Germination Strategies During Grassland Succession

Abstract

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Why do we need permanent plots in the study of long‐term vegetation dynamics?

“…In this case, the number of species indicative of nutrient-poor conditions increased in permanent plots after cessation of fertilizer application; not suddenly, but gradually over a period of 20 yr. On the basis of this information it was hypothesized that a pool of highquality organic matter was slowly disappearing, leading to a gradual decrease in N-mineralization rates. This was then confirmed by in situ measurement of N-mineralization rates in a chronosequence, which was validated using permanent plot information (Olff et al 1994b). Long-term studies have also provided valuable data about the dependence of forest community succession, after clearcutting, on the dynamics of the soil nutrient pool (Bormann & Likens 1979;Reiners 1992) or about the pollution-induced changes in biogeochemical processes and resulting changes in vegetation structure and composition (Tamm & Popovic 1995;Falkengren-Grerup 1995).…”

Effect of scarification and temperature on seed germination of two Mexican species of Mimosa (Leguminosae-Mimosoideae)

“…Saturation Rate (SR).-it is defi ned as the time for germination in relation to the germination percentage: SR = Σ(n i t i )/N, where n i = number of germinated seeds in one day (i); t i = number of days after sowing, N = total number of seeds sown. Optimum Temperature (OT).-it was calculated as the average of all temperatures, weighted with the total seed germination percentage, at each temperature (Olff et al, 1994).…”

Impact of different‐sized herbivores on recruitment opportunities for subordinate herbs in grasslands

“…From rabbits, fresh droppings were collected within a few m 2 per sample (distance between samples at least 10 m). The dung samples were weighed and stored for two weeks at 5 ∞C to improve germination of the seeds (Olff et al 1994). Afterwards, the dung samples were spread out in a tray in the greenhouse on sterilized potting soil topped with white river sand.…”