Response of plant nutrient stoichiometry to fertilization varied with plant tissues in a tropical forest

Qifeng Mo,Rong Mao,Weixin Zhang,Jianwu Tang,Yao Chen,Yingwen Li,Bi Zou,Xiaobo Li,Zhian Li,Yongzhen Ding,Xiankai Lu,Jun Wang,Faming Wang

doi:10.1038/srep14605

Abstract

Plant N:P ratios are widely used as indices of nutrient limitation in terrestrial ecosystems, but the response of these metrics in different plant tissues to altered N and P availability and their interactions remains largely unclear. We evaluated changes in N and P concentrations, N:P ratios of new leaves (<1 yr), older leaves (>1 yr), stems and mixed fine roots of seven species after 3-years of an N and P addition experiment in a tropical forest. Nitrogen addition only increased fine root N concentrations. P addition increased P concentrations among all tissues. The N × P interaction reduced leaf and stem P concentrations, suggesting a negative effect of N addition on P concentrations under P addition. The reliability of using nutrient ratios as indices of soil nutrient availability varied with tissues: the stoichiometric metrics of stems and older leaves were more responsive indicators of changed soil nutrient availability than those of new leaves and fine roots. However, leaf N:P ratios can be a useful indicator of inter-specific variation in plant response to nutrients availability. This study suggests that older leaf is a better choice than other tissues in the assessment of soil nutrient status and predicting plant response to altered nutrients using nutrients ratios.

Highlights

Generally believed that plant growth might be limited by P in tropical forests[6,7,8]
We expect that: 1) due to high N deposition in this region, the forest should be P limited; and N addition would have a relatively weak effect on N concentrations and N:P ratios while P addition would dramatically increase/ decrease P concentrations/N:P ratios of plant tissues; 2) N and P concentrations would vary among different plant tissues, and the values in older leaves, stems and fine roots would be more greatly altered by changed nutrient status than those in new leaves
There was a 10–80% increase of stem N concentrations in + N plots compared with control treatment (CT) in four out of seven species (Fig. S1 a, c, d & g)

Summary

Introduction

Generally believed that plant growth might be limited by P in tropical forests[6,7,8]. This difference affects the understory frugivores, and had a critical role in canopy trees regeneration These differences suggest that plant community in Asian tropical forest may have different response to nutrient fertilization as those in the neotropics. We expect that: 1) due to high N deposition in this region, the forest should be P limited; and N addition would have a relatively weak effect on N concentrations and N:P ratios while P addition would dramatically increase/ decrease P concentrations/N:P ratios of plant tissues; 2) N and P concentrations would vary among different plant tissues, and the values in older leaves, stems and fine roots would be more greatly altered by changed nutrient status than those in new leaves

Methods

Results

Discussion

Conclusion