Effects of soil moisture regimes on growth and survival of black willow (Salix nigra) posts (cuttings)

A study was conducted under greenhouse conditions to examine the effects of various soil moisture regimes on black willow (Salix nigra) posts (cuttings). Five treatments representing a range of soil moisture regimes, from continuous flooding to mild drought, were imposed separately. A well-watered, well-drained treatment served as the control. Leaf gas exchange (stomatal conductance and net photosynthesis), survival, and biomass production of posts were evaluated. The stomatal conductance and net photosynthesis data clearly demonstrated the sensitivity:of willow posts to low oxygen conditions (under flooded treatments) as well as to soil drought. Growth and biomass were also adversely affected by flooding and drought treatments. The patterns of roof development along the posts seemed to be associated with the watering regime. Root biomass was depressed in zones subjected to flooding and low soil redox potential. In addition, leaf area, leaf biomass, and shoot (leaf + branch) biomass were significantly lower in the continuously-hooded and drought treatments as compared to control plants. Results indicated that maximum photosynthesis and growth in willow posts required ample soil-moisture (but-non-waterlogging conditions) and adequate drainage in the top 60 cm of soil. The use of willow posts for streambank restoration remains as a viable strategy; however, considerations should be given to water-table elevations, soil Eh conditions, soil moisture regime, and soil texture in order to improve the prospect for successful results.