Effect of woody vegetation clearing on nutrient and carbon relations of semi-arid dystrophic savanna

Schmidt, Susanne, Lamble, Rebecca E., Fensham, Rod J. and Siddique, Ilyas (2010) Effect of woody vegetation clearing on nutrient and carbon relations of semi-arid dystrophic savanna. Plant and Soil, 331 1-2: 79-90. doi:10.1007/s11104-009-0233-5


Author Schmidt, Susanne
Lamble, Rebecca E.
Fensham, Rod J.
Siddique, Ilyas
Title Effect of woody vegetation clearing on nutrient and carbon relations of semi-arid dystrophic savanna
Journal name Plant and Soil   Check publisher's open access policy
ISSN 0032-079X
1573-5036
Publication date 2010-06-01
Year available 2009
Sub-type Article (original research)
DOI 10.1007/s11104-009-0233-5
Open Access Status Not yet assessed
Volume 331
Issue 1-2
Start page 79
End page 90
Total pages 12
Editor Hans Lambers
Wim van der Putten
Place of publication The Hague, Netherlands
Publisher Kluwer
Language eng
Subject C1
960510 Ecosystem Assessment and Management of Sparseland, Permanent Grassland and Arid Zone Environments
960906 Forest and Woodlands Land Management
070508 Tree Nutrition and Physiology
Abstract Throughout the savanna biome, woody vegetation is cleared to increase productivity of herbaceous pasture. While clearing can result in increased pasture production of semi-arid dystrophic savannas in the short term, it is uncertain whether production is sustained in the long term. There is insufficient knowledge of how clearing affects soil nutrient and organic carbon (SOC) stocks. Using cleared-uncleared site pairs, we evaluated techniques for time-integrated assessment of nutrient and carbon relations in Australian savanna. Short-term in situ resin incubation showed that soil at cleared sites had a higher time-integrated availability of ammonium and nitrate, indicating that nitrogen (N) may turn over faster and/or is taken up slower at cleared sites than uncleared savanna. Nitrate and ammonium availability was approximately 2-fold higher in spring than in summer, likely due to greater uptake and/or loss of nitrate during summer rains. Nitrate was a prominent N source for evergreen trees, especially before summer rain, pointing to a role of trees as permanent N sinks. Stable isotope signatures of soil and vegetation indicate that N input occurs via N(2) fixing microbiotic crusts and Acacia species. 30 years after clearing, SOC contained more C(4) grass-derived carbon than uncleared savanna, but this shift in C source was not associated with the net C gain often observed in grasslands. Interactions between altered nutrient and C relations and composition of the understorey should be assessed in context of introduced buffelgrass (Cenchrus ciliaris) which had higher macronutrient concentrations than native grasses. Heterogeneity of the studied soils highlights the need for replication at several spatial scales to infer long-term dynamics with space-for-time chronosequences. We conclude that the techniques presented here are useful for gaining knowledge of the biogeochemical processes governing savannas and the systems that result from clearing.
Formatted abstract
Throughout the savanna biome, woody vegetation is cleared to increase productivity of herbaceous pasture. While clearing can result in increased pasture production of semi-arid dystrophic savannas in the short term, it is uncertain whether production is sustained in the long term. There is insufficient knowledge of how clearing affects soil nutrient and organic carbon (SOC) stocks. Using cleared-uncleared site pairs, we evaluated techniques for time-integrated assessment of nutrient and carbon relations in Australian savanna. Short-term in situ resin incubation showed that soil at cleared sites had a higher time-integrated availability of ammonium and nitrate, indicating that nitrogen (N) may turn over faster and/or is taken up slower at cleared sites than uncleared savanna. Nitrate and ammonium availability was approximately 2-fold higher in spring than in summer, likely due to greater uptake and/or loss of nitrate during summer rains. Nitrate was a prominent N source for evergreen trees, especially before summer rain, pointing to a role of trees as permanent N sinks. Stable isotope signatures of soil and vegetation indicate that N input occurs via N2 fixing microbiotic crusts and Acacia species. 30 years after clearing, SOC contained more C4 grass-derived carbon than uncleared savanna, but this shift in C source was not associated with the net C gain often observed in grasslands. Interactions between altered nutrient and C relations and composition of the understorey should be assessed in context of introduced buffelgrass (Cenchrus ciliaris) which had higher macronutrient concentrations than native grasses. Heterogeneity of the studied soils highlights the need for replication at several spatial scales to infer long-term dynamics with space-for-time chronosequences. We conclude that the techniques presented here are useful for gaining knowledge of the biogeochemical processes governing savannas and the systems that result from clearing.
© Springer Science + Business Media B.V. 2009
Keyword 15-N natural abundance
13-C natural abundance
Eucalyptus savanna
Macronutrients
Soil organic carbon
Soil nitrogen
Tree clearing
Open eucalypt woodlands
N-15 Natural-abundance
Soil-nitrogen status
Gayanus gamba grass
Australian Savanna
Central Queensland
Pasture productivity
Northern Australia
Water availability
Grazing systems
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Published online: 25 November 2009

Document type: Journal Article
Sub-type: Article (original research)
Collections: Non HERDC
School of Biological Sciences Publications
 
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Created: Sun, 30 May 2010, 10:01:01 EST