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 effec ts of various soil moisture regimes on black willow (Salix nigra) post s (cuttings). Five treatments representing a range of soil moisture re gimes, from continuous flooding to mild drought, were imposed separate ly. 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 conducta nce and net photosynthesis data clearly demonstrated the sensitivity:o f willow posts to low oxygen conditions (under flooded treatments) as well as to soil drought. Growth and biomass were also adversely affect ed by flooding and drought treatments. The patterns of roof developmen t along the posts seemed to be associated with the watering regime. Ro ot biomass was depressed in zones subjected to flooding and low soil r edox 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 indicate d that maximum photosynthesis and growth in willow posts required ampl e soil-moisture (but-non-waterlogging conditions) and adequate drainag e in the top 60 cm of soil. The use of willow posts for streambank res toration 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 successf ul results.