Linking forest transition, plant invasion and forest succession theories: socioeconomic drivers and composition of new subtropical andean forests

Highlights

• We empirically explored a framework  aimed to identify the socio-environmental conditions that facilitate different pathways of spontaneous forest transitions in a subtropical mountane watershed.
• Specific social features favor the establishment of two exotic trees over native ones.
• Ligustrum lucidum expansion is associated with population growth in rural areas.
• Gleditsia triacanthos expansion depends on rural out-migration and livestock use.
• Through different mechanisms, socio-economic changes affect both land use dis-intensification and availability of seed pools that control early forest succession, so defining the ecological properties of forests for decades

Abstract

The patterns and causes of forest transition have been extensively studied, identifying socioeconomic drivers of land use deintensification and the associated forest expansion. However, most studies do not take into account the origin of the dominant species of new forests (i.e. native or exotic), which affects biodiversity and the provision of ecosystem services. We develop a framework integrating forest transition, forest succession and biological invasion theories to identify the socio-environmental conditions that facilitate different pathways of spontaneous forest transitions in a subtropical mountain basin. We used Landsat images and Random forest classifier to detect land cover changes over 30 years (1988–2017). We used generalized additive models to identify socioeconomic and biophysical variables associated with expansion of native and exotic-dominated forests. Expanding native forests are scattered throughout the whole basin under a broad spectrum of socioeconomic and environmental conditions. In contrast, the new forests dominated by exotic species were aggregated around their focal introduction areas and their expansion was associated with accessibility and specific land uses (livestock or residential use). Understanding the pathways of alternative forest transition involves the integration of land science, forest succession theory and invasion ecology. Land science explains the availability of sites to be reforested. The species composition of new forests depends on the availability of propagules, dispersal agents and competitive relationships between species (forest succession theory). Invasion ecology explains the role of introduction areas (which are often associated with residential use) of exotic species in the successional process.