@misc{NathanHorvitzHeetal.2011, author = {Nathan, Ran and Horvitz, Nir and He, Yanping and Kuparinen, Anna and Schurr, Frank Martin and Katul, Gabriel G.}, title = {Spread of North American wind-dispersed trees in future environments}, series = {Ecology letters}, volume = {14}, journal = {Ecology letters}, number = {3}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1461-023X}, doi = {10.1111/j.1461-0248.2010.01573.x}, pages = {211 -- 219}, year = {2011}, abstract = {P>Despite ample research, understanding plant spread and predicting their ability to track projected climate changes remain a formidable challenge to be confronted. We modelled the spread of North American wind-dispersed trees in current and future (c. 2060) conditions, accounting for variation in 10 key dispersal, demographic and environmental factors affecting population spread. Predicted spread rates vary substantially among 12 study species, primarily due to inter-specific variation in maturation age, fecundity and seed terminal velocity. Future spread is predicted to be faster if atmospheric CO2 enrichment would increase fecundity and advance maturation, irrespective of the projected changes in mean surface windspeed. Yet, for only a few species, predicted wind-driven spread will match future climate changes, conditioned on seed abscission occurring only in strong winds and environmental conditions favouring high survival of the farthest-dispersed seeds. Because such conditions are unlikely, North American wind-dispersed trees are expected to lag behind the projected climate range shift.}, language = {en} } @article{SarmentoBondMidgleyetal.2011, author = {Sarmento, Juliano Sarmento and Bond, William J. and Midgley, Guy F. and Rebelo, Anthony G. and Thuiller, Wilfried and Schurr, Frank Martin}, title = {Effects of harvesting flowers from shrubs on the persistence and abundance of wild shrub populations at multiple spatial extents}, series = {Conservation biology : the journal of the Society for Conservation Biology}, volume = {25}, journal = {Conservation biology : the journal of the Society for Conservation Biology}, number = {1}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0888-8892}, doi = {10.1111/j.1523-1739.2010.01628.x}, pages = {73 -- 84}, year = {2011}, abstract = {Wildflower harvesting is an economically important activity of which the ecological effects are poorly understood. We assessed how harvesting of flowers affects shrub persistence and abundance at multiple spatial extents. To this end, we built a process-based model to examine the mean persistence and abundance of wild shrubs whose flowers are subject to harvest (serotinous Proteaceae in the South African Cape Floristic Region). First, we conducted a general sensitivity analysis of how harvesting affects persistence and abundance at nested spatial extents. For most spatial extents and combinations of demographic parameters, persistence and abundance of flowering shrubs decreased abruptly once harvesting rate exceeded a certain threshold. At larger extents, metapopulations supported higher harvesting rates before their persistence and abundance decreased, but persistence and abundance also decreased more abruptly due to harvesting than at smaller extents. This threshold rate of harvest varied with species' dispersal ability, maximum reproductive rate, adult mortality, probability of extirpation or local extinction, strength of Allee effects, and carrying capacity. Moreover, spatial extent interacted with Allee effects and probability of extirpation because both these demographic properties affected the response of local populations to harvesting more strongly than they affected the response of metapopulations. Subsequently, we simulated the effects of harvesting on three Cape Floristic Region Proteaceae species and found that these species reacted differently to harvesting, but their persistence and abundance decreased at low rates of harvest. Our estimates of harvesting rates at maximum sustainable yield differed from those of previous investigations, perhaps because researchers used different estimates of demographic parameters, models of population dynamics, and spatial extent than we did. Good demographic knowledge and careful identification of the spatial extent of interest increases confidence in assessments and monitoring of the effects of harvesting. Our general sensitivity analysis improved understanding of harvesting effects on metapopulation dynamics and allowed qualitative assessment of the probability of extirpation of poorly studied species.}, language = {en} }