French broom5/26/2023 ![]() ![]() In autumn 1999, broom seeds were sifted directly from the soil and counted and classified as germinable, deeply dormant or dead. All non-germinating and non-viable seeds were classified as dead. Non-germinating but viable seeds were classified as deeply dormant. Viability for those scarified but not germinating, was assessed via tetrazolium red tests. If the seed turned green and imbibed water it was classified as shallowly dormant. Dormancy was checked by scarring the seed coat with a scalpel and placing the seed on damp filter paper overnight. "California Exotic Pest Plant Council (CEPPC) group" - species highlighted as causing serious problems in California wildlandsĪfter germination appeared to have ceased, the soil was sifted to remove any ungerminated broom seeds. Native forbs - important components of diversity and indicators of grassland healthĮxotic annual grass and exotic forb s - primarily of Mediterranean origin and making up a large percentage of California grassland species and coverĮxotic perennial grasses - of European origin, relatively recent introductions and potentially very aggressive, invaders Native perennial grasses - typically the focus of grassland restoration and management activities Seedlings of all species were identified, counted and removed as they appeared. Broom germination in California occurs from December through July. The volume of soil collected was within the range recommended for characterization of grassland seed banks.Īutumn 1998 samples were spread individually into small trays with potting soil and placed in a lathehouse to germinate from November 1998 to August 1999. A soil core depth of 10 cm was used as Scotch broom seeds do not germinate below 8 cm depth and very few broom seeds occur below 10 cm. ![]() In larger stands, two transects were placed to best cover the centre area, and up to 10 cores taken. For small stands (<6 m diameter), one transect was placed through the centre and pairs of cores taken every metre. The seed bank of each broom stand was sampled with soil cores (5.5 cm diameter x 10 cm depth) at regular intervals along transect lines. However, land managers verified the age estimates. These ages are an estimate of the minimum stand age, as in California, Scotch broom plants live up to 17 years, and French broom around 15 years, so the oldest plants may have died by the time of sampling. Stand age was assessed by counting growth rings of plants with the largest stem diameter. Stand age and seed bank sampling: In autumn 19, 13 broom stands that had established within grasslands were sampled. French and Scotch broom have similar life histories and for the purposes of this study, no distinction between their seeds was made. In a few cases, Scotch broom Cytisus scoparius (another introduced European species) was also present but where it occurred made up less than 5% of plants with a correspondingly small seed bank. ![]() Sites were chosen with dense French broom cover. and brome Bromus spp., with a mix of native and exotic forbs. oat Avena spp., annual fescue Vulpia spp. Common species in the study areas include many naturalized annual grasses of European origin, e.g. The climate is Mediterranean, with cool wet winters and warm dry summers. Study sites: The effects of prescribed burning on invasive French broom Genista monspessulana was undertaken on coastal grassland sites within protected areas in Marin County, California, southwest USA. The relationship between broom stand age and seed bank size was also examined. This study examined the effect of repeated burning on French broom and associated grassland species. Prescribed burning has been used in attempts to reduce broom cover and the seed bank. In coastal grasslands of California, USA, exotic French broom Genista monspessulana (native to Europe) may be invasive, forming dense stands and accumulating an abundant seed bank belowground. ![]()
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