Increase in nonnative understorey vegetation cover after nonnative conifer removal and passive restoration

Martha Sample, Clare E. Aslan, Nahuel Policelli, Robert L. Sanford, Erik Nielsen, Martín A. Nuñez

Research output: Contribution to journalArticle

Abstract

Nonnative conifers are widespread in the southern hemisphere, where their use as plantation species has led to adverse ecosystem impacts sometimes intensified by invasion. Mechanical removal is a common strategy used to reduce or eliminate the negative impacts of nonnative conifers, and encourage native regeneration. However, a variety of factors may preclude active ecological restoration following removal. As a result, passive restoration – unassisted natural vegetation regeneration – is common following conifer removal. We asked, ‘what is the response of understorey cover to removal of nonnative conifer stands followed by passive restoration?' We sampled understorey cover in three site types: two- to ten-year-old clearcuts, native forest and current plantations. We then grouped understorey species by origin (native/nonnative) and growth form, and compared proportion and per cent cover of these groups as well as of bare ground and litter between the three site types. For clearcuts, we also analysed the effect of time since clearcut on the studied variables. We found that clearcuts had a significantly higher average proportion of nonnative understorey vegetation cover than native forest sites, where nonnative vegetation was nearly absent. The understorey of clearcut sites also averaged more overall vegetation cover and more nonnative vegetation cover (in particular nonnative shrubs and herbaceous species) than either plantation or native forest sites. Notably, 99% of nonnative shrub cover in clearcuts was the invasive nonnative species Scotch broom (Cytisus scoparius). After ten years of passive recovery since clearcutting, the proportion of understorey vegetation cover that is native has not increased and remains far below the proportion observed in native forest sites. Reduced natural regeneration capacity of the native ecosystem, presence of invasive species in the surrounding landscape and land-use legacies from plantation forestry may inhibit native vegetation recovery and benefit opportunistic invasives, limiting the effectiveness of passive restoration in this context. Abstract in Spanish is available with online material.

Original languageEnglish (US)
JournalAustral Ecology
DOIs
StateAccepted/In press - Jan 1 2019

Fingerprint

clearcutting
vegetation cover
understory
conifers
coniferous tree
Cytisus scoparius
plantation
plantations
invasive species
vegetation
shrub
shrubs
regeneration
plantation forestry
ecosystems
ecological restoration
ecosystem
natural regeneration
growth form
Southern Hemisphere

Keywords

  • ecological restoration
  • Nonnative conifers
  • nonnative species removal
  • Patagonia
  • Scotch broom
  • vegetation regeneration

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology

Cite this

Increase in nonnative understorey vegetation cover after nonnative conifer removal and passive restoration. / Sample, Martha; Aslan, Clare E.; Policelli, Nahuel; Sanford, Robert L.; Nielsen, Erik; Nuñez, Martín A.

In: Austral Ecology, 01.01.2019.

Research output: Contribution to journalArticle

Sample, Martha ; Aslan, Clare E. ; Policelli, Nahuel ; Sanford, Robert L. ; Nielsen, Erik ; Nuñez, Martín A. / Increase in nonnative understorey vegetation cover after nonnative conifer removal and passive restoration. In: Austral Ecology. 2019.
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