1,721,078 research outputs found
Small-scale spatial structure in a remnant calcareous grassland
No full textI investigated the relative importance of abiotic factors in species assemblage distribution in remnant calcareous grassland heavily grazed by sheep. A TWINSPAN classification recognized seven vegetation types. Direct gradient analysis (using CCA) revealed that the prevalent pattern in this grassland was represented by species-poor patches (grassland with Carduus pycnocephalus), versus species-rich patches (grassland with Cerastium ligusticum and grassland with Eryngium campestre). Species exclusive to dry grasslands and pastures, such as Carlina corymbosa, Anthemis tinctoria and Xeranthemum inapertum, were positively correlated with low nutrient availability, while species common to disturbed habitats, such as Hordeum murinum,
Dasypyrum villosum and Bromus sterilis, were correlated with high nutrient availability and with deposition of dung and urine by grazing animals. The variations in environmental factors
is only partially responsible for the spatial patterns in the species data. Open grassland in general agreed with the classification based on species data when considering environmental
variables, while Prunus spinosa scrubland showed 65% of the samples misclassified and shrubby grassland with Cerastium arvense, as well as Juniperus communis scrubland did not
show any sample classified in their own vegetation type. The results of the present study are discussed in the context of the conservation and restoration of this vegetation type
Long-term experimental restoration in a calcareous grassland: Identifying the most effective restoration strategies
No full textCalcareous grasslands are among the most diverse habitats, supporting species-rich vegetation. Propagule limitation and availability of microsites for germination represent major constraints to the successful restoration of these grasslands. To date, little information is available on the effectiveness of seed addition and soil disturbance on the restoration success of encroached semi-natural calcareous grasslands. Here, we conducted a 1 year before -9 year after control-impact (BACI) study aimed at testing the effect of the addition of seeds of native species and livestock grazing on calcareous grasslands. Each restoration measure and their combination differed in their impact on these communities and varied over time. Grazing had a significant, beneficial, impact on these communities, although the impact was species-specific. On average, grazed plots were characterized by a higher number of species and a lower vegetation cover. Nine years after treatment application, grazed site were dominated by Trifolium incarnatum subsp. molinerii, Xeranthemum cylindraceum, Orlaya grandiflora, Teucrium chamaedrys and Bromus erectus while ungrazed sites were dominated by B. erectus, X. cylindraceum, O. grandiflora and Prunus spinosa. Only 8 out of 34 species responded significantly to disturbance or/and disturbance and seed addition while 22 species were significantly affected by the sampling year and 18 by a blocking factor. The low recruitment from added seeds and the fact that seed addition is a time-and labor-consuming activity suggests that an adequate level of disturbance and natural regeneration represent the most cost-effective approach to the restoration of these calcareous grasslands. © 2011 Elsevier Ltd. All rights reserved
Germinable soil seed-bank of former grassland converted to coniferous plantation
No full textThe influence of afforestation with cedars on field layer vegetation and on the germinable soil seed-bank were investigated along a 60-m transect merging from open grassland to sparse and dense canopy cover. A total of 132 species were found, 76 in the seed-bank and 109 in the vegetation, with 53 species in common. Conifer cover was not found to be associated with a decrease in total number of species in the vegetation or seed-bank, but the mean number of species in the vegetation, total cover in field layer vegetation and mean number of individuals in the seed-bank decreased significantly from grassland to forest stands. The grassland seed-bank was dominated by Saxifraga tridactylites and Veronica agrestis; the seed-bank of plots of scattered cedars was dominated by Trifolium incarnatum ssp. molinerii; and that of dense cedar plantations was dominated by Campanula rapunculus. The number and cover of grassland species of field layer vegetation decreased in the forest, with respect to open grassland, and the same trend was found for density of individuals in the seed-bank. It is concluded that grassland restoration by cutting cedars cannot rely on the presence of grassland species in the soil seed-bank
Long-term effects of climate and phosphorus fertilisation on serpentine vegetation
No full textThe long-term effects of phosphorus fertilisation and climate on serpentine plant communities in Tuscany, central Italy have been investigated by using data from a 12 year before-after control-impact (BACI) experiment. Using the point quadrat method, data on plant communities were collected in June of each year from 1994 to 2005 in eight 2 × 2 m plots, four fertilised with phosphorus and four used as controls. Climatic data were obtained from a nearby meteorological station and summarised in 24 variables. Phosphorus addition significantly affected vegetation cover of both vascular and cryptogamic vegetation but did not influence species richness. The effects on species composition were clear but not marked, and consisted in promoting the abundance of some species already present in the community but not leading to the colonisation of other species. Interannual climate differences affected vegetation cover in the fertilised plots but not in the control ones, while climate affected the species richness values of different/various life-forms in both groups of plots, with more evident effects in the fertilised one. The effects of climate on plant community composition were weak once both the variability among individual plots and the successional dynamics were subtracted from the variance in species composition
Evaluation and monitoring of the flora in a nature reserve by estimation methods
