Mironov, V.L., S.I. Grabovik, P.А. Ignashov & L.V. Kantserova. Geotropic curvatures of Sphagnum: environmental features of their genesis
and trial application for estimation shoot length increment
Arctoa (2016) 25: 353–363
doi: 10.15298/arctoa.25.27
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.