Effect of particle sizes of biochar on CO2 emissions in a poplar plantation of ancient Yellow River channel, China

Abstract

Forest soil is a vital pool of organic carbon, which is sensitive to management. Biochar addition could change the CO₂ emissions from soil, but its effects are still ambiguous. Moreover, the impacts of particle sizes of biochar on CO₂ emissions are still unknown. In this study, a series of field experiments were conducted to investigate the effects of biochar addition on CO₂ emissions in a poplar plantation (Populus nigra), China. Biochar with two application rates of (10 and 50 t/ha) and three particle sizes (3-1 mm, 1-0.1 mm, and <0.1 mm) was applied into the surface soil (0-10 cm), and the soil without biochar was set as control. The results showed that a high level of fine biochar addition (1-0.1 mm and <0.1 mm) had similar and positive effects on CO₂ emissions by increasing the contents of soil ammonium, available phosphorus, easily oxidizable carbon, soil moisture, soil capillary pore, and the activity of β-glucosidase. However, biochar addition (1-0.1 mm and <0.1 mm) reduced the bioavailability of dissolved organic carbon (DOC), producing a negative relationship between DOC content and CO₂ emissions. This investigation highlights the importance of biochar with different particle sizes in adjusting CO₂ emissions from temperate soils.

Keywords: Biochar; CO(2) emissions; Northern China; Particle size; Temperate forest.