How fragmentation and corridors affect wind dynamics and seed dispersal in open habitats

Abstract

Determining how widespread human-induced changes such as habitat loss, landscape fragmentation, and climate instability affect populations, communities, and ecosystems is one of the most pressing environmental challenges. Critical to this challenge is understanding how these changes are affecting the movement abilities and dispersal trajectories of organisms and what role conservation planning can play in promoting movement among remaining fragments of suitable habitat. Whereas evidence is mounting for how conservation strategies such as corridors impact animal movement, virtually nothing is known for species dispersed by wind, which are often mistakenly assumed to not be limited by dispersal. Here, we combine mechanistic dispersal models, wind measurements, and seed releases in a large-scale experimental landscape to show that habitat corridors affect wind dynamics and seed dispersal by redirecting and bellowing airflow and by increasing the likelihood of seed uplift. Wind direction interacts with landscape orientation to determine when corridors provide connectivity. Our results predict positive impacts of connectivity and patch shape on species richness of wind-dispersed plants, which we empirically illustrate using 12 y of data from our experimental landscapes. We conclude that habitat fragmentation and corridors strongly impact the movement of wind-dispersed species, which has community-level consequences.H abitat loss and fragmentation sever movement pathways, posing major risks to population persistence and community diversity (1). As a result, landscape connectivity--the degree to which landscapes facilitate movement--is receiving growing attention as a means to increase long-distance dispersal (LDD) of individuals and persistence of species under global change (2, 3). In particular, habitat corridors, or linear strips of habitat connecting otherwise isolated habitat patches, have become one of the most commonly applied conservation tools (4, 5). However, corridors (and connectivity more generally) are almost exclusively considered a conservation strategy for animals or animaldispersed organisms, not for the great diversity of species that are passively transported by wind.Wind is a frequent means of movement for many organisms, including plant seeds, pollen, spores, insects, and pathogens (6-8). The changes in habitat structure (e.g., edge creation) that accompany habitat fragmentation and connectivity may strongly influence the flow of air, particularly the amount of vertical uplifting--a critical factor known to drive LDD of seeds by wind (9-11). Over the past decade, our mechanistic understanding of wind-driven seed dispersal has substantially increased (12, 13) and models have begun to incorporate landscape heterogeneity (11,(14)(15)(16)(17)(18). Combining mechanistic insight from dispersal models with dispersal patterns from real landscapes is the next frontier in understanding dispersal in fragmented habitats (12, 19-21).Gaining a mechanistic understanding of how habitat fragmentation and connecti...

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