>>Department of Ecological Modelling >> Personal homepage Thorsten Wiegand >>
A model for Pyrenean Treeline: from individuals to landscapes under a changing climate
Isa was PhD Student at the Departamento de Biología de Organismos y Sistemas, University of Oviedo, in northern Spain. To conduct point-pattern analyses for her thesis she stayed two months in Leipzig. In 2008 she starts a Marie Curie Postdoctoral project on impact of climate change on treeline dynamics in the Pyrenees. This project is a close collaboration with Chechu Camerero and Emilia Gutierrez, continuing our work on treelines.
Alpine ecosystems belong to the most endangered ecosystems in the word given their high sensibility to human induced impacts. Recent studies have detected a response of the boundary between subalpine forests and alpine zones (i.e. the treeline) to climate change, but there is an ongoing controversy about whether or not and how treelines may advance or retreat in response to current climate trends. This question however is of great interest for the biodiversity of the alpine ecotone, and changes in the tree line would have important implications for the global carbon cycle. Thus, there is a need to understand the mechanisms shaping treelines and how different physical and biological interactions operate on them both at local and landscape scales. This project is designed to disentangle treeline dynamics, i.e. its spatiotemporal variation and long-term responses to climatic forcing and biological interactions using advanced modelling techniques and an extensive dataset of tree growth, individual position, size, age and recruitment patterns of Pinus uncinata in four stands at Central Pyrenees.
To attain this objective, spatially-explicit, individual-based models will be employed to simulate treeline spatiotemporal dynamics including both abiotic (temperature and precipitation, especially snow) and biotic factors (e.g. seed viability and dispersal, tree growth), as well as its potential interactions (synergies). First, modeling efforts will focus on local scale interactions and then, the entire Pyrenean range will be modeled by upscaling the local scale model, retaining only the relevant local detail to appropriately describe broad scale dynamics. Finally, the landscape scale model will be used to project treeline dynamics forced under different climate change scenarios generated through regional climate models. In all stages, a pattern-oriented modeling strategy will be used to examine the sensitivity of the model predictions and assumptions, and to optimize model performance. The project will make a significant advance in finding reliable conservation policies for alpine areas, especially those related to climate change mitigation.
Krummholz at the Ordesa treeline.
Chechu mostreando en el treeline de Ordesa
Isa’s research interests are focused in the study of plant-animal interactions during plant reproduction, i.e. through fruit production, seed dispersal, post-dispersal seed predation and seedling germination and survival. Within these topics, she is pursuing a PhD at the University of Oviedo (Asturias, NW Spain) under the supervision of Prof. José Ramón Obeso and Dr. Daniel García.
She used the tree community in secondary temperate forest as study system. In the Cantabrian range, these forest are mainly composed of fleshy fruited trees (holly Ilex aquifolium, yew Taxus baccata, and hawthorn Crataegus monogyna), and dry fruited tree species like beech Fagus sylvatica and hazel Corylus avellana.
One of the main objectives of her work is to disentangle the factors determining seedling survival. In this sense, she visits the OESA to collaborate with Thorsten Wiegand to study a spatio-temporal pattern of seedling emergence and survival during four yearly seasons. The aim is to identify the role of processes such as competition, facilitation or dispersal as signals of segregation or aggregation on individual survival patterns.
Isa mapped all stems in a plot of an old-growth forest and monitored seedlings in 1m2 plots distributed over different micro sites within the plot. She used this data to perform detailed point-pattern analysis using Programita to describe (1) the pattern of individual species, the association pattern between pairs of species, (3) the pattern of seedlings relative to adults, and (4) the spatio-temporal pattern of seedlings. The aim of these analyses was to accumulate evidence against or in favor of hypotheses about mechanisms and processes determining community dynamics and to derive new hypotheses to be evaluated in the field.
View from one of the study sites of Isa in the Cantabrian Mountains
|Modified: 21.12.2007||Resp.: Thorsten Wiegand||webmaster|