Plant Protection Quarterly Vol.26(2) 2011 47 populations where they are invading na- tive plant communities. Specifi cally, we Seed dynamics of the invasive geophyte Lachenalia investigated seed viability and persistence in the soil seed bank of L. refl exa. refl exa Thunb. in south-west Australia Methods Kate Brown and Grazyna Paczkowska, Department of Environment and Study area and seed burial site Conservation, Swan Region, PO Box 1167, Bentley Delivery Centre, Western The site chosen for the burial of L. refl - Australia 6983, Australia. exa seed was on the Swan Coastal Plain in Woodvale Nature Reserve (31°47'03"S, 115°46'55"E), within close proximity to the city of Perth, Western Australia. The dis- turbed Banksia attenuata, Eucalyptus wood- land on the Spearwood Dune System of the reserve are species rich, (average of Summary and Longman 2004). Protection and res- 55.2 species in a 10 × 10 m quadrat) with Geophytes from South Africa’s Cape toration of remnant vegetation across the an understorey of shrubs, herbs, sedges Province are a particularly serious group region often requires an understanding of and grasses (Gibson et al. 1994). Dense of invasive plants in south-west Aus- how to manage invasive geophytes. populations of L. refl exa were present in tralia. They threaten natural biodiversity Lachenalia, in the family Asparagaceae, the understorey of the woodlands at the across the region, invading relatively is a genus of around 120 species of winter seed burial site. undisturbed habitat and displacing na- growing geophytes endemic to South Af- tive plant communities. Their success as rica and Namibia (Duncan et al. 2005). Na- Initial seed viability invaders has been linked to rapid and tive to the Cape Floristic Region, Lachenalia Seed was collected at Woodvale Nature profuse seedling germination, however refl exa (yellow soldier) was fi rst recorded Reserve from mature fruits of approxi- studies on a number of species have doc- as naturalized in south-west Australia mately 200 plants scattered through natu- umented short lived soil seed banks. This in 1938 (Western Australian Herbarium ralized populations of L. refl exa in Novem- study investigates seed viability and soil 1998–2010). It is now a serious weed of ber 2004. seed bank persistence of the Cape geo- Banksia/Eucalyptus woodlands on the Initial seed viability was determined phyte, Lachenalia refl exa Thunb. where western side of the Swan Coastal Plain in germination tests carried out in Janu- it is invading Banksia woodlands on the and has recently been the target of a re- ary 2005. Five replicates of 25 seed were Swan Coastal Plain, Western Australia. gional weed strategy in south-west Aus- placed on agar (0.75%) and placed in Seed was collected from naturalized tralia (Bettink 2009). With a single annu- growth cabinets at 15°C with a 12 hour populations in the summer of 2004/2005 ally renewed bulb, L. refl exa disperses into photo period. Seeds that did not germi- and placed in nylon mesh bags buried at bushland mainly by small (2 mm) shiny nate after 10 weeks were assessed for vi- two different soil depths, in replicated black seed that have a tiny arilode. Papery ability using a cut test. Seeds were scored plots across fi eld sites (February 2005). capsules contain 60–100 seed and there as viable if a fi rm, white, moist endosperm Samples were retrieved and assessed in are up to 10 capsules per plant. Seed is was present (Ooi et al. 2004). May, July and September 2005, Septem- released in late spring or summer and ap- ber 2006 and September 2007. pears to disperse via water into bushland Soil seed bank persistence Initial tests found 95% seed viability. following autumn rain. Seed was placed in 15 × 20 cm nylon mesh More than 90% germinated or rotted in Although appropriate control methods bags containing 200 g sterile sand to keep the fi rst autumn/winter. No viable seed are well documented (Brown et al. 2002, individual seed separated, and buried in remained at the 10 cm depth by Septem- Brown and Brooks 2003) there is little February 2005 in fi ve plots placed across ber 2006 or at the 1 cm depth by Septem- known about ecology or reproductive bi- naturalized populations of L. refl exa. In ber 2007. The results show that L. refl exa ology where L. refl exa is invading native each plot 20 bags were buried, each bag seed have high initial viability but do plant communities. In particular, seed via- containing 500 seeds. Ten bags were bur- not persist in the soil seed bank for more bility, patterns of seedling emergence and ied in the top 1 cm of soil and ten bags than three years. persistence of naturalized populations in were