Landscape characteristics of non-native pine plantations and invasions in Southern Chile.
The spread of non-native conifers into areas naturally dominated by other vegetation types is a growing problem in South America. This process results in a landscape transformation as the conifers suppress native vegetation leading to reduced biodiversity, lower water availability and altered nutrient dynamics. Previous research highlights the broad spatial extents of land cover change in parts of Chile. However, in Southern Chile, the extent of plantations and the landscape characteristics associated with plantations and ongoing pine invasions are poorly understood. Here, we characterised non-native pine land cover within one Landsat scene (World Reference System 2 Path 232/Row 92; ∼34 000 km2) in Southern Chile. We created training data based on historical high-resolution imagery, derived land cover predictors from time series of Landsat observations and used a Random Forest classifier to map the distribution of non-native pines. The overall classification accuracy was 88%, and the accuracy of the non-native pine class exceeded 90%. Although 71% of non-native pine patches were within 500 m of other non-native pine patches, isolated non-native pine patches were found to occur up to 55 km from the nearest neighbour. These distant plantations could exacerbate invasion risk by creating propagule sources for novel invasion fronts. In relation to landscape characteristics, non-native pines were found to be more likely to occur in low slope and mid-elevation areas. Because most of the study area is native forest, most non-native pine patches border native forest. However, non-native pine patches were almost three times more likely than random patches to border grass/agriculture. This suggests that grasslands and disturbed sites, which have low resistance to non-native pine invasion, are disproportionately exposed to pine propagules. Our results indicate that non-native pine plantations are extensive across Southern Chile, and well poised to cause future invasion.