Plant genotype determines biomass response to flooding frequency in tidal wetlands

Abstract

Abstract. The persistence of tidal wetland ecosystems like salt marshes is threatened by human interventions and climate change. In particular, the threat of accelerated sea level rise (SLR) has increasingly gained the attention of the scientific community recently. However, studies investigating the effect of SLR on plants and vertical marsh accretion are usually restricted to the species or community level and do not consider phenotypic plasticity or genetic diversity. To investigate the response of genotypes within the same salt-marsh species to SLR, we used two known genotypes of Elymus athericus (Link) Kerguélen (low-marsh and high-marsh genotypes). In a factorial marsh organ experiment we exposed both genotypes to different flooding frequencies and quantified plant growth parameters. With increasing flooding frequency, the low-marsh genotype showed higher aboveground biomass production compared to the high-marsh genotype. Additionally, the low-marsh genotype generally formed longer rhizomes, shoots and leaves, regardless of flooding frequency. Belowground biomass of both genotypes decreased with increasing flooding frequency. We conclude that the low-marsh genotype is better adapted to higher flooding frequencies through its ability to allocate resources from below- to aboveground biomass. Given the strong control of plant biomass production on salt-marsh accretion, we argue that these findings yield important implications for our understanding of ecosystem resilience to SLR as well as plant species distribution in salt marshes.

Plant genotype controls wetland soil microbial functioning in response to sea-level rise

“…In support of the notion that the soil microbial activity response to increasing flooding frequency follows the response of plant aboveground processes, we found a significant relationship between aboveground biomass and microbial N-acquisition activity (aminopeptidase + chitinase activity, sensu Sinsabaugh et al, 2009Sinsabaugh et al, , 2008 across all flooding treatments (r = 0.41; p ≤ 0.01, Table 2) and to an even larger degree within the daily flooding treatment (r = 0.63; p = 0.01), where effects on aboveground biomass and N-acquisition activity existed (Table 2 and Figure 2; (Reents et al, 2021)). Soil enzyme activity is tightly https://doi.org/10.5194/bg-2021-41 Preprint.…”

“…whereas the unadapted genotype showed a strong reduction of aboveground biomass at our highest flooding treatment (Reents et al, 2021). Consequently, only the flooding-sensitive unadapted genotype showed changes in soil microbial activity, whereas the adapted genotype was able to maintain microbial enzyme activities at a constant level over the entire flooding gradient (Table 1; Figure 2).…”

Comment on bg-2021-41

“…Two genotypes of the dominant tidal-wetland grass Elymus athericus have been identified, an unadapted plant genotype, found in high-marsh environments, and an adapted plant genotype, found in lowmarsh environments. The adapted genotype shows no reduction of aboveground biomass even in response to extreme increases of flooding frequency (Reents et al, 2021). Given the overriding control of plant aboveground processes on microbial functioning in tidal wetland soils, we hypothesize that the adapted genotype buffers the response of the soil microbial community to increasing flooding frequency.…”

“…Plants were collected in April 2015 from Elymus athericus stands on the island Schiermonnikoog, the Netherlands, that have previously been demonstrated to be dominated by genetically distinct populations of Elymus, i.e. unadapted and adapted genotypes (Bockelmann et al, 2003;Reents et al, 2021). The plants were transferred to pots and kept in a common garden at Universität Hamburg for 24 months before the experiment commenced.…”

“…Here, we study the interaction effect of flooding frequency and plant genotype on soil microbial community structure and functioning, using the dominant tidal-wetland grass Elymus athericus as a model species (Bockelmann and Neuhaus, 1999). Two genotypes of Elymus athericus, which differ in their adaptation to flooding frequency, have been identified: a flooding-sensitive genotype from the high marsh (to simplify hereafter referred to as unadapted genotype) and a less flooding-sensitive genotype from the low marsh (hereafter adapted genotype) (Bockelmann et al, 2003;Reents et al, 2021). Given the overriding control of plant processes on microbial functioning in wetland soils, we hypothesize that flooding effects on microbial decomposition and microbial community structure are strong in soils with the unadapted plant genotype, but absent or buffered in soils of the adapted plant genotype (Figure 1).…”