Old-Growth Coniferous Stands on Fertile Drained Organic Soil: First Results of Tree Biomass and Deadwood Carbon Stocks in Hemiboreal Latvia

Laura Ķēniņa,Valters Samariks,Daiga Zute,Āris Jansons,Ieva Jaunslaviete

doi:10.3390/f13020279

Abstract

Organic soils store a large amount of carbon stock, but they are also a large source of greenhouse gas emissions in a forest. Results of previous studies do not provide whole-country representative data of carbon stock in drained fertile organic soil forests in Europe, as the effects of stand age and dominant tree species are significant. Moreover, the growing role of old-growth stands has triggered interest in empirical data about drained organic soils. These data might serve as a reference of theoretical carbon carrying capacity that could be achieved in hemiboreal Latvia. We aimed to characterize tree biomass and deadwood carbon pools in coniferous old-growth stands on fertile, drained organic soils. Seven old-growth Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) dominated stands (131–174 years) were measured. Both groups of stands had similar carbon stocks, reaching 167 and 154 t C ha−1 in tree biomass and 11 and 10 t C ha−1 in deadwood, respectively. A large variation in deadwood carbon storage was found across sample plots, ranging from 0.6 to 26.6 t C ha−1. Dead standing trees and downed logs store a great share of the total deadwood carbon, 5 and 4 t C ha−1, respectively. Significantly less carbon was stored in dead standing trees with broken tops (1 t C ha−1). Further assessment of soil carbon stock and fluxes is ongoing to reduce uncertainty in the soil carbon evaluation of old-growth stands in the context of climate change mitigation targets in a hemiboreal region.

Highlights

Forests are expected to increase carbon removal from the atmosphere and decrease greenhouse gas emissions to achieve global climate change mitigation goals
Similar standing volume in pine-dominated and spruce-dominated stands indicated that a mixture of Scots pine and Norway spruce did not provide significantly higher standing volume [22]
We found similar mean carbon stocks of tree biomass in pine-dominated and spruce-dominated old-growth stands in Myrtillosa turf.mel, 167 ± 22.3 t C ha−1 and 154 ± 23.7 t C ha−1, respectively

Summary

Introduction

Forests are expected to increase carbon removal from the atmosphere and decrease greenhouse gas emissions to achieve global climate change mitigation goals. Organic soils store a large amount of carbon stock [1], but drained areas are an especially large source of greenhouse gas emissions in the forest land of many European countries [2,3]. In hemiboreal Latvia, more than 20% of the total forest area is located on organic soils, and almost one-third of the total forest area (29.7%) has been drained, according to the National Forest Inventory (NFI). In an earlier study of forests with organic soils (both naturally wet and drained sites), it was concluded that forest age is an important factor affecting carbon stock in dynamics, demonstrating that carbon stocks subsequently decrease in decaying forests [3,6]. With increasing interest in promoting carbon sequestration in forests in a climate policy context, local reference data from old-growth stands on drained organic soils is needed to use this information in decision support tools, because old-growth stands have a great influence on biodiversity conservation [8]

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