Abstract
Research Highlights: The estimation of soil and litter carbon stocks by the Land Use, Land-Use Changes, and Forestry (LULUCF) sectors has the potential to improve reports on national greenhouse gas (GHG) inventories. Background and Objectives: Forests are carbon sinks in the LULUCF sectors and therefore can be a comparatively cost-effective means and method of GHG mitigation. Materials and Methods: This study was conducted to assess soil at 0–30 cm and litter carbon stocks using the National Forest Inventory (NFI) data and random forest (RF) models, mapping their carbon stocks. The three main types of forest in South Kora were studied, namely, coniferous, deciduous, and mixed. Results: The litter carbon stocks (t C ha−1) were 4.63 ± 0.18 for coniferous, 3.98 ± 0.15 for mixed, and 3.28 ± 0.13 for deciduous. The soil carbon stocks (t C ha−1) were 44.11 ± 1.54 for deciduous, 35.75 ± 1.60 for mixed, and 33.96 ± 1.62 for coniferous. Coniferous forests had higher litter carbon stocks while deciduous forests contained higher soil carbon stocks. The carbon storage in the soil and litter layer increased as the forest grew older; however, a significant difference was found in several age classes. For mapping the soil and litter carbon stocks, we used four random forest models, namely RF1 to RF4, and the best performing model was RF2 (root mean square error (RMSE) (t C ha−1) = 1.67 in soil carbon stocks, 1.49 in soil and litter carbon stocks). Our study indicated that elevation, accessibility class, slope, diameter at breast height, height, and growing stock are important predictors of carbon stock. Soil and litter carbon stock maps were produced using the RF2 models. Almost all prediction values were appropriated to soil and litter carbon stocks. Conclusions: Estimating and mapping the carbon stocks in the soil and litter layer using the NFI data and random forest models could be used in future national GHG inventory reports. Additionally, the data and models can estimate all carbon pools to achieve an accurate and complete national GHG inventory report.
Highlights
Forests have an important role as carbon sinks; through tree growth and CO2 removal from the atmosphere, they store more than 80% of all terrestrial aboveground carbon and 70% of soil organic carbon [1,2,3]
Concerning the soil carbon stocks (t C ha−1 ), it was deciduous that accounted for the largest values at 44.11 ± 1.54, followed by 35.75 ± 1.60 for mixed, and 33.96 ± 1.62 for coniferous in descending order
The coniferous forest generally had higher litter carbon stocks than others (p < 0.05), while mineral soil carbon stocks were higher in the deciduous forest than others (p < 0.05)
Summary
Forests have an important role as carbon sinks; through tree growth and CO2 removal from the atmosphere, they store more than 80% of all terrestrial aboveground carbon and 70% of soil organic carbon [1,2,3]. And efficiently quantifying forest carbon stocks is crucial in understanding their response in mitigating rising climate change issues [4]. Mitigation through activities in the forest sector, either by increasing the removal of greenhouse gases (GHG) or by reducing emissions from carbon sources, can be comparatively cost-effective [5,6]. Convention on Climate Change (UNFCCC) should adopt a nationally determined contributions (NDC). This bottom-up system takes each nation’s differing capabilities, circumstances and common yet distinct responsibilities into account to reduce global GHG [8]. The Land Use, Land-Use Change, and Forestry (LULUCF) sectors will be a key component of the Paris Agreement on NDCs as a net carbon sink [10]. The LULUCF is expected to contribute at a global level as much as 20%
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