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High-End Climate Change in Europe, ISBN:978-954-642-861-5

Dynamic vegetation models (DVMs) follow a process‐based approach to simulate plant population demography, and have been used to address questions about disturbances, plant succession, community composition, and provisioning of ecosystem services under climate change scenarios. Despite their potential, they have seldom been used for studying species range dynamics explicitly. In this perspective paper, we make the case that DVMs should be used to this end and can improve our understanding of the factors that influence species range expansions and contractions. We review the benefits of using process‐based, dynamic models, emphasizing how DVMs can be applied specifically to questions about species range dynamics. Subsequently, we provide a critical evaluation of some of the limitations and trade‐offs associated with DVMs, and we use those to guide our discussions about future model development. This includes a discussion on which processes are lacking, specifically a mechanistic representation of dispersal, inclusion of the seedling stage, trait variability, and a dynamic representation of reproduction. We also discuss upscaling techniques that offer promising solutions for being able to run these models efficiently over large spatial extents. Our aim is to provide directions for future research efforts and to illustrate the value of the DVM approach., Ecography, 37 (12), ISSN:0906-7590, ISSN:1600-0587

Context Pasture-woodlands are semi-natural landscapes that result from the combined influences of climate, management, and intrinsic vegetation dynamics. These landscapes are sensitive to future changes in land use and climate, but our ability to predict the impact on ecosystem service provisioning is limited due to the disparate scales in time and space that govern their dynamics. Objectives To develop a process-based model to simulate pasture-woodland landscapes and the provisioning of ecosystem services (i.e., livestock forage, woody biomass and landscape heterogeneity). Methods We modified a dynamic forest landscape model to simulate pasture-woodland landscapes in Switzerland. This involved including an annual herbaceous layer, selective grazing from cattle, and interactions between grazing and tree recruitment. Results were evaluated within a particular pasture, and then the model was used to simulate regional vegetation patterns and livestock suitability for a similar to 98,000 ha landscape in the Jura Vaudois region. Results The proportion of vegetation cover types at the pasture level (i.e., open, semi-open and closed forests) was well represented, but the spatial distribution of trees was only broadly similar. The entire Jura Vaudois region was simulated to be highly suitable for livestock, with only a small proportion being unsuitable due to steep slopes and high tree cover. High and low elevation pastures were equally suitable for livestock, as lower forage production at higher elevations was compensated by reduced tree cover. Conclusions The modified model is valuable for assessing landscape to regional patterns in vegetation and livestock, and offers a platform to evaluate how climate and management impact ecosystem services.

Forest ecosystems play an integral role in the earth system (e.g., by regulating biogeochemical cycles) and provide a wide range of services to human societies. It is therefore of crucial importance to understand the effects of a changing climate and changing disturbance regimes on forest dynamics. To date, most studies of forest dynamics have focused on trees, thus neglecting the herbaceous understorey (e.g., grass, ferns, herbs) although an increasing number of empirical studies suggest that the interaction between herbs and trees can profoundly alter forest dynamics. In particular, competition for light and water by the herbaceous understorey has been shown to change the structure and composition of tree regeneration, and thus to delay and potentially even arrest forest succession. When ignoring this interaction, thresholds in ecosystem responses to changing climate and disturbance regimes may remain undetected. However, due to the restrictions of empirical studies little is known on the implications of overstorey-understorey interactions for forest dynamics at larger spatio-temporal scales. Dynamic vegetation models (DVMs) have been developed to overcome this restriction and explore vegetation dynamics at large temporal scales (>100 years). Among the various types of DVMs, forest landscape models (FLMs) are specifically designed to investigate vegetation interactions under changing climate and disturbance regimes at large spatial scales. I used the process-based FLM LandClim to investigate the long-term effect of overstorey-understorey interactions on forest dynamics in central European landscapes, specifically focusing on (1) competition for light in mesic forest landscapes, (2) competition for water under present and future climate conditions in a drought-prone landscape, and (3) the potential of disturbances (browsing, windthrow, timber harvest) to promote delayed and arrested succession. In Chapter I, I implemented an understorey component in the FLM LandClim, with a focus on competition for light as the main mode of interaction. Simulation results for two mesic landscapes in Central Europe (Feldberg in the Black Forest and Dischma valley in the central Alps) showed spatio-temporal patterns that were in line with trends reported in empirical studies from chronosequences and species elevation distributions. The presence of an herbaceous understorey had a strong impact on tree regeneration and forest growth during early succession, but a much smaller effect on the late-successional stage. Also, the strength of overstorey-understorey interactions varied considerably across the landscape, causing large delays in forest growth at low and mid-elevations. Furthermore, the understorey was found to act as a differential filter for tree establishment, inducing a shift towards more shade-tolerant species, which translated into altered overstorey composition for up to 200 years. I was thus able to upscale the effects of understorey competition that are evident from empirical studies at the plot level (i.e., a few square metres) and at the short time scale (