title: An integrative analysis of the dynamics of landscape- and local-scale colonization of Mediterranean woodlands by Pinus halepensis.
abstract: Afforestation efforts have resulted in extensive plantations of either native or non-native conifers, which in many regions has led to the spread of those conifers into surrounding natural vegetation. This process of species colonization can trigger profound changes in both community dynamics and ecosystem processes. Our study disentangled the complexity of a process of colonization in a heterogeneous landscape into a simple set of rules. We analyzed the factors that control the colonization of natural woodland ecosystems by Pinus halepensis dispersing from plantations in the Mediterranean region of Israel. We developed maximum-likelihood models to explain the densities of P. halepensis colonizing natural woodlands. Our models unravel how P. halepensis colonization is controlled by factors that determine colonization pressure by dispersing seeds and by factors that control resistance to colonization of the natural ecosystems. Our models show that the combination of different seed arrival processes from local, landscape, and regional scales determine pine establishment potential, but the relative importance of each component varied according to seed source distribution. Habitat resistance, determined by abiotic and biotic conditions, was as important as propagule input in determining the density of pine colonization. Thus, despite the fact that pine propagules disperse throughout the landscape, habitat heterogeneity within the natural ecosystems generates significant variation in the actual densities of colonized pine. Our approach provides quantitative measures of how processes at different spatial scales affect the distribution and densities of colonizing species, and a basis for projection of expected distributions. Variation in colonization rates, due to landscape-scale heterogeneity in both colonization pressure and resistance to colonization, can be expected to produce a diversity of new ecosystems. This work provides a template for understanding species colonization processes, especially in light of anthropogenic impacts, and predicting future transformation of natural ecosystems by species invasion.
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey,United States of America.
authors.forename: Efrat
authors.initials: E
authors.lastname: Sheffer
authors.affiliation: Cary Institute of Ecosystem Studies, Millbrook, New York, United States of America.
authors.forename: Charles D
authors.initials: CD
authors.lastname: Canham
authors.affiliation: The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Jaime
authors.initials: J
authors.lastname: Kigel
authors.affiliation: Department of Agronomy and Natural Resources, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel.
authors.forename: Avi
authors.initials: A
authors.lastname: Perevolotsky
mesh_terms: D017753:Ecosystem; D058865:Introduced Species; D007557:Israel; D016013:Likelihood Functions; D019083:Mediterranean Region; D028223:Pinus / Q000502:physiology*; D011157:Population Dynamics; D058614:Seed Dispersal / Q000502:physiology*; D012639:Seeds / Q000502:physiology*; D014197:Trees