Geotropic curvatures of Sphagnum: environmental features of their genesis and trial application for estimation shoot length increment

Abstract

The genesis of geotropic curvatures in the natural habitat of Sphagnum mosses is described in detail on the basis of in situ observations. A novel method of estimation of length increment of Sphagna shoots is developed, based on their geotropic curvatures, which are the markers of physical impacts. The snow load in northern areas is an example of the most typical impact on Sphagnum cover and further geotropic response of stems. Deviation in stem growth causes the curves which may form after snowmelt or under the snow layer. First attempt to use the snow induced markers, named further as "nival geotropic curvatures", for estimation of shoot increment rate of Sphagna stems were made in the late 20th century. However, first researchers ignored other than snow cover common factors that are responsible for the formation of similar markers during the growing season. Therefore, measuring increment from these markers may result in incorrect estimation, because they could be formed neither due to the snow load nor the beginning of the growing season. Our method takes into account these shortcomings. Several Sphagnum species were involved in the research for experimental comparison of the novel method with the classical tied thread method. Experimental plots were studied during a two-year period on Karelian mires. The length increment values obtained by both methods show some differences. Shoot increment values obtained by the method of the nival geotropic curvatures markedly exceed values obtained by the classical tied thread method in all cases. The difference ranged from 7.5 to 18.6 % in 2014 and from 20.8 to 45.8 % in 2015. The results could be explained by the negative effect of the tied thread method on the growth of moss, that was described in the literature. The coefficients of variation estimated by the method of nival curvatures are reliably lower than those obtained by the tied thread method for practically all samples. In 2014, mean value of the coefficients of variation were 20.3±4.2 % for samples obtained by tied thread method and 13.0±4.7 % for samples obtained by nival geotropic curvatures method. In 2015, the coefficients of variation were estimated at 21.1±5.3 % and 8.7±2.2 %, respectively.The differences are assumed to be due to the difference in the degree of impact on the structure of Sphagnum cover. РезюмеНа основании наблюдений in situ детально описан генезис геотропических изгибов стеблей в естественной среде обитания сфагнов. Разработан новый метод определения прироста побегов сфагновых мхов, в основу которого положено использование геотропических изгибов, образующихся в результате внешних физических воздействий. Снеговая нагрузка, характерная для северных регионов -пример наиболее типичного физического воздействия, вызывающего геотропическую реакцию побегов. Отклонение растущих побегов вызывает образование изгибов после снеготаяния или под снежным покровом. Первые попытки использования вызываемых действием снега маркеров (называемых нами в дальнейшем «нивальные геотропические изгибы») на ...

Growth of Sphagnum riparium is strongly rhythmic: Contribution of the seasonal, circalunar and third rhythmic components

“…The length increment of S. riparium in this study was 37.9 to 42.2cm, which is among record-high values for this species. A nearly identical increment was previously reported for S. riparium which was found growing 36km away from our range, in the drainage ditches of Rittusuo mire (Mironov et al, 2016). Similar increment levels are also known for other species of wet habitats (Overbeck & Happach, 1957;Brock & Bregman, 1989).…”

“…According to Pouliot et al (2010), increment demonstrated by innate markers would be 33-112% higher than when artificial markers are used. According to Mironov et al (2016), this difference for S. riparium is 10-80%.…”

“…35% of the fixed N 2 is supplied to Sphagnum shoots, intensifying its production (Berg et al, 2013). This is, probably, partly why S. riparium in wet habitats can have an annual increment of up to 42cm (Mironov et al, 2016), and productivity up to 1800g/m 2 (Grabovik & Kuznetsov, 2016). Due to such passive protection against drought and high growth rates, this species appears to be a convenient model system for monitoring growth.…”

“…Here, we measured growth using geotropic curvatures, a method designed by the authors (Mironov, 2015;Mironov et al, 2016), and improved upon compared to its nearest analogs (Korchagin, 1960;Camill et al, 2001;Vitt, 2007). These innate markers are induced by a negative geotropic response to capitulum declination from the vertical.…”

“…In contrast to our previous paper (Mironov & Kondratev, 2017), the aim of this study is to analyze growth rate patterns in S. riparium from the perspectives of all rhythmic components. Data gathered by the geotropic curvatures method of our own design during a three-year high-precision growth monitoring effort were used to this end (Mironov, 2015;Mironov et al, 2016). In all, three rhythmic components have been identified, which collectively explain 51-78% of the moss growth rate.…”