Optimality of nitrogen distribution among leaves in plant canopies
- 672 Downloads
The vertical gradient of the leaf nitrogen content in a plant canopy is one of the determinants of vegetation productivity. The ecological significance of the nitrogen distribution in plant canopies has been discussed in relation to its optimality; nitrogen distribution in actual plant canopies is close to but always less steep than the optimal distribution that maximizes canopy photosynthesis. In this paper, I review the optimality of nitrogen distribution within canopies focusing on recent advancements. Although the optimal nitrogen distribution has been believed to be proportional to the light gradient in the canopy, this rule holds only when diffuse light is considered; the optimal distribution is steeper when the direct light is considered. A recent meta-analysis has shown that the nitrogen gradient is similar between herbaceous and tree canopies when it is expressed as the function of the light gradient. Various hypotheses have been proposed to explain why nitrogen distribution is suboptimal. However, hypotheses explain patterns observed in some specific stands but not in others; there seems to be no general hypothesis that can explain the nitrogen distributions under different conditions. Therefore, how the nitrogen distribution in canopies is determined remains open for future studies; its understanding should contribute to the correct prediction and improvement of plant productivity under changing environments.
KeywordsCanopy photosynthesis Light extinction coefficient Nitrogen allocation Nitrogen use Optimization
I thank Professors Niels Anten and Ülo Niinemets for helpful comments and Professor Tadaki Hirose for providing data on Solidago altissima canopy. The study was supported by KAKENHI (2114009, 25660113, 25440230, 25291095) and CREST, JST, Japan.
- Anten NPR, Hikosaka K, Hirose T (2000) Nitrogen utilization and the photosynthetic system. In: Marshal B, Roberts J (eds) Leaf development and canopy growth. Sheffield Academic, Sheffield, pp 171–203Google Scholar
- Charles-Edwards DA, Stutzel H, Ferraris R, Beech DF (1987) An analysis of spatial variation in the nitrogen content of leaves from different horizons within a canopy. Ann Bot 60:421–426Google Scholar
- DeJong TM, Doyle JF (1985) Seasonal relationships between leaf nitrogen content (photosynthetic capacity) and leaf canopy light exposure in peach (Prunus persica). Plant Cell Environ 8:701–706Google Scholar
- Hikosaka K, Hirose T (1997) Leaf angle as a strategy for light competition: optimal and evolutionarily stable light-extinction coefficient within a canopy. Écoscience 4:501–507Google Scholar
- Hikosaka K, Yasumura Y, Muller O, Oguchi R (2014) Resource allocation and trade-offs in carbon gain of leaves under changing environment. In: Tausz M, Grulke N (eds) Trees in a changing environment. Plant ecophysiology, vol 9. Springer, DordrechtGoogle Scholar
- Hikosaka K, Anten NPR, Borjigidai A, Kamiyama C, Sakai H, Hasegawa T, Oikawa S, Iio A, Watanabe M, Koike T, Nishina K, Ito A (2016b) A meta-analysis of leaf nitrogen distribution within plant canopies. Ann Bot (in press)Google Scholar
- Pons TL, Schieving F, Hirose T, Werger MJA (1989) Optimization of leaf nitrogen allocation for canopy photosynthesis in Lysimachia vulgaris. In: Lambes H, Cambridge ML, Konings H, Pons TL (eds) Causes and consequence of variation in growth rate and productivity of higher plants. SPB Academic Publishing, The Hague, pp 175–186Google Scholar
- Schieving F, Pons TL, Werger MJA, Hirose T (1992) Vertical distribution of nitrogen in photosynthetic activity at different plant densities in Carex acutiformis. Plant Soil 142:9–17Google Scholar
- Tyree MT (2003) Hydraulic limits on tree performance: transpiration, carbon gain and growth of trees. Trees 17:95–100Google Scholar