Pioneer root invasion and fibrous root development into disturbed soil space observed with a flatbed scanner method
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Fine roots with thick diameter preferentially elongated into disturbed soil space, indicating positive invasion of pioneer roots that recolonize distal root systems.
Fine roots and their morphological traits are related to below-ground resource dynamics at physiological and ecological levels. Established approaches for investigating fine root dynamics inevitably cause artificial soil disturbance due to root excavation or instrument installation into the soil. Soil disturbance can have considerable effects on fine root dynamics. The aim of the present study was to clarify the temporal changes of morphological traits of fine roots produced after soil disturbance. The flatbed scanner method was employed in cypress (Chamaecyparis obtusa Endl.) and deciduous oak (Quercus serrata Thunb.) stands, and changes in length and diameter of elongated roots were measured for 4 years after soil disturbance. In both stands, specific trends of diameter and length production of fine roots were observed. Root length production increased extensively, and diameter was greater in an initial phase after soil disturbance. However, temporal patterns varied between the two stands. Soil disturbance affected fine root dynamics for a longer duration in the cypress stand, but more intensively in the oak stand. These results indicate that soil disturbance can affect fine root morphology and can induce invasion of thick fine roots, which are traditionally grouped as pioneer roots. Moreover, the results showed high length production continued for a longer period than that of larger diameter roots, suggesting recolonization of fine root systems by elongating pioneer roots followed by the branching of absorptive fibrous roots in order to recover root uptake capacity lost due to soil disturbance.
KeywordsFine root Morphology Pioneer root Scanner method Soil disturbance
I thank T. Miyaura and Satoyama Research Center of Ryukoku University who allowed us the use of Ryukoku Forest for data and sample collection. A. Osawa is gratefully acknowledged for creating the study environment, providing image data of fine roots and correcting my manuscript. Fellow students, including J. An, H. Schäfer, Y. Kameda, H. Nakamura, K. Hattori, A. Kawamura, M. Ishii, helped various aspects of the study particularly for image acquisition by root scanners or stand measurement. Y. Kameda also supported me for the image analysis. In addition, I am grateful to M. Dannoura for giving useful comments and checking the manuscript in the process of revising, and I would like to thank Editage for English language editing.
The present study was supported in part by a Grant-in-Aid of Scientific Research no. 16 J10182 from the Japan Society for the Promotion of Science to R. N. (DC1).
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