Source: local data frame [4 x 2]

   site mean_volume
  (int)       (dbl)
1     1    23.82600
2     2    26.56333
3     3    23.05167
4     4    57.09600

Source: local data frame [3 x 2]

  experiment mean_volume
       (int)       (dbl)
1          1    22.03800
2          2    53.80425
3          3    22.06050