Influences of cutting diameter and soil moisture on growth and survival of black willow, Salix nigra

ABSTRACT:

Streambank restoration projects utilize large black willow (Salix nigra) cuttings otherwise known as posts; however, potential exists that smaller size cuttings alone or in combination may improve success efforts. Furthermore, the effects of soil moisture conditions and the potential interaction between size of the cutting and soil moisture regime have not been tested. Therefore, a greenhouse study was conducted to quantify cutting performance in response to the combined effects of soil moisture and diameter size. Replicated cuttings with basal diameters measuring 1, 5, or 10 cm (0.4, 2, or 4 in) were placed in three soil moisture regimes including well-watered, periodic flooding and drought. Biomass accumulation and partitioning, height, and survival were measured. Under periodic flooded conditions, 10 cm (4 in) cuttings had greater leaf number and weight (p<.05), leaf area index (p<.05), shoot weight (p<.05), root weight (p<.05), and height growth (p<.05) compared to 1 and 5 cm (0.4 and 2 in) cuttings (p<.05). Survival was best for 1 cm (0.4) cuttings in all three moisture regimes (100 percent) and for 10 cm (4 in) cuttings under flooded conditions (100 percent). Growth and biomass of 10 cm (4 in) cuttings were reduced by drought compared to periodic flooding treatment (p=.02). Based on the data, it appears that planting strategies using 1 cm (0.4 in) cuttings of black willow in any given moisture regime may lead to increased survival rates. Planting larger cuttings may improve overall restoration success. The technique of planting a combination of these two diameters may help to further stabilize streambanks.