Leguminosae taxa of forest communities in NE Greece
This study presents the legume flora of the forest vegetation in northeast Greece. NE Greece is characterized by a high diversity in forest habitats, as in this area both Central-European (Picea abies, Betula pendula, Alnus incana forests) as well as typical Mediterranean vegetation types (maquis, Pinus halepensis ssp. halepensis, Pinus halepensis ssp. brutia forests) occur. The floristic catalogue was based on bibliographic data as well as on collections made during the spring and summer of 2005. The habitat types and the areas in which the taxa were recorded, are given. Most of the legume taxa were recorded in evergreen shrublands, while the smallest number of taxa was found for the coniferous forests of the mountainous and subalpine zone (Picea abies and Pinus sylvestris forests). Chalkidike Peninsula and Mt. Chortiatis were found as the richest areas in legume taxa, but this result is probably affected by the fact that for the latter areas more floristic and phytosociological data exist, in comparison with the other areas of NE Greece.
Biotic, ecological and chorological analysis of the genus Trifolium in Greece
The taxa of the genus Trifolium are considered as worldwide valuable plant resources for rangelands. Their significance is found in their economic role, as they provide grazing animals with protein resources, and their ecological role, as they comprise of the major nitrogen pools in the soil. The Greek flora sustains 109 out of a total of 250 taxa, approximately reported worldwide. Information concerning the specific localities of Greece, where Trifolium taxa were reported, is found elsewhere in this volume. Extending the analysis, the present research aims at classifying the 109 taxa into a) life-duration classes, b) biotic types, and c) classes of chorological origin. The analysis was based in the elaboration of several research efforts and the available bibliographic information. The results showed that 6 out of 109 Trifolium taxa (92 species, 16 subspecies, 1 hybrid) are Greek endemics. Also, a high percentage of them (72% of 109) are annual therophytes. The majority of them (64% of 109) are Mediterranean elements. The results point out Greece as a prominent center of distribution of the genus Trifolium, and consequently an important “gene-pool” country, worldwide.
Seasonal change of hydraulic resistance in Melilotus officinalis L. tissues under water deficit
The possible appearance of desertification phenomena in the Mediterranean zone necessitates the study of ecophysiological mechanisms of range plant tolerance to water deficit. Towards this direction several hydrodynamic (water potential, relative water content) and physiological parameters (stomatal conductance, transpiration) were measured while, at the same time, the seasonal change of hydraulic resistance was calculated in Melilotus officinalis (L.) under two different water regimes (well watered and water stressed plants). The results indicate that the well watered plants showed higher hydraulic resistance, possibly attributed to an effort of saving the soil water resources during the dry period. On the other hand, water stressed plants seemed to maintain their transpirational flow through a less sensitive stomatal apparatus, exhibiting a higher water transport capacity at the soil-plant-atmosphere continuum, indicating a capacity of phenotypic plasticity.
Ecosystem response of Mediterranean grasslands to the dominance of the plant invader Oxalis pes-caprae L.
One of the most aggressive invaders of the Mediterranean-type ecosystems is the exotic plant species Oxalis pes-caprae L., which comes from the Cape of South Africa. This research studies the ecosystem response of the herbaceous vegetation understory of olive groves in SE Lesbos to the dominance of the plant invader O. pes-caprae. They were selected 30 and 28 observational stations for the year 2004 and 2005, respectively. Each station consists of a pair of plots: the reference plot and the invaded one. The plant invader O. pes-caprae was absent from the reference plot, while it was dominant in the invaded one. In each pair of plots, it was estimated the total biomass production (above- and belowground biomass production) and the aboveground biomass per functional groups (grasses, legumes, forbs and the invader). The dominance of plant invader O. pes-caprae has caused a significant decrease of the aboveground biomass production for both years, while the belowground biomass production has showed a significant increase, contributing to a significant increase of the total biomass production in the invaded plots for the second years of this study.
Effects of cutting and burning on grazed vegetation of wet meadows at Lake Agra
The expansion of reed (Phragmites australis) in wetlands constitutes a great threat for bird fauna, while it increases the grazing pressure from domestic animals, as a result of the decreased wet meadow coverage. In this study, the effectiveness of cutting and burning in combination with livestock grazing to control helophytic vegetation was investigated. Specifically, mechanical cutting of reedbed was applied using a portable slashing machine. At the same time, paired plots 3×3 m each (protected and freely grazed) were established. In addition, burning was applied in areas covered by Cladium mariscus, Juncus effusus, Cirsium palustre and Carex davalliana. They were measured cover, species composition of herbage, production and utilization percentage at the sites where cutting and burning were applied. It was found that grasses, on the average, were the dominant cover group in the total area, in both treatments. Cutting reduced helophytes and favoured the growth of grasses. In contrast, burning resulted in a more severe reduction of herbage production compared in cutting. When grazing was combined with the two treatments, helophyte re-growth was controlled by livestock, especially of the reed.
