highly significantp ≤ 0.001
The highly significant agreement ( p ≤ 0.001) in ring width variations of radius a and b (i.e., a : b ) and radius a and mean of radii c and d (i.e., a : cd ), as well as mean of radii a and b and c and d (i.e., ab : cd ), are striking ( Figure 4 a–c).