Nitrogen dynamics in land cleared of alien vegetation (Acacia Saligna) and impacts on groundwater at Riverlands nature reserve (Western Cape, South Africa)

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dc.contributor.authorJovanovic N.Z.
dc.contributor.authorIsrael S.
dc.contributor.authorTredoux G.
dc.contributor.authorSoltau L.
dc.contributor.authorLe Maitre D.
dc.contributor.authorRusinga F.
dc.contributor.authorRozanov, A.
dc.contributor.authorvan der Merwe N.
dc.date.accessioned2011-05-15T15:58:09Z
dc.date.available2011-05-15T15:58:09Z
dc.date.issued2009
dc.description.abstractWoody invading alien plants, many of which are nitrogen-fixing legumes (Fabaceae family), are currently cleared in South African catchments to reduce water loss and preserve streamflow, and for the restoration of the ecosystem. This study tested the hypothesis that clearing invasive alien vegetation may disturb the vegetation-micro-organism-soil N cycling system by producing a large once-off input of fresh tree litterfall rich in N and by eliminating a large N sink. Three experimental plots were established at the Riverlands Nature Reserve (Western Cape, South Africa): a site invaded by Acacia saligna to be used as control; a site cleared of Acacia saligna; and a site with natural vegetation to be used as background. Nitrogen concentrations in soil and groundwater, volumetric soil water contents, root density and weather conditions were measured during 2007. Oxidised forms of nitrogen, in particular NO3-, were dominant in the system. Recharge and leachate were simulated with the HYDRUS-2D model and used as inputs into Visual MODFLOW to predict the spatial distribution of nitrate plus nitrite (NOx) in groundwater. NOx levels in soil and groundwater were higher in alien-invaded areas compared to fynbos-covered land. A quick release of NOx into groundwater was observed due to high residual N reserves in the rooting zone, decreased evapotranspiration and increased recharge in the treatment cleared of alien vegetation. In the long run, high NOx concentrations in groundwater underlying cleared land will last only until all the excess nitrogen has been leached from the soil. A decrease in NOx concentration in groundwater can be expected thereafter. Clearing land of alien invasive legumes may therefore have a beneficial effect by reducing groundwater contamination from NOx and reducing water losses in catchments.
dc.description.versionArticle
dc.identifier.citationWater SA
dc.identifier.citation35
dc.identifier.citation1
dc.identifier.issn3784738
dc.identifier.urihttp://hdl.handle.net/10019.1/10805
dc.subjectAcacia saligna
dc.subjectForest clearing
dc.subjectGroundwater contamination
dc.subjectNitrate leaching
dc.subjectRiverlands nature reserve
dc.subjectCatchments
dc.subjectContamination
dc.subjectEvapotranspiration
dc.subjectForestry
dc.subjectGroundwater
dc.subjectGroundwater pollution
dc.subjectHydrogeology
dc.subjectLeaching
dc.subjectNitrogen
dc.subjectNitrogen fixation
dc.subjectRunoff
dc.subjectSize distribution
dc.subjectSoil moisture
dc.subjectUnderground reservoirs
dc.subjectUnderwater soils
dc.subjectVegetation
dc.subjectWater supply
dc.subjectWater treatment
dc.subjectcatchment
dc.subjectconcentration (composition)
dc.subjectevapotranspiration
dc.subjectforest clearance
dc.subjectgroundwater flow
dc.subjectgroundwater pollution
dc.subjecthydrogeochemistry
dc.subjecthydrological modeling
dc.subjecthypothesis testing
dc.subjectintroduced species
dc.subjectleachate
dc.subjectleaching
dc.subjectlegume
dc.subjectnitrogen cycle
dc.subjectnitrogen fixation
dc.subjectnitrogen oxides
dc.subjectpollution control
dc.subjectrecharge
dc.subjectrestoration ecology
dc.subjectsoil nitrogen
dc.subjectsoil water
dc.subjectstreamflow
dc.subjectForestry
dc.subjectGeology
dc.subjectGround Water
dc.subjectLand
dc.subjectLeaching
dc.subjectNatural Resources
dc.subjectNitrate Groups
dc.subjectNitrogen
dc.subjectPollution
dc.subjectReserves
dc.subjectRivers
dc.subjectSoil Analysis
dc.subjectTranspiration
dc.subjectWater Quality
dc.subjectWater Treatment
dc.subjectAfrica
dc.subjectRiverlands Provincial Nature Reserve
dc.subjectSouth Africa
dc.subjectSouthern Africa
dc.subjectSub-Saharan Africa
dc.subjectWestern Cape
dc.subjectAcacia
dc.subjectAcacia saligna
dc.subjectFabaceae
dc.titleNitrogen dynamics in land cleared of alien vegetation (Acacia Saligna) and impacts on groundwater at Riverlands nature reserve (Western Cape, South Africa)
dc.typeArticle
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