Leaf litter input mediates tadpole performance across forest canopy treatments

Abstract

Understanding the mechanisms limiting the distributions of organisms is necessary for predicting changes in community composition along habitat gradients. In many areas of the USA, land originally cleared for agriculture has been undergoing a process of reforestation, creating a gradient of canopy cover. For small temporary wetlands, this gradient can alter abiotic conditions and influence the resource base of wetland food webs by affecting litter inputs. As distributions of amphibians and many other temporary wetland taxa correlate with canopy cover, we experimentally manipulated shade levels and litter types in pond mesocosms to explore mechanisms limiting species performance in wetlands with canopy cover. Most differences between ponds were mediated by litter type rather than direct effects of shading. Although all three amphibian species tested are open-canopy specialists, spring peepers were the only species to show decreased survival in shaded ponds. Pond litter type generally had strong effects on growth and development rates, with tadpoles of two species in grass litter ponds growing to twice the size of, and metamorphosing 7 days earlier than, those in leaf litter ponds. Contrary to our initial hypothesis, shade level and litter type showed very few significant interactions. Our results indicate that the effects of shading cannot be considered in isolation of vegetation changes in pond basins when evaluating the effects of forest succession on temporary pond communities.

Wetland Reserve Program Enhances Site Occupancy and Species Richness in Assemblages of Anuran Amphibians in the Mississippi Alluvial Valley, USA

“…The extent of canopy cover over breeding ponds and the amount and composition of leaf litter in pond basins are factors that play a strong role in the distribution and abundance of some species of amphibians. The presence of canopy and composition of leaf litter and detritus may influence primary productivity, nutrient cycling, hypoxia and, consequently, larval development (Skelly et al 2002;Halverson et al 2003;Rubbo and Kiesecker 2004;Mokany et al 2008;Williams et al 2008;Sacerdote and King 2009;Maerz et al 2010;Stephens et al 2013). For example, in Michigan, litter from Green Ash -a tree species often planted at WRP sites in our study -significantly increased growth, development and survival of larval Wood Frogs (Lithobates sylvaticus), compared to litter composed of other tree species (Stephens et al 2013).…”

The Effects of Habitat Structure on Winter Aquatic Invertebrate and Amphibian Communities in Pine Flatwoods Wetlands

“…Overall, little is known about how leaf litter inputs affect invertebrate communities in ephemeral wetlands and some studies have documented differential effects (Magnusson and Williams 2006;Batzer and Palik 2007). For amphibian larvae, Williams et al (2008) found that shifting from grassdominated litter to hardwood tree litter negatively impacted amphibian success, likely because of decreased phytoplankton growth rates. Further, large amounts of organic matter can decrease DO levels during decomposition (Magnusson and Williams 2006).…”

Direct and Indirect Effects of Climate Change on Amphibian Populations

“…Canopy openings and shifts in species composition of vegetation can alter microclimatic factors such as the duration and intensity of light, levels of temperature and moisture, as well as the accumulation, quality and decomposition of leaf litter [111]. In turn, the extent of canopy cover over wetlands [112][113][114] and the composition of leaf litter in the pond basin [115,116] may play a strong role in the reproductive success of some aquatic-breeding amphibians.…”