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...
Aim Large‐scale patterns linking energy availability, biological productivity and diversity form a central focus of ecology. Despite evidence that the activity and abundance of animals may be limited by climatic variables associated with regional biological productivity (e.g. mean annual precipitation and annual actual evapotranspiration), it is unclear whether plant–granivore interactions are themselves influenced by these climatic factors across broad spatial extents. We evaluated whether climatic conditions that are known to alter the abundance and activity of granivorous animals also affect rates of seed removal. Location Eleven sites across temperate North America. Methods We used a common protocol to assess the removal of the same seed species (Avena sativa) over a 2‐day period. Model selection via the Akaike information criterion was used to determine a set of candidate binomial generalized linear mixed models that evaluated the relationship between local climatic data and post‐dispersal seed predation. Results Annual actual evapotranspiration was the single best predictor of the proportion of seeds removed. Annual actual evapotranspiration and mean annual precipitation were both positively related to mean seed removal and were included in four and three of the top five models, respectively. Annual temperature range was also positively related to seed removal and was an explanatory variable in three of the top four models. Main conclusions Our work provides the first evidence that energy and precipitation, which are known to affect consumer abundance and activity, also translate to strong, predictable patterns of seed predation across a continent. More generally, these findings suggest that future changes in temperature and precipitation could have widespread consequences for plant species composition in grasslands, through impacts on plant recruitment.
Dispersal is a critically important process in the spread of invasive plants. Although knowledge of dispersal will be crucial to preventing the spread of invasive plants, little research has been performed within this context. Many important invasive or agricultural weeds disperse their seeds via tumbling, yet only one previously published paper investigated this dispersal mechanism. Field and wind tunnel experiments were conducted to quantify and model tumbling dispersal. We developed competing models for diffuse knapweed seed dispersal from wind tunnel experiments and compared predictions to data collected from a field site in Colorado. Seeds were retained in plants that had traveled hundreds to as much as 1,039 m (3,408 ft). Although neither model accurately predicted dispersal when compared with independent field data, surprisingly, seed retention with distance was somewhat better described as a linear process than as exponential decay. Wind tunnel trials showed no evidence that the number of seeds deposited per meter depended on plant size. Thus, fecundity might be a key factor determining seed dispersal distances; plants with higher fecundity might disperse seeds over longer distances than those with fewer seeds.
Although diffuse knapweed, kochia, and Russian thistle are important tumbleweeds of the western United States, environmental factors contributing to their dispersal are not well understood. Bolting rosettes of these species were transplanted to pots and reared in a common garden to determine the affect of postsenescence water on stem strength. There were no differences in stem strength among three water treatments for Russian thistle. Kochia, under moderate water treatment, required more than twice the force to break compared to plants under the zero and high water treatments. In contrast, diffuse knapweed plants under zero water treatment required four to six times greater force to break compared to plants under the moderate and high water treatments. There was a strong difference in diffuse knapweed stem strength between field collection sites that corresponded to observed differences in proportion of plants tumbling. A wind tunnel was used to develop a conversion factor between force and wind velocity. Wind velocities necessary to break diffuse knapweed stems ranged from 16 to 37 m/s (36 to 77 mph).
Dispersal is a key component of plant population and community dynamics and the spread of weeds. Although many species of economic concern disperse via tumbleweed mechanisms, our ability to estimate relevant dispersal parameters can be hindered by the lack of a controlled environment that can be provided by a wind tunnel. Established wind tunnels are typically closed-circuit, clean systems and are therefore unsuitable for biological or ecological research. We designed and constructed a wind tunnel to estimate dispersal parameters for diffuse knapweed. Our design was a tunnel that utilizes the Venturi effect to obtain maximum flow velocity while pulling, rather than pushing, air through the test section. Flow velocity was continuously variable from 0 to 8 m/s, and the tunnel was equipped with instrumentation for measuring the force exerted on plants by wind. Our modular design provided a way to effectively estimate key parameters that govern the dispersal of tumbleweeds, and was readily constructed and stored in research facilities.
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