Restoration of southern hemisphere beech (Nothofagaceae) forests: a meta‐analysis

Abstract

Nothofagus (southern beech) species form a major component of southern hemisphere forests, and in many regions are becoming an important focus for restoration efforts. However, restoration projects are predominantly carried out at small, local scales using a wide range of different techniques that have produced mixed results. In order to improve outcomes and develop general strategies for southern beech restoration, we review and compare data from previous trials to determine what techniques have been scientifically tested, identify the most effective methods, and pinpoint gaps in current practices. We assessed the effects of restoration techniques, applied in 91 trials from 22 publications across the southern hemisphere, on seedling survival and growth. Providing shelter improved both seedling survival and growth, controlling weeds improved survival, and protecting from herbivores improved seedling growth. Despite being one of the most commonly applied techniques, fertilizer application only marginally improved seedling survival and did not significantly influence seedling growth. Other techniques, such as increasing glasshouse container size or growth time or manipulating soil before planting, showed mixed results. Surprisingly, no trials examined the use of ectomycorrhizal fungal inoculum as a restoration technique. We discuss the outcomes of this review in the context of our current understanding of southern beech regeneration ecology, to inform future Nothofagus restoration practices and suggest where future research should be directed.

Barriers to seedling establishment in grasslands: Implications forNothofagusforest restoration and migration

“…We applied fertiliser to determine whether increased nutrients might reduce the reliance of seedlings on ectomycorrhizae, as ectomycorrhizae are thought to be less important in highly fertile soils (Allen, 1987; Weijtmans et al, 2007). We observed no differences in ectomycorrhizal colonization, seedling emergence and early survival between fertilised and unfertilised plots, in line with other Nothofagus restoration trials (van Galen et al, 2021). However, survival was higher in fertilised plots at the third assessment, so extra nutrients may be an advantage once seedlings begin to grow.…”

“…The pressures faced by establishing seedlings often involve many interacting factors (Morrison et al, 2019; Wearne & Morgan, 2001). Quantifying these interactions is important for both understanding the ability of forests to naturally migrate and for selecting appropriate restoration techniques when actively establishing forests (Bhadouria et al, 2017; van Galen et al, 2021). Multifactorial studies are required to quantify interactions, but such studies are lacking for many forest systems (Bhadouria et al, 2017).…”

“…Nothofagus (southern beech; Govaerts, 2022) species are widespread and ecologically important across the southern hemisphere, and are known for their relatively stable forest boundaries (Haase, 1989; Harsch et al, 2012; Navarro‐Cerrillo et al, 2020; Read & Hill, 1983; Rogers, 1989; Wardle, 1970, 1980). Particularly in drier areas, anthropogenic influences have reduced forest cover to small remnant patches that rarely spread into neighbouring grass‐dominated ecosystems (Haase, 1989; Wardle, 1980), often requiring active restoration to re‐establish trees (van Galen et al, 2021). Although different Nothofagus species have varying niche requirements, the regeneration ecology of Nothofagus is relatively consistent and most species face similar establishment challenges outside forest boundaries (Veblen et al, 1996).…”

“…Whilst it is clear that these factors play a role in the ability of Nothofagus to establish outside patch boundaries, their relative importance and whether interactions exist is not well understood (van Galen et al, 2021). For example, ectomycorrhizae can be less important for seedlings in highly fertile soils (Allen, 1987; Weijtmans et al, 2007), so a lack of immediate access to fungi may not be a barrier when nutrients are abundant.…”

Flammability trajectories following destocking and forestation: a case study in the New Zealand high country

“…During early stages of passive forestation where woody species are colonizing non‐woody vegetation, the species composition and therefore flammability of the understorey will be the most important risk factor for surface fires. During active forestation, existing vegetation is often partially or completely cleared, but frequently regrows to form dense understorey vegetation that can out‐compete tree seedlings (Standish et al 2009; Paul et al 2020; van Galen et al 2020). Selective herbicides such as Haloxyfop provide a means by which understorey vegetation can be manipulated at large scales, reducing competition from grasses but retaining some herbaceous ground cover.…”