| Disruption of any community is usually followed by the almost immediate appearance of earlier successional species. This has been related to the presence of buried viable seed. To test for the presence of viable seed, soil samples were collected at Harvard Forest at 16 sites, representative of secondary succession in Massachusetts. These ranged from a 1-yr abandoned field to an 80-yr white pine stand that supported an understory of young hardwoods. When soil samples were collected, a list was compiled of all ground cover species at each site. Fifty-five ground cover species were recorded at the 16 stations, and of these, 41 were restricted to open fields and young pine stands, and 14 to a mature 80-yr pine stand. There were no ground cover plants in any of the fully-stocked, 21 to 47-yr pine stands. Germination tests of soils from all sites produced quantities of seedlings. In these tests 65 species, averaging 20 species per station were recorded. The 3474 seedlings recovered represented an average of 220 per square foot of soil surface sampled, with a low of 116 and a high of 466. Many of the field species occurred in essentially all soils tested, and 40 of the 64 which appeared in field samples produced 88.5% of the total seedling crop. The field species thus prevailed and dominated all samples except those from the mature pine stand. With maturation and opening of the stands, late successional and climax species appeared. Both short-lived and long-lived seed were among the seedlings recovered. The latter group included Juncus tenuis, Panicum capillare, Rumex acetosella and Danthonia spicata. It is proposed that viable seed in the forest soils had not been carried into the stands where they then filtered down through the litter-humus layers, but that they remained viable during long burial in the soils. The universality of secondary succession is assured by long term storage of seed in soils. |
Buried viable seed (file pdf, 1.270 KB)
