Health of remnant woodlands in fragments under distinct grazing regimes

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BushfireTopic: 
Ecology and Biodiversity
Fuel Management
ResearchAdoption: 
Prescribed burning
Project Reference: 
Tree Decline in the Absence of Fire
TitleHealth of remnant woodlands in fragments under distinct grazing regimes
Publication TypeJournal Article
Year of Publication2008
AuthorsClose, DC, Davidson, NJ, Watson, T
JournalBiological Conservation
Volume141
Issue9
Pagination2395 - 2402
Date Published09/2008
AbstractFragmented remnant woodlands in agricultural landscapes are of high conservation value world-wide. Many eucalypts in agricultural landscapes of Australia are in decline. We aimed to investigate nutrient enrichment as a process that may contribute to eucalypt decline. We studied remnant woodlands that had been exposed to distinct recent and current livestock grazing treatments: Currently Intense Grazed; Recently Intense Grazed (until 3 years ago); Recent Intermediate Grazed; and Recent Lightly Grazed by livestock. We assessed soil nutrient status and penetrability, eucalypt foliar nutrition and stable isotope ratios for N and C, attributes of understorey vegetation, and tree health. Soils of the Currently Intense Grazed treatment had high levels of ammonium and Colwell-P. Total N, P, C:N ratio and soil penetrability were generally high in Currently Intense Grazed and Recently Intense Grazed treatments relative to Recent Intermediate Grazed and Recent Lightly Grazed treatments. Foliar N, N stable isotope ratios, P and carbon stable isotope ratios (δ13C) were generally higher (less negative δ13C) in trees on Currently Intense Grazed and Recently Intense Grazed treatments than in trees on Recent Intermediate Grazed and Recent Lightly Grazed treatments. Soil surface litter, tall and low shrubs and rock were positively correlated with tree health. Grasses and eucalypt foliar N, P and δ13C were negatively correlated with tree health. Soil nutrient enrichment increased with increasing grazing intensity and was associated with increased weed invasion and with poor tree health that was in turn correlated to increased foliar N and P and less negative δ13C in woodland trees in this study. We argue that minimising soil nutrient enrichment of fragmented remnant woodlands is important, given the association of elevated soil nutrition with poor tree health, to ensure the persistence of eucalypts in agricultural landscapes.
DOI10.1016/j.biocon.2008.07.006
Short TitleBiological Conservation
Refereed DesignationRefereed