Fine-root turnover rates of European forests revisited: an analysis of data from sequential coring and ingrowth cores

I Brunner,C Jourdan,H Persson,H S Helmisaari,C Miguel Pérez,T D Eldhuset,M R Bakker,M Lukac,I Ostonen,X Aranda,B Konôpka,I Børja,Y Hirano,B C López,R G Björk

doi:10.1007/s11104-012-1313-5

Abstract

Forest trees directly contribute to carbon cycling in forest soils through the turnover of their fine roots. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values. We compiled available European data and applied various turnover rate calculation methods to the resulting database. We used Decision Matrix and Maximum-Minimum formula as suggested in the literature. Mean turnover rates obtained by the combination of sequential coring and Decision Matrix were 0.86 yr−1 for Fagus sylvatica and 0.88 yr−1 for Picea abies when maximum biomass data were used for the calculation, and 1.11 yr−1 for both species when mean biomass data were used. Using mean biomass rather than maximum resulted in about 30 % higher values of root turnover. Using the Decision Matrix to calculate turnover rate doubled the rates when compared to the Maximum-Minimum formula. The Decision Matrix, however, makes use of more input information than the Maximum-Minimum formula. We propose that calculations using the Decision Matrix with mean biomass give the most reliable estimates of root turnover rates in European forests and should preferentially be used in models and C reporting.

Highlights

Turnover of tree fine roots is one of the major carbon (C) pathways in forests
Mean turnover rates obtained by the combination of sequential coring and Decision Matrix were 0.86 yr−1 for Fagus sylvatica and 0.88 yr−1 for Picea abies when maximum biomass data were used for the calculation, and 1.11 yr−1 for both species when mean biomass data were used
We propose that calculations using the Decision Matrix with mean biomass give the most reliable estimates of root turnover rates in European forests and should preferentially be used in models and C reporting

Summary

Introduction

Turnover of tree fine roots is one of the major carbon (C) pathways in forests. The cause of the large C flux through this biomass pool is the rather limited lifespan of tree roots less than 2 mm in diameter. Given the estimated size of the C flux associated with the limited lifespan (synonyms: ‘longevity’ or ‘turnover time’, inverse of ‘turnover rate’) of fine roots, thought to reach 0.5 to 3 tC ha−1 yr−1 in steady-state forest ecosystems (Gill and Jackson 2000; Brunner and Godbold 2007), we clearly need to have a good understanding of the turnover rate at which fine roots die and contribute to soil C pools. Given the role of scientists in this debate, it is down to those who study root dynamics to provide the knowledge basis that permits modellers and C reporters to utilise the most realistic turnover values. In this study we aimed to calculate root turnover rates of common European forest tree species and to compare them with most frequently published values

Objectives

Methods

Results

Discussion

Conclusion