Impact of soil water on soil organic C mineralization with the use of ~(14)C-tracer

摘要

To understand the impacts of soil water content on the mineralization of added organic materials and soil organic carbon (SOC), and on the priming effect, upland soil was amended with uniformly ~(14)C-labelled straw (~(14)C-straw) and incubated at 30, 45, 60, 75, 90 and 105% water holding capacity (WHC) at 25℃ and 100% humidity for 100 days. Control (i.e. unamended) treatments were incubated at same laboratory conditions at 45, 75 and 105% WHC. In added straw treatment, during the 100 day incubation period, cumulative mineralization amounts of added ~(14)C-straw and native SOC were 146 μg C g~(-1) soil and 764 μg C g~(-1) soil at 105% WHC, which were 1.2～1.7 times and 1.3～3.0 times to amounts at other %WHCs. Over the entire incubation period, compared to control treatment, straw addition produced negative priming effect of -6.7% at 45% WHC, but the addition had little effect on SOC mineralization at 75%WHC. However, positive priming effect of +5.4% was produced at 105% WHC. Our study revealed that increasing %WHC over a certain range can improve the mineralization of added straw C and SOC. Soil water content can also significantly influence the priming effect in upland soil.