Tree-scale spatial variability of soil carbon cycling in a mature oil palm plantation

Goodrick, Iain, Nelson, Paul N., Nake, Steven, Webb, Michael J., Bird, Michael I., and Huth, Neil (2016) Tree-scale spatial variability of soil carbon cycling in a mature oil palm plantation. Soil Research, 54 (4). pp. 397-406.

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Soil carbon fluxes are highly variable in space and time under tree crops such as oil palm, and attempts to model such fluxes must incorporate an understanding of this variability. In this work, we measured soil CO2 emission, root biomass and pruned frond deposition rates and calculated carbon fluxes into and out of the soil in a mature (20-year-old, second planting cycle) oil palm plantation in Papua New Guinea. Tree-scale spatial variability in CO2 emission and root biomass was quantified by making measurements on a 35-point trapezoid grid covering the 38.5-m2 repeating unit of the plantation (n = 4 grids). In order to obtain an overall mean soil CO2 emission rate within 5% of the most accurate estimate, >24 measurement points were required. Soil CO2 emissions were spatially correlated with calculated carbon inputs (r2 = 0.605, slope 1 : 1), but not with soil water content or temperature. However, outputs were higher than inputs at all locations, with a mean overall output of 7.24 umolm–2 s–1 and input of 3.02 umolm–2 s–1. Inputs related to fronds, roots and groundcover constituted 60%, 36% and 4% of estimated inputs, respectively. The spatial correlation of carbon inputs and outputs indicates that mineralisation rate is controlled mostly by the amount rather than the nature or input depth of the additions. The spatially uniform net carbon emission from soil may be due to inaccuracies in calculated fluxes (especially root-related inputs) or to non-biological emissions.

Item ID: 45798
Item Type: Article (Research - C1)
ISSN: 1838-6768
Keywords: plant carbon inputs, root respiration, root biomass, soil CO2 emissions, soil respiration
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A version of this publication was included as Chapter 3 of the following PhD thesis: Goodrick, Iain (2018) Soil carbon dynamics under oil palm plantations. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Centre for International Agricultural Research (ACIAR)
Projects and Grants: ACIAR SMCN-2009-013
Date Deposited: 21 Sep 2016 03:49
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4101 Climate change impacts and adaptation > 410101 Carbon sequestration science @ 40%
41 ENVIRONMENTAL SCIENCES > 4106 Soil sciences > 410603 Soil biology @ 40%
30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3002 Agriculture, land and farm management > 300202 Agricultural land management @ 20%
SEO Codes: 96 ENVIRONMENT > 9614 Soils > 961402 Farmland, Arable Cropland and Permanent Cropland Soils @ 40%
82 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 8203 Industrial Crops > 820399 Industrial Crops not elsewhere classified @ 30%
97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 30%
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