Modeling Social-Ecological Feedback Effects in the Implementation of Payments for Environmental Services in Pasture-Woodlands

International audienceAn effective implementation of payment for environmental services (PES) must allow for complex interactions of coupled social-ecological systems. We present an integrative study of the pasture-woodland landscape of the Swiss Jura Mountains combining methods from natural and social sciences to explore feedback between vegetation dynamics on paddock level, farm-based decision making, and policy decisions on the national political level. Our modeling results show that concomitant climatic and socioeconomic changes advance the loss of open grassland in silvopastoral landscapes. This would, in the longer term, deteriorate the historical wooded pastures in the region, which fulfill important functions for biodiversity and are widely considered as landscapes that deserve protection. Payment for environmental services could counteract this development while respecting historical land-use and ecological boundary conditions. The assessed policy feedback process reveals that current policy processes may hinder the implementation of PES, even though a payment for the upkeep of wooded pasture would generally enjoy the backing of the relevant policy network. To effectively support the upkeep of the wooded pastures in the Jura, concomitant policy changes, such as market deregulation, must also be taken into account

Mechanisms of woody plant succession in extensively grazed prealpine fens

Die Gehölzentwicklung in ehemals artenreichen Offenland-Ökosystemen nach Nutzungsaufgabe (Gehölzsukzession) ist eine der wesentlichen Ursachen für Biodiversitätsverluste und tiefgreifende Landschaftsveränderungen in den letzten Jahrzehnten. Eine wichtige Voraussetzung für ein effektives Management von Offenlandbiotopen ist ein mechanistisches Verständnis des Verbuschungsvorganges: Nach der Identifikation von Ursache-Wirkungs-Zusammenhängen im Sukzessionsgeschehen kann die naturschutzfachlich bedeutsame Frage nach den Entstehungsbedingungen und der Stabilität von Verbuschungsstadien, sowie ihrer Dichte und räumlichen Ausdehnung beantwortet werden. Beispielhaft werden die Mechanismen der Gehölzsukzession in extensiv beweideten, voralpinen Kleinseggenriedern auf mesotrophem Kalkflachmoor (Caricion davallianae) untersucht. Nach dem individualistischen Konzept in der Sukzessionsforschung resultiert der Verbuschungsprozess aus einer Abfolge von Teilprozessen (Sukzessionsmechanismen), die über die Lebensprozesse der Hauptbaumart, der Schwarzerle (Alnus glutinosa L.), definiert werden. Diese sind die individuelle Samenproduktion von Altbäumen, die großräumige Samenausbreitung durch Wind, die kleinräumigen Keimungs- und Etablierungsprozesse in Mikrostandorten in der Grasschicht und die intraspezifische Konkurrenz in Dickungen. Die Teilprozesse laufen (1) auf unterschiedlichen Maßstabsebenen ab (erfasst in Form eines hierarchischen patch-Mosaikes) und sind (2) durch den Lebensweg der Gehölzindividuen in Form einer Prozesskette chronologisch geordnet, wodurch (3) die Richtung von Ursache-Wirkungs-Zusammenhängen im Sukzessionsverlauf vorgegeben ist. Die kausale Analyse der Entstehung von Verbuschungsstrukturen auf Biozönoseebene durch die Lebensprozesse von Gehölzindividuen erfolgt in einem individuenbasierten gedanklichen Modell, dessen Formulierung der Sequenz der Prozesskette folgt. Zur Charakterisierung der Teilprozesse werden eigene und fremde Geländedaten ausgewertet: Die Samenproduktion fluktuiert näherungsweise in einem 3-Jahres-Rhythmus (Mastjahreszyklus). Die Ausbreitung von Samen folgt einer potentiellen Ausbreitungsfunktion mit variierenden maximalen Ausbreitungsdistanzen. Nur erhabene, nicht dauernasse Mikrostandorte an Bulten der zertretenen Mooroberfläche, die gut mit Licht versorgt sind, bieten für die Schwarzerle Etablierungsmöglichkeiten. Das Wachstum der Schwarzerle folgt einer exponentiellen Wachstumsfunktion. Die Abschätzung der Konsequenzen der initialen Teilprozesse Samenproduktion und Samenausbreitung für den Verbuschungsprozess (bottom-up-Ansatz) führt zur Definition von vier typischen Ausbreitungsmustern (räumliche Verteilung von Samen). Durch upscaling der Etablierungshabitate (Schutzstellen, micro-Ebene) wird gestützt auf die Vergrasungszustände der Grasschicht (differenziert auf meso-Ebene) und die Dichte der Strauchschicht (differenziert auf macro-Ebene) die Verteilung des Schutzstellpotentials auf unterschiedlichen Standorten abgeleitet. Um die Rolle der Teilprozesse im langfristigen Sukzessionsgeschehen abzuschätzen, wird das gedankliche Modell der Gehölzsukzession mit den Teilprozesscharakteristiken parametrisiert: Zur Modellbildung nach der Methode des pattern-oriented modeling werden dem Modell die Teilprozesse in zunehmend komplexerer Form hinzugefügt, bis ein zufriedenstellender Erklärungsgrad von beobachteten Verbuschungsmustern erreicht ist (top-down-Ansatz). Sowohl die Samenproduktion, die Samenausbreitung, die Keimung und Etablierung, als auch die Etablierungshemmung für Erlenkeimlinge in Dickungen und self-thinning beeinflussen die Struktur von Verbuschungsgradienten. Flächige Besiedlungsstrukturen mit einem ausgeprägten Gradienten in der Individuendichte entstehen auf Flächen mit zeitlich konstantem, homogenem Schutzstellenpotential der Grasschicht (nasse, stark zertretene Niedermoorflächen). Bestimmte Abfolgen von Ausbreitungsmustern