Measurement and estimation of land use e

Conclusions

Land-uses had a profound impact on soil properties near to the soil surface. Even with the large within-site variability at the sites studied, significant land-use effects were found for the range of soil properties examined. This was particularly true of the near-surface soil layers. Woodland soils in this environment had consistently higher values for carbon and nitrogen and lower bulk density in the surface soil layers.

Data for soil carbon assessment should account for equivalent mass since this significantly modifies carbon densities, particularly for the lighter, woodland soils. Soil carbon density (corrected for equivalent soil mass) was consistently and significantly higher under woodland compared to all other land-use types, and in order to maintain the largest quantity of carbon in this landscape, retaining trees and woodland is the most effective option.

Analysis of spatial variability of sampling sites for monitoring allows us to make informed decisions regarding sampling intensity and the precision and confidence of soil property estimation. The required soil sampling intensity to achieve de fined outcomes of precision and confidence differed between the land uses and soil properties examined. Broadly, 10 samples across a sample area 25 by 25 m were

at 90% confidence at the sites and soil types we studied. We believe that, on the basis of our results, similar sampling principles can be applied more broadly across the landscapes of NSW.

Selection of a sampling area size across a range of recommended dimensions suggests that sampling size is largely arbitrary. The most significant recommendation with respect to sample area size is that it should be consistent to promote comparability of existing and future datasets.

Acknowledgments

The authors gratefully acknowledge the assistance of the various landholders across the Northern Tablelands for their assistance in accessing and establishing soil monitoring and research sites. We also acknowledge the funding support of the NSW Department of Environment, Climate Change and Water through the Statewide Land and Soil Condition Monitoring Program. Special thanks are extended to Greg Chapman, Peter Barker, and Brian Murphy for constructive comments on the work reported. Thanks also to ananymous referees for constructive comments on our original manuscript.

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Manuscript received 13 August 2009, accepted 4 March 2010