Chapter 2 Aboveground forest biomass varies across continents, ecological zones and successional stages: refinement of IPCC default values for tropical and subtropical forests 13Chapter 3 Estimating aboveground net biomass change for tropical and subtropical forests: Refinement of IPCC default rates using forest plot data 39Chapter 4 Variation in aboveground biomass in forests and woodlands in Tanzania along gradients in environmental conditions and human use 69Chapter 5 Forest disturbance and recovery in Peruvian Amazonia 87Chapter 6 Synthesis 109References 127Acknowledgements 159About the author 163
PE&RC Training and Education Statement 167For the UNFCCC parties it is necessary to quantify and understand current (sub)tropical forest carbon sources, stocks and sinks, as well as identify ways in which stocks and sinks can be enhanced. For these purposes, the Intergovernmental Panel on Climate Change (IPCC) supports the UNFCCC by providing monitoring guidelines as well as up-to-date scientific information on GHG emissions and removals from land use, land use changeRecently, the extent of undisturbed forests has been decreasing through deforestation and degradation. The latter process has led to the increase of disturbed forests (Lewis et al., 2015;Potapov et al., 2017). It is estimated that 30% of existing tropical forests and 40% of existing subtropical forests considered as degraded (Mercer, 2015). Due to the extent, importance and vulnerability of disturbed forests, disturbed forests need to be integrated into GHG monitoring frameworks (Bustamante et al., 2016).Plot-level AGB (in Mg ha −1 ) is calculated as the sum of tree-level AGB estimates (in Mg) per plot size (in ha). The size of plots can vary greatly: in this thesis, forest plot sizes range from 0.001 to 42 ha. To represent large areas of forests, we expect better plot-level estimates in larger plots (Hernández-Stefanoni et al., 2018;Mauya et al., 2015). However,
Thesis overviewThis PhD thesis is divided into 6 chapters. Chapter 1, which you are now reading, provides a brief introduction into the current state of knowledge regarding aboveground forest carbon stocks and sinks, current research gaps and possibilities to address them. The following four chapters seek to answer both research objectives by leveraging AGB forest plot data from different sources with remote sensing products and analysis, considering varying environmental and human use gradients and providing AGB and ∆AGB estimates at different scales. Figure 1.2 provides a conceptual overview of how Chapters 2 through 5 relate to R.O.1 and R.O.2. Chapter 2 provides a refinement of the IPCC 2006 default AGB values for natural forests in (sub)tropical forest ecozones. This is done by incorporating AGB data from forest plots, and deriving separate estimates for young secondary forests, older secondary forests and for old-growth (i.e. undisturbed) forest. For areas where plot data is not available, remote-sensing datasets are used to estimate default values. Furthermore, areas with limited forest ...