2006-2008
The Royal Swedish Academy of Sciences
Ninot Sugrañes, Josep M. (IP). Batriu Vila, Efrem. Carrillo Ortuño, Amparo. Grau Fernández, Oriol. Illa Bachs, Estela.


A contribution to the functional knowledge of subarctic and alpine dwarf-scrubs: a comparative study of tree invasiveness across latitude and altitude gradients

Treeline dynamics have been widely studied in the recent years, but little attention has been put on the effect of shrubs at the forest-alpine grassland and forest-tundra ecotones. There are positive and negative interactions between shrubs and tree seedlings, which may change across altitudinal and latitudinal gradients due to changes in abiotic or biotic stress. It may be hypothesised that such interactions may change under varying environmental conditions and that they may affect seedling recruitment across the timberline.

In order to gain insight into this topic we initiated this study, which is based on transplantation experiments of tree seedlings under simulated changes in temperature (+/- open top chambers), nutrient availability (+/- NPK fertiliser) and shrub cover (presence or absence of shrub), both above and below the timberline at two distinct latitudes. In 2006, this full factorial experiment was established in the subarctic Scandes with Betula pubescens ssp. czerepanovii seedlings and Vaccinium myrtillus mats. A similar experiment was started in the central Pyrenees with Pinus uncinata seedlings and Rhododendron ferrugineum low shrubs.

Several variables have been measured at the beginning and ending of the growing seasons: leaf and stem size, survival, abiotic leaf damage and herbivory. Shrubs played a key role in seedling recruitment and performance in both study areas, by facilitating seedling establishment. Facilitation seems to be one of the controlling factors of the treeline dynamics and densification processes observed in the forest-tundra and forest-alpine grassland ecotones. However, the relative importance of the interactions between these species varies across the timberline. Environmental changes have caused significant responses in both areas, especially in the Scandes, but longer-term monitoring should be made before drawing robust conclusions.


Research field:
Ecology of plant communities


Project results: