Ecosystem assembly rules: the interplay of green and brown webs during salt marsh succession

Abstract

Abstract. Current theories about vegetation succession and food web assembly are poorly compatible, as food webs are generally viewed to be static, and succession is usually analyzed without the inclusion of higher trophic levels. In this study we present results from a detailed analysis of ecosystem assembly rules over a chronosequence of 100 years of salt marsh succession. First, using 13 yearlong observations on vegetation and soil parameters in different successional stages, we show that the space-for-time substitution is valid for this chronosequence. We then quantify biomass changes for all dominant invertebrate and vertebrate species across all main trophic groups of plants and animals. All invertebrate and vertebrate species were assigned to a trophic group according to feeding preference, and changes in trophic group abundance were quantified for seven different successional stages of the ecosystem. We found changes from a marine-fueled, decomposer-based (brown) food web in early stages to a more terrestrial, plant-based, herbivore-driven (green) food web in intermediate succession stages, and finally to a decomposer-based, terrestrial-driven food web in the latest stages. These changes were accompanied not only by an increase in live plant biomass and a leveling toward late succession but also by a constant increase in the amount of dead plant biomass over succession. Our results show that the structure and dynamics of salt marsh food webs cannot be understood except in light of vegetation succession, and vice versa.

Evaluating the success of managed realignment for the restoration of salt marshes: Lessons from invertebrate communities

“…Our main results fit well to the assembly rule found by Schrama et al (2012) in an European salt-marsh, through a chronosequence of 100 years. They indeed described that, at the beginning of the succession, most incoming fluxes of organic matter and decomposers are mostly marine, whereas the importance of terrestrial matter and invertebrates increases over time.…”

Ecological succession reveals potential signatures of marine–terrestrial transition in salt marsh fungal communities

“…This stage has previously been shown to have a peak in plant diversity (Schrama et al, 2012). The extent of mycorrhizal colonization of the plants occurring at the study sites was not explored.…”

“…The study site presents a well-documented salt marsh chronosequence that has been calibrated using topographic maps, aerial photographs and monitoring permanent plots at different successional stages for over 20 years (Olff et al, 1997;Schrama et al, 2012). For this study, five successional stages were identified and estimated as 0, 5, 35, 65 and 105 years of succession (hereafter referred as 'Stage' followed by the corresponding year) in May 2012 (Supplementary Figure S1).…”

“…This environmental gradient has served as a natural laboratory for plant and animal ecology studies over the past 40 years (Bakker, 2014). The focus of previous works has been to understand the trophic and nontrophic community interactions (see, for example, Schrama et al, 2013) and the multilevel food-web dynamics (Schrama et al, 2012). Moreover, there is evidence for the contention that this chronosequence evolves by a gradual decoupling from the marine environment.…”

“…In particular, early-soil sites are 'allochthonous', being mostly fuelled by external input of nutrients and organisms (that is, the so-called 'brown' food web). As succession proceeds, these influences are progressively curbed, and belowground nutrient dynamics is increasingly governed by the soil microbiota (that is, the so-called 'green' food web) (Schrama et al, 2012).…”