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Soil–atmosphere exchange of greenhouse gases in a Eucalyptus marginata woodland, a clover‐grass pasture, and Pinus radiata and Eucalyptus globulus plantations
Author(s) -
LIVESLEY S. J.,
KIESE R.,
MIEHLE P.,
WESTON C. J.,
BUTTERBACHBAHL K.,
ARNDT S. K.
Publication year - 2009
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2008.01759.x
Subject(s) - pinus radiata , environmental science , pasture , soil water , eucalyptus globulus , agronomy , eucalyptus , woodland , agroforestry , forestry , ecology , soil science , biology , geography
Soils provide the largest terrestrial carbon store, the largest atmospheric CO 2 source, the largest terrestrial N 2 O source and the largest terrestrial CH 4 sink, as mediated through root and soil microbial processes. A change in land use or management can alter these soil processes such that net greenhouse gas exchange may increase or decrease. We measured soil–atmosphere exchange of CO 2 , N 2 O and CH 4 in four adjacent land‐use systems (native eucalypt woodland, clover‐grass pasture, Pinus radiata and Eucalyptus globulus plantation) for short, but continuous, periods between October 2005 and June 2006 using an automated trace gas measurement system near Albany in southwest Western Australia. Mean N 2 O emission in the pasture was 26.6 μg N m −2 h −1 , significantly greater than in the natural and managed forests (< 2.0 μg N m −2 h −1 ). N 2 O emission from pasture soil increased after rainfall events (up to 100 μg N m −2 h −1 ) and as soil water content increased into winter, whereas no soil water response was detected in the forest systems. Gross nitrification through 15 N isotope dilution in all land‐use systems was small at water holding capacity < 30%, and under optimum soil water conditions gross nitrification ranged between < 0.1 and 1.0 mg N kg −1 h −1 , being least in the native woodland/eucalypt plantation < pine plantation < pasture. Forest soils were a constant CH 4 sink, up to −20 μg C m −2 h −1 in the native woodland. Pasture soil was an occasional CH 4 source, but weak CH 4 sink overall (−3 μg C m −2 h −1 ). There were no strong correlations ( R < 0.4) between CH 4 flux and soil moisture or temperature. Soil CO 2 emissions (35–55 mg C m −2 h −1 ) correlated with soil water content ( R < 0.5) in all but the E. globulus plantation. Soil N 2 O emissions from improved pastures can be considerable and comparable with intensively managed, irrigated and fertilised dairy pastures. In all land uses, soil N 2 O emissions exceeded soil CH 4 uptake on a carbon dioxide equivalent basis. Overall, afforestation of improved pastures (i) decreases soil N 2 O emissions and (ii) increases soil CH 4 uptake.