COS 217-2 - CANCELLED - Big trees matter most: Measurement optimization for ground-based tropical forest carbon inventories

Background/Question/Methods

Big diameter trees dominate the biomass of the world’s naturally regenerated forests despite their low stem density per area. In wet lowland tropical forest of Costa Rica, we field tested the measurement time cost of using big Basal Area Factor (big BAF)­­ ––a double sampling point variant minimizing tree height measurement time––to capture these big trees versus more widely used nested plots. We compared the accuracy and precision of both nested and big BAF designs against full census referents for aboveground live tree biomass calculations.

Results/Conclusions

Both big BAF points and nested plots, by optimizing measurement time for big trees that drive biomass, reduced plot measurement time by 50% compared to referents and without accuracy penalties. However, big BAF points consistently produced the most precise biomass estimates by multiple measures compared to the nested plots. Using the 0.5 hectare size and 20 cm diameter threshold and the 0.1 hectare size and 10 cm diameter threshold of the Panamanian and Costa Rican national forest inventories respectively we show how big BAF points may be incorporated into existing permanent nested plot designs at either country or offset project spatial scales.