum 1: 67. 1753. "Habitat in Europae pascuis." RCN: 569. Neotype (Soreng in Cafferty & al. in Taxon 49: 256. 2000): Hudson 16, Herb. Linn. No. 87.9 (LINN). Current name: Poa trivialis L. (Poaceae). Note: In the absence of original material for the name, a neotype was designated by Soreng (who also discussed other elements linked to the name)., Published as part of Jarvis, Charlie, 2007, Chapter 7: Linnaean Plant Names and their Types (part P), pp. 718-782 in Order out of Chaos. Linnaean Plant Types and their Types, London :Linnaean Society of London in association with the Natural History Museum on page 753, DOI: 10.5281/zenodo.291971

Cool season turfgrass have difficulties to grow and persist with good quality under shade in the summer. The objective of this study was to evaluate the ability and persistence of three cool season species suitable for turfgrass under different levels of shade, in the Province of Cordoba, Argentina (33°07' lat. S, 64°14' long. O). Density, cover, overall quality and dry weight of live and dead biomass were evaluated in Festuca rubra L., Poa trivialisL .and Agrostis stolonifera L. var.palustris (Huds.) Farw. growing under 0, 25, 50 and 80% light reduction. The shade was produced with black plastic shading mesh. The behaviour of the turf was modified over time, with the genotype and the level of shade in which it grew (p ≤ 0.001). In all the variables there were interactions between species × time (p ≤ 0.001); shade level × time (p ≤ 0.001) and species × shade level (p ≤ 0.05). None of the varieties of the studied grasses can be used as a single genotype to form turfgrass under full sunlight. Under 25% of shade, only A. tolonifera produced good quality turf as single species, surviving until the beginning of the second warm season. Under 50% of light reduction, A. stolonifera is the only species that persisted two years from its establishment, with very good quality in the first year and just acceptable in the second year. At 80% of shading, A. stolonifera and P. trivialis persisted until the second early summer with acceptable quality, but only A. stolonifera survived two warm seasons. Los céspedes de especies mesotérmicas presentan dificultades para crecer y persistir bajo sombra en el verano con calidad aceptable. El objetivo fue evaluar la aptitud y persistencia de tres especies mesotérmicas para formar céspedes como especie única, bajo diferentes niveles de sombra, en la Provincia de Córdoba, Argentina (33°07’ lat. S, 64°14’ long. O). Se evaluó densidad, cobertura, apariencia y peso seco de la biomasa aérea viva y muerta en Festuca rubra L., Poa trivialisL. y Agrostis stolonifera L. var. palustris (Huds.) Farw., con 0, 25, 50 y 80% de reducción lumínica usando mallas sombreadoras plásticas negras. El comportamiento del césped se modificó a lo largo del tiempo, según el genotipo evaluado y el nivel de luz en que creció (p ≤ 0,001). En todas las variables hubo interacción entre especie × tiempo (p ≤ 0,001); nivel de sombra × tiempo (p ≤ 0,001) y especie × nivel de sombra (p ≤ 0,05). Ninguna de las variedades de las especies estudiadas puede emplearse como genotipo único para formar céspedes bajo luz solar plena. Con sombras del 25%, sólo A. stolonifera produce cubiertas cespitosas de buena calidad, como especie única, persistiendo hasta el inicio de la segunda estación estival. Con 50% de sombra, A. stolonifera es la única especie que persiste dos años a partir de su implantación, con muy buena calidad durante el primer año y sólo aceptable en el segundo. Con 80% de sombra, A. stolonifera y P. trivialis persisten con calidad aceptable hasta el inicio de la segunda estación estival, pero sólo A. stolonifera puede sobrevivir durante dos veranos.

Monocultures of thirteen perennial C3 grass species that co-occur in temperate semi-natural grassland communities in Europe were compared in a factorial field design of two levels of N supply and two levels of cutting frequency. Above-ground yield of dry matter (DM), crude protein (CP) concentration and pepsin-cellulase DM digestibility of herbage were measured in two successive years. Species was the largest source of variability in yield of DM and DM digestibility of herbage, while CP concentration of herbage responded more to management factors. The highest mean DM yields and values of DM digestibility of herbage were achieved in spring for Festuca arundinacea and in autumn for Phleum pratense. Poa trivialis and Festuca rubra had the lowest DM yield and DM digestibility values, respectively, regardless of seasons and treatments. For all species CP concentration in herbage increased in response to an increase in cutting frequency and N supply by an average of 46 and 34 g kg−1 DM respectively. Differences between years and seasons indicated the importance of plant phenology on nutritional variables and the influence of environmental factors on species performance. Species ranking was compared according to their annual digestible DM and CP yields. The results show that some grasses have a nutritive value which is comparable to that of forages selected for high yields.

