Environment and dynamics of weed seed banks and seedling emergence.

BENECH ARNOLD R.L.; BATLLA D.

Persistence Strategies of Weeds.

Wiley

Año: 2022; p. 87 - 105

Weedy species that rely on sexual reproduction perpetuate themselves via seeds. Seeds dispersed to the soil from the mother plant can germinate immediately, or they can remain as non-germinated for an indefinite time period. Seeds in the soil, whether on the surface or buried at different depths, form what is called "the seed bank". Depending on the physiological attributes of the seeds that form them (i.e., dormancy, longevity, requirements for germination, etc.), these banks can function as highly efficient sources of seedling emergence and dispersion over time. Since their recognition as such, seed banks have been classified based on different aspects which determine their function. The most used classification has been that of Thompson and Grime (1979) which identifies four types of seed banks: Type I and Type II are considered transient (i.e. no seed lasts more than a year in the soil) and normally correspond to species that germinate in early fall or early spring, respectively. The seeds of species that form Type I banks are present in the soil during the summer only, while those of species that form Type II banks remain only during winter. Seeds that form both types of bank normally exhibit dormancy which is relieved by high temperatures in summer in the case of species that form banks Type I, and by the cold winter temperatures for species that form Type II seed banks. In Type III and IV banks, a lesser or greater fraction of the seed population becomes part of a persistent bank and survives for more than a year (Thompson and Grime, 1979). Thompson et al. (1997) proposed a new classification with only three categories, which better takes into account the longevity of the seeds more than the previous classification: i) species whose seeds last less than one year in the soil form transient banks. ii) species whose seeds survive one to five years in the soil form banks of short persistence; iii) species whose seeds last for at least five years form banks of long persistence.