Cross-ecosystem carbon flows connecting ecosystems worldwide

Abstract

Ecosystems are widely interconnected by spatial flows of material, but the overall importance of these flows relative to local ecosystem functioning remains unclear. Here we provide a quantitative synthesis on spatial flows of carbon connecting ecosystems worldwide. Cross-ecosystem flows range over eight orders of magnitude, bringing between 10−3 and 105 gC m−2 year−1 to recipient ecosystems. Magnitudes are similar to local fluxes in freshwater and benthic ecosystems, but two to three orders of magnitude lower in terrestrial systems, demonstrating different dependencies on spatial flows among ecosystem types. The strong spatial couplings also indicate that ecosystems are vulnerable to alterations of cross-ecosystem flows. Thus, a reconsideration of ecosystem functioning, including a spatial perspective, is urgently needed.

Litter movement pathways across terrestrial–aquatic ecosystem boundaries affect litter colonization and decomposition in streams

“…In temperate regions, lateral inputs can constitute 7%–23% of total litterfall (Abelho, ) and 81% of total leaf litter (Benfield, ) entering streams. The flux of leaf litter to streams has strong bottom‐up effects because it enters at low trophic levels in the recipient food webs (Allen & Wesner, ), but the degree of integration can depend on the characteristics of the litter introduced (Gounand, Little, Harvey, & Altermatt, ). During periods of terrestrial exposure, leaf litter may have been already decomposing (Abelho, , ) and is likely to constitute a resource differing notably in quality from leaf litter falling directly into the water.…”

Stream network geometry and the spatial influence of aquatic insect subsidies across the contiguous United States

“…The remaining, more complex models were estimated using Hamiltonian Monte Carlo (HMC). We fit all models in program R (Version 3.5), using the map or map2stan (HMC) functions in rethinking package (McElreath 2016) or the stan_betareg function in rstanarm package (Goodrich et al 2018). For each model, we sampled from 4 independent chains using 10,000 sampling iterations with a 5000-iteration warm-up.…”

“…Aquatic and terrestrial ecosystems comprise a meta-ecosystem (Loreau et al 2003), where the aquatic and terrestrial components are reciprocally linked by flows of material and energy across their boundaries (i.e., spatial subsidies or resource subsidies; Polis et al 1997, Richardson et al 2010, Allen and Wesner 2016, Gounand et al 2018. Emergent aquatic insects are aquaticderived energy and nutrient subsidies transported to terrestrial ecosystems (Baxter et al 2005, Schindler andSmits 2017) and counteract gradational forces commonly associated with cross-ecosystem subsidies (Loreau et al 2003, Leroux and Loreau 2008, Subalusky and Post 2018.…”

Nutritional hotspots? Prey from one ecosystem provide key fatty acids required for consumers in multiple ecosystems

“…Though the quantities of materials flowing into an ecosystem are certainly important, the quality of inflowing materials is thought to be a key factor in determining their importance for recipient consumers (Marcarelli, Baxter, Mineau, & Hall, ; Subalusky & Post, ). Yet, the hundreds of studies that have been published on this topic have generally focused on the magnitude of consumer responses to removals of these connections (Allen & Wesner, ) or on the magnitude of these fluxes themselves (Gounand et al, ). Studies that explicitly focus on the quality of cross‐ecosystem energetic fluxes are far less common, representing a key knowledge gap in the field.…”

“…For example, seaweed produced in marine ecosystems that washes onto shorelines can increase the abundance of terrestrial primary consumers and their predators (Spiller et al, 2010). It is not uncommon that the quantity of carbon flowing into an ecosystem can exceed in situ carbon production (Gounand, Little, Harvey, & Altermatt, 2018).…”