Contains fulltext : 57821.pdf (Publisher’s version ) (Open Access) Question: Does disturbance reduce competition intensity and thus favour weak competitors that are presumably less affected by disturbance than strong competitors? Methods: We used a single flooding event with increasing duration to simulate disturbance with increasing intensity. Six flood-plain grass species, typical of different flood regimes were grown in monocultures and in an additive species mixture. Flooding took place early in the first growing season and changes were monitored until the end of the second growing season. Results: Longer flooding durations initially decreased competition, but only a single species (Agrostis) increased its abundance in mixtures after flooding. The two weakest competitors in our selection (Poa trivialis and Elytrigia repens) failed to benefit from flooding because direct losses from flooding exceeded gains from reduced competition. Accordingly, we found no trade-off between flooding tolerance and competitive ability indicating that floods affect strong and weak competitors equally, although some species tolerated floods better than others. Conclusions: Since competition is only temporarily weakened after disturbance, increased competitive ability relative to other species may provide a more effective strategy for persistence in flood-disturbed sites. Above-ground runners seem an important prerequisite for enhanced competitive ability of clonal species in flood-disturbed sites.

Stimulation of nitrification and denitrification by long term (from years to decades) grazing has commonly been reported in different grassland ecosystems. However, grazing generally induces important changes in plant species composition, and whether changes in nitrification and denitrification are primarily due to changes in vegetation composition has never been tested. We compared soil nitrification- and denitrification-enzyme activities (NEA and DEA, respectively) between semi-natural grassland sites experiencing intensive (IG) and light (LG) grazing/mowing regimes for 13 years. Mean NEA and DEA (i.e. observed from random soil sampling) were higher in IG than LG sites. The NEA/DEA ratio was higher in IG than LG sites, indicating a higher stimulation of nitrification. Marked changes in plant species composition were observed in response to the grazing/mowing regime. In particular, the specific phytomass volume of Elymus repens was lower in IG than LG sites, whereas the specific volume of Lolium perenne was higher in IG than LG sites. In contrast, the specific volume of Holcus lanatus, Poa trivialis and Arrhenatherum elatius were not significantly different between treatments. Soils sampled beneath grass tussocks of the last three species exhibited higher DEA, NEA and NEA/DEA ratio in IG than LG sites. For a given grazing regime, plant species did not affect significantly soil DEA, NEA and NEA/DEA ratio. The modification of plant species composition is thus not the primary factor driving changes in nitrification and denitrification in semi-natural grassland ecosystems experiencing long term intensive grazing. Factors such as trampling, N returned in animal excreta, and/or modification of N uptake and C exudation by frequently defoliated plants could be responsible for the enhanced microbial activities.

We investigated whether leaf dark respiration (nonphotorespiratory mitochondrial CO2 release) is inhibited by light in several Poa species, and whether differences in light inhibition between the species are related to differences in the rate of leaf net photosynthesis. Four lowland (Poa annua L., Poa compressa L., Poa pratensis L., and Poa trivialis L.), one subalpine (Poa alpina L.), and two alpine (Poa costiniana Vick. and Poa fawcettiae Vick.) Poa species differing in whole plant relative growth rates were grown under identical controlled conditions. Nonphotorespiratory mitochondrial CO2 release in the light (Rd) was estimated according to the Laisk method. Photosynthesis was measured at ambient CO2 partial pressure (35 Pa) and 500 [mu]mol photons m-2 s-1. The rate of photosynthesis per unit leaf mass was positively correlated with the relative growth rate, with the slow-growing alpine Poa species exhibiting the lowest photosynthetic rates. Rates of both Rd and respiration in darkness were also substantially lower in the alpine species. Nonphotorespiratory CO2 release in darkness was higher than Rd in all species. However, despite some variation between the species in the level of light inhibition of respiration, no relationship was observed between the level of inhibition and the rate of photosynthesis. Similarly, the level of inhibition was not correlated with the relative growth rate. Our results support the suggestion that rates of leaf respiration in the light are closely associated with rates in darkness.