Priming effects in forest soils with different parent materials

Abe, Yukiko; Nakayama, Masataka  ; Atarashi-Andoh, Mariko  ; Koarashi, Jun   

Subsoils contain more than half of the global soil carbon. Decomposition of organic matter accumulated in the subsoil is thought to contribute significantly to heterotrophic respiration, and the supply of new organic matter to the subsoil may accelerate the decomposition of soil organic matter (priming effect). However, the carbon dynamics in the subsoil are unknown. The aim of this study was to evaluate the decomposition response to a new supply of organic matter, focusing on the differences in the interaction between organic matter and minerals in the presence and absence of volcanic ash. The surface and subsoil layers of four study sites with volcanic and non-volcanic ash soils were prepared to 64% of water holding capacity (WHC) and incubated at 20C and 30C after addition of 1% of WHC or a sucrose solution labeled at C. Sucrose addition had a positive priming effect in the lower layers of the volcanic ash soils, but the difference in carbon release after 90 days of incubation was about half of the addition in all soils, with and without sucrose addition. Therefore, sucrose addition to the soil enhanced organic matter decomposition, but it was suggested that some of the sucrose may remain in the soil.