Resin, I am picking your brain about something very arcane. Larix occidentalis is the largest growing larch. Why did the UK choose the summer-rainfall preferring Japanese larch for plantations? Seems like the western US one would have been at least as adaptable? Other western US conifers do great in the UK.
Thanks! Yes, Larix occidentalis grows the largest in the wild, eventually, but it is very slow-growing compared to European and Japanese Larches; also, being an interior species (its closest to the Pacific coast is over 150 km inland), it isn't well adapted to Britain's oceanic climate – the western US conifers that do so well here are all coastal (e.g. Sitka Spruce, rather than the Engelmann's Spruce that occurs together with Western Larch). The tallest UK Western Larch is only 34 m and is very slender, compared to the tallest UK European Larch at 48 m and Japanese at 45 m. For comparison, the UK's tallest: Coast Douglas-fir – 71 m Sitka Spruce – 66 m Grand Fir – 65 m Hope that helps!
Resin is there any recent academic research on why P. ramorum could target the larch plantations in the UK? Are larches in their native habitats like Japan considered threatened, too? Were any resistant ecotypes discovered?
Sorry, don't know the answer to that! I'd guess it is the particular strain of P. ramorum in Britain; and yes, if that strain were to reach Japan, it would likely hit the larches there too. Just have to hope that phytosanitary regs keep it out.
But as as counterpoint I did an informal study of the plant records for Larix kaempferi at, IIRC, MOBOT. At the time, years ago, they were one of the only gardens (along UC Berkeley) that had extensive records about provenance online. It seemed all of the supposed Japanese larches from non-wild seed suppliers had died...presumably of root rot. Most or all of the ones collected in Japan were still alive. This makes me think that the vast majority of non-wild-collected Japanese larches in the west had gone through a very narrow genetic bottleneck at some point. With animals, any immunologist will tell you the first thing that goes with inbreeding is the immune system. It's looking like the same might be true of plants, for obviously different reasons. Of course this isn't to say the current strain of P. ramorum in the UK isn't so strong that it might attack wild populations with high genetic diversity, so I agree it should be controlled insofar as that is feasible.
