Modelling the habitat preference of two key <i>Sphagnum</i> species in a poor fen as controlled by capitulum water retention

Abstract

<p><strong>Abstract.</strong> Current peatland models generally lack dynamic feedback between the plant community structure and the environment, although the vegetation dynamics and ecosystem functioning are tightly linked. Realistic projections of peatland response to climate change requires including vegetation dynamics in ecosystem models. In peatlands, <i>Sphagnum</i> mosses are key engineers. The species composition in a moss community varies primarily following habitat moisture conditions. Hence, modelling the mechanisms in controlling the habitat preference of Sphagna is a good first step for modelling the community dynamics in peatlands. In this study, we developed the Peatland Moss Simulator (PMS), a process-based model, for simulating community dynamics of the peatland moss layer that results in habitat preferences of <i>Sphagnum</i> species along moisture gradients. PMS employed an individual-based approach to describe the variation of functional traits among shoots and the stochastic base of competition. At the shoot-level, growth and competition were driven by net photosynthesis, which was regulated by hydrological processes via capitulum water retention. The model was tested by predicting the habitat preferences of <i>S. magellanicum</i> and <i>S. fallax</i>, two key species representing dry (hummock) and wet (lawn) habitats in a poor fen peatland (Lakkasuo, Finland). PMS successfully captured the habitat preferences of the two <i>Sphagnum</i> species, based on observed variations in trait properties. Our model simulation further showed that the validity of PMS depended on the interspecific differences in capitulum water retention being correctly specified. Neglecting the water-retention differences led to the failure of PMS to predict the habitat preferences of the species in stochastic simulations. Our work highlights the importance of capitulum water retention to the dynamics and carbon functioning of <i>Sphagnum</i> communities in peatland ecosystems. Studies of peatland responses to changing environmental conditions thus need to include capitulum water processes as a control on the vegetation dynamics. For that our PMS model could be used as an elemental design for the future development of dynamic vegetation models for peatland ecosystems.</p>

Morphological and biochemical responses ofSphagnummosses to environmental changes

“…Such result was expected as Sphagnum species often have narrow habitat niches (Andrus et al, 1983;Johnson et al, 2015). Sphagnum species with different morphological and physiological constraints often replace each other along WTD gradient (Clymo and Hayward, 1982;Gong et al, 2019;Laing et al, 2014). The ability of Sphagnum to transport water to the capitula and retain cytoplasmic water are important traits controlling the moss community dynamic across peatland habitats (Bengtsson et al, 2020a;Gong et al, 2019;Hájek, 2020).…”

“…Sphagnum species with different morphological and physiological constraints often replace each other along WTD gradient (Clymo and Hayward, 1982;Gong et al, 2019;Laing et al, 2014). The ability of Sphagnum to transport water to the capitula and retain cytoplasmic water are important traits controlling the moss community dynamic across peatland habitats (Bengtsson et al, 2020a;Gong et al, 2019;Hájek, 2020). Water-retention traits are key to supply sufficient moist in Sphagnum apical parts, minimize evapotranspiration (Rydin and McDonald, 1985;Titus and Wagner, 1984), and thus maintain important physiological processes such as photosynthesis (Bengtsson et al, 2020a;Gong et al, 2019;Jassey and Signarbieux, 2019).…”

“…The ability of Sphagnum to transport water to the capitula and retain cytoplasmic water are important traits controlling the moss community dynamic across peatland habitats (Bengtsson et al, 2020a;Gong et al, 2019;Hájek, 2020). Water-retention traits are key to supply sufficient moist in Sphagnum apical parts, minimize evapotranspiration (Rydin and McDonald, 1985;Titus and Wagner, 1984), and thus maintain important physiological processes such as photosynthesis (Bengtsson et al, 2020a;Gong et al, 2019;Jassey and Signarbieux, 2019). We evidenced that species with the highest water holding capacity also exhibited the highest antioxidant capacity, as showed by the high flavonoid and enzymatic activities in their tissues (Nakabayashi et al, 2014).…”

“…However, despite these general properties, we still lack a clear understanding of the species-specific characteristics, or traits, controlling Sphagnum growth and/or survival at global and local scale (Bengtsson et al, 2020a). Sphagnum species indeed show a high interspecific variability in their inhered anatomical and biochemical traits (Bengtsson et al, 2020b(Bengtsson et al, , 2018(Bengtsson et al, , 2016Chiapusio et al, 2018;Dorrepaal et al, 2005;Gong et al, 2019). While Sphagnum anatomical traits are more and more used to explain how Sphagnum species adapt to environmental conditions (Bengtsson et al, 2020b;Jassey and Signarbieux, 2019) , our knowledge on Sphagnum biochemical traits, how they vary among species and phylogeny, how they relate to anatomical traits and how they respond to local and global changes remain limited.…”

Biochemical traits enhance the trait concept in Sphagnum ecology

“…However, despite these general properties we still lack a clear understanding of the species‐specific characteristics, or traits, controlling Sphagnum growth and/or survival at global and local scale (Bengtsson et al 2020a). Sphagnum species exhibit high interspecific variability in their inherited anatomical, morphological and biochemical traits (Dorrepaal et al 2005, Bengtsson et al 2016, 2018, 2020b, Chiapusio et al 2018, Gong et al 2020). While Sphagnum anatomical and morphological traits are increasingly used to explain how Sphagnum species interact with environmental conditions (Jassey and Signarbieux 2019, Bengtsson et al 2020b, Laine et al 2021), we lack knowledge on interspecific differences in Sphagnum biochemical traits, their relationship with anatomical and morphological trait, and how they are affected to local and regional changes.…”