title: Aboveground tree growth varies with belowground carbon allocation in a tropical rainforest environment.
abstract: Young secondary forests and plantations in the moist tropics often have rapid rates of biomass accumulation and thus sequester large amounts of carbon. Here, we compare results from mature forest and nearby 15-20 year old tree plantations in lowland Costa Rica to evaluate differences in allocation of carbon to aboveground production and root systems. We found that the tree plantations, which had fully developed, closed canopies, allocated more carbon belowground - to their root systems - than did mature forest. This increase in belowground carbon allocation correlated significantly with aboveground tree growth but not with canopy production (i.e., leaf fall or fine litter production). In contrast, there were no correlations between canopy production and either tree growth or belowground carbon allocation. Enhanced allocation of carbon to root systems can enhance plant nutrient uptake, providing nutrients beyond those required for the production of short-lived tissues such as leaves and fine roots, and thus enabling biomass accumulation. Our analyses support this deduction at our site, showing that enhanced allocation of carbon to root systems can be an important mechanism promoting biomass accumulation during forest growth in the moist tropics. Identifying factors that control when, where and for how long this occurs would help us to improve models of forest growth and nutrient cycling, and to ascertain the role that young forests play in mitigating increased atmospheric carbon dioxide.
authors.affiliation: Department of Ecology, Evolution & Organismal Biology, Iowa State University, Ames, Iowa, United States of America.
authors.forename: James W
authors.initials: JW
authors.lastname: Raich
authors.affiliation: Department of Biology, University of Missouri-St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Clark
authors.affiliation: School of Environment, The University of Auckland, Auckland, New Zealand.
authors.forename: Luitgard
authors.initials: L
authors.lastname: Schwendenmann
authors.affiliation: United States Department of Agriculture Forest Service, International Institute of Tropical Forestry, Rio Piedras, Puerto Rico; Fundación Puertorriqueña de Conservación, San Juan, Puerto Rico.
authors.forename: Tana E
authors.initials: TE
authors.lastname: Wood
mesh_terms: D002244:Carbon / Q000378:metabolism*; D003364:Costa Rica; D018515:Plant Leaves / Q000502:physiology; D065947:Rainforest; D013045:Species Specificity; D014197:Trees / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D002244:Carbon