The impact of exotic weed competition on a rare New Zealand outcrop herb, Pachycladon cheesemanii (Brassicaceae)

Alice L. Miller, R.P. Duncan

    Research output: Contribution to journalArticle

    7 Citations (Scopus)

    Abstract

    Nearly one quarter of New Zealand's unique vascular plant flora is threatened, and weed invasion is implicated in the decline of more than half of these threatened species. However, there is little experimental evidence showing that invasive weeds have a direct impact on threatened native plants. This study experimentally tested the hypothesis that competition with invasive weeds threatens the rare outcrop plant Pachycladon cheesemanii (Brassicaceae). Pachycladon cheesemanii is a threatened South Island, New Zealand endemic with a distribution nearly confined to rock outcrops. It has disappeared from historical record sites throughout its range. The effects of weed competition and habitat on P. cheesemanii establishment, growth and survival were investigated by sowing seed into replicated plots subject to three treatments: weed removal, soil disturbed and unweeded control, in three habitat types: forested and open rock outcrops and open tussock grassland. The experiments were carried out at three locations: Mt Somers (Canterbury), Wye Creek and Diamond Lake (Otago). Within weedy rock outcrop habitat, weed removal significantly increased the rate of P. cheesemanii germination, and appeared to increase seedling growth rates, implying that weeds can negatively impact populations. Relative to rock outcrop habitat, P. cheesemanii germination was very low in adjacent open grassland habitat regardless of weeding treatment. Demographic monitoring of four natural populations of P. cheesemanii revealed that seed production is highly variable among populations and may be limited by browse and mechanical damage to inflorescences. Pachycladon cheesemanii does produce a persistent seed bank but most seed is found close to parent populations. Our results suggest that competition with invading weeds threatens current P. cheesemanii populations, that plant establishment can be enhanced by weed removal, and that considerable potential exists for artificially expanding populations by sowing seed into appropriate weed-free habitat.
    Original languageUndefined
    Pages (from-to)113-124
    Number of pages12
    JournalNew Zealand Journal of Ecology
    Volume28
    Issue number1
    Publication statusPublished - 2004

    Cite this

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    title = "The impact of exotic weed competition on a rare New Zealand outcrop herb, Pachycladon cheesemanii (Brassicaceae)",
    abstract = "Nearly one quarter of New Zealand's unique vascular plant flora is threatened, and weed invasion is implicated in the decline of more than half of these threatened species. However, there is little experimental evidence showing that invasive weeds have a direct impact on threatened native plants. This study experimentally tested the hypothesis that competition with invasive weeds threatens the rare outcrop plant Pachycladon cheesemanii (Brassicaceae). Pachycladon cheesemanii is a threatened South Island, New Zealand endemic with a distribution nearly confined to rock outcrops. It has disappeared from historical record sites throughout its range. The effects of weed competition and habitat on P. cheesemanii establishment, growth and survival were investigated by sowing seed into replicated plots subject to three treatments: weed removal, soil disturbed and unweeded control, in three habitat types: forested and open rock outcrops and open tussock grassland. The experiments were carried out at three locations: Mt Somers (Canterbury), Wye Creek and Diamond Lake (Otago). Within weedy rock outcrop habitat, weed removal significantly increased the rate of P. cheesemanii germination, and appeared to increase seedling growth rates, implying that weeds can negatively impact populations. Relative to rock outcrop habitat, P. cheesemanii germination was very low in adjacent open grassland habitat regardless of weeding treatment. Demographic monitoring of four natural populations of P. cheesemanii revealed that seed production is highly variable among populations and may be limited by browse and mechanical damage to inflorescences. Pachycladon cheesemanii does produce a persistent seed bank but most seed is found close to parent populations. Our results suggest that competition with invading weeds threatens current P. cheesemanii populations, that plant establishment can be enhanced by weed removal, and that considerable potential exists for artificially expanding populations by sowing seed into appropriate weed-free habitat.",
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    pages = "113--124",
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    The impact of exotic weed competition on a rare New Zealand outcrop herb, Pachycladon cheesemanii (Brassicaceae). / Miller, Alice L.; Duncan, R.P.

