Habitat restoration affects immature stages of a wetland butterfly through indirect effects on predation

Published source details Aschehoug E.T., Sivakoff F.S., Cayton H.L., Morris W.F. & Haddad N.M. (2015) Habitat restoration affects immature stages of a wetland butterfly through indirect effects on predation. Ecology, 96, 1761-1767.
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This study is summarised as evidence for the following.

	Action	Category
	Remove tree canopy to reduce pond or waterway shading Action Link
	Install artificial dams in streams to raise water levels Action Link
	Remove, control or exclude native predators Action Link
	Cut large trees/shrubs to maintain or restore disturbance: freshwater marshes Action Link
	Raise water level to restore degraded freshwater marshes Action Link

Remove tree canopy to reduce pond or waterway shading

A replicated, randomized, paired, controlled study in 2011–2012 in a pine forest in North Carolina, USA (Aschehoug et al. 2015) found that removing trees to reduce stream shading reduced the survival of Appalachian brown Satyrodes appalachia caterpillars and pupae, but did not affect egg survival. In plots where trees were removed, the survival of Appalachian brown eggs (12–36%) was not significantly different to plots where trees remained (56–74%), but the survival of caterpillars and pupae was lower (trees removed: 7%; trees remained: 20%). In plots where trees were removed and artificial dams were installed, both egg (33–42%) and caterpillar and pupal (14%) survival were similar to plots where trees remained and artificial dams were not installed (egg: 56–74%; caterpillars and pupae: 20%). In May 2011, four 30 × 30 m plots in each of four blocks were randomly assigned to four treatments: manual removal of 90% of trees, installation of temporary dams, tree removal and dam installation, and no manipulation. The 0.5-m high dams spanned the downstream edge of their plot. From 15 May–15 June and 7 July–7 August 2012, a potted sedge Carex mitchelliana plant was placed in the centre of each plot. Each plant had a known number of butterfly eggs, laid by caged wild-caught females prior to placement. The number of eggs on each plant which survived after 48 hours was counted. In addition, in each of three arenas/plot (created from polyethylene food drums), centred on mature sedge, five captive-reared caterpillars (first to third instar) were released and the number of emerging adults was counted.

(Summarised by: Andrew Bladon)
Install artificial dams in streams to raise water levels

A replicated, randomized, paired, controlled study in 2011–2012 in a pine forest in North Carolina, USA (Aschehoug et al. 2015) found that installing artificial dams in headwater streams to raise water levels did not increase the survival of Appalachian brown Satyrodes appalachia eggs, caterpillars or pupae. In plots where dams were installed, the survival of Appalachian brown eggs (23–43%) and caterpillars and pupae (37%) was not significantly different from plots where dams were not installed (eggs: 56–74%; caterpillars and pupae: 20%). In plots where artificial dams were installed and trees were removed, both egg (33–42%) and caterpillar and pupal (14%) survival were also similar to plots where dams were not installed and trees remained (egg: 56–74%; juvenile: 20%). In May 2011, four 30 × 30 m plots in each of four blocks were randomly assigned to four treatments: installation of temporary dams, manual removal of 90% of trees, tree removal and dam installation, and no manipulation. The 0.5-m high dams spanned the downstream edge of their plot. From 15 May–15 June and 7 July–7 August 2012, a potted sedge Carex mitchelliana plant was placed in the centre of each plot. Each plant had a known number of butterfly eggs, laid by caged wild-caught females prior to placement. The number of eggs on each plant which survived after 48 hours was counted. In addition, in each of three arenas/plot (created from polyethylene food drums), centred on mature sedge, five captive-reared caterpillars (first to third instar) were released and the number of emerging adults was counted.

(Summarised by: Andrew Bladon)
Remove, control or exclude native predators

A replicated, randomized, paired, controlled study in 2011–2012 in a pine forest in North Carolina, USA (Aschehoug et al. 2015) found that excluding native predators increased the survival of Appalachian brown Satyrodes appalachia eggs, caterpillars and pupae. In plots where predators were excluded, the survival of Appalachian brown eggs (48–94%) and caterpillars and pupae (35–60%) was higher than on plots left open to predators (eggs: 12–74%; caterpillars and pupae: 7–37%). In May 2011, four 30 × 30 m plots in each of four blocks were established. From 15 May–15 June and 7 July–7 August 2012, two potted sedge Carex mitchelliana plants were placed in the centre of each plot. To exclude predators, one plant/plot was enclosed in a fine mesh fabric cage, and had a 15-cm band of sticky resin painted on its pot. Each plant had a known number of butterfly eggs, laid by caged wild-caught females prior to placement. The number of eggs on each plant which survived after 48 hours was counted. In addition, in each of six arenas/plot (created from polyethylene food drums), centred on mature sedge, five captive-reared caterpillars (first to third instar) were released and the number of emerging adults was counted. Three arenas were enclosed with tulle netting, and potential predators (mainly spiders and ants) were removed prior to the release of caterpillars.

(Summarised by: Andrew Bladon)
Cut large trees/shrubs to maintain or restore disturbance: freshwater marshes

A replicated, randomized, paired, controlled, before-and-after study in 2011–2012 aiming to restore marsh patches in a pine forest in North Carolina, USA (Aschehoug et al. 2015) found that thinning trees increased understory vegetation cover, including sedges. In plots where trees were thinned, there were increases in total understory vegetation cover (from 34% one month before thinning to 57% one year after) and total cover of sedges Carex spp. (from 7% to 22%). These increases were significantly larger than in plots where trees were not thinned (total understory cover: increase from 44% to 48%; sedge cover: decrease from 10% to 8%). The effect of tree thinning was statistically similar in dammed and undammed plots (reported as a statistical model result). Methods: In May 2011, sixteen 30 x 30 m plots were established (in four blocks of four) in wet patches of a pine forest. Development of sedge marshes in wet patches of the forest had been restricted by fire suppression and the extirpation of beavers Castor canadensis. In eight plots (two/block), 90% of the trees were manually removed. Trees were not thinned in the other plots. Four thinned and four unthinned plots were also dammed. Vegetation cover was visually estimated one month before (April 2011) and one year after (April 2012) intervention.

(Summarised by: Nigel Taylor)
Raise water level to restore degraded freshwater marshes

A replicated, randomized, paired, controlled, before-and-after study in 2011–2012 of marshes within a pine forest in North Carolina, USA (Aschehoug et al. 2015) found that damming to raise the water table limited understory vegetation cover, but had no significant effect on sedge cover. In rewetted plots, there was no change in total understory vegetation cover (42% one month before thinning and 42% one year after). However, in plots that remained drained, understory vegetation cover increased (from 35 to 58%). Total sedge Carex spp. cover increased by statistically similar amounts in rewetted plots (from 11 to 17%) and drained plots (from 6 to 15%). Methods: In May 2011, sixteen 30 x 30 m plots were established (in four blocks of four) on tree-colonized marshes within a pine forest. Maintenance of open marsh had been restricted by fire suppression and the extirpation of beavers Castor canadensis. Dams were installed on the downstream edge of eight plots (two/block), raising the water table. About a third of each plot was flooded. The other eight plots remained drained. Trees were also thinned in four rewetted and four drained plots. Vegetation cover was visually estimated one month before (April 2011) and one year after (April 2012) intervention.

(Summarised by: Nigel Taylor)