Analysis of phenological behaviour of some Mediterranean shrub species in responses to warming and drought conditions

Phenology is potentially a powerful tool for monitoring the response of plant and animal to climate change. In fact, phenological observations are a valuable source of information for investigating the relationship between climate and weather variation and plant and animal development. In mid-latitude the timing of stages, such as leafing or flowering, and the onset of the growing season are highly dependent on air temperature, in terms of heat accumulation above a threshold level. Flowering is considered to be one of the most significant phenological stages by which the sensitivity to climate variability can be evaluated. Higher air temperature in spring induces an earlier start of plant development within the year. If temperature is considered the driving factor of phenological timing in most climate areas, the effect of temperature needs to be adjusted incorporating functions for water availability in Mediterranean regions. A Climatic manipulations were carried out on Mediterranean macchia ecosystem which includes sclerophyll species, some scattered shrubs and several herbaceous plants. Six experimental plots were manipulated by night-time warming and extending summer drought. The responses to the treatments were compared to three untreated control plots during the years 2001-2003. The warming treatment was obtained covering the vegetation with an automated aluminum curtain at night. In the drought treatment the curtain material is transparent to infrared radiation and the movement of the curtains is determined by rainfall events. The drought treatment was carried out for a 3-month period in autumn. Phenological observations were conducted on three Mediterranean shrubs and effects of treatments on timing of stages appearance were analysed.