Quality matters: stoichiometry of resources modulates spatial feedbacks in aquatic-terrestrial meta-ecosystems

Abstract

Species dispersal and resource spatial flows can greatly affect connected ecosystems functioning and their response to environmental changes. So far, research on meta-ecosystems has mainly focused on the quantitative effect of subsidy flows. Yet, resource exchanges at the terrestrial-aquatic ecotones display a stoichiometric asymmetry that likely matters for production. Here, we joined ecological stoichiometry and the meta-ecosystem framework to understand how subsidy stoichiometry mediates the response of meta-ecosystem to subsidy flows. Our results demonstrate that resource flows between ecosystems can induce a positive spatial feedback loop, leading to higher production at meta-ecosystem scale by relaxing local ecosystem limitations ("spatial complementarity"). Furthermore, we show that spatial flows can also have an unexpected negative impact on production when accentuating the stoichiometric mismatch between local resources and basal species needs. This study paves the way for new studies on the quality dimension of connectedness at the landscape extent.

Integrating ecological feedbacks across scales and levels of organization

“…Given their contribution to the functioning and stability of ecological systems, acknowledging the links connecting species and ecosystems (i.e., ecological interdependencies) could help improve the design of effective conservation and restoration measures that integrate local and spatial dependencies. (Pulliam 1988, Rietkerk and van de Koppel 1997, Klausmeier 1999, Harding and McNamara 2002, De Roos and Persson 2002, Hui et al 2004, Kéfi et al 2007, Bump et al 2009, Gravel et al 2010, Carr et al 2010, Marleau et al 2010, Bartels et al 2012, Lever et al 2014, Gounand et al 2014, Fronhofer et al 2015, Barraquand et al 2017, Maxwell et al 2017, Graham et al 2018, Schwarz et al 2018, Hastings et al 2018, Klemmer et al 2020, Gil et al 2020, McCann et al 2021, Benkwitt et al 2021, Monk and Schmitz 2022, Temmink et al 2022, Pichon et al 2023, Johnson-Bice et al 2023) (Fontaine et al 2004, Croll et al 2005, Gómez-Aparicio 2009, Young et al 2010, Gaines et al 2010, Hawlena et al 2012, Wilmers et al 2012, Tanentzap et al 2014, Dirzo et al 2014, Silliman et al 2015…”

“…These flows of species and resources generate negative and positive spatial feedbacks between a donor and a recipient ecosystem (Montagano et al 2018). Resource flows between ecosystems can relax local limitations in nutrients or carbon in each local ecosystem, therefore generating a mutually beneficial spatial loop (Pichon et al 2023). However, spatial feedbacks can also be negative, when dispersing individuals carry parasites or diseases that decrease the demography of local populations (anti-rescue effect; Harding and McNamara 2002) or when subsidy flows correspond to low-quality resources (Kelly et al 2014; see Emergent properties section).…”

“…when nutrients and detritus are spatially exchanged and meet the local needs of communities within each ecosystem (i.e., the exported by-products of an ecosystem brings the resource limiting the other). In that case, a positive feedback loop can emerge at the landscape scale, fostering the landscape-scale production and maximizing the use of nutrients and carbon between ecosystems (Pichon et al 2023; see also Modulators section). Taken together, we notice similar autogenic development of ecological systems driven by autocatalytic loops at different spatial scales.…”

“…This happens when a large magnitude of nutrient-poor terrestrial litter falls into lakes or streams (Kelly et al 2014), and leads to reduced secondary production, eutrophication, or hypoxia (Subalusky et al 2015, Dutton et al 2018. In this case, terrestrial and aquatic ecosystems are involved in a negative feedback loop: terrestrial ecosystems benefit from nutrient-rich spatial subsidies, while stoichiometric mismatch impairs freshwater functioning (Pichon et al 2023).…”

A general meta‐ecosystem model to predict ecosystem functions at landscape extents

“…We expect this outcome as different ecosystem types are highly asymmetric in their primary production (terrestrial ecosystems are more autotrophic while on average aquatic ecosystems are more heterotrophic) (Gounand et al 2020) and in their trophic efficiency (aquatic ecosystems move energy faster while terrestrial ecosystems tend to accumulate stock) (Shurin et al 2002, Chapin et al 2012). Thus, energy in a landscape tends to move among ecosystems that potentially share some levels of complementarity in functioning that should lead to emerging positive impact of spatial flows on productivity and trophic efficiency at the meta‐ecosystem scale (Bartels et al 2012, Gounand et al 2017, Osakpolor et al 2023, Pichon et al in pressin press).…”