From Herbs to Canopy: Spatiotemporal Patterns of Forest Plant Communities in Northern Andean Patagonia

Abstract

The temperate Andean forests of Patagonia form a biogeographic island shaped by climatic gradients, volcanic soils, and a distinctive evolutionary history. This chapter explores the spatial and temporal patterns of plant communities within these forests, with a focus on the northern Patagonian Andes (41–42 °S). We adopt a top-down approach, beginning with regional biogeography and environmental filters and narrowing to community structure, diversity, and disturbance responses at the local scale. We first describe the abiotic template: sharp west-east precipitation and elevational gradients structure forest types, soil formation, and nutrient availability. Volcanic ash soils retain moisture and carbon but show strong spatial variation in plant-available water, reinforcing vegetation differences across the landscape. These gradients drive floristic transitions from humid Valdivian rainforests to xeric Austrocedrus chilensis woodlands and subalpine Nothofagus pumilio forests. Species composition responds predictably to climate, soil, and topography, but is also shaped by disturbance. Fire, grazing, and logging have produced heterogeneous successional trajectories and alternative stable states—particularly fire-adapted shrublands—that now dominate mid-elevation, frequently disturbed areas. We highlight key insights from spatial analyses, including shifts in diversity and beta diversity across climate and elevation, and the role of topographic refugia in maintaining unique assemblages. We then examine the legacy effects and current impacts of fire, herbivory, non-native species, and forest management. These drivers interact non-linearly, often reinforcing vegetation shifts towards open, flammable, and species-poor systems. Synergies between fire and grazing, for instance, promote feedback loops that hinder forest regeneration. Finally, we discuss management strategies that balance biodiversity conservation and ecosystem resilience. We emphasize the value of topographic heterogeneity, post-disturbance recovery, and active intervention to support native forest composition, reduce homogenization, and adapt to future climate risks.