The annual number of trees (total n = 160) assumed to have arisen by asexual regeneration was related to: (1) summer temperature (mean = 10.0 °C, SE = 0.14); (2) summer precipitation (mean = 84 mm, SE = 3.46); (3) moth damage to birch, possibly affecting aspen asexual reproduction and survival; high positive values point to increased damage (mean = -0.03 negative birch-minus-pine indices, SE = 0.03).