Duration: 2008-2011
Research project group: Distinct projects 1 - Structure and function of forest ecosystems
Limited understanding of fine root turnover time is a key constraint in quantifying terrestrial carbon cycling and predicting the impacts of global environmental change. Especially, fine root and rhizome longevity, and longevity of their structural carbon, is not well understood or determined.
Trees and dwarf shrubs can bind carbon in their coarse root and rhizome structures for tens of years. However, fine roots of trees and understorey do not live as long, and can be renewed even once a year. Therefore, carbon inputs into forest soil in fine root litter may be several times larger than the inputs from canopy litter. The knowledge on the longevity of fine roots and rhizomes is essential for determining forest carbon balances.
The aim of this study is to increase understanding on the longevity of fine roots of different tree species, and how it is related to environmental factors. The further aim is to assess the age of rhizomes and roots of understorey grasses and dwarf shrubs. This is especially important, since there are hardly any estimates available on the understorey belowground longevity. Thus, the results will serve national and global forest carbon balance modelling, and reporting of the greenhouse gas balances of Finland.
Radiocarbon isotopes is a new method which we will use for determining the age of structurally bound carbon in roots. The radiocarbon approach takes advantage of the elevated levels of 14C in atmospheric carbon dioxide that resulted from thermonuclear weapons testing in the early 1960s. This 14C isotope can be used to trace the time elapsed since carbon in plant tissues was fixed from the atmosphere by photosynthesis, and to estimate its cycling rates in ecosystems.
For finding out the relation of fine root longevity to environmental factors, this research will be done on selected sites on a climate gradient from southern Estonia to northern Finland, and on sites varying in their soil fertility. To test the reliability of the radiocarbon method for determining root age, we will analyse our archive fine roots with known maximum age. We will determine if all carbon bound in growing roots originates from current photosynthesis at the time of growth or if it e.g. has at first been stored elsewhere in the plant. We will also compare the radiocarbon results on fine root age with our results using other methods on the same sites, e.g. minirhizotrones (see project "Carbon and nutrient dynamics in forest soil under environmental change").
Funding by Academy of Finland 2008-2011
prof. Högne Jugner & Dr. Markku Oinonen, University of Helsinki, Dating laboratory
Dr. Charlotte Bryant, NERC Radiocarbon Laboratory, Scotland
prof. Krista Lõhmus and Dr, Ivika Ostonen, University of Tartu, Estonia
Dr. John Derome, Metla
Dr. Maija Salemaa, Metla
Cost-network FP 0803 Belowground carbon turnover in European forests, 2009-2013
Project leader:
Helmisaari, Heljä-Sisko
Other researchers: Sah, Shambhu (2008-10)
Updated 24.05.2012
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