Re A. araucana:
At some times of the year I presume those branches, bristling with pointed leaves, must be good at garnering moisture by condensation overnight and from mists. I know some animals (beetles) and plants do that in Chile, but I'm not sure in which parts; presumably as an adaptation it is most likely in areas of low rainfall.
As saplings, the tough and pointed leaves must be a deterrent to browsing animals. But one could wonder why they retain their pointedness when older and/or above browsing height. Could be a reflection of the existence o tree-dwelling/climbing browsers that are now extinct, I guess. Holes in that argument, though.
Just thinking aloud, wondering if the pointed leaves were a particular adaptation or an incidental characteristic.