Marram has been planted at Mason Bay since the 1930s, initially at Kilbride at the
southern end of the bay. Marram was probably also established from marinedispersed rhizome. When the Department of Conservation was formed in 1987 all
of the main Stewart Island dune systems contained marram grass, although many
of these systems contained large areas that were free of marram. Fiordland and
Rakiura National Parks now contain almost a third of New Zealand dune systems
of national conservation significance (Johnson 1992; Hilton 2006). The Department of Conservation is committed to eradicating marram from both areas.
Marram sites in Fiordland are sprayed annually, over just 1 or 2 days, using a
helicopter to access sites where marram has been recorded. In contrast, the marram
eradication operations on the west coast of Stewart Island involve the deployment
of 4–5 personnel over a 6-month period, from November to May. This operation is
probably the largest marram eradication program attempted.
The herbicide employed is a systemic, grass-specific chemical—native grasses
are probably more vulnerable to the herbicide than marram grass. At many
locations this has proved a minor issue, since marram commonly forms uniform
stands and the key native grasses have already been displaced. At some sites aerial
operations have been avoided to ensure that non-target species have not been
affected. Precision mapping with the aid of GPS has facilitated this process.
Nongrass species were monitored in a series of permanent quadrats in the
Doughboy Bay dunes for 6 years, from (and just before) the first application of
herbicide in 1999 till 2006. No decline in vigor was noted. A decline in species
diversity did occur, however, as a result of renewed sedimentation following
marram necrosis.
Marram is capable of rapid invasion of both progradational and transgressive
dune systems in southern New Zealand. Marram was planted at Kilbride in Mason
Bay in the 1930s and then spread north, by marine-dispersed rhizome. It became
established in the foredune north of Martins Creek in the early 1950s, and then
spread to the hinterland of the dune system by wind-blown seed. Some sections of
the dunes were also planted by farmers in the 1960s (possibly earlier). Marram
grass was also well established in Doughboy Bay by the late 1950s. By 1998
marram had occupied most available habitat in Doughboy Bay (30 ha) and was
established across 676 ha (68 %) of active dunes in Mason Bay. The rate of spread
was rapid—Hilton et al. (2005) estimated that areas of dense marram ([50 %
cover) increased from 1.4 ha in 1958 to 74.9 ha in 1998. Without intervention,
marram grass would likely have invaded most of the dune system by between 2023
and 2043 (Jul 1998).
Marram control on the southern barrier of Doughboy Bay, Stewart Island
(Rakiura) was initiated by the Department of Conservation in an attempt to restore
natural processes and patterns of sedimentation and dune flora and fauna. Information from the southern barrier, one of three in the bay, is presented. This barrier
contains a sequence of four foredune ridges that have developed in conjunction
with marram. Marram had become the dominant foredune species in Doughboy
Bay by 1958 (Hilton et al. 2005; Hilton and Konlechner 2010). Prior to the
establishment of marram grass the southern barrier probably comprised a simple
78
P. A. Hesp and M. J. Hilton
southern end of the bay. Marram was probably also established from marinedispersed rhizome. When the Department of Conservation was formed in 1987 all
of the main Stewart Island dune systems contained marram grass, although many
of these systems contained large areas that were free of marram. Fiordland and
Rakiura National Parks now contain almost a third of New Zealand dune systems
of national conservation significance (Johnson 1992; Hilton 2006). The Department of Conservation is committed to eradicating marram from both areas.
Marram sites in Fiordland are sprayed annually, over just 1 or 2 days, using a
helicopter to access sites where marram has been recorded. In contrast, the marram
eradication operations on the west coast of Stewart Island involve the deployment
of 4–5 personnel over a 6-month period, from November to May. This operation is
probably the largest marram eradication program attempted.
The herbicide employed is a systemic, grass-specific chemical—native grasses
are probably more vulnerable to the herbicide than marram grass. At many
locations this has proved a minor issue, since marram commonly forms uniform
stands and the key native grasses have already been displaced. At some sites aerial
operations have been avoided to ensure that non-target species have not been
affected. Precision mapping with the aid of GPS has facilitated this process.
Nongrass species were monitored in a series of permanent quadrats in the
Doughboy Bay dunes for 6 years, from (and just before) the first application of
herbicide in 1999 till 2006. No decline in vigor was noted. A decline in species
diversity did occur, however, as a result of renewed sedimentation following
marram necrosis.
Marram is capable of rapid invasion of both progradational and transgressive
dune systems in southern New Zealand. Marram was planted at Kilbride in Mason
Bay in the 1930s and then spread north, by marine-dispersed rhizome. It became
established in the foredune north of Martins Creek in the early 1950s, and then
spread to the hinterland of the dune system by wind-blown seed. Some sections of
the dunes were also planted by farmers in the 1960s (possibly earlier). Marram
grass was also well established in Doughboy Bay by the late 1950s. By 1998
marram had occupied most available habitat in Doughboy Bay (30 ha) and was
established across 676 ha (68 %) of active dunes in Mason Bay. The rate of spread
was rapid—Hilton et al. (2005) estimated that areas of dense marram ([50 %
cover) increased from 1.4 ha in 1958 to 74.9 ha in 1998. Without intervention,
marram grass would likely have invaded most of the dune system by between 2023
and 2043 (Jul 1998).
Marram control on the southern barrier of Doughboy Bay, Stewart Island
(Rakiura) was initiated by the Department of Conservation in an attempt to restore
natural processes and patterns of sedimentation and dune flora and fauna. Information from the southern barrier, one of three in the bay, is presented. This barrier
contains a sequence of four foredune ridges that have developed in conjunction
with marram. Marram had become the dominant foredune species in Doughboy
Bay by 1958 (Hilton et al. 2005; Hilton and Konlechner 2010). Prior to the
establishment of marram grass the southern barrier probably comprised a simple
78
P. A. Hesp and M. J. Hilton