Biomass, photosynthesis and water use efficiency of woody swamp species subjected to flooding and elevated water temperature

Seedlings of water tupelo (Nyssa aquatica L.), bald cypress (Taxodium distichum (L.) Richard) and button bush (Cephalanthus occidentalis L.) and cuttings of black willow (Salix nigra Marshall) were established in pots and included in a complete factorial experiment with three water temperatures (maximums of about 30, 35 or 40 degrees C) and three water levels (maximum flood depth was 6 cm above soil level). Flooding for 3 months at 30 degrees C reduced dry weight of roots and shoots in all species except water tupelo. At 40 degrees C, however, flooding significantly reduced growth of water tupelo as well as the other species. High water temperatures reduced stomatal conductance and photosynthetic rates in water tupelo and black willow, but not in the other species. In combination with flooding, high temperature reduced water use efficiency in all species except button bush and most sharply in water tupelo.