title: Evidence for environmentally enhanced forest growth.
abstract: Forests in the middle and high latitudes of the northern hemisphere function as a significant sink for atmospheric carbon dioxide (CO2). This carbon (C) sink has been attributed to two processes: age-related growth after land use change and growth enhancement due to environmental changes, such as elevated CO2, nitrogen deposition, and climate change. However, attribution between these two processes is largely controversial. Here, using a unique time series of an age-class dataset from six national forest inventories in Japan and a new approach developed in this study (i.e., examining changes in biomass density at each age class over the inventory periods), we quantify the growth enhancement due to environmental changes and its contribution to biomass C sink in Japan's forests. We show that the growth enhancement for four major plantations was 4.0∼7.7 Mg C⋅ha(-1) from 1980 to 2005, being 8.4-21.6% of biomass C sequestration per hectare and 4.1-35.5% of the country's total net biomass increase of each forest type. The growth enhancement differs among forest types, age classes, and regions. Our results provide, to our knowledge, the first ground-based evidence that global environmental changes can increase C sequestration in forests on a broad geographic scale and imply that both the traits and age of trees regulate the responses of forest growth to environmental changes. These findings should be incorporated into the prediction of forest C cycling under a changing climate.
authors: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China;State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China; jyfang@urban.pku.edu.cn fangjingyun@ibcas.ac.cn.
authors: Jingyun
authors: J
authors: Fang
authors: Research Faculty of Agriculture, Hokkaido University, Sapporo, Hokkaido 060-8589, Japan;
authors: Tomomichi
authors: T
authors: Kato
authors: Department of Ecology, College of Urban and Environmental Sciences, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing 100871, China;
authors: Zhaodi
authors: Z
authors: Guo
authors: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
authors: Yuanhe
authors: Y
authors: Yang
authors: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
authors: Huifeng
authors: H
authors: Hu
authors: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
authors: Haihua
authors: H
authors: Shen
authors: State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
authors: Xia
authors: X
authors: Zhao
authors: National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki 305-8604, Japan;
authors: Ayaka W
authors: AW
authors: Kishimoto-Mo
authors: National Institute for Environmental Studies, Tsukuba, Ibaraki 305-0053, Japan; and.
authors: Yanhong
authors: Y
authors: Tang
authors: Woods Hole Research Center, Falmouth, MA 02540.
authors: Richard A
authors: RA
authors: Houghton
mesh_terms: D000367:Age Factors; D018533:Biomass; D057965:Carbon Sequestration / Q000502:physiology*; D004777:Environment; D005843:Geography; D007564:Japan; D008954:Models, Biological; D012044:Regression Analysis; D014197:Trees / Q000254:growth & development*
keywords: biomass carbon sink; forest age; forest inventory