Empirical seasonal predictive models of production and cover of above ground biomass in relation to climatic parameters in a subalpine grassland of Tymfristos mountain – prefecture of Evrytania
Ecosystems’ productivity is strongly related to climatic conditions. Specifically, the productivity of Mediterranean rangeland ecosystems is depended to the degree of time- and space-irregularity of precipitations’ distribution. The use of climatic parameters in the construction of empirical mathematical models towards the prediction of cover and production of the above ground biomass is a powerful tool for management purposes. The present research deals with the exploration and construction of mathematical seasonal predictive models having above ground biomass and cover as dependent variables and climatic variables as explanatory ones. The research was conducted in 2000 in ungrazed grassland of Rovia location of Evrytania. Vegetation data were collected in a monthly basis from April to September and models were set up using climatic data obtained from the Institute of Mediterranean Forest Ecosystems & Forest Product Technology of Athens. For climatic data time depth was obtained from the start of the raining season of the previous year (September 1999) until the antecedent month of vegetation’s data collection. A total of 288 models (linear and non linear) included (and not included) a constant term in their mathematical expression were examined. It was found that only the sigmoid model with a constant term is statistically fitted to precipitation and dead biomass data. On the contrary, when the constant term is not included it was found that only 10 from 144 models were not statistically fitted to climatic and vegetation data. In the case of constant term’s exclusion the selected seasonal predictive models were the power, the “S”, and the growth ones.
Herbage production per plant functional type in relation to land use changes in Mediterranean rangelands
During the last few decades, lowland and semi-mountainous rangelands in the Mediterranean region have faced significant socioeconomic changes. The extensification and abandonment of traditional management practices, such as livestock raising and fuelwood collection, have led to major changes in structure and function of rangeland ecosystems through the extensive woody plant invasion and the evolution of natural vegetation towards next successional stages. In this study, plant functional types (PFT’s) were used in order to assess above ground herbage production dynamics in different stages of secondary succession along an extensification gradient. The study was carried out in Lagadas County, Thessaloniki, northern Greece at an altitude of 500 m a.s.l. During spring 2003, above ground herbage production was measured across four vegetation types representing sequential successional stages (abandoned fields, grasslands, open and dense shrublands, respectively). Live biomass was harvested at its peak stage in a total of 16 replicate plots of 3030 m., whereas in the Laboratory plant species were sorted and classified into plant functional groups based on their life cycle, life form and photosynthetic pathway. Each group’s herbage production was correlated with each vegetation type in order to identify patterns related to land use change and production dynamics. It was found that above ground herbage production significantly decreased towards later successional stages, while grasses and legumes were the most sensitive groups to land use change. Annual C3 grasses and annual forbs were making the majority of the total herbage production at the early stages, whereas perennial C4 grasses took over at the late ones. It was concluded that plant functional types can be a useful tool for the assessment of above ground herbage production dynamics in Mediterranean rangelands across different successional stages after the abandonment of prior use.
Productivity, composition and frequency of species in a grassland under two grazing regimes
Traditionally grasslands of the Ioannina plateau are cut for hay at the end of May and grazed till next March. (CG). The aim of this work was to examine how the continuous grazing (G) without clipping, as well as Nitrogen fertilization affect the productivity, species composition and frequency of species. Fertilization increased significantly the total biomass production (31%) during the first year due to the significant increase of grasses (40%). There were also similar results in the last year (2000) and the relative increments were 34% and 74% respectively. The dominant species Bromus hordeaceus and Alopecurus urticulatus increased 89% and 102% respectively. On the contrary, there was a significant reduction of forbs (63%) especially of Cichorium intybus, Tragopogon pratensis and Plantago lanceolata species. Finally there was a 50% reduction of the total forbs biomass in G treatment and N fertilization but not in the unfertilized treatment in which there was a significant increment. There were also similar results regarding species composition and frequency. A gradual change was observed for all the above species every year concerning productivity and composition, which was differentiated according to the whether conditions.
An approach of interference between Dichanthium ischaemum (L.) Roberty and Chrysopogon gryllus (L.) Trin. by replacement series experiment
The warm season perennial grass species Dichanthium ischaemum (L.) Roberty and Chrysopogon gryllus (L.) Trin. dominate in the low and middle elevation grasslands in northern Greece. Intraspecific competition and the tolerance to the influence of grazing determine their relative abundance. The experiment was designed to study the interference between D. ischaemum and C. gryllus. It was conducted following the “replacement – series” (de Wit model) experimental design that is based on a constant total density (286 individuals/m2) and different relative proportion 100:0, 75:25, 50:50, 25:75, 0:100. Measurements of the plant height were taken during the growing season. Plant biomass (over- and underground) was measured at the end of the growing season. The index of the Relative Total Yield (RYT) was estimated. Plant height was higher at the proportion 75:25 and 25:75 for D. ischaemum and C. gryllus respectively. The estimated RYT in the above densities was >1 indicating lack of competition and a relationship of symbiotic interference between the species.
Evaluation of two cultivars of Trifolium alexandrinum L. for growth and resistance to drought
Two cultivars of Trifolium alexandrinum L., “Kastalia” and “Pinias”, were grown and tested for their resistance to drought. The experiment was conducted in a glasshouse in Drama, northern Greece. Two water regimes were applied. The measurements were taken in full bloom stage. They included leaf, stem and root weights, leaf area, stomatal conductance and transpiration. Moreover, total and above ground biomass, the allometric relations Leaf Area Ratio (LAR), Leaf Weight Ratio (LWR) and root to shoot ratio (R/S), as well as the total plant transpiration and the Plant Water Use Efficiency (PWUE) were calculated. It was found that a) the two cultivars presented different leaf growth, stomatal conductance and plant water use efficiency, and b) their resistance to drought was similar involving mechanisms that resulted in less root growth reduction compared to shoots, reduced transpiration and increased water use efficiency.
