Plant mycorrhizal associations mediate the zoogeochemical effects of calving subsidies by a forest ungulate

Abstract

Animals interact with and impact ecosystem biogeochemical cycling—processes known as zoogeochemistry. While the deposition of various animal materials (e.g. carcasses and faeces) has been shown to create nutrient hotspots and alter nutrient cycling and storage, the inputs from parturition (i.e. calving) have yet to be explored. We examine the effects of ungulate parturition, which often occurs synchronously during spring green‐up and therefore aligns with increased plant nitrogen demand in temperate biomes. Impacts of zoogeochemical inputs are likely context‐dependent, where differences in material quality, quantity and the system of deposition modulate their impacts. Plant mycorrhizal associations, especially, create different nutrient‐availability contexts, which can modify the effects of nutrient inputs. We, therefore, hypothesize that mycorrhizal associations modulate the consequences of parturition on soil nutrient dynamics and nitrogen pools. We established experimental plots that explore the potential of two kinds of zoogeochemical inputs deposited at ungulate parturition (placenta and natal fluid) in forest microsites dominated by either ericoid mycorrhizal (ErM) or ectomycorrhizal (EcM) plants. We assess how these inputs affect rates of nutrient cycling and nitrogen content in various ecosystem pools, using isotope tracers to track the fate of nitrogen inputs into plant and soil pools. Parturition treatments accelerate nutrient cycling processes and increase nitrogen contents in the plant leaf, stem and fine root pools. The ecosystem context strongly modulates these effects. Microsites dominated by ErM plants mute parturition treatment impacts on most nutrient cycling processes and plant pools. Both plant–fungal associations are, however, equally efficient at retaining nitrogen, although retention of nitrogen in the parturition treatment plots was more than two times lower than in control plots. Our results highlight the potential importance of previously unexamined nitrogen inputs from animal inputs, such as those from parturition, in contributing to fine‐scale heterogeneity in nutrient cycling and availability. Animal inputs should therefore be considered, along with their interactions with plant mycorrhizal associations, in terms of how zoogeochemical dynamics collectively affect nutrient heterogeneity in ecosystems.

Zoogeochemistry of a protected area: Driven by anthropogenic impacts and animal behavior

“…In addition, we recommend that other ways in which animals are connected to the nutrient landscape be investigated in more detail. This ranges from the physical influence on soil properties through trampling or the promotion of bare soil (Trepel et al, 2024) to localized inputs (e.g., calving and the associated release of large amounts of nutrients via the natal fluid in a very small area [Ferraro et al, 2023]). All these impacts can be altered by anthropogenic factors (i.e.…”

Towards a mechanistic understanding of animal–ecosystem interactions

“…Ferraro et al. (2023) begin to fill this gap with the first detailed exploration of localized nutrient input from parturition. In an elegant field experiment, the authors measured effects of ungulate natal fluid and placenta additions on soil microbial biomass, rates of soil carbon (C) and nitrogen (N) turnover and %N of plant tissues.…”

“…Ferraro et al. (2023) observed strong evidence that parturition additions rapidly affect soil processes and plant stoichiometry. Microbial biomass and rates of C mineralization, N mineralization and nitrification were higher under plots with parturition additions than nearby control plots.…”

“…Ferraro et al. 's (2023) novel approach simultaneously advances mechanistic understanding of zoogeochemistry at fine scales and facilitates prediction of ungulate zoogeochemistry at landscape extents. Most empirical studies of zoogeochemistry focus on the net effects of animal exclusion in relatively small areas (100–10,000 m 2 ) over the medium term (0–20 years) (Forbes et al., 2019).…”

Journal of Animal Ecology in 2023: Looking back and looking forward

“…But we are increasingly publishing papers on how animals affect the ecosystems they are embedded in rather than simply respond to changes in the environment (e.g. Ellis‐Soto et al., 2021; Ferraro et al., 2023; Grant et al., 2022; McCary & Schmitz, 2021; Swain et al., 2023).…”