Germination testsFor native species reforestation, species selection is critical. At the same time, accounting for intraspecific variation is critical for its success. Establishment success and growth in plantations may vary substantially within several meters, which may be due to differences in maternal origin (seed source). We found that germination and subsequent survival may differ substantially by maternal origin, with some trees having no germination inter-annually (Sugiyama & Peterson 2013). Seeds with high potential came from maternal trees near the forest edges where fruits and seeds were larger, which are traits easily determined in the field, and which can help in predicting where high-quality seeds may be collected.

Scarification testsMultiple projects on intraspecific variation and seed sourcing are ongoing. In another project, we assessed intraspecific variation in seed characteristics along wide elevational gradients. In species like legumes, seeds have hard seed coats and are under physical dormancy where they do not germinate unless seed coat is damaged. A file, hot water, or sulfuric acid is commonly used to manually scarify seeds but optimal treatment may differ, not only by species but also by the seed source. Because germinating seeds is the first step in obtaining seedlings necessary for restoration, being able to predict and identify the best treatment for each seed source would improve efficiency and reduce seed waste. We studied how optimal scarification conditions may differ by seed source in a tree species that occur over a ~1800 m elevational gradient. To evaluate optimal treatment using hot water, we developed an index (‘scarification index’) which integrates imbibition, germination, germination time, abnormalities, early mortality, seedling growth, and seedling survival. We found that seeds from lower elevation and warmer climate required more intense treatment than seeds from higher elevation (Sugiyama et al. 2021). Even when seed coat was visibly intact and seeds did not absorb water, repeated exposure to hot water had negative effects on post-germination processes although germination was not reduced. By recording how many scarification treatment attempts were required before seeds absorbed water, we showed that we might be able to screen seeds that would result in high-quality seedlings.