Influence of a willow canopy on tree seedling establishment for wetland restoration

Abstract

Black willow (Salix nigra) is a well-known pioneer species of disturbed riparian areas. It competes for nutrients, light, and water, but it may also act as a “nurse” crop, providing shelter for other species from high light and temperature; so, the overall effect on species planted under a willow canopy could be positive or negative. This experiment examined the response of container-grown seedlings of four tree species outplanted into three habitats: 1) an existing willow stand, 2) a similar habitat, but with the willow canopy removed, and 3) an adjacent grass-dominated area free of willow. After three years, survival rates of overcup oak (Quercus lyrata), baldcypress (Taxodium distichum), and water hickory (Carya aquatica) were not reduced under the willow canopy relative to the other two treatments. Laurel oak (Q. laurifolia) was killed by several floods during the first growing season. Height of baldcypress seedlings planted under a willow canopy was less than for seedlings where the willow had been removed. Water hickory and overcup oak height were not affected by the willow canopy. Elevation of the planting sites, indicating probable soil wetness, was a good indicator of survival when used in conjunction with the species flood-tolerance. The existing willow stand was not detrimental to survival of three of the outplanted tree species. Thus, willow removal is unnecessary for successful outplanting, saving time and money.