Study

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

  • Published source details McLeod K.W., Reed M.R. & Nelson E.A. (2001) Influence of a willow canopy on tree seedling establishment for wetland restoration. Wetlands, 21, 395-402.

Actions

This study is summarised as evidence for the following.

Action Category

Remove vegetation that could compete with planted trees/shrubs: freshwater wetlands

Action Link
Marsh and Swamp Conservation

Directly plant trees/shrubs: freshwater wetlands

Action Link
Marsh and Swamp Conservation
  1. Remove vegetation that could compete with planted trees/shrubs: freshwater wetlands

    A replicated, randomized, controlled study in 1994–1996 in a degraded swamp in South Carolina, USA (McLeod et al. 2001) found that clearing black willows Salix nigra before planting tree seedlings reduced survival and increased the average height for one of three planted species, but had no significant effect on the other two. After three growing seasons, baldcypress Taxodium distichum seedlings had a lower survival rate, but survivors were taller, when planted amongst cut willows (survival: 75%; height: 192 cm) than when planted under a willow canopy (survival: 95%; height: 134 cm). For two other planted species, overcup oak Quercus lyrata and water hickory Carya aquatica, survival rates and the height of survivors did not significantly differ between seedlings planted amongst cut willows (survival: 73–78%; height: 112–148 cm) and seedlings planted under a willow canopy (survival: 90%; height: 104–134 cm). At planting, seedlings were 47–85 cm tall and did not significantly differ in height within each species and clearance treatment. Methods: In winter 1993/1994, ten 180-m2 plots were established in a degraded swamp (natural forest killed by heated effluent between 1955 and 1985). In five random plots, all willow trees were cut to within 15 cm of the ground. In five other plots, the willow canopy was left intact. In February 1994, eight seedlings of each species were planted, 2 m apart, into each plot. All seedlings were protected with tree guards. Seedling survival and height were recorded at planting, then each autumn until 1996. This study used the same swamp as (3), but a different experimental set-up.

    (Summarised by: Nigel Taylor)

  2. Directly plant trees/shrubs: freshwater wetlands

    A replicated study in 1994–1996 in a degraded freshwater swamp in South Carolina, USA (McLeod et al. 2001) reported that 0–95% of planted tree seedlings survived over three growing seasons, but that the average height of seedlings increased. Statistical significance was not assessed. Four tree species were planted. After three growing seasons, survival rates were 0% for laurel oak Quercus laurifolia, 73–90% for water hickory Carya aquatica, 78–90% for overcup oak Quercus lyrata and 70–95% for baldcypress Taxodium distichum. When planted, seedlings of the last three species were 47–85 cm tall on average. After three growing seasons, survivors were 104–192 cm tall on average. The study also reported that survival and height change varied with elevation/wetness for all species, and with site conditions (presence of tree canopy or grasses) for baldcypress (see Action: Remove vegetation that could compete with planted vegetation and original paper). Methods: Fifteen 180-m2 plots were established in a degraded swamp (where heated effluent had existing trees between 1955 and 1985). Five plots contained black willow Salix nigra, five were cleared of willow and five were dominated by grasses. In February 1994, four hundred and eighty seedlings (120 seedlings/species) were planted, 2 m apart, into the 15 plots (8 seedlings/species/plot). All seedlings were protected with tree guards. Seedling survival and height were recorded at planting, then each autumn until 1996. This study used the same swamp as (9), but a different experimental set-up.

    (Summarised by: Nigel Taylor)

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