Total soil organic matter and its labile pools following mulga (Acacia aneura) clearing for pasture development and cropping 1. Total and labile carbon
R. C. Dalal A B D , B.P. Harms A B , E. Krull A C and W.J. Wang A BA CRC for Greenhouse Accounting.
B Department of Natural Resources and Mines, Indooroopilly, Qld 4068, Australia.
C CSIRO Land and Water, Glen Osmond, SA 5064, Australia.
D Corresponding author. Email: Ram.Dalal@nrm.qld.gov.au
Australian Journal of Soil Research 43(1) 13-20 https://doi.org/10.1071/SR04044
Submitted: 2 April 2004 Accepted: 17 September 2004 Published: 14 February 2005
Abstract
Mulga (Acacia aneura) dominated vegetation originally occupied 11.2 Mha in Queensland, of which 12% has been cleared, mostly for pasture production, but some areas are also used for cereal cropping. Since mulga communities generally occupy fragile soils, mostly Kandosols and Tenosols, in semi-arid environments, clearing of mulga, which continues at a rate of at least 35 000 ha/year in Queensland, has considerable impact on soil organic carbon (C), and may also have implications for the greenhouse gas emissions associated with land use change in Australia. We report here the changes in soil C and labile C pools following mulga clearing to buffel pasture (Cenchrus ciliaris) and cereal (mostly wheat) cropping for 20 years in a study using paired sites.
Soil organic C in the top 0.05 m of soil declined by 31% and 35% under buffel pasture and cropping, respectively. Land use change from mulga to buffel and cropping led to declines in soil organic C of 2.4 and 4.7 t/ha, respectively, from the top 0.3 m of soil. Using changes in the δ13C values of soil organic C as an approximate representation of C derived from C3 and C4 vegetation from mulga and buffel, respectively, up to 31% of soil C was C4-derived after 20 years of buffel pasture. The turnover rates of mulga-derived soil C ranged from 0.035/year in the 0–0.05 m depth to 0.008/year in the 0.6–1 m depths, with respective turnover times of 29 and 133 years. Soil organic matter quality, as measured by the proportion/amount of labile fraction C (light fraction, < 1.6 t/m3) declined by 55% throughout the soil profile (0–1 m depth) under both pasture and cropping.
There is immediate concern for the long-term sustainable use of land where mulga has been cleared for pasture and/or cropping with a continuing decline in soil organic matter quality and, hence, soil fertility and biomass productivity. In addition, the removal of mulga forest over a 20-year period in Queensland for pasture and cropping may have contributed to the atmosphere at least 12 Mt CO2-equivalents.
Additional keywords: soil C loss, labile C, organic matter quality, greenhouse effect, δ13C.
Acknowledgments
We thank Ian Hill ‘Mulga View’, St George, for his permission to access the site; Bruce Scriven for providing the past history of the site; Rory Whitehead, Christine McCallum, and Analytical Services staff for their technical assistance, Kamal Sangha for statistical analysis; and Nicole Mathers and Roger Gifford for their comments and suggestions.
Balesdent J, Mariotti A
(1996) Measurement of soil organic matter turnover using 13C natural abundance. ‘Mass spectrometry of soils’. (Eds TW Boutton, SI Yamasaki)
pp. 83–111. (Marcel Dekker: New York)
Balesdent J,
Wagner GH, Mariotti A
(1988) Soil organic matter turnover in long-term experiments as revealed by the carbon-13 abundance. Soil Science Society of America Journal 52, 118–124.
Bekele A, Hudnall WH
(2003) Stable carbon isotope study of the prairie-forest transition soil in Louisiana. Soil Science 168, 783–792.
| Crossref | GoogleScholarGoogle Scholar |
Biedenbender SH,
McClaran MP,
Quade J, Welz MA
(2004) Landscape patterns of vegetation change indicated by soil carbon isotope composition. Geoderma 119, 69–83.
| Crossref | GoogleScholarGoogle Scholar |
Bird M,
Kracht O,
Derrien D, Zhou Y
(2003) The effect of soil texture and roots on the stable carbon isotope composition of soil organic carbon. Australian Journal of Soil Research 41, 77–94.
| Crossref | GoogleScholarGoogle Scholar |
Boutton TW
(1996) Stable carbon isotope ratios of soil organic matter and their use as indicators of vegetation and climate change. ‘Mass spectrometry of soils’. (Eds TW Boutton, SI Yamasaki)
pp. 47–81. (Marcel Dekker: New York)
Cerri CC, Andreux F
(1990) Changes in organic carbon content in Oxisols cultivated with sugar cane and pasture, based on 13C natural abundance measurement. Transactions, 14th International Congress of Soil Science, Kyoto IV, 98–103.
Condon RW,
Newman JC, Cunningham GM
(1969) Soil erosion and pasture degradation in Central Australia. Journal of Soil Conservation Service, NSW 25, 47–92.
Christensen BT
(1992) Physical fractionation of soil and organic matter in primary particle size and density separates. Advances in Soil Science 20, 1–90.
Dalal RC, Chan KY
(2001) Soil organic matter in rainfed cropping systems of the Australian cereal belt. Australian Journal of Soil Research 39, 435–464.
| Crossref | GoogleScholarGoogle Scholar |
Dalal RC, Mayer RJ
(1986a) Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. I. Overall changes in soil properties and trends in winter cereal yields. Australian Journal of Soil Research 24, 265–279.
Dalal RC, Mayer RJ
(1986b) Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. II. Total organic carbon and its rate of loss from the soil profile. Australian Journal of Soil Research 24, 281–292.
