Methane uptake in soils from Pinus radiata plantations, a reverting shrubland and adjacent pastures: Effects of land-use change, and soil texture, water and mineral nitrogen

• Published in: Soil biology & biochemistry 2007-07, Vol.39 (7), p.1437-1449
• Main Authors: Tate, K.R., Ross, D.J., Saggar, S., Hedley, C.B., Dando, J., Singh, B.K., Lambie, S.M.
• Format: Article
• Language: English
• Subjects: Aeration status; Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; carbon dioxide; carbon sequestration; Chemical, physicochemical, biochemical and biological properties; Exotic pine forest; forest plantations; forest soils; forest trees; Fundamental and applied biological sciences. Psychology; gas production (biological); Land-use change; methane; Methanotrophs; Microbial biomass; Microbiology; Native shrubland; Nitrogen; nitrogen content; Pastures; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Pinus radiata; PLFAs; shrublands; Soil methane fluxes; Soil science; soil texture; soil water content
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2007.01.005

Afforestation and reforestation of pastures are key land-use changes in New Zealand that help sequester carbon (C) to offset its carbon dioxide (CO 2) emissions under the Kyoto Protocol. However, relatively little attention has been given so far to associated changes in trace gas fluxes. Here, we measure methane (CH 4) fluxes and CO 2 production, as well as microbial C, nitrogen (N) and mineral-N, in intact, gradually dried (ca. 2 months at 20 °C) cores of a volcanic soil and a heavier textured, non-volcanic soil collected within plantations of Pinus radiata D. Don (pine) and adjacent permanent pastures. CH 4 fluxes and CO 2 production were also measured in cores of another volcanic soil under reverting shrubland (mainly Kunzea var. ericoides (A. Rich) J. Thompson) and an adjacent pasture. CH 4 uptake in the pine and shrubland cores of the volcanic soils at field capacity averaged about 35 and 14 μg CH 4–C m −2 h −1, respectively, and was significantly higher than in the pasture cores (about 21 and 6 μg CH 4–C m −2 h −1, respectively). In the non-volcanic soil, however, CH 4–C uptake was similar in most cores of the pine and pasture soils, averaging about 7–9 μg m −2 h −1, except in very wet samples. In contrast, rates of CO 2 production and microbial C and N concentrations were significantly lower under pine than under pasture. In the air-dry cores, microbial C and N had declined in the volcanic soil, but not in the non-volcanic soil; ammonium–N, and especially nitrate–N, had increased significantly in all samples. CH 4 uptake was, with few exceptions, not significantly influenced by initial concentrations of ammonium–N or nitrate–N, nor by their changes on air-drying. A combination of phospholipid fatty acid (PLFA) and stable isotope probing (SIP) analyses of only the pine and pasture soils showed that different methanotrophic communities were probably active in soils under the different vegetations. The C18 PLFAs (type II methanotrophs) predominated under pine and C16 PLFAs (type I methanotrophs) predominated under pasture. Overall, vegetation, soil texture, and water-filled pore space influenced CH 4–C uptake more than did soil mineral-N concentrations.