Abstract
Background and AimsForest 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.MethodsWe 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 ResultsRoot 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.ConclusionsThe 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 environmental 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.
Highlights
Forest peatland ecosystems account for up to 25 % of peatlands globally
The two studied alder forest stands are in close proximity to each other and share a macroclimate but differ in their microclimate (Supplementary Data Table S2)
While biomass of the very fine roots
Summary
Forest peatland ecosystems account for up to 25 % of peatlands globally. They play a major role in the global carbon (C) cycle by sequestering high amounts of C as plant biomass and through long-term storage of C as peat (Zoltai and Martikainen, 1996). Drainage of peatlands and subsequent use for agriculture or forestry have strongly reduced the occurrence of wet alder forest peatlands (Prieditis, 1997). These areas have effectively been turned into C sources through enhanced decomposition of peat, reversing their climate change mitigation function (Joosten et al, 2016; Leifeld et al, 2019). In an effort to counteract these consequences, more and more sites are being rewetted, but so far it is unclear how rewetting will affect
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