Results of Measurement in Reforestations and Old Growth Forests

Two of the 13 reforestation sites that were measured exhibited very poor growth and low biomass content. It was apparent that pre-planting or post-planting management at these sites had been deficient, and the plots were discarded.

A comparison of results of measurement and modeling shows that there is considerable agreement between the carbon per hectare by DBH measurement in the 11 reforestations and the carbon in trees forecast by the toolbox: see Figure 5.5. The results suggest that confidence is warranted in the predictive ability of CAMFor in the NCAS toolbox.

Only one site in old growth forest had been measured in the research so far and it was decided to expand the investigation of sequestered carbon in this type of forest. This investigation was facilitated by the availability of DBH measurements that had been carried out in a 64-hectare block of old growth rainforest, by R. Jensen (personal communication, 2007).

It was found that the variability of the biomass and hence carbon between plots in old growth rainforest was far greater than the variability in mixed native species plantations; the standard deviation in tonnes of carbon per hectare in old growth plots was 142 compared with 30 in a 13-year-old mixed species plantation. This was caused by the greater variation in the size of trees measured in the old growth rainforest. R. Jensen identified 284 tree species in the eight 500m2 measured plots, and in one plot a single massive tree (Ficus obliqua) accounted for two-thirds of the plot's biomass; the size of a typical Ficus obliqua is illustrated in Figure 5.6.

The average C sequestered in the 64 hectares was 308 tonnes per hectare. Figure 5.7 shows the carbon found by measurement in the eight

Years since planting

Notes: Reforestations were of different ages at 11 reforestation sites and at site 12 of old growth tropical rainforest (the 200-year estimate). Estimation was carried out both by use of the National Carbon Accounting System toolbox (CAMFor) and by physical measurement, in north Queensland.

Years since planting

Notes: Reforestations were of different ages at 11 reforestation sites and at site 12 of old growth tropical rainforest (the 200-year estimate). Estimation was carried out both by use of the National Carbon Accounting System toolbox (CAMFor) and by physical measurement, in north Queensland.

Source: Author's own data.

Figure 5.5 Estimation of carbon sequestered per hectare in reforestations plots. Because of the perceived difference between the growth of forests across the terrain, the sample plots were distributed deliberately by Jensen between the ridge top, upper and lower slopes and gully bottom. The sampling procedure adopted achieved results with a 95 percent confidence limit and a confidence interval of 10 percent.

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