Modelling nutrient transport and transformation by pool‐breeding amphibians in forested landscapes using a 21‐year dataset

Abstract

1. Migrations of animals can transfer energy and nutrients through and among terrestrial and aquatic habitats. Pool-breeding amphibians, such as the wood frog (Lithobates sylvaticus), make annual breeding migrations to ephemeral wetlands in forest habitats in the eastern and midwestern United States and Canada. 2. To model the influence of wood frogs on nutrient transport and transformation through time, we coupled long-term population monitoring data from a wood frog population with estimates of the elemental composition of wood frog egg masses and emerging juveniles. 3. Over the 21-year study period, 8.8 kg carbon (C), 2.0 kg nitrogen (N) and 0.20 kg phosphorus (P) were transported from the terrestrial to the aquatic habitat and approximately 21 kg C, 5.5 kg N and 1.2 kg P were exported to the surrounding terrestrial habitat by wood frogs. 4. During the study period, the average net flux of C, N and P was from aquatic to terrestrial habitats, but the magnitude and direction of the net flux was element dependent. Thus, the net flux of C, N and P did not always flow in the same direction. 5. Predicting long-term trends in nutrient and energy flux by organisms with biphasic life cycles should rely on long-term population data to account for temporal variability. This is especially true for organisms that are sensitive to long-term shifts in temperature and precipitation patterns, such as amphibians that breed in ephemeral pools.

Does the Growth Rate Hypothesis Apply across Temperatures? Variation in the Growth Rate and Body Phosphorus of Neotropical Benthic Grazers

“…The effects of the loss of amphibian communities on aquatic ecosystem functions have been well-studied (Connelly et al, 2008;Rugenski et al, 2012;Whiles et al, 2013;Rantala et al, 2015), but both amphibians and many aquatic insects have terrestrial adult stages. The movement of organisms from aquatic ecosystems to the terrestrial environment can represent a significant nutrient sink to aquatic ecosystems and an important subsidy to their surrounding terrestrial counterparts (Sabo and Power, 2002;Vanni et al, 2013;Capps et al, 2015b). Variation in %P among populations of Rhinella and Thraulodes can lead to variation in P export to the surrounding terrestrial ecosystem.…”

Detritus Quality and Locality Determines Survival and Mass, but Not Export, of Wood Frogs at Metamorphosis

“…For example, several studies have shown post-metamorphic survival significantly increases with increased size of post-metamorphic individuals and decreased developmental time–in our study size was greater in individuals raised in treatments with high nutrient quality litter and developmental time was marginally significant. Additionally, export of post-metamorphic anurans can be considered a flux of energy and nutrients into surrounding terrestrial habitat [49,50]. When considering anuran-driven ecosystem functions within lentic and adjacent systems, a decrease in survival will limit the number of individuals present; however, if the individuals are larger due to higher nutrient quality of plant material (invasive or non-invasive) some ecological functions could remain unchanged across wetlands with high nutrient quality plants.…”

Buffer-Mediated Effects of Clearcutting on In-Pool Amphibian Productivity: Can Aquatic Processes Compensate for Terrestrial Habitat Disturbance?

“…They also embody a significant transfer of energy and nutrients from wetland to upland systems [28][29][30]. These roles are especially pronounced for wood frog metamorphs, which are produced by the thousands in boom years, and because wood frogs, having a relatively short life-span, depend on recruitment for persistence [23,61,62].…”

“…Metamorph productivity thus constrains the number of dispersal propagules on the landscape. Second, metamorphs are a significant vector for transfer of energy and nutrients from the aquatic into the terrestrial system [28][29][30]. Finally, since eggmasses and larvae are confined to the pool basin and, unlike adults, cannot escape negative habitat conditions by moving to a different location, treatment impacts may manifest sooner or be more severe in these life stages.…”