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BACKGROUND AND AIMS: Functional traits are indicators of plant interactions with their environment and the resource-use strategies of species can be defined through some key functional traits. The importance of genetic variability and phenotypic plasticity in trait variations in response to a common environmental change was investigated in two subalpine species. METHODS: Two species with contrasted resource-use strategies, Dactylis glomerata and Festuca paniculata, were grown along a productivity gradient in a greenhouse experiment. Functional traits of different genotypes were measured to estimate the relative roles of phenotypic plasticity and genetic variability, and to compare their levels of phenotypic plasticity. KEY RESULTS: Trait variability in the field for the two species is more likely to be the result of phenotypic plasticity rather than of genetic differentiation between populations. The exploitative species D. glomerata expressed an overall higher level of phenotypic plasticity compared with the conservative species F. paniculata. In addition to different amplitudes of phenotypic plasticity, the two species differed in their pattern of response for three functional traits relevant to resource use (specific leaf area, leaf dry matter content and leaf nitrogen content). CONCLUSIONS: Functional trait variability was mainly the result of phenotypic plasticity, with the exploitative species showing greater variability. In addition to average trait values, two species with different resource-use strategies differed in their plastic responses to productivity.

BACKGROUND AND AIMS: Is the release of allelochemicals by the dominant tussock grass Festuca paniculata responsible for its dominance by inhibiting growth of neighbour grasses in subalpine grasslands? As such a community is also structured by mowing practices, what could be the impact of mowing on allelopathy? METHODS: A design was used that isolated allelopathy from resource competition by separating donor plants (Festuca paniculata) from target plants (F. paniculata, Dactylis glomerata and Bromus erectus). Leachates from donor pots containing bare soil, unmown F. paniculata or mown F. paniculata continuously irrigated target pots containing seedlings. Activated carbon was added in half of the target pots to adsorb potential allelochemicals. C and N analyses of target potting soil were used to test for any effect of treatments on resources. Total phenol concentration was measured in the solutions flowing from donor to target pots. RESULTS: Festuca paniculata leachates inhibited seedling growth of D. glomerata and B. erectus. Inhibition was correlated with polyphenol concentration, and was not due to resource competition for nitrogen. Mowing the leaves of the donor plants did not significantly increase this inhibition. The activated carbon treatment was not conclusive as it inhibited the seedling growing under control pots with only bare soil. CONCLUSIONS: The results suggest that allelopathy may be at least partly responsible for F. paniculata dominance in subalpine meadows by inhibition of colonization by neighbouring species.

Allelopathy is recognized as an important process in plant-plant interactions, but how it affects plant communities growing in competitive conditions has not been assessed. This article investigates whether the allelopathic effect of Festuca paniculata is modified by competition between target plants in subalpine grasslands. We hypothesized that plants growing in mixed stands will be more affected by allelochemicals than the same species in monoculture. At Lautaret pass (Northern French Alps), a pot experiment was designed. We used leachates from donor pots (Treatments: 1. Bare soil, 2. F. paniculata clipped, and 3. F. paniculata unclipped) to water target pots (Treatments: 1. Control (soil only), 2. Dactylis glomerata, 3. Agrostis capillaris, and 4. D. glomerata and A. capillaris). Target plants were cultivated during one growing season. The effects of leachates from donor pots and interspecific competition in target pots were evaluated by measuring the final biomass of plants. Soil fertility was controlled in all target pots by measuring NO3 -, NH4 +, N, and C % of the soil. Effect of target treatment under: Both D. glomerata and A. capillaris grew better in monocultures than in mixture. Effect of donor treatment on monocultures: Under bare soil, D. glomerata grew better than under F. paniculata leachates. By contrast, A. capillaris did not respond to donor pot treatment. Effect of donor treatment on mixtures: However, when both species were cultivated together under F. paniculata leachates, the biomass of D. glomerata was similar to that in monoculture under bare soil. Differences in sensitivity to allelopathy reversed the impact of interspecific competition: A. capillaris facilitated D. glomerata under allelopathy, which made allelopathy of F. paniculata on D. glomerata inefficient. The complexity of overlapping mechanisms of plant-plant interactions are highlighted by this semi-natural experiment. In subalpine grasslands, allelopathy not only limits the growth of neighboring plants, but it may also modify community assembly by affecting other plant-plant interactions such as competition. This study contributes to explore the way allelopathy interacts with other plant-plant interactions in natural systems.

