Water use efficiency of two forage species with different photosynthetic pathways
Exchange rates of CO2 and H2O under drought conditions were investigated in two grass species (Dasypyrum villosum, Dichanthium ischaemum) with different photosynthetic pathways (C3, C4) in order to evaluate their water use efficiency (WUE). Our results indicated differences in photosynthetic (Pn) and transpiration rate (Tr) between the two species. At the same values of leaf water potential (LWP) D. villosum (C3) exhibited higher Pn and Tr in relation to D. ischaemum (C4). However, their WUE showed no obvious differentiation. It seems that under drought conditions at late successional stages D. villosum (C3) develops higher photosynthetic rates than D. ischaemum (C4), and about the same values of WUE. Thus, the productivity of C3 and C4 species is probably related not only to the photosynthetic process but also to the ambient conditions in which the plants have been developed.
Correlation of productivity and nutritive value of the herbaceous vegetation with the tree cover of oak and beech trees in Lagadas county of Thessaloniki
Silvopastoral systems are complex systems that produce in the same area forest products and feed for livestock. In this paper the effect of low cover of oak and beech trees (10-35%) was studied on forage production and nutritive value of the understory herbaceous vegetation. The research was conducted in silvopastoral systems of Lagadas county of Thessaloniki, in spring of 2003. The tree cover, the annual production of the herbaceous species were measured in the field while the nutritive value of the production was estimated with laboratory techniques. Regression models were generated that correlates the tree cover with the annual herbage production, ground litter and the nutritive value. The annual herbage production was relatively high (210 kg/0.1ha) and correlated positively with the tree cover but there was no significant correlation between tree cover and the parameters of nutritive value. The relative high herbaceous production and its satisfied nutritive value suggest that the oak and beech silvopastoral systems are important forage resources for meeting the demands of livestock in the county of Lagadas of Thessaloniki.
Changes in forage production in relation to vegetation succession in rangelands of Lagadas county of Thessaloniki prefecture
Οver the last few decades the demographic and socioeconomic changes have reduced the intensity of land use in semi-arid Mediterranean rangelands of Lagadas County. The impact of these changes on rangeland is expressed through the progressive woody plant encroachment during secondary succession. The knowledge of the way that woody and herbaceous production evolves during successive of stages is a critical parameter for the planning of a sustainable management of these areas. The present study took place in Lagadas County, northern Greece, during the summer of 2005. In four rangeland types, with four replications each, representing sequential successional stages related to land use extensification (abandoned fields, grasslands, open and dense shrublands). The aboveground herbage and woody biomass was measured. Sampling was applied during the period of maximum total production. In the laboratory both herbage and woody vegetation was sorted into live (current years) and dead (old) components. All biomass was oven dried and weighed. The total production in grassland, open and dense shrublands was found 1136.7, 2900.1 and 810.6 kgr/ha respectively. Statistical analysis (ANOVA) was applied to all data in order to test if significant differences occur between the four land use types.
Changes in herbage production in relation to shrub cover during the early spring period in semi-arid Mediterranean rangelands
The present study is a contribution towards the assessment of the changes in herbage production in relation to shrub cover during the early spring period in semi-arid Mediterranean rangelands when herbage quantity is low but quality is high. The study was conducted Lagadas county, northern Greece during spring 2004. In the study area four types of vegetation were identified, namely abandoned field, grassland, open and dense shrubland with 0%, 5%, 36% and 49% shrub cover respectively. Sward height, live matter yield and sward bulk density were measured in 15 and 30 April and 15 May. Ιn the Laboratory live matter was sorted by hand from dead matter and then into legumes and other species (grasses and forbs) in order to assess their dry matter contents. In the non-legume fraction the nitrogen and phosphorus nutrient indices were also calculated. It was found that live matter generally decreased as shrub cover increased during the early spring season. On the contrary the growth rate did not differ significantly between the four types. Sward height was significantly higher when shrub cover was maximum in 30 April, whereas sward bulk density was significantly higher when no shrubs occurred during April. Finally, live matter yield was positively related to nitrogen and phosphorus nutrient status, while P supply had an indirect effect on live matter yield through the increase in N index.
Use of plant functional groups to study land use changes in semiarid Mediterranean rangelands
The aim of this paper was to study the changes caused by the abandonment and/ or extensification of traditional land uses in Mediterranean rangelands through the changes of easily identified plant functional groups. Four treatments, which reflect the stages of rangeland evolution after abandonment, were studied in Lagadas county of Thessaloniki: abandoned arable field, grassland, open shrubland and dense shrubland. In these treatments, species frequency was measured. Species were separated into functional groups according to their life cycle, photosynthetic cycle and growth form and the contribution of each group into each treatment was calculated. It was found that early stages of abandonment were dominated by annual, C3 therophyte species. In the advanced stages, perennial hemicryptophyte species prevailed. C4 grasses had a strong presence in the intermediate stages.
