Above-ground Carbon Sequestration by Early-successional Woody Vegetation

Résumé du livre

New Zealand's ratification of the Kyoto Protocol offers considerable opportunity for the sale of 'carbon credits' from newly created forests. Given that forests need to have arisen since 1989 to be eligible for carbon credits, shrublands currently represent the biggest potential for Kyoto-compliant carbon (C) gain on conservation land. Little published information currently exists on the potential annual gain of C (sequestration) in shrublands, or whether significant differences occur between different shrubland types. In this study, change in above-ground C stock was measured over an approximate 5-year period and consequent rates of C sequestration were calculated for six exotic seral and six mānuka (Leptospermum scoparium) shrubland plots. Mean C stocks were 73 ± 13 t CO2/ha for exotic shrubland plots and 76 ± 33 t CO2/ha for mānuka plots. Mean sequestration rates were 2.7 ± 1.5 t CO2/ha/y and 2.0 ± 1.0 t CO2/ha/y for exotic and mānuka shrublands respectively. Given the wide range in transition points between shrub and forest stages of succession with respect to C gain estimated in this preliminary study, we recommend more detailed investigation of long-term consequences of C storage during secondary succession. We also note that widely divergent estimates of sequestration rate could be derived depending on the time interval between measurements of stock change. We tested a simplified shrubland measurement methodology and found that predicted C stocks did not differ significantly from those estimated using the standard method.