Relationship between Very Fine Root Distribution and Soil Water Content in Pre- and Post-Harvest Areas of Two Coniferous Tree Species

Moein Farahnak,Atsushi Kume,Seonghun Jeong,Seyed Mohammad Moein Sadeghi,Takuo Hishi,Ayumi Katayama,Masaaki Chiwa,Kyoichi Otsuki,Keiji Mitsuyasu

doi:10.3390/f11111227

Moein Farahnak, Atsushi Kume + Show 7 more

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https://doi.org/10.3390/f11111227

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Abstract

Tree root system development alters forest soil properties, and differences in root diameter frequency and root length per soil volume reflect differences in root system function. In this study, the relationship between vertical distribution of very fine root and soil water content was investigated in intact tree and cut tree areas. The vertical distribution of root density with different diameter classes (very fine <0.5 mm and fine 0.5–2.0 mm) and soil water content were examined along a slope with two coniferous tree species, Cryptomeria japonica (L.f.) D. Don and Chamaecyparis obtusa (Siebold et Zucc.) Endl. The root biomass and length density of very fine roots at soil depth of 0–5 cm were higher in the Ch. obtusa intact tree plot than in the Cr. japonica intact plot. Tree cutting caused a reduction in the biomass and length of very fine roots at 0–5 cm soil depth, and an increment in soil water content at 5–30 cm soil depth of the Ch. obtusa cut tree plot one year after cutting. However, very fine root density of the Cr. japonica intact tree plot was quite low and the soil water content in post-harvest areas did not change. The increase in soil water content at 5–30 cm soil depth of the Ch. obtusa cut tree plot could be caused by the decrease in very fine roots at 0–5 cm soil depth. These results suggest that the distribution of soil water content was changed after tree cutting of Ch. obtusa by the channels generated by the decay of very fine roots. It was also shown that differences in root system characteristics among different tree species affect soil water properties after cutting.

Highlights

Tree roots are vital components of forest ecosystems because they connect aboveground parts of a tree to the soil
Soil Volumetric Water Content θv was significantly higher in the entire soil profile of Cr. japonica plots than that of Ch. obtusa (Figure 1). θv was distributed in the soil of Cr. japonica intact and cut tree plots
We investigated the relationship between the root distribution and soil water content of trees and stumps of two different coniferous tree species, Cr. japonica and Ch. obtusa, on a hillslope

Summary

Introduction

Tree roots are vital components of forest ecosystems because they connect aboveground parts of a tree to the soil. Coarse roots are responsible for anchoring the tree into the soil, while fine roots explore the soil to take up water and nutrients [1]. The boundary between coarse and fine roots is usually defined as a diameter of 2 mm (e.g., [2,3]). Soil water content is one of the exogenous factors that link to the distribution of very fine and fine roots of a standing tree [7,8,9]. The availability of nutrients integrates with soil water content to affect the distribution of roots in the soil [10,11]. Previous studies have shown that the distribution of fine roots is correlated with soil water content [4,12,13]. In humid and temperate regions, shallow root systems tend to be well developed, resulting in uneven distribution of soil moisture and nutrients [14]

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