Response of some phenological garden species to inter-annual weather variability

The annual timing of spring phenological events is mainly driven by temperature after the dormancy is overcome. Variations in phenological stages are therefore a valuable source of information for investigating the possible impact of climate variability and change on plant species. Recent studies indicating changes in phenological stages in plant and animal species provide evidence that ecosystems are responding to climate change. However, information are still scarce and limited to temperate and cold ecosystems of northern latitude. To investigate the inter-annual variability in the beginning of growing season and flowering phases in Italy, phenological data-sets from two sites of the Italian Phenological Garden network were analyzed. The sites are located in Oristano, Sardinia, Italy (39° 53' N, 8° 37' E, 11 m above sea level) and S. Pietro Capofiume, Emilia Romagna, Italy (44° 39' N, 11° 37' E, 10 m above sea level). They were set up in the early eighties following the directives of the International Phenological Gardens in Europe (IPG). Phenological observations were taken on Mediterranean forest species and shrubs in Sardinia, and on several forest species typical of higher latitude in Emilia Romagna: Pistacia lentiscus, Olea europea, Myrtus communis, Quercus ilex, Spartium junceum, Robinia pseudoacacia, Cercis siliquastrum, Salix chrysocoma, Tilia cordata, Populus tremula, Celtis australis in Oristano and Salix smithiana, Salix viminalis, Ligustrum vulgare, Corylus avellana, Cornus mas, Cornus sanguinea, Quercus robur, Fagus sylvatica, Laburnum anagyroides, Crataegus monogyna, Prunus psinosa, Prunus avium, Spartium junceum in S.Pietro Capofiume. Data analysis was conducted to describe the phenological behavior of native and non-native species, and to assess their sensitivity to weather variability. Based on the results, higher variability in phenological stage occurrence was found for non-native species. In general, inter-annual variability seems to greatly affect phenophase dates but other factors (e.g.: drought period length and intensity, winter low temperature) show to play an important role in determining the timing of plant development.