Root biomass and root traits of Alnus glutinosa show size-dependent and opposite patterns in a drained and a rewetted forest peatland
Schwieger, S., G. Blume-Werry, F. Ciesiolka and Anadon-Rosell, A. 2022.
Abstract
Background: and Aims Forest peatlands represent 25 % of global peatlands and store large amounts of carbon
(C) as peat. Traditionally they have been drained in order to increase forestry yield, which may cause large losses
of C from the peat. Rewetting aims to stop these losses and to restore the initial storage function of the peatlands.
As roots represent major peat-forming elements in these systems, we sampled roots with diameter <5 mm in a
drained and a rewetted forest peatland in north-east Germany to evaluate differences in tree biomass investments
below ground, root functional characteristics and root age.
Methods: We cored soil next to Alnus glutinosa stems and sorted root biomass into <1, 1 - 2 and 2 - 5 mm diameter classes. We measured biomass distribution and specific root area (SRA) in 10-cm depth increments down to
50 cm, and estimated root age from annual growth rings.
Key Results: Root biomass in the rewetted site was more than double that in the drained site. This difference
was mostly driven by very fine roots <1 mm, which accounted for 51 % of the total root biomass and were mostly
(75 %) located in the upper 20 cm. For roots <1 mm, SRA did not differ between the sites. However, SRA of the
1-2 mm and 2-5 mm diameter roots was higher in the drained than in the rewetted site. Root age did not differ
between sites.
Conclusions The size-dependent opposite patterns between root biomass and their functional characteristics
under contrasting water regimes indicate differences between fine and coarse roots in their response to environ-
mental changes. Root age distribution points to similar root turnover rates between the sites, while higher root
biomass in the rewetted site clearly indicates larger tree C stocks below ground under rewetting, supporting the C
sink function of the ecosystem.
Key Words
Alder forest, Alnus glutinosa, annual growth rings, biomass distribution, fine roots, forest peatland, functional traits, root age, rewetting, specific root area.
