Xiaoyong Chen

Publications (3)9.56 Total impact

• Article: Soil organic carbon content at a range of north Australian tropical savannas with contrasting site histories

  Xiaoyong Chen, Lindsay B. Hutley, Derek Eamus
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  ABSTRACT: Soils play an important role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Natural and human impact on soil carbon concentration and storage is poorly understood in native north Australian savanna, yet this represents the largest carbon store in the ecosystem. To gain understanding of possible management impacts on this carbon pool, soil organic carbon (SOC) of the top 1m of red earth sands and sandy loams common in the region was sampled at 5 sites with different vegetation cover and site history (fire regime and tree removal). SOC was high when compared to other published values for savannas and was more comparable with dry-deciduous tropical forests. Sites sampled in this study represent high rainfall savannas of northern Australia (> 1700mm annual rainfall) that feature frequent burning (2 in 3years or more frequent) and a cycle of annual re-growth of tall C4 grasses that dominate the savanna understorey. These factors may be responsible for the higher than expected SOC levels of the surface soils, despite high respiration rates. Medium term fire exclusion (15–20years) at one of the sampled sites (Wildlife Park) dramatically reduced the grassy biomass of the understorey. This site had lower SOC levels when compared to the grass dominated and frequently burnt sites, which may be due to a reduction in detrital input to surface (0–30cm) soil carbon pools. Exclusion of trees also had a significant impact on both the total amount and distribution of soil organic carbon, with tree removal reducing observed SOC at depth (100cm). Soil carbon content was higher in the wet season than that in the dry season, but this difference was not statistically significant. Our results indicated that annual cycle of grass growth and wildfire resulted in small carbon accumulation in the upper region of the soil, and removal of woody plants resulted in significant carbon losses to recalcitrant, deep soil horizons greater than 80cm depth.
  Plant and Soil 12/2004; 268(1):161-171. · 2.73 Impact Factor
• Source

  Available from: Lindsay B. Hutley

  Article: Carbon balance of a tropical savanna of northern Australia.

  Xiaoyong Chen, Lindsay B Hutley, Derek Eamus
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  ABSTRACT: Through estimations of above- and below-ground standing biomass, annual biomass increment, fine root production and turnover, litterfall, canopy respiration and total soil CO(2) efflux, a carbon balance on seasonal and yearly time-scales is developed for a Eucalypt open-forest savanna in northern Australia. This carbon balance is compared to estimates of carbon fluxes derived from eddy covariance measurements conducted at the same site. The total carbon (C) stock of the savanna was 204+/-53 ton C ha(-1), with approximately 84% below-ground and 16% above-ground. Soil organic carbon content (0-1 m) was 151+/-33 ton C ha(-1), accounting for about 74% of the total carbon content in the ecosystem. Vegetation biomass was 53+/-20 ton C ha(-1), 39% of which was found in the root component and 61% in above-ground components (trees, shrubs, grasses). Annual gross primary production was 20.8 ton C ha(-1), of which 27% occurred in above-ground components and 73% below-ground components. Net primary production was 11 ton C ha(-1) year(-1), of which 8.0 ton C ha(-1) (73%) was contributed by below-ground net primary production and 3.0 ton C ha(-1) (27%) by above-ground net primary production. Annual soil carbon efflux was 14.3 ton C ha(-1) year(-1). Approximately three-quarters of the carbon flux (above-ground, below-ground and total ecosystem) occur during the 5-6 months of the wet season. This savanna site is a carbon sink during the wet season, but becomes a weak source during the dry season. Annual net ecosystem production was 3.8 ton C ha(-1) year(-1).
  Oecologia 12/2003; 137(3):405-16. · 3.41 Impact Factor
• Article: Carbon balance of a tropical savanna of northern Australia

  Xiaoyong Chen, LindsayB. Hutley, Derek Eamus
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  ABSTRACT: Through estimations of above- and below-ground standing biomass, annual biomass increment, fine root production and turnover, litterfall, canopy respiration and total soil CO2 efflux, a carbon balance on seasonal and yearly time-scales is developed for a Eucalypt open-forest savanna in northern Australia. This carbon balance is compared to estimates of carbon fluxes derived from eddy covariance measurements conducted at the same site. The total carbon (C) stock of the savanna was 20453ton C ha–1, with approximately 84% below-ground and 16% above-ground. Soil organic carbon content (0–1m) was 15133ton C ha–1, accounting for about 74% of the total carbon content in the ecosystem. Vegetation biomass was 5320ton C ha–1, 39% of which was found in the root component and 61% in above-ground components (trees, shrubs, grasses). Annual gross primary production was 20.8ton C ha–1, of which 27% occurred in above-ground components and 73% below-ground components. Net primary production was 11ton C ha–1 year–1, of which 8.0ton C ha–1 (73%) was contributed by below-ground net primary production and 3.0ton C ha–1 (27%) by above-ground net primary production. Annual soil carbon efflux was 14.3ton C ha–1 year–1. Approximately three-quarters of the carbon flux (above-ground, below-ground and total ecosystem) occur during the 5–6months of the wet season. This savanna site is a carbon sink during the wet season, but becomes a weak source during the dry season. Annual net ecosystem production was 3.8ton C ha–1 year–1.
  Oecologia 10/2003; 137(3):405-416. · 3.41 Impact Factor