Water use efficiency and net production of two semi arid grasslands in different successional stages

Abstract

The productivity of Mediterranean grasslands, which depends on successional stage, climatic factors and human interventions, cannot fulfil forage demands of ruminants during the dry summer pe-riod. The current paper investigates whether the successional stage of vegetation could alter the water use efficiency during the semiarid period of summer and whether the productivity of low elevation Greek grasslands may be approached by the traditional concept of succession. Seasonal trends in physiological parameters, such as net photosynthetic rate and transpiration rate as well as net productivity was recorded in the most dominant species of two grasslands at an early and late successional stage (ESS and LSS re-spectively). The results reveal significant differences in net photosynthetic rate, transpiration rate, and water use efficiency of the most dominant species between the two grasslands throughout the season. Net production was significantly higher in the LSS grassland especially during the drier parts of the season (middle summer). The higher water use efficiency and higher net production in late successional stages of the lowland Mediterranean grasslands that we have examined in the current study suggests a rather sub-stantial divergence from the traditional view of the succession theory regarding productivity.