The genus Sphagnum is an essential component in the formation and maintenance of high latitude peatlands, bogs and mires. The species grows in dense, extended mats of agglomerated shoots that allow it to retain water necessary for its growth. These mats are partly responsible for maintaining the right conditions for other species in these wetlands to thrive. In this issue of Physiologia Plantarum, Mironov et al. (2020) monitored the growth of Sphagnum riparium for a period of 4 years and revealed three distinct growth rhythms: a seasonal temperature dependent, a circalunar and a third one, synchronized with the circalunar. This synchronised nature of Sphagnum growth could contribute to its position as a key species in the maintenance of peatlands.Within Northern (high latitude) peatlands, the genus Sphagnum acts as an ecosystem engineer, rapidly forming an environment, both hydrological and biogeochemical, favourable to its growth (van Breemen 1995). As a consequence, the peat properties and plant species composition largely result from the growth of Sphagnum, a genus that can make up as much as 80% of the species composition in these areas (Weltzin et al. 2003). High latitude peatlands comprise almost one third of the global soil carbon pool and they provide an important sink for atmospheric carbon dioxide even though they cover only 2% of the total land mass (Yu et al. 2010). Sphagnum moss is harvested commercially and used, for example, as insulating material, an ingredient in potting mixes to enhance their moisture retaining value and as a critical substrate for growing mushrooms.As key-species in these environments, knowledge on the ecology, growth and development of Sphagnum spp. is of great interest to aid conservationists' efforts to restore damaged wetlands, necessary as climate change and overexploitation are straining the high latitude wetlands. It is estimated that as much as 52% of active peatlands have been lost to overexploitation (Chapman et al. 2003).To better understand the growth and development of these key species, the authors of this study have tried to assess the biological growth rhythm of Sphagnum riparium, a species covering 90% of their test site in Russian Karelia, using data from a 4-year period. The authors used the angle formed in the stem induced by the weight of the snow cover to measure the annual growth. The growth season starts when temperatures rise and the snow cover disappears, allowing for the use of this bend as 'starting point' of annual growth and the distance between consecutive curvatures as a measure of yearly growth. The authors revealed three growth rhythms (Fig. 1) of which the one contributing most to the annual growth was linked to the seasonal cycle of temperature, which relates to earlier studies into the effect of climate change and the possibility that the area of suitable climate for Sphagnum peatland could expand in the near future, provided that water availability is not greatly reduced (Oke and Hager 2017). The second rhythm, contributing substantially b...

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Individual rankings are often aggregated using scoring rules: each position in each ranking brings a certain score; the total sum of scores determines the aggregate ranking. We study whether scoring rules can be robust to adding or deleting particular candidates, as occurs with spoilers in political elections and with athletes in sports due to doping allegations. In general the result is negative, but weaker robustness criteria pin down a one-parameter family of geometric scoring rules with the scores 0, 1, 1 + p, 1 + p + p 2 , . . .. These weaker criteria are independence from deleting unanimous winner (e.g., doping allegations) and independence from deleting unanimous loser (e.g., spoiler candidates). This family generalises three central rules: the Borda rule, the plurality rule and the antiplurality rule. For illustration we use recent events in biathlon; our results give simple instruments to design scoring rules for a wide range of applications.

We study voting rules with respect to how they allow or limit a majority from dominating minorities: whether a voting rule makes a majority powerful, and whether minorities can veto the candidates they do not prefer. For a given voting rule, the minimal share of voters that guarantees a victory to one of their most preferred candidates is the measure of majority power, and the minimal share of voters that allows them to veto each of their least preferred candidates is the measure of veto power. We find tight bounds on these minimal shares for voting rules that are popular in the literature and in real elections. We order these rules according to majority power and veto power. The instant-runoff voting has both the highest majority power and the highest veto power and the plurality rule has the lowest. In general, the higher the majority power of a voting rule is, the higher its veto power. The three exceptions are: voting with proportional veto power, Black's rule, and Borda rule, which have a relatively low level of majority power and a high level of veto power and thus provide minority protection. Our results can shed light on how voting rules provide different incentives for voter participation and candidate nomination.