Dalal RC, Mayer RJ
(1986c) Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. III. Distribution and kinetics of soil organic carbon in particle-size fractions. Australian Journal of Soil Research 24, 293–300.
Dalal RC, Mayer RJ
(1986d) Long-term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. IV. Loss of organic carbon from different density fractions. Australian Journal of Soil Research 24, 301–309.
Department of Natural Resources and Mines
(2000) Land cover change in Queensland 1997–1999, a Statewide Landcover and Trees Study Report (SLATS) September 2000. pp. 24
,
. (http://www.dnr.qld.gov.au/slats/)
Department of Natural Resources and Mines
(2003) Land cover change in Queensland 1999–2001, a Statewide Landcover and Trees Study (SLATS) Report. pp. 32
. (http://www.dnr.qld.gov.au/slats/)
FAO
(1998) World Reference Base for Soil Resources. World Soil Resource Reports No. 84, Food and Agriculture Organisation of the United Nations, Rome.
Fearnside PM, Barbosa RI
(1998) Soil carbon changes from conversion of forest to pasture in Brazilian Amazonia. Forest Ecology and Management 108, 147–166.
| Crossref | GoogleScholarGoogle Scholar |
Golchin A,
Oades JM,
Skjemstad JO, Clarke P
(1994) Soil structure and carbon cycling. Australian Journal of Soil Research 32, 1043–1068.
Gregorich EG,
Ellert BH, Monreal CM
(1995) Turnover of soil organic matter and storage of corn residue carbon estimated from natural 13C abundance. Canadian Journal of Soil Science 75, 161–167.
Gregorich EG, Janzen HH
(1996) Storage of soil carbon in the light fraction and macroorganic matter. ‘Structure and organic matter storage in agricultural soils’. (Eds MR Carter, BA Stewart)
pp. 167–190. (Lewis Publishers: New York)
Harms B, Dalal R
(2003) Paired site sampling for soil carbon (and nitrogen) estimation—Queensland. NCAS Technical Report No. 37, Australian Greenhouse Office, Canberra.
Houghton RA
(1999) The annual net flux of carbon to the atmosphere from changes in land use 1850–1990. Tellus 51B, 298–313.
Johnson RW, Burrows WH
(1994)
Acacia open-forests, woodlands and shrublands. ‘Australian vegetation’. 2nd edn . ,(Ed. RH Groves)
pp. 257–290. (Cambridge University Press: Cambridge, UK)
Isbell, RF (1996).
‘The Australian Soil Classification.’ (CSIRO Publishing: Melbourne, Vic.)
Krull ES, Skjemstad JO
(2003) δ13C and δ15N profiles in 14C-dated Oxisol and Vertisols as a function of soil chemistry and mineralogy. Geoderma 112, 1–29.
| Crossref | GoogleScholarGoogle Scholar |
McPherson GR,
Boutton TW, Midwood AJ
(1993) Stable carbon isotope analysis of soil organic matter illustrates vegetation change at the grassland/woodland boundary in southeastern Arizona, USA. Oecologia 93, 95–101.
Mills JR
(1986) Degradation and rehabilitation of the mulga ecosystem. ‘The mulga lands’. (Ed. PS Sattler)
(Royal Society of Queensland: Brisbane, Qld)
Murty D,
Kirschbaum MF,
McMurtrie RE, McGilvray H
(2002) Does conversion of forest to agricultural land change soil carbon and nitrogen? A review of the literature. Global Change Biology 8, 105–123.
| Crossref | GoogleScholarGoogle Scholar |
Nadelhoffer KJ, Fry B
(1988) Controls on natural nitrogen-15 and carbon-13 abundances in forest soil organic matter. Soil Science Society of America Journal 52, 1633–1640.
Pate JS,
Unkovich MJ,
Erskine PD, Stewart GR
(1998) Australian mulga ecosystems- 13C and 15N natural abundances of biota components and their ecophysiological significance. Plant, Cell and Environment 21, 1231–1242.
| Crossref | GoogleScholarGoogle Scholar |
Payne, RW (2002).
‘The guide to GenStat Release 6.1, Part 2: Statistics.’ (VSN International Ltd: Oxford, UK)
Peterson BJ, Fry B
(1987) Stable isotopes in ecosystem studies. Annual Review of Ecology and Systematics 18, 293–320.
| Crossref | GoogleScholarGoogle Scholar |
Stewart GR,
Turnbull MH,
Schmidt S, Erskine PD
(1995)
13C natural abundance in plant communities along a rainfall gradient: a biological indicator of water availability. Australian Journal of Plant Physiology 21, 51–55.
Skjemstad JO,
Le Feuvre RP, Prebble RE
(1990) Turnover of soil organic matter under pasture as determined by 13C natural abundance. Australian Journal of Soil Research 28, 267–276.
Skjemstad JO,
Clarke P,
Taylor JA,
Oades JM, McClure SG
(1996) The chemistry and nature of protected carbon in soil. Australian Journal of Soil Research 34, 251–271.
USDA Soil Survey (1975).
‘Soil Taxonomy.’ Handbook No. 436 (United States Department of Agriculture: Washington, DC)
Wedin DA,
Tieszen LL,
Dewey B, Pastor J
(1995) Carbon isotope dynamics during grass decomposition and soil organic matter formation. Ecology 76, 1383–1392.
Wilson BA,
Neldner VJ, Accad A
(2002) The extent and status of remnant vegetation in Queensland and its implication for Statewide vegetation management legislation. The Rangeland Journal 24, 6–35.
