Plant traits are essential for the fitness of plants in their environments and also play key roles on nutrient and carbon cycling via affecting the decomposition of plant debris. The recent progress on the research of plant traits have revealed the lack of coordination between above-ground and below-ground traits. While leaf traits tend to follow a world-wide leaf economics spectrum, root traits, especially root morphology, exhibited a strong phylogenetic conservatism. The phylogenetic effect on root chemical traits is less understood. Most root trait studies only used carbon and nitrogen concentrations to represent root chemistry. A more comprehensive knowledge on molecular-level chemical variations in fine roots and the driving factors would improve our ability to understand and predict belowground processes such as nutrient recycling and carbon fluxes across different biomes. Here we used GC-MS, pyrolysis-GC-MS, and FT-IR to characterize chemical properties of fine roots across 34 temperate species from three major phylogenetic clades of woody angiosperms.
Results/Conclusions
The results from CuO reactions followed by GC-MS and pyrolysis-GC-MS both demonstrated that phylogenetic history did not impose a significant effect on the concentrations of total lignin phenols, but the ratios of different phenol classes in more recently derived groups are significantly different from those in basal angiosperms, indicating a strong phylogenetic signal in lignin composition. Cell-wall bound phenols exhibited the similar trend: concentrations of total bound phenols did not differ significantly among phylogenetic clades, but the composition of bound phenols in recently derived groups is divergent from that of the more ancient angiosperms. In addition, phylogenetic history was not a significant factor explaining the variations in cellulose concentrations and lignin : cellulose ratios in fine roots across species. To our knowledge, this study is the first to provide evidence that the phenolic profiles of fine roots in angiosperm woody species are phylogenetically structured. This finding shed new light on how phylogenetic history can contribute to the understanding of below-ground processes in terrestrial ecosystems.