Evaluation of a field experiment for the conservation of a Magnolia stellata stand using clear-cutting

Magnolia stellata is a rare subcanopy tree species that grows in secondary forests in warm temperate zones. It is now endangered due to habitat degradation by vegetation succession. In an attempt to improve the habitat, a 30 m × 10 m plot (0.03 ha) was set up with all vegetation including M. stellata being clear-cut in January 2012. The number of sprouts increased for 1–2 years after clear-cutting and then gradually decreased or remained constant. Five years after clear-cutting, the numbers of individuals and stems, and the total basal area (BA), were 87.0, 165.5 and 3.2%, respectively, of the values before clear-cutting. BA was highest for Ilex pedunculosa, followed by M. stellata and Hydrangea paniculata. Some sprouted individuals of M. stellata produced flower buds in the second year after clear-cutting, and flowered and fruited in the spring and summer of the third year, respectively. The densities of potential canopy species were 18,533 ha−1 (height > 0.5 m) and 7,267 ha−1 (height > 1.2 m), vastly exceeding the value of the criterion for successful natural regeneration after clear-cutting of warm temperate forests in the region (3,000 ha−1). Based on this criterion, it is thus considered that the natural regeneration has reached completion. However, 45.1% (height > 0.5 m) and 95.5% (height > 1.2 m) of M. stellata individuals were regenerated by sprouting. Further research is needed into how individuals, regenerated from seedlings, develop and reach sexual maturity, and how successive generations change.