Plant and Soil 196: 115–121, 1997.
115
c
1997 Kluwer Academic Publishers. Printed in the Netherlands.
Effect of soil nitrogen, carbon and moisture on methane uptake by dry
tropical forest soils
J.S. Singh
1
, Smita Singh, A.S. Raghubanshi, Saranath Singh, A.K. Kashyap and V.S. Reddy
Department of Botany, Banaras Hindu University, Varanasi-221005 India;
1
Corresponding author
Received 13 December 1996. Accepted in revised form 1 August 1997
Key words: deciduous forest, methane uptake, soil carbon, soil moisture, soil nitrogen
Abstract
Methane uptake was measured for two consecutive years for four forest and one savanna sites in a seasonally dry
tropical region of India. The soils were nutrient-poor and well drained. These sites differed in vegetational cover
and physico-chemical features of the soil. There were significant differences in CH
4
consumption rates during the
two years (mean 0.43 and 0.49 mg m
2
h
1
), and at different sites (mean 0.36 to 0.57 mg m
2
h
1
). The mean
uptake rate was higher (P < 0.05) in dry seasons than in the rainy season at all the sites. There was a significant
season and site interaction, indicating that the effect of different seasons differed across the sites. There was a
positive relation between soil moisture and CH
4
uptake rates during summer (the driest period) and a negative
relation during the rest of the year. The results suggested that seasonally dry tropical forests are a strong sink for
CH
4
, and C and N status of soils regulates the strength of the sink in the long term.
Introduction
Methane (CH
4
) is second only to carbon dioxide in
importanceas agreenhousegas(Andreaeand Crutzen,
1985), having 21-times higher greenhouse warming
potential per molecule than CO
2
(IPCC, 1992). The
major biological sources of methane are decomposi-
tion of organic matter in anaerobic soils and enter-
ic fermentation in ruminants and termites (Blake and
Rowland, 1988; Crutzen, 1991; Pearman and Frazer,
1988).
Although the major sink for atmospheric methane
is its chemical reaction with hydroxyl radicals in the
atmosphere (Lelieveld and Crutzen, 1992), uptake of
ambient methane by some soils could be an additional
significant sink, representing 1–15% of that oxidized
by reaction with hydroxyl radical (Born et al., 1990).
Microbial oxidation of atmospheric CH
4
in terrestri-
al environments is the only known biological sink
(Adamsen and King, 1993). Methane oxidation by
soils in temperate ecosystems (Hutsch et al., 1994;
Mosier et al., 1991), poorly drained Canadian forest
(Lessard et al., 1994), oak dominated forest (Gold-
FAX No.: (91) 542 317074. E-mail: kashyap@banaras.ernet.in
man et al., 1995), temperate German forest (Born et
al., 1990), New England forest (Crill, 1991; Steudler
et al., 1989), coniferous forest of northern Quebeck
(Adamsen and King, 1993), tropical forests (Seiler
et al., 1984), humisol (Megraw and Knowles, 1987),
tundra(WhalenandReeburgh,1990),desert(Strieglet
al., 1992) and cultivated Inceptisol (Singh et al., 1996)
has been reported. The most rapid rates of oxidation
(80
LCH
4
L
1
h
1
) have been reported for neu-
tral woodland soil (Lloyd and Jenkinson, 1995). The
uptake of CH
4
by soils is governed by environmental
variables that regulate the strength of the sink but are
poorly understood (see Dubey et al., 1996 for review).
In the present paper we report CH
4
uptake by well-
drained-soils of seasonally dry deciduous forest and
savanna ecosystems. We present data to show that the
long-term mean CH
4
uptake is governed by soil car-
bon and nitrogen status and the seasonal fluctuations
by soil moisture.
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