The phytocenotic potential of pasture ecosystems of the Tsimlyanskii sand massif using the ecological scales of humidity, soil reaction, and soil richness in mineral nitrogen of G. Ellenberg is studied. This work is based on landscape-bioecological and ecological-morphological research methods using methods for studying the structure, stability and development of plant communities. It has been established that the family types Poaceae , Fabaceae , and Asteraceae play the greatest role in projective coverage. The predominant life form of vegetation at all sites studied are is 40–71%. The average productivity of phytocenoses is 156–287 g/m 2 . The species composition and productivity of pasture phytocenoses changes noticeably depending on the humidity, physicochemical properties, and the richness of the soil in mineral nitrogen. On moist, non-drying, slightly acidic soils with an average nitrogen content, edificators are Agrostis canina L. , A. tenuis Sibth., Thlaspi arvense L., Typha angustifolia L., T. latifolia L., Tanacetum vulgare L., Phragmites australis (Cav.) Trin. ex Steud., and Scirpus lacustris L. Under average moisture conditions, on slightly acidic soils with an average nitrogen content, edificators are Achillea millefolium L., Astragalus arenarius L., Elytrigia repens (L.) Nevski, Medicago falcata L., and Phleum pratense L. Under average moisture conditions, on slightly acidic soils rich in mineral nitrogen, edificators are Apera spica-venti (L.) P.Beauv., Atriplex tatarica L., and Calamagrostis epigeios (L.) Roth. Under average moisture conditions, on neutral soils with an average nitrogen content, edificators are Artemisia abrotanum L . , Cirsium incanum (SG Gmel.) Fisch., Gypsophila paniculata L., Inula germanica L., Juncus gerardii Loisel., and Senecio erucifolius L . On dry, slightly acidic soils with an average nitrogen content, edificators are Chamaecytisus ruthenicus (Fisch. ex Wol) and Festuca valesiaca Gaudin . On dry, slightly acidic and mineral nitrogen-poor soils, edificators are Anisantha tectorum (L.) Nevski, Artemisia campestris L . , A. maritima L., A. marschalliana Spreng . , A. scoparia Waldst. & Kit . , Bromopsis inermis (Leyss.) Holub, Crepis tectorum L., Koeleria glauca (Spreng.) DC., Leymus racemosus (Lam.) Tzvelev, Potentilla incana P. Gaertn., B. Mey. & Scherb . , Psammophiliella muralis (L.) Ikonn . , and Stipa capillata L. Under conditions of sufficient and variable moisture, on neutral and slightly acidic soils with an average nitrogen content, edificators are Agropyron cristatum L. and Thlaspi arvense L. In the brome–bushgrass–wormwood ( Bromopsis inermis , Calamagrostis epigeios , Artemisia marschalliana ) community, there is a large proportion of therophytes (22.9%), which indicates anthropogenic pressure on this territory.

The combustion of fossil fuels and associated warmer temperatures are causing a global increase in the availability of soil nutrients such as nitrogen. This will have pronounced effects on plants at northern latitudes that are adapted to low nutrient conditions. An experiment in northern Canada set up in 1990 has investigated the effects of long-term nutrient enrichment (fertilizer addition) and mammalian herbivore exclusion (fencing) on an understory plant community. We used this experiment to assess how 22 years of fertilization has affected investment in sexual reproduction in four herbaceous understory species. We measured reproductive output at the plot level (proportion of plants flowering) for four species (Mertensia paniculata, Epilobium angustifolium, Achillea millefolium and Festuca altaica) and at the individual plant level (biomass allocation to flower parts) for M. paniculata and E. angustifolium. Fertilization increased the probability of flowering for A. millefolium and resulted in a higher allocation of biomass to flower parts for E. angustifolium. Sexual reproduction in M. paniculata and F. altaica was largely unaffected by increased nutrient supply, and, as expected, herbivore exclusion had almost no effect on any species. Whereas plants in northern ecosystems currently reproduce mainly through clonal growth, rapidly changing environmental conditions and warmer temperatures will likely result in increased benefits of sexual reproduction. This could give a competitive advantage to species such as A. millefolium and E. angustifolium that increase investment in sexual reproduction when released from nutrient limitation.

The differential grasshopper, Melanoplus differentialis (Thomas) (Orthoptera: Acrididae), frequently migrates from highway rights-of-way, pastures, and harvested fields to feed in urban/suburban landscapes and retail/wholesale nurseries across the southern and southwestern U.S.A., as these areas dry down during hot dry summers. Nine selected turfgrasses and 15 species of landscape plants were evaluated for their susceptibility or resistance to this grasshopper. Grasshoppers were collected from stands of Johnsongrass, Sorghum halepense, which was used as a standard host for comparison in both experiments. Based on feeding damage, number of grasshopper fecal pellets produced, and their dry weight, Zoysia matrella cv. ‘Cavalier’ was the least preferred grass followed by Buchloe dactyloides cv. ‘Prairie’ and Z. japonica cv. ‘Meyer’. Festuca arundinacea was significantly the most preferred host and sustained the most feeding damage, followed by Poa pratensis × P. arachnifera cv. ‘Reveille’ and 2 Cynodon spp. cultivars, ‘Tifway’ and ‘Common’. Among the landscape plants, Hibiscus moscheutos cv. ‘Flare’, Petunia violacea cv. ‘VIP’, Phlox paniculata cv. ‘John Fanick’, Tecoma stans cv. ‘Gold Star’, and Campsis grandiflora were the least damaged or most resistant. Plumbago auriculata cv. ‘Hullabaloo’, Glandularia hybrid cv. ‘Blue Princess’, Canna × generalis, Johnsongrass, and Cortaderia selloana cv. ‘Pumila’ sustained the most damage. Based on the number of fecal pellets produced and their weights, Canna × generalis and Glandularia hybrid cv. ‘Blue Princess’ were the most preferred landscape plants tested.

The continuum of responses model (CRM) and the growth rate model (GRM) make conflicting predictions about the effects of soil nutrient availability on the resilience of plants to herbivory. A factorial experiment was conducted in the understory of the boreal forest to examine the effects of fertilization and simulated herbivory on the rate and amount of regrowth of three herbaceous perennial species (Achillea millefolium L., Festuca altaica Trin., and Mertensia paniculata (Aiton) G. Don.).