Hasegawa’s first novel would help us understand, at least through small pieces of evidence, that only Juraian royalty/higher ups hold rights to the usage of trees/powers. Kiyone is revealed to be Jurian, yet does not appear to hold any powers. She also discusses the power struggle between the nobility and the common people of the planet, which could infer both a struggle in the political sense, but one of firepower as well. If the nobles are outnumbered by the sheer amount of civilians, wouldn’t the civilians be able to put up some manner of threat to try and push for greater rights?
Similarly, in Kajishima’s novels he seems to only include nobility in the list of eligible Jurians for pairing with a tree. We only get to see them a handful of times, including the death of Mitsuki Amaki, but the trees with power appear to be inaccessible to civilians. This is cross-referenced between both sets of novels in stating that by pairing with a tree, it extends the Jurian Royalty’s lifespan by a considerable amount. Referring back to Hasegawa’s novels, she claims that the average Jurian’s lifespan was around 200 years, whereas a Jurian Royal would be granted 10 times that, often living upwards of 2,000 years.
While I understand a good chunk of your research does come from the Universe continuity, a majority of the evidence we’ll find is contained within the OVA. Unless explicitly stated otherwise, we should assume they follow similar rules.
