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GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 19, GB2011, doi:10.1029/2004GB002259, 2005

Seasonal and diurnal variations in topsoil and subsoil respiration under snowpack in a temperate deciduous forest

Takashi Hirano

Graduate School of Agriculture, Hokkaido University, Sapporo, Hokkaido, Japan

Abstract

We measured soil CO₂ concentration at half-hour intervals with infrared gas analyzers buried in soil at four depths throughout the snow cover season extending from early December to early April in a deciduous temperate forest. We evaluated soil CO₂ efflux or total soil respiration, topsoil (the A-horizon) respiration, and subsoil (the C-horizon) respiration using a modified flux gradient method. Thereby, we investigated seasonal and diurnal variations in these soil respirations under snowpack. Soil CO₂ concentration and soil respiration changed dynamically under the condition of constant soil temperature. Topsoil respiration decreased rapidly in late autumn and relatively constant until mid-winter, whereas it increased in late winter when snowmelt progressed. On the other hand, subsoil respiration decreased gradually until mid-winter and increased slightly in late winter. Both topsoil and subsoil respirations showed similar diurnal variations with a peak in early or mid-afternoon, respectively, independently of soil temperature. These seasonal and diurnal variations in soil respiration were inferred to result from the supply of labile carbon compounds, which were respiratory substrates for microorganisms, into soil from litter with meltwater. The seasonal sum of topsoil, subsoil, and total respirations for the snow cover period of 4 months were 21.4, 48.0, and 69.4 gC m⁻², respectively; these accounted for 3.0, 27.3, and 7.7% of the annual sum, respectively. The ratio of topsoil respiration to total soil respiration was 0.31 on average during the snow period, which was considerably lower than that in the summer season.

Received 18 March 2004; accepted 1 March 2005; published 23 April 2005.

Keywords: snowpack; soil respiration; temperate forest.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions (0426, 1610); 0330 Atmospheric Composition and Structure: Geochemical cycles (1030); 1615 Global Change: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912).

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Citation: Hirano, T. (2005), Seasonal and diurnal variations in topsoil and subsoil respiration under snowpack in a temperate deciduous forest, Global Biogeochem. Cycles, 19, GB2011, doi:10.1029/2004GB002259.

Copyright 2005 by the American Geophysical Union.