Baldcypress (Taxodium distichum (L.) Rich.) restoration in southeast Louisiana: the relative effects of herbivory, flooding, competition, and macronutrients

Published source details Myers R.S., Shaffer G.P. & Llewellyn D.W. (1995) Baldcypress (Taxodium distichum (L.) Rich.) restoration in southeast Louisiana: the relative effects of herbivory, flooding, competition, and macronutrients. Wetlands, 15, 141-148.
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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
	Add inorganic fertilizer before/after planting trees/shrubs: freshwater wetlands Action Link
	Use fences or barriers to protect freshwater wetlands planted with trees/shrubs Action Link
	Directly plant trees/shrubs: freshwater wetlands Action Link

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

A replicated, randomized, controlled study in 1992 in a freshwater marsh in Louisiana, USA (Myers et al. 1995) found that where competing vines were cleared, planted baldcypress Taxodium distichum seedlings grew more in diameter and less in height than where vines were not cleared. Over one growing season, seedlings in cleared plots grew more in diameter (0.74 cm) than seedlings surrounded by vines (0.43 cm). However, cleared seedlings grew less in height (5.4 cm) than surrounded seedlings (8.7 cm). Clearing vines had a bigger effect on seedlings on diameter growth for seedlings within plastic guards than without (data not reported), but had a similar effect on seedlings whether fertilized (cleared seedlings grew 0.26 cm more than uncleared) or not (cleared seedlings grew 0.28 cm more than uncleared). Methods: In January 1992, four hundred baldcypress seedlings were planted into a marsh – with the aim of restoring the swamp that was logged around 80 years previously. Vines were cleared from around 200 random seedlings every 3–4 weeks after planting, but left to grow around the other 200 seedlings. An equal number of cleared and uncleared seedlings received additional treatments: protection from herbivores and/or fertilization. Seedling diameter and height were measured at planting (January 1992) and after one growing season (October 1992).

(Summarised by: Nigel Taylor)
Add inorganic fertilizer before/after planting trees/shrubs: freshwater wetlands

A replicated, randomized, controlled study in 1992 in a freshwater marsh in Louisiana, USA (Myers et al. 1995) found that adding fertilizer increased growth of planted baldcypress Taxodium distichum seedlings. Over one growing season, fertilized seedlings grew more than unfertilized seedlings in both diameter (fertilized: 0.76 cm; unfertilized: 0.41 cm) and height (data not reported). Fertilizer had a bigger effect on diameter growth for seedlings within plastic guards than without (data not reported), but had a similar effect on diameter growth whether vines were cleared (fertilized seedlings grew 0.31 cm more than unfertilized) or not (fertilized seedlings grew 0.33 cm more than unfertilized). Methods: In January 1992, four hundred baldcypress seedlings were planted into a marsh – with the aim of restoring the swamp that was logged around 80 years previously. Of the 400 seedlings, 200 random seedlings were fertilized (28 kg/ha time-released Osmocote NPK) and 200 were not. An equal number of fertilized and unfertilized seedlings received additional treatments: plastic guards as protection from herbivores and/or clearing competing vines. Seedling diameter and height were measured at planting (January 1992) and after one growing season (October 1992).

(Summarised by: Nigel Taylor)
Use fences or barriers to protect freshwater wetlands planted with trees/shrubs

A replicated, randomized, controlled study in 1992 in a freshwater marsh in Louisiana, USA (Myers et al. 1995) found that planted baldcypress Taxodium distichum seedlings protected with plastic guards or a sticky, insect-repellent oil grew more than unprotected seedlings. Over one growing season, seedlings within plastic guards grew significantly more than unguarded seedlings in both height (data not reported) and diameter (guarded: 0.73–0.85 cm; unguarded: 0.28–0.32 cm). Amongst guarded seedlings, growth was similar whether the guards were PVC tubes (0.74 cm diameter increase) or commercial Tubex guards (0.73–0.85 cm diameter increase). Amongst unguarded seedlings, those painted with sticky oil grew significantly more than unpainted seedlings in height (data not reported) but not diameter (painted: 0.32; unpainted: 0.28 cm diameter increase). Painted seedlings grew less than guarded seedlings in both diameter and height. Methods: In January 1992, four hundred baldcypress seedlings were planted into a marsh – with the aim of restoring the swamp that was logged around 80 years previously. Guards against nutria Myocastor coypus herbivory were placed around 240 random seedlings (80 PVC tubing, 80 beige Tubex, 80 white Tubex). Sticky oil was painted onto the lower third of 80 random seedlings. The final 80 seedlings received no protection. Some protected and unprotected seedlings received additional treatments: fertilization or removal of competing vines. Seedling diameter and height were measured at planting (January 1992) and, for surviving seedlings, after one growing season (October 1992).

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

A study in 1992–1994 in a freshwater marsh in Louisiana, USA (Myers et al. 1995) reported that planted baldcypress Taxodium distichum seedlings grew, but that seedlings exposed to herbivores all died within two years. Statistical significance was not assessed. Over one growing season, seedlings protected from herbivores grew thicker by 0.32–0.85 cm. Unprotected seedlings grew thicker by 0.28 cm. Half of the unprotected seedlings survived the first growing season, but none survived the winter following the second growing season. The study does not report survival rates for the protected seedlings. Methods: In January 1992, four hundred baldcypress seedlings were planted into a marsh (historically a swamp, but logged around 80 years previously). Of these, 320 were protected from herbivores (240 with plastic sleeves, 80 with sticky insect-trapping oil) and 80 were left unprotected. Some protected and unprotected seedlings received additional treatments: fertilization and/or removal of competing vines. Nutria Myocastor coypus were “intensively trapped” in the month before planting. Seedling diameter was measured at planting (January 1992) and after one growing season (October 1992). Survival was monitored until after the second growing season (early 1994).

(Summarised by: Nigel Taylor)