Richard Houghton

Forests in the middle and high latitudes of the northern hemisphere function as a significant sink for atmospheric carbon dioxide (CO2). This carbon (C) sink has been attributed to two processes: age-related growth after land use change and growth enhancement due to environmental changes, such as elevated CO2, nitrogen deposition, and climate change. However, attribution between these two processes is largely controversial. Here, using a unique time series of an age-class dataset from six national forest inventories in Japan and a new approach developed in this study (i.e., examining changes in biomass density at each age class over the inventory periods), we quantify the growth enhancement due to environmental changes and its contribution to biomass C sink in Japan's forests. We show that the growth enhancement for four major plantations was 4.0∼7.7 Mg C⋅ha(-1) from 1980 to 2005, being 8.4-21.6% of biomass C sequestration per hectare and 4.1-35.5% of the country's total net...

Within the United Nationals Framework Convention on Climate Change, countries are continuing to negotiate emission reduction targets and exploring mitigation strategies best suited to their biophysical characteristics. Under the ``REgional Carbon Cycle Assessment and Processes'', we focus on analyzing the carbon budget of the Southeast (SE) Asia region. Following the large 1997/98 El Niño event, anomalous CO2 growth rate (~2.5 ppm/yr) in the atmosphere is measured. Studies suggest forest and peat fires resulted in a carbon emission rate of 1-2 Pg-C/yr from the SE Asia alone. We plan to combine estimates of carbon fluxes from multiple sources, e.g., from atmospheric inverse modeling, ecosystem model simulations, emissions from fire, and land use change based on remote sensing data products, and field observations, to establish the mean annual CO2-C budget for the past 10 years. We will also attempt to link the CO2 flux variability with climate indices for understanding the controlling factors of carbon uptake and release by different ecosystems within the region.

Nearly all lifecycle analyses of the greenhouse gas impacts of substituting biofuels for fossil fuels leave out emissions from land use change. See Appendix A. This paper calculates emissions from worldwide land use change resulting from the expansion of corn-based ethanol in the United States, discusses the applicability of these calculations to other biofuels, and provides qualitative and quantitative sensitivity analysis.