Transition from heathland to scrub in south-eastern Tasmania: extent of change since the 1970s, floristic depletion and management implications

Abstract

Heathland is a speciose and floriferous vegetation type, defined by its stature (\2 m) and dominance by scleromorphic shrubs. Heathland has been in decline globally, and much of its loss has been due to less frequent fire, while in some places more frequent fire has resulted in degradation through the loss of obligate seeding species. The aims of the present study were to determine: (1) the extent of the transition from heathland to scrub in south-eastern Tasmania, Australia between c1976 and 2013; (2) the spatial attributes of heathland that are likely to have been the most instrumental in heathland loss; (3) whether the transition to scrub resulted in the loss of local species richness and changed species composition when taking both above ground vegetation and the soil seed bank into account; and (4) the implications of the answers to the first three questions for heathland management. Changes in heathland and scrub extent were mapped from remote sensing imagery and ground truthing. At one locality with floristic data from the heathland of 1976, the scrub that has replaced the heathland was surveyed and soil collected to determine seed banks under heating and non-heating treatments. Approximately one third of the 1976 heathland had become scrub by 2013, mostly around the margins of heathland patches and near built up areas. Twenty-two species present in 1976 were not found in either the scrub or seed bank, with only three species absent from the scrub, but present in the 1976 heath, being found in the seed bank. The species composition of germinates in the unheated treatment was dominated by taxa that colonise mechanically disturbed areas, such as Juncus, while germinates in the heat treated soils were largely scleromorphic heath species. The depletion of species richness by the transition to scrub, and the large extent of its 123Biodivers Conserv (2015) 24:213-228 DOI 10.1007 incidence, suggest that a higher frequency of planned fire is needed in south-eastern Tasmania.

Holocene heathland development in temperate oceanic Southern Hemisphere: Key drivers in a global context

“…Fire regulates interspecific interactions and resource availability in heathlands and is important in maintenance of heathland structure and composition (Bargmann & Kirkpatrick, 2015). Frequent fires help to prevent the conversion of heathland to scrub and forest by suppressing tree establishment and in some cases, especially in wet climates, reducing soil nutrients required for tree growth by inducing soil erosion/leaching (Jackson, 1977(Jackson, , 1978.…”

Effects of fire regime on plant species richness and composition differ among forest, woodland and heath vegetation

“…Repeated short inter‐fire intervals (<5–7 years) can cause: declines in species richness; local extinction of species that rely on seed for post‐fire regeneration (obligate seeders); and divergence in species composition towards herbaceous, fire‐tolerant species (Cary & Morrison, ; Penman, Binns, & Kavanagh, ; Penman, Binns, Shiels, Allen, & Kavanagh, ). Similarly, long periods of fire exclusion can lead to low plant richness, diversity and evenness by either allowing mid‐storey shrubs to dominate and exclude understorey species (Bargmann & Kirkpatrick, ; Freestone, Wills, & Read, ; Keith & Bradstock, ; Tozer & Bradstock, ), or by exhausting the seed bank of short‐lived species (Lamont, Le Maitre, Cowling, & Enright, ). In contrast, variability in the length of inter‐fire intervals has been associated with greater richness and evenness in plant communities (Morrison et al., ).…”

Impact of changes in lightning fire incidence on the values of the Tasmanian wilderness world heritage area

“…Tis variability relates to the fre adaptations and dispersal capacities of the species present in the previous state and the distance of the area that has experienced a transition from surviving vegetation in the previous state. For example, vegetation that has changed from heathland to scrub may return to a structural heathland after a fre event, but at the cost of the loss of those taxa which do not have a persistent seed store or well dispersed seeds (Bargmann & Kirkpatrick 2015).…”