A test for the resource remobilization hypothesis: Tree sprouting using carbohydrates from above-ground parts

To test the resource remobilization hypothesis, i.e. the hypothesis that some trees sprout from root-collars or from the lower part of trunks using resources obtained from above-ground parts rather than from resources reserved in their roots, we conducted cutting experiments for Euptelea polyandra, a frequently sprouting tree species with little carbohydrate reserves in its roots, Quercus setrata, a frequently sprouting tree species with large reserves in the roots, and Mallotus japonicus, a rarely sprouting tree species. Trees of each species were cut down in winter leaving two kinds of stumps, those approx. 1.5 m in height and those cut off near the ground. The number and total dry weight of newly sprouted shoots per stump were compared between the two treatments and among the three species at the end of the following growing season. In E. polyandra, both the number and total dry weight of sprouts per stump were very small for both treatments and were similar to, or less than, those of M. japonicus. On the other hand, Q. serrata sprouted abundantly in both treatments. These results indicate that E. polyandra cannot sprout sufficiently without a considerably large volume of above-ground parts or that additional structures such as foliage and branches may be necessary for sprouting. We conclude that the resource remobilization hypothesis is supported for this species.