Changes in Soil Carbon Following Afforestation

Dataset · Wed Jan 01 04:00:00 EST 2003

DOI:https://doi.org/10.3334/CDIAC/TCM.008· OSTI ID:1389525

Paul, K. I. ^[1]; Polglase, P. J.; Nyakuengama, J. G.; Khanna, P. K.

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1. OSTI

Quantifying changes in soil C may be an important consideration under large-scale afforestation or reforestation. We reviewed global data on changes in soil C following afforestation, available from 43 published or unpublished studies, encompassing 204 sites. Data were highly variable, with soil C either increasing or decreasing, particularly in young (<10-y) forest stands. Because studies varied in the number of years since forest establishment and the initial soil C content, we calculated change in soil C as a weighted average (i.e. sum of C change divided by sum of years since forest establishment) relative to the soil C content under previous agricultural systems at <10 cm, >10 cm and <30 cm sampling depths. On average, soil C in the <10 cm (or <30 cm) layers generally decreased by 3.46% y–1 (or 0.63% y–1) relative to the initial soil C content during the first five years of afforestation, followed by a decrease in the rate of decline and eventually recovery to C contents found in agricultural soils at about age 30. In plantations older than 30 years, C content was similar to that under the previous agricultural systems within the surface 10 cm of soil, yet at other sampling depths, soil C had increased by between 0.50 and 0.86% y–1. Amounts of C lost or gained by soil are generally small compared with accumulation of C in tree biomass.The most important factors affecting change in soil C were previous land use, climate and the type of forest established. Results suggest that most soil C was lost when softwoods, particularly Pinus radiata plantations, were established on ex-improved pastoral land in temperate regions. Accumulation of soil C was greatest when deciduous hardwoods, or N2-fixing species (either as an understorey or as a plantation), were established on ex-cropped land in tropical or subtropical regions. Long-term management regimes (e.g., stocking, weed control, thinning, fertilizer application and fire management) may also influence accumulation of soil C. Accumulation is maximised by maintaining longer (20-50 year) forest rotations. Furthermore, inclusion of litter in calculations reversed the observed average decrease in soil C, so that amount of C in soil and litter layer was greater than under preceding pasture.

• Research Organization: Environmental System Science Data Infrastructure for a Virtual Ecosystem; Carbon Dioxide Information Analysis Center
• OSTI ID: 1389525
• Report Number(s): doi:10.3334/CDIAC/TCM.008
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Earth Science &gt; Soil Carbon