Growth Responses to Flooding and Recovery of Deciduous Trees

Tree seedling flooding tolerance for 22 species was assessed under controlled field condi­ tions. Initial heights under control (freely draining soil, n = 20 per species) and flooded (stand­ ing water, depth = 10 cm, n = 20 per species) conditions were measured in March 1990. Sur­ vival, height and diameter growth were determined after 120 days. Recovery from flooding effects was assessed in the following growing season from March to August, 1991. Taxodium distichum (L.) L. C. Rich, exhibited enhanced growth when flooded. Acer saccharinum L., Fraxinus excelsior L., and Quercus robur L. increased diameter but not height growth. The following species exhibited reduced growth and/or survival: Acer campestre L., Acer pseudoplatanus L., Acer rubrum L., Betula nigra L., Betula papyrifera Marsh, Betula pubescens Ehrh., Betula pendula Roth, Crataegus monogyna Jacq., Fagus grandifolia Ehrh., Prunus padus L., Prunus serotina Ehrh., Quercus palustris Muenchh., Quercus petraea (Mattuschka) Liebl., Rhamnus cathartica L., Salix purpurea L., Sorbus aucuparia L., Tilia cordata Mill., and Ulmus glabra Huds. emend. Moss. Recovery from flooding in the second growing season was well established with A. saccharinum, C. monogyna, Qu. palustris, Qu. petraea, S. purpurea, U. gla­ bra, while height growth relative to the flooding period was retarded in A. rubrum, F. grandi­ folia, F. excelsior, Qu. robur, Rh. cathartica, and S. aucuparia. Mortality increased with B. pa­ pyrifera and F. grandifolia. Flooded trees o f B. nigra, B. pendula, and Rh. cathartica appeared to be strongly handicapped by losing their natural resistance against frost even in the following growing season. By decreasing shoot height growth and biomass production, long-term flood­ ing is suggested to reduce the competitive ability o f most tree species in the succession o f natu­ ral forests in habitats which will be inundated more frequently in future when precipitation is increased by the predicted climatic change.