Periodic Reporting for period 3 - MICROCLIM (A micro-scale perspective on alpine floras under climate change. Linking observations and models to improve our understanding of the future of European high mountain plants)
Reporting period: 2024-01-01 to 2025-06-30
Microclim is an ERC-AdG project which addresses the role of microclimatic variation for the survival of alpine plants in a warming climate.
Alpine plants are adapted to cold temperatures and are hence considered sensitive to climate change. Standard modelling approaches, which use changes in air temperatures as driving force, predict that these plants would need to shift their current distributions up by hundreds of meters in order to keep the climatic conditions they live in constant. Given that many mountains are conic in shape, and all are limited in altitude, such upslope shifts imply massive habitat loss or even complete extinctions from summits that are too low.
However, the alpine terrain is characterized by pronounced ruggedness. As a consequence, near-surface temperature, which is more relevant for low-stature alpine plants than air temperature, can vary by several degrees over distances of only a few meters. It has been hypothesized that this pronounced microclimatic variation might buffer the alpine flora against climate warming because it guarantees that a certain number of ‘cold spots’ will stay available in each alpine landscape in a warming world. Standard modelling approaches might hence deliver overly pessimistic forecasts of the future fate of alpine floras.
In Microclim, we want to evaluate the empirical evidence for such microclimatic buffering by linking so far separated research strands of monitoring and predictive modelling of alpine plant distribution. In particular, we will, first, compare predictions of standard modelling approaches with the results of 25 years of Europe-wide monitoring of mountaintop floras (https://www.gloria.ac.at(opens in new window)) and analyse the role of spatial scale for possible mismatches between models and observations of change. Second, we will develop a novel modelling framework that simulates the simultaneous range dynamics of many interacting plant species. We will parameterise this model by means of experiments and observational data and evaluate it against monitoring data on an exemplary mountain in the Austrian Alps (Mt. Schrankogel). We will then apply the model to simulate the dynamics of the flora of this mountain over the 21st century at a very fine spatial resolution. We will finally generalize the results achieved in these dynamic simulations to all summits included in the European mountaintop monitoring network to evaluate the proposed rescue effect of microclimatic variation.
Alpine plants are adapted to cold temperatures and are hence considered sensitive to climate change. Standard modelling approaches, which use changes in air temperatures as driving force, predict that these plants would need to shift their current distributions up by hundreds of meters in order to keep the climatic conditions they live in constant. Given that many mountains are conic in shape, and all are limited in altitude, such upslope shifts imply massive habitat loss or even complete extinctions from summits that are too low.
However, the alpine terrain is characterized by pronounced ruggedness. As a consequence, near-surface temperature, which is more relevant for low-stature alpine plants than air temperature, can vary by several degrees over distances of only a few meters. It has been hypothesized that this pronounced microclimatic variation might buffer the alpine flora against climate warming because it guarantees that a certain number of ‘cold spots’ will stay available in each alpine landscape in a warming world. Standard modelling approaches might hence deliver overly pessimistic forecasts of the future fate of alpine floras.
In Microclim, we want to evaluate the empirical evidence for such microclimatic buffering by linking so far separated research strands of monitoring and predictive modelling of alpine plant distribution. In particular, we will, first, compare predictions of standard modelling approaches with the results of 25 years of Europe-wide monitoring of mountaintop floras (https://www.gloria.ac.at(opens in new window)) and analyse the role of spatial scale for possible mismatches between models and observations of change. Second, we will develop a novel modelling framework that simulates the simultaneous range dynamics of many interacting plant species. We will parameterise this model by means of experiments and observational data and evaluate it against monitoring data on an exemplary mountain in the Austrian Alps (Mt. Schrankogel). We will then apply the model to simulate the dynamics of the flora of this mountain over the 21st century at a very fine spatial resolution. We will finally generalize the results achieved in these dynamic simulations to all summits included in the European mountaintop monitoring network to evaluate the proposed rescue effect of microclimatic variation.
In summer 2021, 900 soil temperature loggers and three snow cameras (see https://www.foto-webcam.eu/webcam/wannenkogel/(opens in new window)) were installed on Mt. Schrankogel across an elevational gradient of 1700 m. Plant occurrence and abundance data were recorded on 1 m² associated with each logger and 3500 specimens of 59 plant species were tagged for monitoring. In addition, we experimentally transplanted 4,700 plant individuals and sew 47,000 seeds onto 25 experimental sites in the vicinity of Mt. Schrankogel, also equipped with 100 soil temperature loggers. All tagged and transplanted individuals were re-visited in 2022 to record their survival and growth in dependence on measured temperature, snow conditions and density of interacting species. In addition, we assessed seed germination rates and repeated the germination trial. Furthermore, a resurvey of incidence and abundance of plant species on 67 summits included in the European monitoring of mountaintop floras and vegetation (GLORIA-Europe) was conducted in 2022 and the collected data were digitized, fed into a common database, checked and cleaned. The summits cover a gradient from southern Spain to Norway and the Caucasus.
