Maintaining close canopy cover prevents the invasion of Pinus radiata: Basic ecology to manage native forest invasibility

Abstract

Pine invasion is a global threat that is occurring in native forests of diverse regions of the world. This process is arising in a scenario of rapid forest deforestation and degradation. Therefore, elucidate which forests attributes explain invasibility is a central issue in forest ecology. The Coastal Maulino forest is an endemic forest of central Chile, which has suffered a large history of disturbance, being replaced by large extensions of Pinus radiata plantations. This land transformation conveys high rates of pines invasion into native remnants. In this study we examined to what extent structural features of forest patches explains invasibility of this forest-type. Within eight forest fragments, we sampled 162 plots (10 x 10 m 2 each). We quantified seedling pine density and related these estimates with tree cover, litter depth, PAR radiation, and diversity of the resident community. Our results indicate that canopy cover was the most important variable to determine seedling pine density within forest fragments. Our investigation highlights the importance to conserve the forests cover to reduce significantly their invasibility. This action can be effective even if we cannot avoid pine plantations in the region as a source of a massive seed dispersal to forests with well conserved canopy.

Quantifying the risk of non‐native conifer establishment across heterogeneous landscapes

“…They are considered one of the most problematic non‐native species affecting native forest regeneration on the south–east of Banks Peninsula (Peart & Woodhouse, 2021). However, once dense native vegetation becomes established, further regeneration will be unlikely except following disturbances such as fire (Gómez et al, 2019).…”

“…Pinus radiata (radiata pine, Monterey pine) is the most important non‐native conifer in the global timber industry (Lavery & Mead, 1998), with over 4.5 million ha of plantations worldwide, 90% of which occur in the Southern Hemisphere (Mead, 2013). The species is light demanding (Wyse & Hulme, 2022) and the density of naturally establishing seedlings in a fragmented forest in Chile was found to correlate negatively with canopy cover (Gómez et al, 2019). Roadsides and coastal habitats also provide suitable environments for P. radiata establishment (Williams & Wardle, 2007), while droughts, frost (Burdon & Miller, 1992) and strong browsing pressure from stock and other herbivores (Crozier & Ledgard, 1990) are thought to retard or inhibit establishment.…”

“…Pine seedlings are light demanding, and so are unable to establish beneath dense canopies and are easily supressed by more vigorous species (Langdon et al, 2010;Ledgard, 2001;Richardson et al, 1994). Key habitats for P. radiata establishment on Banks Peninsula included those that represent the early stages of forest However, once dense native vegetation becomes established, further regeneration will be unlikely except following disturbances such as fire (Gómez et al, 2019).…”

“…alien, invasion, laser rangefinder, LiDAR, spatial ecology, species distribution modelling, viewshed analysis, wilding conifer demanding and the density of naturally establishing seedlings in a fragmented forest in Chile was found to correlate negatively with canopy cover (Gómez et al, 2019). Roadsides and coastal habitats also provide suitable environments for P. radiata establishment (Williams & Wardle, 2007), while droughts, frost (Burdon & Miller, 1992) and strong browsing pressure from stock and other herbivores (Crozier & Ledgard, 1990) are thought to retard or inhibit establishment.…”

Light availability influences the invasion of Teline monspessulana (L.) K. Koch in a temperate fragmented forest in Central Chile

“…Currently, Pinus radiata D. Don, Acacia dealbata Link. and Teline monspessulana (L.) K. Koch are listed as the most important woody alien plants that are colonizing this native forest (Aguilera et al 2015, Gómez et al 2019.…”