We combined two existing datasets of vegetation aboveground biomass (AGB) (Saatchi et al., 2011; Baccini et al., 2012) into a pan-tropical AGB map at 1-km resolution using an independent reference dataset of field observations and locally-calibrated high-resolution biomass maps, harmonized and upscaled to 14,477 1-km AGB estimates. Our data fusion approach uses bias removal and weighted linear averaging that incorporates and spatializes the biomass patterns indicated by the reference data. The method was applied independently in areas (strata) with homogeneous error patterns of the input (Saatchi and Baccini) maps, which were estimated from the reference data and additional covariates. Based on the fused map, we estimated AGB stock for the tropics (23.4 N – 23.4 S) of 375 Pg dry mass, 9% – 18% lower than the Saatchi and Baccini estimates. The fused map also showed differing spatial patterns of AGB over large areas, with higher AGB density in the dense forest areas in the Congo basin, Eastern Amazon and South-East Asia, and lower values in Central America and in most dry vegetation areas of Africa than either of the input maps. The validation exercise, based on 2,118 estimates from the reference dataset not used in the fusion process, showed that the fused map had a RMSE 15 – 21% lower than that of the input maps and, most importantly, nearly unbiased estimates (mean bias 5 Mg dry mass ha-1 vs. 21 and 28 Mg ha-1 for the input maps). The fusion method can be applied at any scale including the policy-relevant national level, where it can provide improved biomass estimates by integrating existing regional biomass maps as input maps and additional, country-specific reference datasets.
Tag: carbon balance
No evidence for carryover effect in tree rings based on a pulse-labelling experiment on Juniperus communis in South Germany
Key message: A clear carryover effect of tree-ring formation was not detected based on a pulse-labelling experiment conducted on Juniperus communis in South Germany. Abstract: The inherent linkage between photosynthesis and the formation of wood is important for the understanding of relationships between tree-ring series and climate/environmental data in dendroclimatology studies. However, it is impossible to reach a mechanistic procedure of tree stem radial growth depending on its carbon balance from a traditional statistical point of view alone. Pulse labelling experiment with stable carbon isotope (13CO2) has provided innovative insights into the fate of recently assimilated carbon in organs and carbon-containing compounds. In this study, we conducted an in situ pulse labelling experiment on 27 July 2016 to examine the response of tree ring and different-aged needles to short-term elevated 13CO2 of a juniper shrub growing on a heathland in South Germany. New and old needles from four expositions were sampled before and after the experiment. A wood segment was taken from the main branch and stable carbon isotope composition (δ13C) was analysed at an intra-annual time scale. Before the experiment, the mean δ13C was − 26.8 ± 0.4‰ (mean ± standard deviation) for both needle ages, while woody tissue showed about 3‰ higher δ13C compared to needles. Substantial enriched 13C was detected in the needles after the experiment. New needles showed significant higher δ13C than the old ones 1–7 days after the experiment. Significant enriched δ13C was detected in the wood from 35 to 61% of the annual tree ring in 2016, indicating that the short-term enrichment of 13C can affect wood formation for a large section. No enhancement in 13C signal appeared in the tree ring of the subsequent year 2017, suggesting the absence of a carryover effect. Wood formation did not reply on the carbohydrates stored even 1 year before and thus tree-ring ecophysiological modelling as well as dendrochronological studies should therefore benefit from such result.
Environmental drivers of blue carbon burial and soil carbon stocks in mangrove forests
Mangroves can sequester and store massive amounts of CO2 from the atmosphere in the form of live plant and detrital biomass. Large amounts of autochthonous and allochthonous carbon (C) are also stored in sediments, where waterlogged and anoxic conditions inhibit microbial breakdown of organic matter. As a result, C buried in sediments of mangroves can remain there for millennia if left undisturbed, making them critical long-term C sinks. These high levels of aboveground and belowground C stocks have elevated the importance of mangroves and other blue carbon habitats in climate change mitigation and adaptation as well as efforts to protect and restore them. While methods have been developed for quantifying and reporting C stocks, the environmental drivers that influence the accumulation and retention of C stocks in blue carbon habitats are lesser known. Identifying important drivers of C accumulation in blue carbon habitats will increase conservation and restoration efforts so that they can continue to mitigate climate change by offsetting greenhouse gas emissions. Successful restoration and conservation activities can also be used in nationally determined commitments or in voluntary C markets. This chapter will explore the biological, biogeochemical, and geomorphological drivers that influence C burial in mangrove sediments.