Abstract |
Effective management practices for specific species requires the understanding of species and its habitat characteristics, which determined their distribution and abundance. According to that, the characteristics of the endemic species Asperula crassula was studied, as well as the characteristics of its only habitat, which is located in Mayros Peninsula, in the north - east end of Crete. The species Asperula crassula a) has succulent leaves, b) has hairy leaves and flowers, which reduce the water loss due to transpiration and increase the sun radiation reflection, c) is located in a dry habitat and d) is under salinity stress because of its location adjacent to the sea. These characteristics are common in plants that follow the CAM photosynthetic pathway, and they led to the examination of the photosynthetic behavior of Asperula crassula, and its determinant role in the distribution of the species. The study of leaf active acidity shows that although Asperula crassula has a number of CAM plants characteristics, neither follows the CAM photosynthetic pathway, nor swifts to it from C3 or C4 photosynthetic pathways. These results were not enough to explain the distribution and the abundance of Asperula crassula, in the specific area, so vegetation as well as soil characteristics were studied, in order to examine their role in the species distribution and abundance. Structure and composition of woody species were studied, as well as soil mechanical composition, and CaCO3, organic carbon, nitrogen, assimilative potassium, assimilative sodium, assimilative phosphorus concentrations, pH and electric conductivity. The results from these data point out that the variation in composition and structure of woody species, although is affected by soil characteristics, is not enough in explaining the distribution and the abundance of the species Asperula crassula. Contrary to this, the CaCO3, organic carbon and assimilative potassium concentrations as well as the C/N ratio appear sufficient to explain the species distribution and abundance. Asperula crassula seems to prefer soil with low concentration in nutrients as potassium, high concentrations in CaCO3, and high levels of C/N ratio. It can be said that Asperula crassula prefers soils with low fertility, and takes no advance from the nutrient enrichment by grazing.
|