COS 115-4 - Mixed-species environmental plantings for carbon sequestration: Improved methods for biomass estimation

Thursday, August 11, 2011: 2:30 PM
12B, Austin Convention Center
Stephen H. Roxburgh, CSIRO Land and Water Flagship, CSIRO, Canberra, Australia and Keryn Paul, Ecosystem Sciences & Sustainable Agriculture Flagship, CSIRO

Mixed-species native plantings established on previously cleared land are becoming increasingly popular for their carbon mitigation benefits, as well as contributing to other ecosystem values such as biodiversity and groundwater salinity control. From an economic perspective, investment in such sequestration schemes relies heavily on obtaining sufficiently precise estimates of vegetation biomass. However, obtaining direct (i.e. harvested) biomass estimates in these plantings is both difficult and expensive, and is often associated with large sampling errors and high uncertainty, due primarily to a large variance in stem sizes, combined with a highly aggregated (non-random) planting design.


To address these difficulties we introduce a novel field survey procedure we call ‘precision sampling’ which combines a spatially extensive, non-destructive inventory to provide a proxy index of biomass variation across a site, with a new GIS-based randomisation algorithm for optimising the locations of biomass harvesting plots. The procedure has been applied at two mixed-species planting sites in temperate Australia to (a) quantify the sampling errors associated with alternative sampling designs (e.g. differences in plot size, number of plots, plot shape and plot orientation), and (b) to generate constrained random sampling plans that simultaneously fulfil the requirements of site-level representativeness (by minimising sampling error) and that maintain statistical independence. The results and implications of the approach for improving biomass estimation for carbon sequestration studies will be discussed, including an appraisal of the assumptions underlying the analysis.

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