as extreme duration of droughts, low temperatures, or floods in wetlands can haste
the spreading of alien species. By comparing alien plants to natives ones, it has been
observed that Fraxinus pennsylvanica, Ailanthus altissima, Amorpha fruticosa, and
Morus alba are very resistant to these phenomena (Anastasiu and Negrean 2007).
The actual spreading of alien ligneous species was not entirely based on their
adaptive capacity given that most of them were massively planted in the past
(Anastasiu and Negrean 2009). The species’ resistance to frost is high, even though
its spindles freeze every year. The first small plants begin to appear after the last
frost period of the year when the soil is saturated with water and the evaporation
process of water from soil is intense (Gregory and James 2003; Harold et al. 2005).
The findings of previous studies revealed that the germination of seeds from Amorpha
fruticosa, Fraxinus pennsylvanica, and Robinia pseudoacacia is influenced by both
low temperatures below 16
C and duration (Doroftei et al. 2005). With regard to
distribution within DDBR, it may be mentioned that alien species’ have been
identified in almost all types of areas, environmental conditions, and habitat types.
Fig. 18.2 Mean annual precipitation amounts in the Danube Delta Biosphere Reserve
(1961–2007) (Dragota ˘ et al. 2011)
Fig. 18.3 Mean annual air temperatures in the Danube Delta Biosphere Reserve (1961–2007)
(Dragota ˘ et al. 2011)
18 Potential Impacts of Climate Change on Habitats and Their Effects. . .
273
the spreading of alien species. By comparing alien plants to natives ones, it has been
observed that Fraxinus pennsylvanica, Ailanthus altissima, Amorpha fruticosa, and
Morus alba are very resistant to these phenomena (Anastasiu and Negrean 2007).
The actual spreading of alien ligneous species was not entirely based on their
adaptive capacity given that most of them were massively planted in the past
(Anastasiu and Negrean 2009). The species’ resistance to frost is high, even though
its spindles freeze every year. The first small plants begin to appear after the last
frost period of the year when the soil is saturated with water and the evaporation
process of water from soil is intense (Gregory and James 2003; Harold et al. 2005).
The findings of previous studies revealed that the germination of seeds from Amorpha
fruticosa, Fraxinus pennsylvanica, and Robinia pseudoacacia is influenced by both
low temperatures below 16
C and duration (Doroftei et al. 2005). With regard to
distribution within DDBR, it may be mentioned that alien species’ have been
identified in almost all types of areas, environmental conditions, and habitat types.
Fig. 18.2 Mean annual precipitation amounts in the Danube Delta Biosphere Reserve
(1961–2007) (Dragota ˘ et al. 2011)
Fig. 18.3 Mean annual air temperatures in the Danube Delta Biosphere Reserve (1961–2007)
(Dragota ˘ et al. 2011)
18 Potential Impacts of Climate Change on Habitats and Their Effects. . .
273