A meta-analysis of leaf nitrogen distribution within plant canopies.
Leaf nitrogen distribution in the plant canopy is an important determinant for canopy photosynthesis. Although the gradient of leaf nitrogen is formed along light gradients in the canopy, its quantitative variations among species and environmental responses remain unknown. Here, we conducted a global meta-analysis of leaf nitrogen distribution in plant canopies.



We collected data on the nitrogen distribution and environmental variables from 393 plant canopies (100, 241 and 52 canopies for wheat, other herbaceous and woody species, respectively).



The trends were clearly different between wheat and other species; the photosynthetic nitrogen distribution coefficient (Kb) was mainly determined by leaf area index (LAI) in wheat, whereas it was correlated with the light extinction coefficient (KL) and LAI in other species. Some other variables were also found to influence Kb We present the best equations for Kb as a function of environmental variables and canopy characteristics. As a more simple function, Kb = 0·5KL can be used for canopies of species other than wheat. Sensitivity analyses using a terrestrial carbon flux model showed that gross primary production tended to be more sensitive to the Kb value especially when nitrogen content of the uppermost leaf was fixed.



Our results reveal that nitrogen distribution is mainly driven by the vertical light gradient but other factors such as LAI also have significant effects. Our equations contribute to an improvement in the projection of plant productivity and cycling of carbon and nitrogen in terrestrial ecosystems.
Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan, CREST, JST, Tokyo, Japan, hikosaka@m.tohoku.ac.jp.
Kouki
K
Hikosaka
Center for Crop System Analysis, Wageningen University, PO Box 430, 6700 AK Wageningen, the Netherlands.
Niels P R
NP
Anten
Institute of Chinese Minority Traditional Medicine, Minzu University of China, Beijing, 100081, China.
Almaz
A
Borjigidai
Institute for the Advanced Study of Sustainability, United Nations University, Jingumae 5-53-70, Shibuya, Tokyo 150-8925, Japan.
Chiho
C
Kamiyama
Agro-Meteorology Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan.
Hidemitsu
H
Sakai
Agro-Meteorology Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan.
Toshihiro
T
Hasegawa
Department of Biology, Ibaraki University, Mito 310-8512, Japan.
Shimpei
S
Oikawa
Center for Education and Research in Field Science, Agricultural Faculty, Shizuoka University, Ohya, Shizuoka 422-8529, Japan.
Atsuhiro
A
Iio
Institute of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan.
Makoto
M
Watanabe
Silviculture and Forest Ecological Studies, Hokkaido University, Sapporo 060-8589, Japan.
Takayoshi
T
Koike
National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan.
Kazuya
K
Nishina
National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan Japan Agency for Marine-Earth Science and Technology, Yokohama 236-0001, Japan.
Akihiko
A
Ito
D002244:Carbon / Q000378:metabolism*; D008027:Light; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D014908:Triticum / Q000502:physiology* / Q000528:radiation effects
D002244:Carbon; D009584:Nitrogen
Canopy photosynthesis; functional group; leaf area index; light distribution; light extinction coefficient; model; nitrogen allocation; nitrogen use; optimization