Europe-wide plant occurrence records to be used in modelling changes of European summit floras for comparison with observations were compiled and are about to be cleaned. Earlier developed software to simulate the migration of individual plant species was updated, optimized and published as a software package. Extensions of the software to the simultaneous simulation of many species were tested in a proof-of-concept work published in a major ecological journal. An approach to downscale remotely-sensed snow cover data to fine-resolutions to be used as driver in fine-scale plant simulations has been developed and is about to be published.
First analyses of the data collected so far suggest that microtopography, an important determinant of microclimate, has a recognizable but limited effect on alpine plant distribution. The results indicate an overriding impact of the frequency of species in the surroundings of a microsite onto the species composition of this microsite. As a corollary, isolated and fragmented cold spots might have limited capacity to guarantee the long-term persistence of cold-adapted species under climate warming. A further analysis supports these conclusions in demonstrating a strong effect of dispersal limitation on the colonization of new sites observed on Mt. Schrankogel.
Europe-wide plant occurrence records to be used in modelling changes of European summit floras for comparison with observations were compiled and are about to be cleaned. Earlier developed software to simulate the migration of individual plant species was updated, optimized and published as a software package. Extensions of the software to the simultaneous simulation of many species were tested in a proof-of-concept work published in a major ecological journal. An approach to downscale remotely-sensed snow cover data to fine-resolutions to be used as driver in fine-scale plant simulations has been developed and is about to be published.
First analyses of the data collected so far suggest that microtopography, an important determinant of microclimate, has a recognizable but limited effect on alpine plant distribution. The results indicate an overriding impact of the frequency of species in the surroundings of a microsite onto the species composition of this microsite. As a corollary, isolated and fragmented cold spots might have limited capacity to guarantee the long-term persistence of cold-adapted species under climate warming. A further analysis supports these conclusions in demonstrating a strong effect of dispersal limitation on the colonization of new sites observed on Mt. Schrankogel.
The established soil temperature and snow observation campaign on Mt. Schrankogel is the most intensive of its kind so far and will allow for deeper insights into the effects of microclimatic variation on alpine plant distribution. The monitoring of specimens will enable us to detect correlations between demography and the physical environment as well as the density of co-occurring species for a set of plant species of unprecedented size. The data on the link between plant demography and co-occurring plant species will be used to simulate the simultaneous range dynamics of interacting plant species across an entire mountain landscape. This will allow for insights into the controversial impact of climate vs. biotic interactions on how alpine plant populations will develop in a warming climate. It will moreover enable a better understanding of the value of microclimatic refugia for alpine plant survival in the context of species interactions and dispersal limitations.
The extended data from the European mountaintop monitoring campaign will show whether recent “thermophilization” trends of summit floras are continued, whether biotic homogenisation among mountaintops and regions is measurable and whether extinctions of cold-adapted species are accelerating as suspected. The comparison with model predictions will further be the first real-data based validation of this standard modelling approach in the field of alpine plant ecology and allow to assess to which degree microclimatic variation interferes with and confounds their predictions.
The results of Microclim should improve our understanding of how climate change will affect the fate of the rich and peculiar alpine flora in a warming world. Its findings will provide further scientific evidence to support assessments of the magnitude of the biodiversity crisis and its current and future drivers. In evaluating the risk that a changing climate poses onto alpine floras they can also help in prioritizing conservation targets, e.g. to minimize other pressures on alpine habitats and their biota.
The extended data from the European mountaintop monitoring campaign will show whether recent “thermophilization” trends of summit floras are continued, whether biotic homogenisation among mountaintops and regions is measurable and whether extinctions of cold-adapted species are accelerating as suspected. The comparison with model predictions will further be the first real-data based validation of this standard modelling approach in the field of alpine plant ecology and allow to assess to which degree microclimatic variation interferes with and confounds their predictions.
The results of Microclim should improve our understanding of how climate change will affect the fate of the rich and peculiar alpine flora in a warming world. Its findings will provide further scientific evidence to support assessments of the magnitude of the biodiversity crisis and its current and future drivers. In evaluating the risk that a changing climate poses onto alpine floras they can also help in prioritizing conservation targets, e.g. to minimize other pressures on alpine habitats and their biota.