Biomass production and carbon sequestration of dense downy birch stands on cutaway peatlands

ABSTRACT

The establishment of biomass plantations with short-rotation forestry principles is one of the after-use options for cutaway peatlands. We studied biomass production and carbon sequestration in the above- and below-ground biomass of 25 naturally afforested, 10–30 years old downy birch (Betula pubescens Ehrh.) stands located in peat cutaway areas in Finland. Self-thinning reduced the stand density from 122,000 trees ha⁻¹ (stand age of 10 years) to 10,000 trees ha⁻¹ (25–30 years), while the leafless above-ground biomass increased from 17 Mg ha⁻¹ up to 79–116 Mg ha⁻¹. The total leafless biomass (including stumps and roots) varied from 46 to 151 Mg ha⁻¹. The mean annual increment (MAI) of the above-ground biomass increased up to the stand age of 15 years, after which the MAI was on the average 3.2 Mg ha⁻¹a⁻¹. With below-ground biomass, the MAI of the stands older than 15 years was 4.7 Mg ha⁻¹. The organic matter accumulated in the O-layer on the top of the residual peat increased linearly with the stand age, reaching 29.3 Mg ha⁻¹ in the oldest stand. The O-layer contributed significantly to the C sink, and the afforestation with downy birch converted most of sites into C sinks.

KEYWORDS:

• Downy birch
• above-and below-ground biomass
• self-thinning
• C sequestration
• cutaway peatland

Acknowledgements

We would like to thank Jorma Issakainen, Pauli Alavataja, Taisto Jaakola, Jaakko Miettinen, Ari Ryynänen, Eero Saari and Seppo Vihanta, for locating and measuring of the stands. Seppo Vihanta is acknowledged also for assisting in the calculations and Kaisa Jaakola in laboratory analysis.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Jyrki Hytönen http://orcid.org/0000-0001-8475-3568