[Spatiotemporal Distribution Characteristics of Soil Organic Carbon and Carbon Sequestration Potential in Cultivated Land in Hebei Province in the Past 40 Years].

Abstract

Exploring the spatiotemporal distribution characteristics， influencing factors， and carbon sequestration potential of soil organic carbon density （SOCD） and soil organic carbon stock （SOCS） in the whole profile （0-120 cm） of cultivated land in major grain-producing areas is significant for regional agricultural sustainable development and farmland carbon management. Based on the data of the second soil survey in Hebei Province （1980） and the measured soil profile data of cultivated land in 2020， we estimated the SOCD and SOCS in cultivated land in Hebei Province at different soil depths and under different soil types. We revealed the spatiotemporal distribution characteristics of soil organic carbon （SOC） in cultivated land in Hebei Province， analyzed the influencing factors of SOC using a geographic detector model， and estimated the carbon sequestration potential of cultivated land soil using the saturation value method. The conclusions are as follows： ① From 1980 to 2020， the average values of SOCD in surface soil （0-20 cm）， middle soil （20-70 cm）， and deep soil （70-120 cm） in Hebei Province increased by 0.511， 0.340， and 0.599 kg·m^-2， respectively. In terms of spatial distribution， the SOCD in the northern， southern， and western regions of central-southern Hebei showed an increasing trend， while SOCD in the southern part of Tangshan City， Zhangjiakou City， and the northern part of Chengde City showed a decreasing trend during the 40 years. From the perspective of each soil type， the SOCD increased in fluvo-aquic soils， cinnamon soils， castanozems， and castano-cinnamon soils and decreased in brown earths in the whole soil profile. In terms of influencing factors， the explanatory power of annual precipitation， annual temperature， normalized difference vegetation index， pH， and total nitrogen varied across different layers. The interaction between any two influencing factors had a stronger explanatory power for changes in SOCD than either factor alone， exhibiting non-linear enhancement or two-factor enhancement characteristics. ② From 1980 to 2020， the SOCS in the middle soil accounted for approximately 40%-45% of total SOCS in the whole profile. During the 40 years， the increases in SOCS of the surface layer and deep layer accounted for 35.24% and 41.31% of the total increase in SOCS of the whole soil profile， respectively. As the main soil types in Hebei Province， the sum of SOCS in fluvo-aquic soils and cinnamon soils accounted for 73.35% and 75.65% of total SOCS in the two periods， respectively. ③ Cultivated land in Hebei Province was a "carbon sink" area. The soil carbon sequestration potential of cultivated land in the whole profile of Hebei Province was 148.762 Tg， with the carbon sequestration potentials of the surface， middle， and deep layers being 46.740， 38.117， and 63.905 Tg， respectively， accounting for 31.42%， 25.62%， and 42.96% of the total. In the future， we should further enhance the SOC in cultivated land in Hebei Province， including surface and deep layers and major soil types， taking into account the combined effects of influencing factors， with a view to improving regional soil carbon sequestration capacity and grain production capacity. The study can provide data support for the precise implementation of farmland carbon management.