Sorry about the long winded post...
...you never know who knows what so sometimes I try to just getit otta the way.
I see your point as this is beta, I wonder if it has to do with pollen.
I've read and watched videos on the re circulation of rads past through plants and the rise in beta counts as they release them with the spring budding.
I can't find the video on this right now but here's a article from japan on pollen studies...
http://fukushima-diary.com/2015/03/2540 ... 0-of-2011/