Conserving weedy natives: Two Tasmanian endangered herbs in the Brassicaceae

Abstract

Two species of endangered Brassicaceae, Barbarea austratis and Lepidiuni iiyssopifolium, occur in a few small populations in Tasmania. The former species is associated with streams where it occurs in vegetation with numerous exotics. The latter species is usually found in the root zone of exotic large trees, usually on roadsides, and often in the absence of many other native species. Populations of both species have disappeared since European settlement, some in the last two decades. Both species are rapid and prolific producers of easily germinated seed. Both species are absent from places grazed moderately or intensively by sheep or cattle. The establishment of new individuals of Leptdiuni occurs only on relatively bare ground. The species is tolerant of root competition and intolerant of above ground competition. It will also establish from soil-stored seed after mechanical disturbance. Its future is linked to the survival of grazing-free locations where above ground competition from herbs and grasses is subdued. Barbarea is a ruderal that requires freedom from stock grazing for its persistence in Tasmanian riparian habitats. These results reinforce the importance of some degraded ecosystems for biodiversity conservation, and the critical role of disturbance regimes in influencing the survival or extinction of a subset of native plant species. In the fragmented and variegated landscapes of today, weedy natives cannot necessarily be expected to survive in non-weedy environments.

Fire management in Tasmania’s Wilderness World Heritage Area: Ecosystem restoration using Indigenous‐style fire regimes?

“…Such segregation into remnants has occurred in temperate lowland grasslands and grassy woodlands on the mainland of Australia (Lunt 1997). An extreme case is that of the endangered herb, Lepidium hyssopifolium , which now largely depends on the survival of large exotic trees on ungrazed roadsides and farmyards (Kirkpatrick & Gilfedder 1998). The reinstatement of an Indigenous‐style fire regime in all remnants of lowland native grassland could be a recipe for accelerated extinction.…”

Frequent mowing is better than grazing for the conservation value of lowland tussock grasssland at Pontville, Tasmania

“…Scarlett & Parsons 1990;Gilfedder & Kirkpatrick 1994, 1998bPyrke 1994;Morgan 1995;Kirkpatrick & Gilfedder 1998) and in maintaining the condition of these ecosystems (Stuwe & Parsons 1977;Fensham & Kirkpatrick 1989;Prober & Thiele 1995;Gilfedder & Kirkpatrick 1998a), the aim of the present paper is to determine whether frequent mowing with removal of slash is a better option for lowland tussock grassland, and the rare or threatened species that occur within it, than a moderate level of sheep grazing.…”

The positive and negative conservation impacts of sheep grazing and other disturbances on the vascular plant species and vegetation of lowland subhumid Tasmania

“…In the early 1990s, the abundance of each of several rare or threatened plant species was measured in plots across their ranges (e.g. Gilfedder & Kirkpatrick 1994; Kirkpatrick & Gilfedder 1998). These populations were revisited in 2002 and notes made of their persistence, decline or increase, and any change in land use.…”

“…However, there is a growing recognition that the survival of many other native vascular plant species may depend upon the persistence of some of these disturbances and disturbance regimes (e.g. Cropper 1993; Gilfedder & Kirkpatrick 1994; Lunt 1997; Kirkpatrick & Gilfedder 1998).…”