title: Temperature drives global patterns in forest biomass distribution in leaves, stems, and roots.
abstract: Whether the fraction of total forest biomass distributed in roots, stems, or leaves varies systematically across geographic gradients remains unknown despite its importance for understanding forest ecology and modeling global carbon cycles. It has been hypothesized that plants should maintain proportionally more biomass in the organ that acquires the most limiting resource. Accordingly, we hypothesize greater biomass distribution in roots and less in stems and foliage in increasingly arid climates and in colder environments at high latitudes. Such a strategy would increase uptake of soil water in dry conditions and of soil nutrients in cold soils, where they are at low supply and are less mobile. We use a large global biomass dataset (>6,200 forests from 61 countries, across a 40 °C gradient in mean annual temperature) to address these questions. Climate metrics involving temperature were better predictors of biomass partitioning than those involving moisture availability, because, surprisingly, fractional distribution of biomass to roots or foliage was unrelated to aridity. In contrast, in increasingly cold climates, the proportion of total forest biomass in roots was greater and in foliage was smaller for both angiosperm and gymnosperm forests. These findings support hypotheses about adaptive strategies of forest trees to temperature and provide biogeographically explicit relationships to improve ecosystem and earth system models. They also will allow, for the first time to our knowledge, representations of root carbon pools that consider biogeographic differences, which are useful for quantifying whole-ecosystem carbon stocks and cycles and for assessing the impact of climate change on forest carbon dynamics.
authors.affiliation: Department of Forest Resources, University of Minnesota, St. Paul, MN 55108; Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW 2751, Australia; preich@umn.edu.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Reich
authors.affiliation: Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China;
authors.forename: Yunjian
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Southwest Biological Science Center, US Geological Survey, Flagstaff, AZ 86001;
authors.forename: John B
authors.initials: JB
authors.lastname: Bradford
authors.affiliation: IBG-2 Plant Sciences, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany;
authors.forename: Hendrik
authors.initials: H
authors.lastname: Poorter
authors.affiliation: Northern Research Station, US Department of Agriculture Forest Service, St. Paul, MN 55108; and.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Perry
authors.affiliation: Department of Forest Resources, University of Minnesota, St. Paul, MN 55108; Institute of Dendrology, Polish Academy of Sciences, PL-62-035, Kornik, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Oleksyn
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism; D057231:Climate Change; D016208:Databases, Factual; D065928:Forests; D006358:Hot Temperature; D018515:Plant Leaves / Q000254:growth & development*; D018517:Plant Roots / Q000254:growth & development*; D018547:Plant Stems / Q000254:growth & development*
chemical_list: D002244:Carbon
keywords: allocation; allometry; biogeography; biomass fraction; root:shoot