buried at 10 cm. These depths were Keywords: Invasive, geophyte, germi- the soil seed bank are not well understood. chosen to refl ect natural seed burial depths nation, viability, soil seed bank, Lache- This information is critical for understand- following dispersal with 1 cm represent- nalia refl exa. ing how to manage invading populations ing superfi cial surface burial versus burial over time including the length of any con- resulting from substantial soil disturbance Introduction trol program. (10 cm). Chicken wire was secured over A detailed understanding of the biology of There are few detailed studies on the each plot to protect the site from rabbit invasive plant species underpins effective seed ecology of individual species of and bandicoot diggings. The soils across weed management strategies (Hobbs and geophytes where they occur naturally in the site were uniform grey to orange light Humphries 1995, Mortensen et al. 2000). South Africa. However it is generally as- sand. Knowledge of seed biology in particular sumed that seed of many geophytes are One bag per soil depth was recovered provides an understanding of patterns in not persistent in the soil seed bank (Man- from each plot in May, July and September recruitment of an invasive species and the ning et al. 2002, Keeley et al. 2006). There is of 2005, September 2006 and September potential persistence of populations over also evidence that for some species seed- 2007. Seeds recovered in May and July time. ling recruitment and population expan- were scored as either potentially viable With the capacity to invade undisturbed sion occurs in a small window following if they were fi rm and intact or as germi- bushland and form dense monocultures, fi re (Le Maitre and Brown 1992, Keeley nated/rotted if they were not. It was not South African geophytes are a particularly and Bond 1997). possible to separate germinated from rot- serious group of invasive plants in south- The objective of this study was to in- ted seed. Following retrieval in Septem- west Australia. A total of 53 species have vestigate the seed biology of L. refl exa and ber 2005, 2006 and 2007, seed that were been recorded as naturalized (Keighery gain an understanding how to manage still intact were assessed for viability in 48 Plant Protection Quarterly Vol.26(2) 2011 growth cabinets at 15°C with a 12 hour 600 photo period. Seed that did not germinate after 10 weeks were assessed using a cut test and were scored as viable if a fi rm, 500 white, moist endosperm was present. 400 Results Initial germination tests indicated seed 1 cm was 95.2% viable with all germination oc- 300 curring within 18 days. 10 cm Of the seed buried at 1 cm, 18.8% (±1.3) were still viable when retrieved in May 200 2005 and 8.74% (±3.8) were still viable in July. By September 2005, 3.3% (±1.5) re- 100 mained viable. In September 2006 1.3% seed viable of Number (±1.1) remained viable and by September 2007 no seed of L. refl exa buried at 1 cm 0 remained viable. Feb-05 May-05 Jul-05 Sep-05 Sep-06 Sep-07 Of the seed buried in the fi eld in Febru- ary 2005 at 10 cm, 5.96% (±1.9) were still viable when retrieved in May and 0.24% Figure 1. Number of seed that remained viable buried at 1 cm and 10 cm (±0.2) were still viable in July. By Septem- over three years. ber 2005, 0.04% (±0.4) was still viable. By September 2006 bags buried at 10 cm con- tained no viable seed (Figure 1). seed bank persistence of native geophytes California chaparral. International Jour- Discussion of the Californian chaparral (Keeley 1994, nal of Wildland Fire 18 (5), 623-30. The results of our study indicate that the Tyler and Borchert 2002, Keeley et al. Brown, K. and Brooks, K. (2003). ‘Bush- seed from naturalized populations of L. 2006). land weeds: a practical guide to their refl exa has high viability (95.2%) with ger- While seed plays a crucial role in the management’. (Environmental Weeds mination occurring relatively rapidly, all recruitment of individuals and expansion Action Network, Greenwood). within 18 days, under controlled condi- of populations, the persistence of popula- Brown, K. and Paczkowska, G. (2008). tions. With more than 80% of seed ger- tions over time depends on the annually Seed biology of two invasive South Af- minating/rotting within three months of renewed bulbs of L. refl exa. While care- rican geophytes and implications for burial (May 2005) in the fi eld, indications fully targeted, selective herbicide appli- natural area management. Ecological are that germination also occurs relatively cation over one or two years will result Management and Restoration 9 (3), 232- rapidly under fi eld conditions.