Data from: Direct and indirect effects of pine silviculture on the larval occupancy and breeding of declining amphibian species

1. Plantation silviculture is increasing globally and is particularly
intensive in temperate coniferous forests, where densely planting trees
requires practices common to non-conifer systems that can alter forest
floor microhabitat, and potentially threaten amphibian persistence. Most
declining amphibian species depend on specific forest microhabitats as
terrestrial refugia, but amphibian extirpation associated with tree
harvest alone appears unlikely, suggesting that impacts of planting
forests on groundcover might better predict recent declines in amphibian
occupancy. 2. We repeatedly sampled larval presence or absence of 10
amphibian species native to temperate coniferous forest in the
Southeastern United States for one year at 62 isolated wetlands located in
either naturally regenerating or planted forest (plantation) to assess
three direct ways that planted forests might reduce amphibian breeding
site occupancy by: 1) increasing conifer densities, 2) decreasing
groundcover, and 3) an indirect pathway, whereby increased tree densities
at plantations might reduce groundcover and thus amphibian site occupancy.
3. After controlling for wetland traits and accounting for differences in
detection, breeding site occupancy for 8/10 amphibian species was
dependent upon whether forests were planted surrounding wetlands (within
300 m). Herbaceous groundcover, not canopy, most commonly influenced
occupancy and increased occupancy for declining surface active or
fossorial amphibians. 4. Path analyses showed that, by directly and
indirectly reducing groundcover (via conifer densities), plantations had
significantly lower occupancy of two declining surface active or fossorial
frog species, whereas two common aquatic frog species were tolerant to
planting conifers. Among declining species, salamanders showed a greater
reduction in occupancy than anurans, likely because of greater
vulnerability to the drier forest floor conditions of plantation than
naturally regenerating forests. 5. Synthesis and applications: Direct
negative impacts of coniferous plantation on amphibians can be addressed
by limiting groundcover and soil impacts, including switching from high
intensity practices, such as mechanical chopping vegetation or bedding
soil, to lower intensity site preparation treatments that are less likely
to significantly disturb groundcover. Indirect negative effects of dense
canopy cover at planted forests could be lowered by periodically thinning
canopies prior to final harvest, thus increasing intact forest groundcover
and the conservation of both common and declining amphibians.