Variation of carbon age of fine roots in boreal forests determined from 14C measurements
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Background and aims
The main objectives of this study were to determine how the carbon age of fine root cellulose varies between stands, tree species, root diameter and soil depth. In addition, we also compared the carbon age of fine roots from soil cores of this study with reported values from the roots of the same diameter classes of ingrowth cores on the same sites.
We used natural abundance of 14C to estimate root carbon age in four boreal Norway spruce and Scots pine stands in Finland and Estonia.
Age of fine root carbon was older in 1.5–2 mm diameter fine roots than in fine roots with <0.5 mm diameter, and tended to be older in mineral soil than in organic soil. Fine root carbon was older in the less fertile Finnish spruce stands (11–12 years) than in the more fertile Estonian stand (3 and 8 years), implying that roots may live longer in less fertile soil. We further observed that on one of our sites carbon in live fine roots with the 1.5–2 mm diameter was of similar C age (7–12 years) than in the ingrowth core roots despite the reported root age in the ingrowth cores – being not older than 2 years.
From this result, we conclude that new live roots may in some cases use old carbon reserves for their cellulose formation. Future research should be oriented towards improving our understanding of possible internal redistribution and uptake of C in trees.
KeywordsBoreal forest Carbon Root age 14C Pine Spruce
This research work was funded by the Academy of Finland (grant no. 122281). We thank the teams of people who contributed to sampling and sorting of the original root material: the staff of the Salla Office of the Finnish Forest Research Institute and Mr. Risto Ikonen and Dr. Kirsi Makkonen. We gratefully acknowledge the 14C sample preparation and analysis carried out by staff at NERC Radiocarbon Facility and SUERC AMS Facility, East Kilbride. Root studies in Estonia were supported by the Estonian Science Foundation (grant 2487) and the EU through the European Regional Development Fund (Centre of Excellence ENVIRON).
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