Northeast China holds huge wetland soil organic carbon storage: an estimation from 819 soil profiles and random forest algorithm

Abstract

Abstract Purpose As a huge natural carbon storage, wetlands play an important role in the global carbon cycle. However, the spatial pattern and storage of soil organic carbon (SOC) in wetland ecosystems remain largely uncertain due to large spatial heterogeneity and insufficient field observations. Methods In this study, we predict the spatial pattern of SOC density and estimated SOC storage in wetlands of Northeast China based on 819 field samples and multiple geospatial data using random forest algorithm. Results The results showed that climate, vegetation, and topography had notable impacts on the SOC density at different soil depths. The wetland SOC density in the surface layer (0–30 cm) was affected mainly by climatic factors (e.g., temperature, r = 0.54, p < 0.001), while the SOC density in the middle layer (30–60 cm) was mainly influenced by both climatic factors and vegetation factors. Moreover, topography (r = 0.35, p < 0.001) had greater impacts on wetland SOC density in the deeper soil layer (60–100 cm). Our estimation showed that Northeast China holds huge wetland SOC storage in the amount of 3.40 ± 0.13 Pg C. The average wetland SOC density was 44.30 ± 1.72 kg C m− 2, which decreased gradually from north to south in the study area. The wetland SOC storage in the Greater Khingan Mountains Region was 2461.87 ± 92.21 Tg C, while that in the Liao River Plain was only 26.73 ± 1.33 Tg C. Conclusion We used random forest algorithm to achieve high-precision estimation of the wetland SOC storage in Northeast China, avoiding the geographic location-based dependence of traditional interpolation methods. Our results examined the relationship between wetland SOC and environmental factors, which benefits the understanding of the responses of wetland SOC to climate change.