Abstract
BackgroundTropical rainforests are frequently limited by soil nutrient availability. However, the response of the metabolic phenotypic plasticity of trees to an increase of soil nutrient availabilities is poorly understood. We expected that increases in the ability of a nutrient that limits some plant processes should be detected by corresponding changes in plant metabolome profile related to such processes.Methodology/Principal findingsWe studied the foliar metabolome of saplings of three abundant tree species in a 15 year field NPK fertilization experiment in a Panamanian rainforest. The largest differences were among species and explained 75% of overall metabolome variation. The saplings of the large canopy species, Tetragastris panamensis, had the lowest concentrations of all identified amino acids and the highest concentrations of most identified secondary compounds. The saplings of the “mid canopy” species, Alseis blackiana, had the highest concentrations of amino acids coming from the biosynthesis pathways of glycerate-3P, oxaloacetate and α-ketoglutarate, and the saplings of the low canopy species, Heisteria concinna, had the highest concentrations of amino acids coming from the pyruvate synthesis pathways.Conclusions/SignificanceThe changes in metabolome provided strong evidence that different nutrients limit different species in different ways. With increasing P availability, the two canopy species shifted their metabolome towards larger investment in protection mechanisms, whereas with increasing N availability, the sub-canopy species increased its primary metabolism. The results highlighted the proportional distinct use of different nutrients by different species and the resulting different metabolome profiles in this high diversity community are consistent with the ecological niche theory.
Highlights
Nutrient limitation has been widely observed in forests at a global scale [1]
In the PERMANOVAS conducted for each species separately, T. panamensis was most sensitive to nutrient availability
The most significant differences in metabolic profile were between T. panamensis and A. blackiana, which were separated along the first PC axis (Fig 1)
Summary
Nutrient limitation has been widely observed in forests at a global scale [1]. The weathering of bedrock is the primary source of P and K, and their availability tends to decline as soils age [2,4]. N is largely absent in most rocks, its primary sources are N fixation and atmospheric N deposition, and its availability increases with time, reaching a maximum in moderately leached soils, and declining in highly leached soils [5,6]. Tropical rainforests are frequently limited by soil nutrient availability. We expected that increases in the ability of a nutrient that limits some plant processes should be detected by corresponding changes in plant metabolome profile related to such processes
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