How do sun spots affect tree growth?
This area of research has a long history, since a record of tree growth is found in the thickness of the rings seen in a cross-section of a tree trunk. In addition, the proportion of Carbon 14 contained in trees is another proxy indicator of solar activity. There have been many studies of the variation of these quantities over the past 20,000 years which reveal temporal periods that are also known to exist in the solar activity cycle. However, the physical mechanisms linking sunspots and tree growth are poorly understood. The mechanism linking sunspots and Carbon 14 is fairly well-established to be the modulation of cosmic rays by the solar cycle. I am not up to date in this area, but here is a review volume from 1991 which has articles which may be useful: “The Sun In Time” –CP Sonett, MS Giampapa, & MS Matthews, U. Arizona Press. In particular, the articles starting on pages 360 and 562 are relevant. You might also consider contacting Charles P. Sonett (one of the editors & authors