    In: New Zealand Journal of Ecology, Vol. 28, No. 1, 2004, p. 113-124.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - The impact of exotic weed competition on a rare New Zealand outcrop herb, Pachycladon cheesemanii (Brassicaceae)

    AU - Miller, Alice L.

    AU - Duncan, R.P.

    N1 - cited By 7

    PY - 2004

    Y1 - 2004

    N2 - Nearly one quarter of New Zealand's unique vascular plant flora is threatened, and weed invasion is implicated in the decline of more than half of these threatened species. However, there is little experimental evidence showing that invasive weeds have a direct impact on threatened native plants. This study experimentally tested the hypothesis that competition with invasive weeds threatens the rare outcrop plant Pachycladon cheesemanii (Brassicaceae). Pachycladon cheesemanii is a threatened South Island, New Zealand endemic with a distribution nearly confined to rock outcrops. It has disappeared from historical record sites throughout its range. The effects of weed competition and habitat on P. cheesemanii establishment, growth and survival were investigated by sowing seed into replicated plots subject to three treatments: weed removal, soil disturbed and unweeded control, in three habitat types: forested and open rock outcrops and open tussock grassland. The experiments were carried out at three locations: Mt Somers (Canterbury), Wye Creek and Diamond Lake (Otago). Within weedy rock outcrop habitat, weed removal significantly increased the rate of P. cheesemanii germination, and appeared to increase seedling growth rates, implying that weeds can negatively impact populations. Relative to rock outcrop habitat, P. cheesemanii germination was very low in adjacent open grassland habitat regardless of weeding treatment. Demographic monitoring of four natural populations of P. cheesemanii revealed that seed production is highly variable among populations and may be limited by browse and mechanical damage to inflorescences. Pachycladon cheesemanii does produce a persistent seed bank but most seed is found close to parent populations. Our results suggest that competition with invading weeds threatens current P. cheesemanii populations, that plant establishment can be enhanced by weed removal, and that considerable potential exists for artificially expanding populations by sowing seed into appropriate weed-free habitat.

    AB - Nearly one quarter of New Zealand's unique vascular plant flora is threatened, and weed invasion is implicated in the decline of more than half of these threatened species. However, there is little experimental evidence showing that invasive weeds have a direct impact on threatened native plants. This study experimentally tested the hypothesis that competition with invasive weeds threatens the rare outcrop plant Pachycladon cheesemanii (Brassicaceae). Pachycladon cheesemanii is a threatened South Island, New Zealand endemic with a distribution nearly confined to rock outcrops. It has disappeared from historical record sites throughout its range. The effects of weed competition and habitat on P. cheesemanii establishment, growth and survival were investigated by sowing seed into replicated plots subject to three treatments: weed removal, soil disturbed and unweeded control, in three habitat types: forested and open rock outcrops and open tussock grassland. The experiments were carried out at three locations: Mt Somers (Canterbury), Wye Creek and Diamond Lake (Otago). Within weedy rock outcrop habitat, weed removal significantly increased the rate of P. cheesemanii germination, and appeared to increase seedling growth rates, implying that weeds can negatively impact populations. Relative to rock outcrop habitat, P. cheesemanii germination was very low in adjacent open grassland habitat regardless of weeding treatment. Demographic monitoring of four natural populations of P. cheesemanii revealed that seed production is highly variable among populations and may be limited by browse and mechanical damage to inflorescences. Pachycladon cheesemanii does produce a persistent seed bank but most seed is found close to parent populations. Our results suggest that competition with invading weeds threatens current P. cheesemanii populations, that plant establishment can be enhanced by weed removal, and that considerable potential exists for artificially expanding populations by sowing seed into appropriate weed-free habitat.

    M3 - Article

    VL - 28

    SP - 113

    EP - 124

    JO - New Zealand Journal of Ecology

    JF - New Zealand Journal of Ecology

    SN - 0077-9946

    IS - 1

    ER -