Aboveground carbon stocks and sinks in recovering tropical forests

Tropical and subtropical forests have many valuable roles, one of them within the carbon cycle. Within this cycle they are an essential terrestrial component, functioning as carbon reservoirs and sinks. The importance of (sub)tropical forests in climate change mitigation has been highlighted in recent climate change policies, such as the Paris Agreement, with signatory countries working towards a robust monitoring of their forest carbon stocks and sinks. Additionally, efforts to enhance forest carbon sinks through the restoration of degraded land has been highlighted by the Bonn Challenge, with currently more than 70 pledges in 60 countries underway.Until recently, large-scale assessments and country-level reporting of forest carbon stocks and sinks have been relying on coarse estimates provided in 2006 by the Intergovernmental Panel on Climate Change (IPCC). However, these estimates were based on a handful of studies per global ecological zone (also known as ecozone), did not provide methods for their derivation nor measures of uncertainty, and did not distinguish between forest successional stages.Furthermore, little is known about the drivers of variations in carbon stocks and sinks across (sub)tropical forests, particularly in forests with limited forest plot data availability. In this respect, insights for variations in forests and woodlands in the African dry tropics and in forests recovering from recent disturbance remains limited. Understanding how forest carbon stocks and sinks vary is essential for monitoring greenhouse gas (GHG) fluxes as well as for improving forest conservation and restoration endeavours.Over time, research on (sub)tropical forest carbon stocks and sinks has progressed, as well as country-level monitoring efforts to improve forest GHG reporting. This has led to the increase in availability of forest plot data. Simultaneously, large-scale remote sensing products have become available and region-specific methods for the monitoring of forest disturbance/recovery dynamics have improved over time. Thus, the opportunity to combine forest plot data with remote sensing to evaluate carbon stocks and sinks in (sub)tropical forests at different stages of recovery arises.The overall aim of this thesis is to integrate forest plot data with remote sensing to contribute towards understanding and quantifying aboveground forest carbon stocks (aboveground biomass; AGB) and sinks (aboveground biomass change; ΔAGB) in (sub)tropical forests. More specifically, this thesis has the objectives of (1) improving estimations of (sub)tropical aboveground forest carbon stocks and sinks under varying disturbance types for GHG reporting and of (2) understanding the drivers of aboveground carbon stocks and sinks in recovering forests in the (sub)tropic