Elevation, competition control, and species affect bottomland forest restoration

Published source details McLeod K.W., Reed M.R. & Wike L.D. (2000) Elevation, competition control, and species affect bottomland forest restoration. Wetlands, 20, 162-168.
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This study is summarised as evidence for the following.

	Action	Category
	Remove vegetation that could compete with planted trees/shrubs: freshwater wetlands Action Link
	Directly plant trees/shrubs: freshwater wetlands Action Link

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

A replicated, paired, controlled study in 1993–1996 in a degraded swamp in South Carolina, USA (McLeod et al. 2000) found that clearing competing vegetation after planting tree seedlings typically had no significant effect on their survival or average height. After four growing seasons and averaged across species, seedling survival rates did not significantly differ between plots where vegetation was cleared (57–63%) and plots where vegetation not cleared (66%), regardless of the clearance method. For five of six planted species, the average height of surviving seedlings was statistically similar in cleared plots (100–311 cm) and uncleared plots (145–265 cm), regardless of the clearance method. For the other species, baldcypress Taxodium distichum, seedlings were taller in cleared plots (253–285 cm) than uncleared plots (213 cm): significantly so for three of four clearance methods. At planting, seedlings were 40–94 cm tall and did not significantly differ in height within each species and clearance method. Methods: In April 1993, tree seedlings were planted into 25 plots (6 seedlings/species/plot; seedlings 2 m apart) in a degraded swamp (natural forest killed by heated effluent between 1955 and 1985). In spring/summer 1993 and 1994, five plots received each vegetation clearance treatment: mowing whole plot; mowing 1 m strips in which seedlings were planted; applying herbicide (Accord®) to whole plot; applying herbicide to 1 m strips in which seedlings were planted; no clearance. 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 (4), but a different experimental set-up.

(Summarised by: Nigel Taylor)
Directly plant trees/shrubs: freshwater wetlands

A replicated study in 1993–1996 in a degraded freshwater swamp in South Carolina, USA (McLeod et al. 2000) reported that 14–87% of planted tree seedlings survived over four growing seasons, and that the average height of seedlings increased. Statistical significance was not assessed. Six tree species were planted. After four growing seasons, survival rates were 14% for cherrybark oak Quercus falcata var. pagodaefolia, 54% for willow oak Quercus phellos, 62% for water tupelo Nyssa aquatica and Nuttall oak Quercus nuttallii, 83% for overcup oak Quercus lyrata and 87% for baldcypress Taxodium distichum. When planted, seedlings were 42–89 cm tall on average. After four growing seasons, survivors were 153–285 cm tall on average. The study also reported that survival and height change varied with elevation/wetness for some species, but found that clearing competing vegetation typically had no significant effect on survival or growth (see Action: Remove vegetation that could compete with planted vegetation and original paper). Methods: In April 1993, tree seedlings were planted (25 plots; 6 seedlings/species/plot; seedlings 2 m apart) into a degraded swamp. Heated effluent had killed existing trees between 1955 and 1985. All seedlings were protected with tree guards. In 20 plots, competing vegetation was cleared in summer 1993 and 1994, by mowing or applying herbicide. Seedling survival and height were recorded at planting, then each autumn until 1996. This study used the same swamp as (10), but a different experimental set-up.

(Summarised by: Nigel Taylor)