Altered plant carbon partitioning enhanced forest ecosystem carbon storage after 25 years of nitrogen additions

• Published in: The New phytologist 2021-05, Vol.230 (4), p.1435-1448
• Main Authors: Eastman, Brooke A., Adams, Mary B., Brzostek, Edward R., Burnham, Mark B., Carrara, Joseph E., Kelly, Charlene, McNeil, Brenden E., Walter, Christopher A., Peterjohn, William T.
• Format: Article
• Language: English
• Subjects: Acquisition; Biogeochemistry; Biological fertilization; Biomass; Carbon; Carbon capture and storage; carbon cycling; Carbon sequestration; Ecosystem; experimental N addition; Fertilization; Forest ecosystems; Forests; Litter; N acquisition strategies; Nitrogen; optimal allocation theory; Partitioning; plant biomass allocation; Soil; Soil testing; Soils; Stocks; Symbionts; temperate forest; terrestrial carbon sink; Terrestrial ecosystems; Trees; Vegetation; Watersheds
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.17256

• Decades of atmospheric nitrogen (N) deposition in the northeastern USA have enhanced this globally important forest carbon (C) sink by relieving N limitation. While many N fertilization experiments found increased forest C storage, the mechanisms driving this response at the ecosystem scale remain uncertain. • Following the optimal allocation theory, augmented N availability may reduce belowground C investment by trees to roots and soil symbionts. To test this prediction and its implications on soil biogeochemistry, we constructed C and N budgets for a long-term, whole-watershed N fertilization study at the Fernow Experimental Forest, WV, USA. • Nitrogen fertilization increased C storage by shifting C partitioning away from belowground components and towards aboveground woody biomass production. Fertilization also reduced the C cost of N acquisition, allowing for greater C sequestration in vegetation. Despite equal fine litter inputs, the C and N stocks and C : N ratio of the upper mineral soil were greater in the fertilized watershed, likely due to reduced decomposition of plant litter. • By combining aboveground and belowground data at the watershed scale, this study demonstrates how plant C allocation responses to N additions may result in greater C storage in both vegetation and soil.