Light responses of mire mosses – a key to survival after water‐level drawdown?

Abstract

Mosses are important ecosystem engineers in mires. Their existence may be threatened directly or indirectly by anthropogenic drying, which further leads to shading and changed competition conditions via increased arboreal plant cover. Yet, some species are able to acclimate to the changing habitat, while some give way to new colonizers. In the shaded conditions, acclimation or adaptation to low light levels is likely to be a winning strategy to survive. We studied the light responses of photosynthesis and photosynthetic pigment concentrations in mosses from an open mire and its shaded, i.e. drained and forested counterpart. Against our expectations, the Sphagnum species found only in the open habitat had lower photosynthetic capacity and maximum quantum yield than those found to grow in the shade. Chlorophyll fluorescence results suggested that photoinhibitory damage to photosystem II is responsible for the low photosynthetic performance of the Sphagna of the open habitat, which were inefficient to utilize any light level. In the shaded habitat, Sphagnum mosses showed adaptation to lower light conditions only by possessing a higher chlorophyll content. Pleurozium schreberi reached photosynthetic light saturation at half the irradiance level compared to Sphagna. The lack of efficient photoprotection or repair mechanism after photodamage may constrain the success of these species in the open habitat. Thus, the dominant Sphagna in the open pristine conditions seem to be stress tolerant, while the dominants of the shaded drained mire appear to be species capable of maximizing their growth and production to compete in the unstressful conditions in terms of light and desiccation.

Bulk partitioning the growing season net ecosystem exchange of CO<sub>2</sub> in Siberian tundra reveals the seasonality of its carbon sequestration strength

“…Light stress in tundra moss species has also been shown to be greater early in the season, with subsurface morphological adaptations to this stress sustaining more late-season photosynthesis and delayed senescence (Zona et al, 2011). Similar morphological adaptations have been seen in open bog boreal Sphagnum species (Hájek et al, 2009). A partition method should then be receptive to the possibility of light and temperature sensitivities that change through the season.…”

Sphagnum growth and ecophysiology during mire succession

“…U PSII can then be used to calculate the linear electron transport rate (ETR), which is related to the overall photosynthetic capacity in the prevailing environmental conditions (e.g., Maxwell and Johnson 2000). This technique was successfully used in earlier Sphagnum studies (Murray et al 1993;Granath et al 2009aGranath et al , b, 2010Hájek et al 2009). Measurements were performed during August 2008 for 6-14 samples of each of the Sphagnum species on the day of sample collection.…”

“…Gross photosynthesis (P G ) at each light level was calculated by subtracting the dark respiration (R D ) from the net CO 2 exchange (P N ) results. Similarly to Hájek et al (2009), we used the following equation to describe the light response curve of P G :…”

Sphagnum abundance and photosynthetic capacity show rapid short-term recovery following managed burning

“…Given the relatively rapid recovery of S. capillifolium F v /F m following fire-induced heating, at least during the first 100 days (Taylor et al 2017), and its resilience to other disturbances such as drought (Hájek and Vicherová 2014) and high exposure to light (Maraschall and Proctor 2004), we hypothesise that sustained differences between burnt and unburnt plants are a result of microclimatic changes brought about by fire. These may have included increased water stress due to increased evaporative demand following the removal of the Calluna canopy and increased solar irradiation (Hájek et al 2009;Laing et al 2014;Leonard et al 2017). The higher variability in photosynthetic capacity in the burnt plots in the immediate postfire period is likely to be due to the substantial heterogeneity in fire severity at small spatial scales (Fernandes et al 2000;Bova and Dickinson 2008).…”