Stemflow-induced spatial heterogeneity of radiocesium concentrations and stocks in the soil of a broadleaved deciduous forest

Naohiro Imamura; Delphis F Levia; Jumpei Toriyama; Masahiro Kobayashi; Kazuki Nanko

doi:10.1016/j.scitotenv.2017.05.017

Stemflow-induced spatial heterogeneity of radiocesium concentrations and stocks in the soil of a broadleaved deciduous forest

Sci Total Environ. 2017 Dec 1:599-600:1013-1021. doi: 10.1016/j.scitotenv.2017.05.017. Epub 2017 May 11.

Authors

Naohiro Imamura¹, Delphis F Levia², Jumpei Toriyama³, Masahiro Kobayashi⁴, Kazuki Nanko⁵

Affiliations

¹ Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: nimamura@ffpri.affrc.go.jp.
² Department of Geography, University of Delaware, Newark, DE 19716-2541, USA; Departments of Plant and Soil Sciences, University of Delaware, Newark, DE 19716-1303, USA.
³ Kyushu Research Center, Forestry and Forest Products Research Institute, 4-11-16 Kurokami, Chuo-ku, Kumamoto 860-0862, Japan.
⁴ Center for Forest Restoration and Radioecology, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
⁵ Department of Disaster Prevention, Meteorology and Hydrology, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.

PMID: 28505882
DOI: 10.1016/j.scitotenv.2017.05.017

Abstract

The transport of radiocesium from the canopy and quantification of the spatial distribution of radiocesium in the soil of konara oak forests are important to better understand the variability of ¹³⁷Cs stocks in the soil between proximal and distal stem areas as well as fine-scale variations around the tree trunk. Moreover, a better understanding of fine-scale spatial variabilities of ¹³⁷Cs concentrations and stocks will provide insights for optimizing soil sampling strategies to provide a more robust estimation of contamination at the stand scale. This study aims to elucidate the transport of ¹³⁷Cs by stemflow in a radioactively contaminated konara oak forest in Tsukuba, Japan by describing and quantifying the fine-scale spatial distribution of ¹³⁷Cs in the soil and preferential flowpaths of stemflow on the tree stem by a dye tracing experiment. ¹³⁷Cs concentrations and stocks were higher in the soils of the proximal stem area than distal stem area when they corresponded with the preferential flowpaths of stemflow. There was a significant relationship between canopy projection area of individual trees and average soil ¹³⁷Cs concentrations and stocks, even though canopies of the trees overlapped. Our results demonstrate that the spatiality of ¹³⁷Cs concentrations and stocks in the soil of the proximal stem area are governed (at least partially) by the preferential flowpaths of stemflow along the tree trunk. In addition, higher ¹³⁷Cs concentrations and stocks in the near-trunk soils of trees with larger crown areas might be caused by an enhanced ability to capture dry deposition.

Keywords: Double funneling; Forest soils; Konara oak; Proximal area; Stemflow.