No full textWe tested the use of non-parametric estimators of species richness to evaluate the flora of a relatively large (431 ha) nature reserve, using a sampling area much lower than that used in previous studies. Different estimation methods were applied to floristic data obtained from 50 random plots: the number of observed species, the extrapolated accumulation curves based on the Michaelis-Menten model and the non-parametric estimators based on incidence data (Chao2, first-order Jackknife, second-order Jackknife and bootstrap). To test the performance of the estimators, five data sets were created on the basis of life-forms. The estimates were compared with reference values obtained by traditional floristic and vegetation sampling. The power of the different estimation methods could not definitively be determined, but the first- and second-order Jackknives seem to be the most precise. Although total species richness was underestimated, the sample-based approach provided accurate information for quantitative comparison of time series of data related to ecological changes, vegetation dynamics and environmental changes. This sample-based data included basic statistics on species richness and species frequency distributions as well as the life-form spectrum, at the plot and the whole site scales. (C) 2001 Elsevier Science Ltd. All rights reserved
Structure and species diversity of Bromus erectus grassland of biancana badlands
No full textSpecies richness, diversity and structure were studied in Bromus erectus grasslands on the top of biancana landforms of the Orcia Valley, Tuscany (central Italy). Three community types were recognized : uneven B. erectus grasslands on less stable morphologies, and compact B. erectus grasslands and B. erectus grasslands colonized by Spartium junceum scrub, both on more stable morphologies. The main difference between them was a dramatic decline in species richness and diversity from the former to the latter. The number and cover of annual herbs, many of which are low-growing species (e.g. legumes and graminoids), also decreased significantly in the same order. The frequency of B. erectus was constant (100%) in all three types of community, whereas percentage cover increased sharply (54.2 vs. 85.5%) between uneven and compact grasslands, remaining high in the scrub communities (83.8%). Cover of phanerophytes showed low values in the uneven and compact grasslands, but reached 80% in the scrub communities. The increase in cover of B. erectus caused the disappearance of species typical of the pioneer vegetation of Pliocene clay soils with Artemisia cretacea. Colonization of the compact grasslands by S. junceum induced a reduction in grassland species of the class Festuco-Brometea. The implications of these findings for the conservation of B. erectus grasslands and biancana badlands are discussed
Germination of nine species of a pioneer plant community of pliocene clay soils of central western Italy under different photo- and thermo-periods
No full textGermination response under different photo- and thermo-periods was investigated in nine species of the association Parapholido-Artemisietum cretacene, a typical plant community of clay badland vegetation in central western Italy. The species showed: (i) more rapid germination under the photo- and thermo-period emulating autumn conditions than under the one emulating early spring conditions; (ii) different germination rates under condition emulating periods with high diurnal insolation followed by high or low nocturnal heat dispersion: Aegilops geniculata, Parapholis strigosa and Artemisia cretacea were indifferent, Hordeum maritimum, Trifolium scabrum, Brachypodium distachyum and Parapholis incurva responded positively to higher thermal dispersion, whereas Medicago minima and Scorpiurus muricatus responded negatively; (iii) different responses to a constant low temperature of 2 degrees C: Artemisia cretacea, Parapholis incurva, Parapholis strigosa and Scor piurus muricatus showed complete or very high dormancy; the other species showed a germination capacity between 55 and 87% in the following decreasing order: Medicago minima > Hordeum maritimum > Trifolium scabrum > Aegilops geniculata > Brachypodium distachyum. All species had delayed and reduced germination responses at 2 degrees C. Grasses showed prompt, quick and high germination as environmental conditions became more favourable; legumes showed a similar response when their coat-imposed dormancy was removed, while the asteracea A. cretacea showed only a moderate germination capacity and one of the lowest germination rates
Germination of Nine Species of A Pioneer Plant Community of Pliocene Clay Soils of Central Western Italy Under Different Photo- and Thermo-Periods
No full textGermination response under different photo- and thermo-periods was investigated in nine species of the association Parapholido-Artemisietum cretaceae, a typical plant community of clay badland vegetation in central western Italy. The species showed: (i) more rapid germination under the photo- and thermo-period emulating autumn conditions than under the one emulating early spring conditions; (ii) different germination rates under condition emulating periods with high diurnal insolation followed by high or low nocturnal heat dispersion: Aegilops geniculata, Parapholis strigosa and Artemisia cretacea were indifferent, Hordeum maritimum, Trifolium scabrum, Brachypodium distachyum and Parapholis incurva responded positively to higher thermal dispersion, whereas Medicago minima and Scorpiurus muricatus responded negatively; (iii) different responses to a constant low temperature of 2°C: Artemisia cretacea, Parapholis incurva, Parapholis strigosa and Scorpiurus muricatus showed complete or very high dormancy; the other species showed a germination capacity between 55 and 87% in the following decreasing order: Medicago minima > Hordeum maritimum > Trifolium scabrum > Aegilops geniculata > Brachypodium distachyum. All species had delayed and reduced germination responses at 2°C. Grasses showed prompt, quick and high germination as environmental conditions became more favourable; legumes showed a similar response when their coat-imposed dormancy was removed, while the asteracea A. cretacea showed only a moderate germination capacity and one of the lowest germination rates. Nomenclaure: Pignatti (1982)
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