Ohia trees are dying rapidly, Why?

[Midnight Rambler]

Part of the "yes, but" with ohia and albizia is that yes, ohia do indeed do just fine with more nitrogen. The problem is that it also does pretty well with low nitrogen, while other invasive plants that are nitrogen-limited can outcompete it when growing under albizia. Also, ohia requires a lot of sun in growing up, and albizia creates dense shade while koa doesn't. Ohia is very good at surviving as a small seedling or sapling for years until a treefall opens up a light gap, but albizia itself is so fast-growing that it's often able to fill in gaps from fallen albizia trees.

Also, the ohia rust fungus doesn't kill large ohia trees, or even affect them very much (thankfully). But it can severely weaken or even kill small seedlings, which happened to one I was growing, so it may be a long-term problem. There are many different strains of this fungus, which all attack plants in the same family as ohia but vary in how badly they affect different plant species. The one we have here killed nearly all the rose apple (which you can see big dead stands of in Hamakua), along with the Oahu nioi, a native relative of mountain apple that's barely surviving as small plants instead of the big trees that used to be around.

We can only hope that one doesn't get here that has the same effect on ohia, because our politicians and bureaucrats have shown little interest in stopping imports of cut eucalyptus branches for flower arrangements, which is how the fungus got here. OTOH, if one arrived that was deadly to strawberry guava, that would be the ultimate biocontrol for it!