Ecosystems dominated by herbaceous vegetation can highlight plant-soil-water relationship and its effect on production processes. Therefore, one of the challenges in ecology is to quantify climate change effects on primary production of annuals. Results/Conclusions:
We use field data and a recently published spatio-temporally explicit model to study factors affecting long-term variation in annuals production in two water-restricted ecosystems: semi-arid and mediterranean. Both ecosystems are dominated by annual vegetation. The model was operated in both patch and landscape scales and was executed along 30 years (1979-2008) at the semi-arid site and along 21 years (1986-1990; 1993-2008) at the mediterranean site. Model predictions were validated against harvested samples that were taken from each site at the end of the growing season, in 15 seasons (1994-2008) at the semi-arid site (0.63
The model was programmed for random simulations, based on climatological forecasts, of the following five climate change scenarios: 1) reduction of seasonal rainfall depth at the range 5-35%; 2) change in rainfall frequency along the wet season; 3) increase of seasonal mean temperature by 1.5Cº and evaporation rate by 10%; 4) change in rainfall distribution along the wet season; and finally 5) increase of rainfall amount at the beginning of the season at, in both Mediterranean (ME) and Semi arid (AR) sites.
The results show: 1) no significant reduction in primary production occurred as a result of a decrease in rainfall amount; 2) random change in rainfall frequency along the wet season showed significant effect on habitats stability at AR. However, it did not affect significantly the productivity in ME; 3) the other three scenarios did not affect primary production.
According to our simulations, the predicted changes in herbaceous production, as a result of the forecasted climate change, appears to be rather limited comparing to the inter-annual variations in productivity under the current climatic conditions. One may assume that water stress that the herbaceous vegetation suffers during present rainfall fluctuations in both Mediterranean and semi-arid environments make it adapted to climatic changes. Therefore, only long dry spell will significantly affect the primary production of herbaceous vegetation in these areas