The High Input of Soil Organic Matter from Dead Tree Fine Roots into the Forest Soil

Hans Å Persson

doi:10.1155/2012/217402

Abstract

The spatial and temporal dynamics of tree fine roots were investigated in six boreal forests types in Eastern Sweden, close to the Swedish Forsmark and Laxemar nuclear power plants. Four dry and two wet forest types were included in the study. The amount of live and dead fine roots in terms of dry weight was estimated in soil cores. The live/dead ratios of fine roots (<1 mm in diameter) decreased with depth; very low ratios were observed in two wet forest sites. The proportions of dead fine roots to the total amounts of fine roots in the mineral soil horizons of those wet sites were 63 and 86%. The corresponding proportions in the mineral soil in dry forest sites were 45 and 45% and 49 and 48% at Forsmark and Laxemar, respectively. Sequential soil core sampling demonstrated a high variation in live and dead amounts of fine roots during the growth period. A high accumulation of carbon from dead tree fine root was found in all six forest types, in particular in the wet forest sites, but also in deeper soil horizons. Consequently, substantial amounts of organic matter from dead fine roots are continuously accumulated in the soil in boreal forests.

Highlights

Tree fine roots of forest trees are for their function forced to penetrate dry soil volumes often against mechanical resistance in densely packed soil layers
A substantial variation with depth in the total amount of live and dead tree fine roots was observed at the different forest sites (Figure 1)
High amounts of dead fine roots were indicated in the mineral soil horizons

Summary

Introduction

Tree fine roots of forest trees are for their function forced to penetrate dry soil volumes often against mechanical resistance in densely packed soil layers. In spite of those difficulties, tree root systems explore the uppermost parts of the soil profile with a network of growing root tips. The high tree density in this forest stand (1095 ha−1) made it clear that the uppermost parts of the soil profile must have been completely interwoven by tree fine roots. The lateral roots in a nearby 120-year-old Scots pine stand (tree density = 393 ha−1) reached 15–20 m from the tree trunks [3]. The wide-spread network of fine roots on the structural roots increases the total surface area and length of the root system [4]

Methods

Results

Conclusion