© 2007 Heron Publishing—Victoria, Canada
Fine root biomass in relation to site and stand characteristics in Norway spruce and Scots pine stands
Heljä-Sisko Helmisaari (1, 2), John Derome (3), Pekka Nöjd (1) and Mikko Kukkola (1)
1. Finnish Forest Research Institute, Vantaa Research Unit, P.O.Box 18, FI-01301 Vantaa, Finland / 2. Corresponding author (helja-sisko.helmisaari@metla.fi) / 3. Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland / Received July 12, 2006; accepted October 3, 2006; published online July 3, 2007
Summary
Variations in fine root biomass of trees and understory in 16 stands throughout Finland were examined and relationships to
site and stand characteristics determined. Norway spruce fine root biomass varied between 184 and 370 g m–2, and that of Scots pine ranged between 149 and 386 g m–2. In northern Finland, understory roots and rhizomes (< 2 mm diameter) accounted for up to 50% of the stand total fine root
biomass. Therefore, the fine root biomass of trees plus understory was larger in northern Finland in stands of both tree species,
resulting in a negative relationship between fine root biomass and the temperature sum and a positive relationship between
fine root biomass and the carbon:nitrogen ratio of the soil organic layer. The foliage:fine root ratio varied between 2.1
and 6.4 for Norway spruce and between 0.8 and 2.2 for Scots pine. The ratio decreased for both Norway spruce and Scots pine
from south to north, as well as from fertile to more infertile site types. The foliage:fine root ratio of Norway spruce was
related to basal area and stem surface area. The strong positive correlations of these three parameters with fine root nitrogen
concentration implies that more fine roots are needed to maintain a certain amount of foliage when nutrient availability is
low. No significant relationships were found between stand parameters and fine root biomass at the stand level, but the relationships
considerably improved when both fine root biomass and stand parameters were calculated for the mean tree in the stand. When
the northern and southern sites were analyzed separately, fine root biomass per tree of both species was significantly correlated
with basal area and stem surface area per tree. Basal area, stem surface area and stand density can be estimated accurately
and easily. Thus, our results may have value in predicting fine root biomass at the tree and stand level in boreal Norway
spruce and Scots pine forests.
Keywords:
boreal forest, carbon allocation, Picea abies, Pinus sylvestris, understory.
