Experimental canopy removal enhances diversity of vernal pond amphibians

Abstract

Vernal ponds are often treated as protected environments receiving special regulation and management. Within the landscapes where they are found, forest vegetation frequently dominates surrounding uplands and can grow to overtop and shade pond basins. Two bodies of research offer differing views of the role of forest canopy for vernal pond systems. Studies of landscape conversion suggest that removing forest overstory within uplands can cause local extinctions of amphibians by altering terrestrial habitat or hindering movement. Studies of canopy above pond basins imply an opposite relationship; encroachment of overstory vegetation can be associated with local extinctions potentially via changes in light, thermal, and food resource environments. Unresolved uncertainties about the role of forest canopy reveal significant gaps in our understanding of wetland species distributions and dynamics. Any misunderstanding of canopy influences is simultaneously important to managers because current practices emphasize promoting or conserving vegetation growth particularly within buffers immediately adjacent to ponds. We evaluated this apparent contradiction by conducting a landscape-scale, long-term experiment using 14 natural vernal ponds. Tree felling at six manipulated ponds was limited in spatial scope but was nevertheless effective in increasing water temperature. Compared with eight control ponds, manipulated ponds maintained more amphibian species during five years post-manipulation. There was little evidence that any species was negatively influenced, and the reproductive effort of species for which we estimated egg inputs maintained pretreatment population densities in manipulated compared with control ponds. Overall, our experiment shows that a carefully circumscribed reduction of overhead forest canopy can enhance the capacity of vernal ponds to support wildlife diversity and suggests a scale dependence of canopy influences on amphibians. These findings have implications for the connection between current wetland management practices and the goals of wetland stewardship and conservation of wetland-dependent species.

Functional traits reveal environmental constraints on amphibian community assembly in a subtropical dry forest

“…), in temperate forests canopy cover negatively affects primary productivity and food availability, reducing tadpole larval growth and development rates (Skelly et al . ; Rowland et al . ).…”

“… for diversity responses to hydroperiod, and Skelly et al . and references therein for importance of canopy cover). According to our results, variations in hydroperiod and canopy cover of Chaco ponds constrain community assembly of pond‐breeding amphibians via selection upon different combinations of functional traits.…”

Conserving amphibians in the face of land development: integrating field experiments as a planning tool

“…Habitat quality is assessed rapidly using a wetland classification systems such as the Cowardin Classification system, which defines wetlands based on plants, soils, and flooding frequency (Cowardin et al 1979). Other factors, such as canopy cover or wetland gradients are not considered, despite evidence of the importance of these physical traits (Werner et al 2007;Skelly et al 2013). Wide buffers, watersheds and pond interconnectivity are generally inadequately integrated into conservation regulations given the importance of upland habitat quality, metapopulation dynamics and water quality on performance.…”

Indicators of wood frog (Lithobates sylvaticus) condition in a suburbanizing landscape

“…Changes in vegetation may also alter community interactions involving tadpoles. Submerged vegetation may reduce predation risk by providing cover for larvae (Formanowicz andBobka 1989, Kopp et al 2006), and reductions in canopy cover may increase the amphibian species richness (Skelly 2014), potentially changing competition and predation pressures.…”