Chorological and ecological analysis of tribe Trifolieae, family Fabaceae, in the prefecture of Thessaloniki
The genera Medicago, Melilotus, Ononis, Trifolium and Trigonella, of the tribe Trifolieae, family Fabaceae, include some of the most important plants for grasslands, with great economic and ecological value. In this work, which is based on a literature review, all taxa of tribe Trifolieae of the Thessaloniki prefecture are recorded. The total number of taxa is 76 and most of them are therophytes (71.1%). The euri-mediterranean (44.8%), eurasiatic (27.6%) and steno-mediterranean (19.8%) floristic elements are the most dominant. The results of the analysis of the ecological demands of plants, show that most of the plants of the tribe have the optimum of their growth in warm sites with relatively high intensity of solar radiation with dry soils, poor in nutrient supply.
Invasibility of three native plant communities tο the establishment of the plant invader Oxalis pes-caprae L.
Although some invasive plants are cosmopolitan, not all ecosystems are invaded to the same degree. Yet, there is little experimental work on how ecosystem resistance to invasion at the establishment phase differs among ecosystems. We conducted a field experiment to examine establishment of the plant invader Oxalis pes-caprae in coastal dunes, shrublands and herbaceous understory of olive groves in Lesbos. We selected thirty (30) observational stations, ten per native plant community. Each station consists of a pair of plots: the invaded plot and the reference one. In each invaded plot, we sowed a hundred bulbs of O. pes-caprae, measured the number of seedlings of the plant invader and estimated local species richness, diversity and evenness of native plant communities. In addition, we recorded not only the geographical longitude, the geographical latitude and the elevation in each observational station, but also precipitation and mean temperature for the period between sowing and sampling. Local species richness and vegetation structure were not a good predictor for seedling establishment in costal dunes and herbaceous understory of olive groves. All abiotic factors did not determine the ecosystem invasibility of native plant communities. Finally, we found out that differences in local species richness and diversity of shrublands were only associated to differences in establishment rates of plant invader. Consequently, we concluded that any species poor shrublands are more susceptible to the invasion of the plant invader O. pes-caprae.
Vegetation types of Lake Chimaditis before the artificial increase of its water level
The wetland vegetation of Lake Chimaditis is composed of manifold plant communities, most of which are dominated by only one species. Additionally, these almost mono-specific plant communities cover the greatest part of the lake surface, a fact indicating the intense degradation of some wetland types of the lake, which, however, still hosts important populations of rare bird species. The aim of the present paper is to present the different vegetation types of Lake Chimaditis according to its present status, as a gradual increase (by 70 cm) of the maximum water level is planned with the rise of the northern peripheral bank under construction that aims at reducing the lake area covered by high emergent vegetation, increasing the water volume of the lake and at improving the habitats of protected bird species. Specifically, from the interior open water areas towards the shore, the following habitat types were distinguished as zones: submerged plant communities (Myriophyllum spicatum), helophytes (Schoenoplectus lacustris, Typha latifolia, T. angustifolia, Phragmites australis, Carex riparia and Juncus acutus, peatlands with Cladium mariscus, wet meadows with Juncus inflexus), terrestrial communities (Ononis spinosa, Salix alba). The increase of the lake water level is expected to cause significant changes in the area and structure of most vegetation zones. At the same time, for the conservation of habitat types of great importance for the aquatic bird fauna (e.g. wet meadows), it is estimated that management practices, including systematic grazing and summer cutting of the vegetation of the littoral zone, will have to be implemented at specific locations of the lake.
Geographical distribution and soil preferences of genus Medicago species in Greece
Greece having 35 species of Medicago genus is the second country in the world in species number. Their geographical distribution is either broad or very localized. Many species of this genus are found in natural and semi-natural ecosystems, grazed by herbivores. M. sativa ssp. sativa is the most cultivated species used for hey production. On the contrary, in Australia many cultivars of annual Medicago are cultivated. Most species develop in calcareous, limestone and schist parental material, in sandy, sandy loam and loam soil texture and in pH mainly alkali to medium acidic. Many species, like M. lupulina, are adapted to a wide range of conditions and others, as M. marina, are restricted in very specific habitat. The knowledge of soil preferences, needed for Medicago species’ growth, is important for the characteristics of each species, for its possible use in agricultural practice, as well as for the protection of rare and endemic species.
The tenacity of perennial graminaceae to intense grazing
The effect of intense grazing on the increase and the production of the perennial species Dactylis glomerata and Phalaris aquatica was studied. Ten similar individuals were selected for both species from natural populations. In half from the individuals of each species the herbaceous biomass was cut 5cm high above the ground in the middle of the growing period. For both treatments the increase of leaf length was measured, during the growing period. The production of biomass and the leaf area were measured for both treatments. Also, the rate of grazing recovery (R.G.R.) and the coefficient of grazing tolerance (C.G.T.) were calculated. The results showed that intense cutting, as imitation of grazing, favored the growth of new leaves and stems for both species. Higher values of R.G.R (Rate of grazing recovery) and C.G.T. (Coefficient of grazing tolerance) than those of Phalaris aquatica showed that Dactylis glomerata is more tenacious in terms of intense grazing.
