Articles | Volume 15, issue 7
https://doi.org/10.5194/bg-15-2033-2018
https://doi.org/10.5194/bg-15-2033-2018
Research article
 | 
09 Apr 2018
Research article |  | 09 Apr 2018

Shrub type dominates the vertical distribution of leaf C : N : P stoichiometry across an extensive altitudinal gradient

Wenqiang Zhao, Peter B. Reich, Qiannan Yu, Ning Zhao, Chunying Yin, Chunzhang Zhao, Dandan Li, Jun Hu, Ting Li, Huajun Yin, and Qing Liu

Abstract. Understanding leaf stoichiometric patterns is crucial for improving predictions of plant responses to environmental changes. Leaf stoichiometry of terrestrial ecosystems has been widely investigated along latitudinal and longitudinal gradients. However, very little is known about the vertical distribution of leaf C : N : P and the relative effects of environmental parameters, especially for shrubs. Here, we analyzed the shrub leaf C, N and P patterns in 125 mountainous sites over an extensive altitudinal gradient (523–4685 m) on the Tibetan Plateau. Results showed that the shrub leaf C and C : N were 7.3–47.5 % higher than those of other regional and global flora, whereas the leaf N and N : P were 10.2–75.8 % lower. Leaf C increased with rising altitude and decreasing temperature, supporting the physiological acclimation mechanism that high leaf C (e.g., alpine or evergreen shrub) could balance the cell osmotic pressure and resist freezing. The largest leaf N and high leaf P occurred in valley region (altitude 1500 m), likely due to the large nutrient leaching from higher elevations, faster litter decomposition and nutrient resorption ability of deciduous broadleaf shrub. Leaf N : P ratio further indicated increasing N limitation at higher altitudes. Interestingly, drought severity was the only climatic factor positively correlated with leaf N and P, which was more appropriate for evaluating the impact of water status than precipitation. Among the shrub ecosystem and functional types (alpine, subalpine, montane, valley, evergreen, deciduous, broadleaf, and conifer), their leaf element contents and responses to environments were remarkably different. Shrub type was the largest contributor to the total variations in leaf stoichiometry, while climate indirectly affected the leaf C : N : P via its interactive effects on shrub type or soil. Collectively, the large heterogeneity in shrub type was the most important factor explaining the overall leaf C : N : P variations, despite the broad climate gradient on the plateau. Temperature and drought induced shifts in shrub type distribution will influence the nutrient accumulation in mountainous shrubs.

Download
Short summary
We found larger shrub leaf C, C : N and lower leaf N, N : P levels compared to other terrestrial ecosystems. Alpine shrubs exhibited the greatest leaf C at low temperatures, whereas the largest leaf N and P occurred in valley deciduous shrubs. The large heterogeneity in nutrient uptake and physiological adaptation of shrub types to environments explained the largest fraction of leaf C : N : P variations, while climate indirectly affected leaf C : N : P via its interactive effects on shrub type or soil.
Altmetrics
Final-revised paper
Preprint