Results

Discussion.

Fine root morphology and physiology differed between fast- and slow-growing species only among the finest two orders of roots. If there are differences in root lifespan in the root systems of fast- and slow-growing species, we would expect to find them in the finest two orders of roots. We calculated that fine roots of the fast-growing species would reach their peak efficiency earlier than roots of the slow-growing species. This may suggests that lifespan of roots of the fast-growing species is shorter. Root attributes were found to have large effects on time needed to reach peak root efficiency.

When the components of root cost and benefit were examined through model simulation, fine roots of the fast-growing species were found to be more efficient than roots of the slow-growing species. Roots with higher nutrient uptake rates, as was seen in roots of fast-growing species, would be expected to have a higher construction cost due to the higher concentration of proteins needed for nutrient uptake. Respiration would also be expected to be higher due to higher root activity. Respiration, however, was only slightly higher in roots of fast-growing species while uptake was much higher. While there are other costs involved with maintaining fine roots, such as the production of defense compounds, these costs should accounted for, in part, by respiration. Roots used in this study were non-mycorrhizal and it remains to be seen if mycorrhiza may account for the difference in root efficiency between the fast- and slow-growing species.

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