Worldwide cross-ecosystem carbon subsidies and their contribution to ecosystem functioning

Abstract

Ecosystems are widely inter-connected by spatial flows of resources 1,2 , yet primarily studied in a local context. Meta-ecosystem models suggest that cross-ecosystem subsidies can play an essential role in ecosystem functioning, notably by controlling local availability of resources for biological communities 3-6 . The general contribution of these resource connections to ecosystem functioning, however, remains unclear in natural systems, due to the heterogeneity and dispersion of data across the ecological literature.Here we provide the first quantitative synthesis on spatial flows of carbon connecting ecosystems worldwide. These cross-ecosystem subsidies range over eight orders of magnitude, between 10 -3 and 10 5 gC m -2 yr -1 , and are highly diverse in their provenance.We found that spatial carbon flows and local carbon fluxes are of the same order of magnitudes in freshwater and benthic ecosystems, suggesting an underlying dependency of these systems on resources provided by connected terrestrial and pelagic ecosystems respectively. By contrast, in terrestrial systems, cross-ecosystem subsidies were two to three orders of magnitude lower than local production (grasslands and forests), indicating a weaker quantitative influence on functioning. Those subsidies may still be qualitatively important, however, as some have high nutrient content 7,8 . We also find important gaps in carbon flow quantification, notably of cross-ecosystem subsidies driven by animal movements, which likely leads to general underestimations of the magnitude and direction of cross-ecosystem linkages 9 . Overall, we demonstrate strong ecosystem couplings, suggesting that ecosystems can be vulnerable to alterations of these flows and pointing to an urgent need to re-think ecosystem functioning in a spatial perspective.

Information use during movement regulates how fragmentation and loss of habitat affect body size

“…This confirms the significance of immigration as a mechanism maintaining fundamental genetic variation [5]. Some rate of immigration is realistic as open communities are the rule rather than the exception in nature [3,61].…”

“…Habitat loss and fragmentation can alter species composition but can also cause shifts in body size at both the population and community level [1,2]. Eventually, shifts in size distributions impact ecosystem dynamics (including fluxes of nutrients) and functioning [3,4]. As such, a better understanding of how habitat loss and fragmentation alter selection on body size distributions is crucial [5].…”

Landscape configuration alters spatial arrangement of terrestrial-aquatic subsidies in headwater streams

“…Embedded in a terrestrial matrix, streams, rivers, lakes, and ponds are defined by flows of resources and organisms to and from adjacent ecosystems. One major flux is the allochthonous input of carbon and nutrients (Fisher and Likens 1973;Chapin et al 2006;Gounand et al 2018). Headwater stream reaches are primarily heterotrophic (Marcarelli et al 2011).…”

“…The diversity of terrestrial ecosystem types contribute different subsidies to freshwater ecosystems (Fuß et al 2017;Gounand et al 2018), with important consequences for communities and for ecosystem functioning. Among naturally-occurring types of land cover, forests, for example, contribute large amounts of leaf detritus and woody debris (Elosegi et al 2007), while grasslands can contribute less-recalcitrant grass materials and roots (Whiting et al 2011).…”

On Embedding Meta-ecosystems into a Socioecological Framework: A Reply to Renaud et al.

“…Spatial flows of organisms and resources are increasingly recognized as key elements of ecosystem functioning [1,2]. In a previous article [3], we called for an update of the metaecosystem framework, a key conceptual and theoretical framework regarding spatial dynamics [4].…”