Plants on the move: the effect of microclimate and anthropogenic disturbances on plant species distributions in mountains.
27 April 2018
UAntwerp Campus Drie Eiken, O7 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Biology
Ivan Nijs & Ann Milbau
Public defence of the PhD thesis of Mr. Jonas Lembrechts - Faculty of Science - Department of Biology
Recent climate warming and increased human presence at high elevations and latitudes have caused rapid upward and poleward movement of both non-native and native plant species. Moreover, the number of studies reporting unexpected downward shifts is increasing rapidly. These rapid shifts in distributions in what has often been seen as a slow-reacting ecosystem make it timely to undertake a thorough assessment of what drives them, in order to accurately predict the future of those vulnerable ecosystems in a changing world.
Here, I show the results of a series of global observations, models and experiments along cold-climate elevation gradients, aimed to increase our mechanistic understanding of the local factors influencing plant species’ range limits – and shifts - at the cold end of their distribution. To disentangle the role of all possible drivers, I used different techniques: 1) a global observational network monitoring the distribution of native and non-native species along mountain roads, 2) experiments with non-native plant species at and beyond their cold limit in sub(ant)arctic mountains in Sweden and Chile, and 3) theoretical models on the role of climate at the smallest scale. This range of techniques allowed assessing the role of human interventions (i.e., disturbance, nutrient increase and propagule input), climatic factors and their interactions on shifts in plant species distributions.
By acknowledging the interactions of the plants with small-scale abiotic (e.g. microclimate, soil properties) and biotic (e.g. facilitation, competition) factors, we found that disturbance – in the shape of vegetation removal like in roadsides - played a defining role along all elevation gradients, a.o. through its effects on microclimate, biotic interactions, soil suitability and seed influx. In that regard, it often trumps climate as driver of species (re)distributions in mountains. Undisturbed vegetation, on the other hand, was surprisingly hard to colonize by new-comers. Additionally, the local nature of my approach shows how microscale variation in environmental conditions like climate significantly affects regional species distributions.
These results - consistent within both our observational and experimental studies - suggest that mountain ecosystems are still relatively resistant to change, unless disrupted by anthropogenic disturbances. However, the underlying results also highlight the urgent need to include local-scale mechanisms, both abiotic, biotic and anthropogenically driven, in our assessments of species distribution changes, especially in light of a future with rapidly changing climate and increasing anthropogenic pressure. Only then, we can provide relevant insights for the management of species (re)distributions and the novel ecosystems that result from them. I thus advocate the use of recent developments in observations and modelling to move towards a more mechanistic, dynamic and appropriately-scaled approach to species distribution modelling to answer to the challenges ahead in a more and more dynamic world.