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The patterns of grazed pasture associated with scattered trees across an Australian temperate landscape: An investigation of pasture quantity and quality

journal contribution
posted on 31.10.2018, 00:00 by P Barnes, BR Wilson, Mark Trotter, DW Lamb, N Reid, T Koen, L Bayerlein
Scattered paddock trees occur across agricultural landscapes in Australia. However, in the temperate regions of Australia their numbers are rapidly declining and they may be lost across much of the landscape in 200 years. Here we examined the spatial distribution of green (GDB), senescent (SDB) and total (TDB) dry pasture biomass, and nutrient status of the GDB fraction around scattered Eucalyptus trees on three parent materials (basalt, granite and meta-sediment) in native and sown pastures across a range of grazed temperate landscapes in northern New South Wales. We used a combination of destructive harvests and a handheld active optical canopy reflectance sensor (AOS) with an integrated GPS to examine pasture biomass around scattered trees. The harvested pasture biomass data indicated that under grazed conditions the presence of scattered trees did not introduce significant radial trends in TDB or GDB out to a distance of 3.5 canopy radii regardless of tree species or parent material. The red and near-infrared reflectance-based Normalised Difference Vegetation Index (NDVI), as measured by the AOS, did indicate a consistent azimuthal trend with larger GDB on the southern side of the tree and lower GDB on the northern side in the native pasture. However, this observation must be qualified as the regression coefficient for the relationship between NDVI and GDB was significant but weak (best r2=0.42), and SDB reduced its predictive capacity. We also found a higher percentage of GDB under the canopy than in the open paddock. We suggest that the combination of these results may indicate higher grazing pressure under trees than in the open paddock. Pasture nutrient concentration (P, K and S) was higher in both native and sown pastures beneath the tree canopy compared with the open paddock. This study indicates that, in this temperate environment, scattered trees do not adversely affect pasture production, and that they can improve some pasture nutrients. © 2011 Australian Rangeland Society.

History

Volume

33

Issue

2

Start Page

121

End Page

130

Number of Pages

10

Start Date

20/07/2008

Finish Date

23/07/2008

ISSN

1036-9872

Publisher

CSIRO Publishing

Place of Publication

Victoria

Peer Reviewed

Yes

Open Access

No

Acceptance Date

21/02/2011

External Author Affiliations

University of New England; NSW Department of Environment, Climate Change and Water

Era Eligible

Yes

Journal

The Rangeland Journal

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