Can anyone shed some light on the symbiosis between alder and sequoia sempevirens? We grow various provenances of sequoia sempevirens (coast redwoods) here on Mauna Kea in Hawaii. We're in a cooler higher elevation where ample moisture makes it very easy to grow redwoods. We discovered that the redwoods grow better in the companionship of alders (in this case Alnus Acuminata which looks identical to the red Alder of the PNW.) It's a Frankie bacteria nitrogen fixer, but not all nitrogen fixers are necessarily good companions. Any insight would be appreciated.
I'm not seeing a lot in the scientific literature, mostly incidental references to Alnus when discussing co-occurring species in Sequoia forests, e.g., https://digitalcommons.calpoly.edu/...er=&httpsredir=1&article=1016&context=nrm_fac What is the soil like for nitrogen in general? I'm seeing this article, but it's on the much older Kauai: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6323096/ Glad to learn of your bioreserve! Maybe I will book a tour next time I'm there!
Red Alder is morphologically similar to many other taxa and shows a close relationship to the south and central American species A. acuminata, A. jorullensis and A. oblongifolia, it is also similar to A. incana; in the absence of provenance details A. rubra can be distinguished from these taxa by its recurved leaf margin. It is also distinguishable by its ovate leaves with coarse toothing, and smooth grey bark Alnus rubra - Trees and Shrubs Online
Daniel, happy to host you for a tour. I tried Google and got this result: https://gualalariver.org/nature/tre...rest Succession,groves and under the redwoods. So apparently they grow together mostly further up the coast where it's wetter. I was hoping to get additional anecdotal info here. Soils here are nitrogen, calcium, sodium and magnesium deficient. The magnesium and sodium deficiency is a great thing since redwoods dislike both. (https://ucanr.edu/sites/forestry/Ecology/Identification/Coast_Redwood_Sequoia_sempervirens_198/) But the nitrogen deficiency can be a problem. Now conifers as a whole are nitrogen sparing which may be why they grow so well. But my experience with nitrogen fixers is that not all are beneficial. For example Inga feuieii from the Andes has highly competitive and aggressive roots that outcompete surrounding trees. I've only had success using it as a nitrogen fixer by aggressively pruning to keep small. As a whole, after about 3-5 years any conifers planted here stops needing any sort of care.
I'd assume it is most likely due to nitrogen enhancement by those Frankia bacteria. Do other conifers elsewhere in the range of Red Alder also benefit? If it is nitrogen fixation, I'd think other conifers would benefit.
