How nitrogen-fixing trees change soil carbon

Nitrogen-fixing tree species have larger effects on forest soils than other species, and these effects include consistent increases in soil organic matter and carbon (Q. Across 19 case studies, an increase of 1 g N was associated with an increase of 12 to 15 g C. Few studies have examined the mechanisms behind the accumulation of soil C; documented processes include reduced decomposition of older, stabilized soil C, increased rates of formation of stabilized soil C, and higher rates of input of C in detritus. The influences of N-fixing trees on stabilized soil C may not derive directly from the increased supply of N, as fertilization with inorganic N did not alter soil C. More experimentation is needed on the influence of N-fixing trees on the soil biotic community, as the soil microbes and invertebrates may hold the key to the influence of N-fixation on soil C.