Effect of fire on the topsoil seed banks of rehabilitated bauxite mine sites in the jarrah forest of Western Australia

Abstract

Summary Germinable seed stores of 5‐ and 8‐year‐old rehabilitated bauxite mine pits in south‐west Western Australia were assessed before and after burning. These seed stores were compared to those of adjacent unmined Jarrah (Eucalyptus marginata) forest, to identify at what age fire can be reintroduced, in order to measure restoration success and reduce fire hazard. Soils were sampled in early summer (before fire) and late autumn (after fire). Before fire, the mean topsoil seed bank of 5‐year‐old sites was 2121 seeds per m2 while 8‐year‐old sites had a mean of 1520 seeds per m2. Only the 5‐year‐old sites were significantly different from the forest mean of 1478 seeds per m2 for the same season. After summer burns (and possibly due to seasonal effects) topsoil seed banks of rehabilitated areas (sampled in autumn) decreased by an average of 53 per cent. Topsoil seed banks of 5–8‐year‐old sites were resistant to lower intensity burns, with 362 seeds per m2 of native species surviving mild burns and 108 seeds per m2 of native species surviving after an intense summer fire. The topsoil seed reserve of 5–8‐year‐old rehabilitated areas had a high proportion of annual weed species while the forest sites had high levels of subshrubs and native annuals. Low‐intensity burns did not alter the composition of life‐forms in the soil seed bank, while intense burns favoured annual weed and shrub species. The results indicate that it is not appropriate to introduce fire to rehabilitated areas before 8 years, due to limited fuel reduction benefits and possible adverse effects on obligate seeding species. The large proportion of weed species in the soil seed bank of young rehabilitated areas is a concern, and remains a major consideration for future disturbance of these areas.

Long-term impact of prescribed burning on the nutrient status and fuel loads of rehabilitated bauxite mines in Western Australia

“…From these studies, papers have been published on fire behaviour, vegetation structure and fuel loads (Grant et al, 1997a;Smith et al, 2003), post-burn tree characteristics (Grant et al, 1997b), understorey vegetation characteristics (Grant and Loneragan, 1999), community and successional studies (Grant and Loneragan, 2001), and topsoil seed stores (Grant and Koch, 1997;Smith et al, 2000). However, only one previous study has examined the impact of fire on the nutrient status of rehabilitated areas (Ward et al, 1991) and this study only examined the immediate effects of fire on nutrients in older style rehabilitation.…”

Structural development of vegetation on rehabilitated North Stradbroke Island: Above/belowground feedback may facilitate alternative ecological outcomes

“…While the suppression of fire is a beneficial part of the rehabilitation process to prevent scorching of juvenile species, it likely inadvertently influenced the accumulation of Black Sheoak litter among certain rehabilitated forest blocks and further exacerbated its detrimental effects on the development of mid-storey and ground-storey vegetation therein. Since black sheoak is part of the native coastal landscape, the implementation of selective thinning and carefully managed fire regimes would help to reduce the incidence of mono-dominant stands in favour of the desired native mixed-eucalypts, as suggested by Chaffey and Grant (2000), Smith et al (2001Smith et al ( , 2004, and later Shackleford et al (2013) for the management of undesirable species among similar Australian forest ecosystems.…”

Phosphorus fertilisation and large legume species affect jarrah forest restoration after bauxite mining

“…Furthermore, since the large seeded legumes are all in the re-seeder category, these species were excluded from analyses of the effect of P and large legumes on re-seeder species. Species were classified as re-sprouters and re-seeders based on published literature (Bellairs and Bell, 1990;Bell et al, 1993;Ward et al, 1997;Smith et al, 2000;Norman et al, 2006;Burrows et al, 2008). Native ephemerals and weed species were classified based on the FloraBase database (Western Australian Herbarium, 2012).…”