Freshly-collected seeds of twenty species of annual weeds were uniformly mixed with 2-5, 7-5 or 15 cm of soil confined in cylinders sunk in the ground outdoors. The soil was either cultivated four times a year or left undisturbed, seedling emergence was recorded, and after 5 years the numbers of viable seeds remaining were determined.Total seedling emergence from seeds incorporated to 2 5, 7-5 and 15 cm amounted to 75, 65 and 54% respectively of those added when the soil was cultivated, and 58, 36 and 21% where it was left undisturbed. The corresponding numbers of viable seeds remaining after 5 years were 2_-3, 4-0 and 7-7% respectively for cultivated soil, and 6-8, 16-5 and 31-6% of the seeds initially added and then not disturbed. Individual species varied in their responses to increasing depth of incorporation and to cultivation; these differences are discussed in relation to the dormancy characterbtics of the seeds. Devenir des semences de quelques mauvaises herbes annuelles d differentes profondeur dans un sol cultivS et non cultivêZusammenfassung. Frisrh gesammelte Samen von zwanzig Arten annueller Unkrauter wurden mit Boden gleichiormig gemischt und In Zylindern in 2,5; 7,5 oder 15 cm Tiefe draussen im Boden gclagert. Der Boden wurde entweder viermal im Jahr bearbeitet oder blieb unbcarbeitet. Das Auflaufen der Samen wurde ermittelt, und nach 5 Jahren wurde die Zahl der lebensfahig gebliebenen Samen bestimmt. Der gesamte Auflauf der Samen, die in 2,5; 7,5 und 15 cm Tiefe eingebracht worden waren, belief sich bei dem bearbeiteten Boden auf 75; 65 und 54% der untcrgemischten Samen. Im nicht bearbeiteten Boden waren cs 58; 36 und 21%. Die entsprechende Anzahl der nach 5 Jahren noch lebensfahig gebliebenen Samen belief sich im bearbeiteten Boden auf2,3; 4,0 und 7,7% und im nicht bearbeiteten Boden auf 6,8; 16,5 und 31,6% der ausgcbrachten Samen. Vcrsrhiedene Arten zeigten in ihrer Reaktion aufdie zunehmende Tiefe ihrer Aussaat und aufdie Bearbeitung ein abweichendes Verhalten. Diese Unterschiede werden in Bczug zu den DormanzcharaktcHstika der Samen diskutiert.

No abstract

Summary. In a 6‐year experiment with a naturally occurring population of viable weed seeds, the numbers in the top 9 in. of soil decreased exponentially from year to year in the absence of further seeding. The rates of loss were equivalent to 22% per year in undisturbed soil, 30% per year on plots dug twice a year (March and September) and 36% per year on those dug four times a year (March, June, September, December). Seed numbers of individual species also decreased exponentially, although not all at the same rates. On the dug plots, the numbers of seedlings that emerged each year decreased exponentially once the regimes had become established. The proportions of the viable seeds which gave rise to seedlings in the course of a year were 7 % on plots dug twice and 9 % on those dug four times a year; although there was some variation, these proportions remained much the same from year to year. On undisturbed soil the number of seedlings that emerged declined rapidly, and in the 4th year represented no more than 03% of the viable seeds still present in the top 9 in. of soil.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Applied Ecology. SUMMARY(1) The extent to which plants form a persistent seed bank and the time of year at which seedlings arise from it both have a bearing on the establishment of vegetation after disturbance. These attributes were determined for seventy dicotyledons from a range of habitats by mixing freshly-collected seeds with the top 7.5 cm of soil confined in cylinders sunk in the ground, cultivating three times yearly, and recording emergence for 5 years.(2) In about one-third of the species, few seeds persisted for longer than a year and most seedlings emerged in the autumn of sowing (Sherardia arvensis*, Galium mollugo) or early in the following spring (Chaerophyllum temulentum, Pimpinella saxifraga, Agrimonia eupatoria, Tragopogon pratensis).(3) The remaining species formed a persistent seed bank in cultivated soil from which seedlings arose in each year for which the experiments continued. Some exhibited a consistent pattern of emergence entirely (Odontites verna, Linum catharticum) or mainly (Brassica nigra, Silene dioica) in spring, while others (Hyoscyamus niger, Erodium cicutarium, Amaranthus retroflexus) emerged in late spring and summer. Emergence of Arenaria serpyllifolia, Cerastium glomeratum and Anthriscus caucalis was mainly in early autumn, while that of Legousia hybrid began in autumn and continued into spring.(4) Other species showed no pronounced pattern of emergence in successive years. Although there was often a tendency for most seedlings to emerge in spring or autumn, some appeared throughout the growing season with flushes following soil disturbance. Included in this group were Barbarea vulgaris, Coronopus didymus, Ballota nigra and Dipsacus sylvestris.(5) There were consistent differences between species in the extent of immediate emergence, seed survival in disturbed soil and in the seasonal pattern of emergence. Seeds of annual weeds of arable land were all relatively long-lived, but otherwise there appeared to be little relationship between seed persistence and habitat. The results provide indications of the potential for regeneration by different species from the seed bank after disturbance of a plant community and of the times of year at which it is likely to take place.

Summary. Four replicated experiments were begun in successive years to study the behaviour of viable seeds of eleven species of annual weeds when mixed with a 3 in. layer of cultivated soil. The soil was confined in pots sunk in the ground outdoors, seedling emergence was recorded, and the numbers of viable seeds remaining at the end of the experiments were assessed. One experiment was continued for 3 years, the others for 5 lull calendar years after the freshly collected seeds had been sown. Initial emergence was greatest with Stellaria media, Senecio vulgaris and Poa annua, and least with Chenopodium album and Thlaspi arvense. Subsequently, the numbers of seedlings which emerged each year declined at a rate which was constant for each species. In the fifth year after sowing, the number of seedlings of Senecio vulgaris was only 0.3% of the initial number of viable seeds, while for Thlaspi arvense and Veronica hederifolia the figure was 3.2%. The proportions of viable seeds which produced seedlings ranged from 37 to 86%, while from 0 to 11% were still present in the dormant state after 5 years. Most species showed marked patterns in the seasonal distribution of emergence which were modified by variations in weather from year to year, but in any one year, the distribution of emergence was not influenced by the length of time the seeds had been in the soil. Germination et longévité dans des sots cultivés de semences de quelques mauvaises herbes annuelles