TY - JOUR
T1 - Indirect effects of land-use legacies determine tree colonization patterns in abandoned heathland
AU - Kepfer Rojas, Sebastian
AU - Verheyen, Kris
AU - Johannsen, Vivian Kvist
AU - Schmidt, Inger Kappel
PY - 2015/7/1
Y1 - 2015/7/1
N2 - Questions: How do land-use legacies and distance to forest patches influence tree colonization at a post-agricultural heathland? Are colonizing species with different life-history traits affected differently by these factors? Is the effect of increased nutrient availability from land-use legacies mediated by the understorey vegetation? Location: Nørholm hede, a 350-ha heathland in southwest Denmark developing naturally after abandonment of traditional agricultural practices in 1895. Methods: Using 140 plots (0.03 ha), we quantified the vegetation structure, soil properties and natural recruitment of tree/shrubs in the heathland. Further, we used high-resolution LiDAR data to classify the vegetation and identify forest patches. In the analysis, we first used a logistic mixed model to test whether colonization of tree and shrub species differed between areas with different land-use history and whether it was influenced by the distance to forest patches and life-history traits (seed mass) of colonizing species. Then, to determine how different factors influence colonization, we explored the direct and indirect relationships among nutrient availability, density of adult trees, canopy cover, cover of Deschampsia flexuosa and the probability of seedling colonization in each plot using a confirmatory multilevel path analysis. Results: The probability of seedling colonization for small- and large-seeded species decreased with distance to forest patches. This response was more pronounced at the previously cultivated area. Multilevel path analysis showed that colonizing species with different life-history traits were affected by different factors. Small-seeded species were negatively affected by increased nutrient availability mediated by an increase in the cover of D. flexuosa. This effect was not found for large-seeded species. Moreover, the density of trees/shrubs (>2 m) increased the probability of colonization of small-seeded species, whereas higher canopy cover had a positive effect on large-seeded species. Conclusions: Our analyses demonstrate that the interactions between abiotic factors, biotic interactions and life-history traits of colonizing species can lead to distinct patterns of tree colonization. Land-use legacies can have long-lasting, indirect effects on tree colonization by altering the composition of the understorey vegetation, which in turn can delay tree encroachment and slow down the succession from heathland to forest. Many factors can determine tree encroachment in unmanaged heathlands. We examine the interacting effects of land use legacies, distance from sources and vegetation structure (overstory and understory). Colonizing species responded differently to these factors depending on life-history traits. Colonization by small-seeded species was hindered by competition with grasses mediated by nutrient availability whereas large-seeded species were not affected.
AB - Questions: How do land-use legacies and distance to forest patches influence tree colonization at a post-agricultural heathland? Are colonizing species with different life-history traits affected differently by these factors? Is the effect of increased nutrient availability from land-use legacies mediated by the understorey vegetation? Location: Nørholm hede, a 350-ha heathland in southwest Denmark developing naturally after abandonment of traditional agricultural practices in 1895. Methods: Using 140 plots (0.03 ha), we quantified the vegetation structure, soil properties and natural recruitment of tree/shrubs in the heathland. Further, we used high-resolution LiDAR data to classify the vegetation and identify forest patches. In the analysis, we first used a logistic mixed model to test whether colonization of tree and shrub species differed between areas with different land-use history and whether it was influenced by the distance to forest patches and life-history traits (seed mass) of colonizing species. Then, to determine how different factors influence colonization, we explored the direct and indirect relationships among nutrient availability, density of adult trees, canopy cover, cover of Deschampsia flexuosa and the probability of seedling colonization in each plot using a confirmatory multilevel path analysis. Results: The probability of seedling colonization for small- and large-seeded species decreased with distance to forest patches. This response was more pronounced at the previously cultivated area. Multilevel path analysis showed that colonizing species with different life-history traits were affected by different factors. Small-seeded species were negatively affected by increased nutrient availability mediated by an increase in the cover of D. flexuosa. This effect was not found for large-seeded species. Moreover, the density of trees/shrubs (>2 m) increased the probability of colonization of small-seeded species, whereas higher canopy cover had a positive effect on large-seeded species. Conclusions: Our analyses demonstrate that the interactions between abiotic factors, biotic interactions and life-history traits of colonizing species can lead to distinct patterns of tree colonization. Land-use legacies can have long-lasting, indirect effects on tree colonization by altering the composition of the understorey vegetation, which in turn can delay tree encroachment and slow down the succession from heathland to forest. Many factors can determine tree encroachment in unmanaged heathlands. We examine the interacting effects of land use legacies, distance from sources and vegetation structure (overstory and understory). Colonizing species responded differently to these factors depending on life-history traits. Colonization by small-seeded species was hindered by competition with grasses mediated by nutrient availability whereas large-seeded species were not affected.
U2 - 10.1111/avsc.12169
DO - 10.1111/avsc.12169
M3 - Journal article
SN - 1402-2001
VL - 18
SP - 456
EP - 466
JO - Applied Vegetation Science
JF - Applied Vegetation Science
IS - 3
ER -
