Because in Mount St. Helen some seeds and species were left and some turned back on their time causing the ecosystem of the area develop again.
Explanation:
Succession is a process in which change in a population or ecological community occurs due to disturbances or new colonization at a new habitat occurs such as Mount St. Helen's volcanic eruption.
The Mount St Helen's volcanic witnessed the major geological changes in 20th century. The full-grown forest got destroyed because of this and causing loss to flora and fauna.
There were species which completely perished and others survived.
The hibernating burrowing nocturnal animals were hiding deep in the furrow and survived the volcano.
The spring arrived late, it was another advantage as the ice covered lake has fishes and salamanders in the which were saved.
Some plants as willow, vine maple, black cotton survived the volcano and re sprouted because they had their roots protected in the moist soil.
Also, the birds migrated after spring when affects were over their population also increased.
The increase in plants attracted insects, butterflies, mammoth etc.
In history there are examples when whole life has perished at the volcanic site but in Mount St. Helen species fought back and made most from the ecological disturbance caused.