im Sukzessionsverlauf erzeugen in der Besiedlungsstruktur charakteristische Altersgradienten bzw. Stufen im Wuchshöhengradient. Diese Strukturen fehlen im Fall stochastisch-heterogenen Schutzstellenpotentials auf trockenen, schwach zertretenen Niedermoorflächen: Im langfristigen Sukzessionsgeschehen zerstreut die raumzeitliche Zufälligkeit in der Schutzstellenverfügbarkeit die Regelhaftigkeit von Ausbreitungsmustern und führt zur „Auflösung“ potentieller flächiger Besiedlungsstrukturen in lückige Muster aus Einzelbäumen. Das gedankliche Modell zur Gehölzsukzession stützt sich auf die Ergebnisse detaillierter Kurzzeituntersuchungen ihrer Teilprozesse, als auch auf die Analyse ihrer langfristigen Konsequenzen (Verbuschungsmuster). Es bringt die Entstehung von flächigen und verinselten Besiedlungsstrukturen, von mehrstufigen und einstufigen Wuchshöhenprofilen, sowie von großen und geringen räumlichen Schrittweiten der Verbuschung in ein geschlossenes Konzept aus unterschiedlichen Wirkungskonstellationen von Teilprozessen der Gehölzsukzession.Woody plant succession following the abandonment of formerly species-rich grassland ecosystems has been one of the most important reasons for biodiversity losses and severe changes in landscape structure during recent decades. A necessity for successful management of open landscapes in terms of nature conservation (i.e. avoidance of shrub encroachment) is a mechanistic understanding of the succession process: Having identified cause-effect-relationships, the question can be answered of how shrubs develop during succession and to which density and extent they cover the formerly open land. For these reasons the mechanisms of woody plant succession in extensively grazed prealpine mesotrophic calcareous fens (Caricion davallianae) are analyzed. Applying the individualistic theory of succession, the process of shrub encroachment emerges from a sequence of mechanisms, that are defined as life-processes of individuals of the dominant tree species, Black Alder (Alnus glutinosa L.). The life-processes, that drive succession, are individual seed production, far reaching seed dispersal by wind, germination and establishment in small scale habitats and intraspecific competition in thickets. The mechanisms of succession (1) run on different scales (conceptualized as hierarchical patch-mosaic) and (2) are put into chronological order by the life-history of the tree individuals. Through this natural order (3) the direction of cause-effect-relationships is predefined. Analysis of the emergence of structures in the shrub-biocoenosis from life-processes of individuals is done using a conceptual individual-based model, that is based on the sequence of mechanisms of succession. Field data are used to characterize the life-processes under local conditions. Seed production of isolated trees fluctuates in a 3-years-cycle (mast-years). Seed dispersal follows a power function, while the distance of seed dispersal varies from year to year. Only raised microsites on hummocks, that are not constantly saturated and that receive a high proportion of radiation, provide suitable conditions for successful establishment of Alder (safe sites). The growth of Alder follows an exponential curve. The consequences of the initial mechanisms of succession for the process of shrub encroachment are evaluated following a bottom-up-approach: seed production together with seed dispersal result in four different types of seed shadows. The potential for establishment of Alder on different sites is derived through an upscaling procedure that starts from safe sites for seedlings (micro-scale) and integrates the density of the field layer (meso-scale) and of stands of shrubs and trees (macro-scale). In order to evaluate the role of the mechanisms of succession in the long run, the conceptual model of woody plant succession is parameterized with the mechanism's characteristics known from field data. Model building follows the protocol of pattern-oriented modeling, i.e. the variability of mechanisms is integrated into the model stepwise leading to higher complexity of the model. This procedure is stopped when structures of observed encroachment-patterns can be explained satisfactorily by the model (top-down-approach). The formation of patterns of shrub encroachment is influenced by seed production, seed dispersal, germination and establishment, suppression of Alder seedlings in thickets and self-thinning. On sites with a potential for establishment of Alder that is constant in time, homogenous and low (wet and trampled calcareous fen) dense colonization structures develop. Here, a specific sequence of seed shadows induce characteristic age structures in the colonization pattern. These structures lack on sites where the potential of establishment of Alder is stochastic and heterogeneous (comparatively dry and slightly trampled conditions): Stochasticity of safe sites in time and space leads to dispersion of the regularity of seed shadows and results in a separation of dense colonization structures into a single tree-pattern. The conceptual model of woody plant succession is equally based on short term field data as on the analysis of the long term consequences of the succession process (encroachment patterns). The conceptual model explains dense and single tree-colonization patterns, age structures and different spatial extent of shrub encroachment as results from different sets of cause-effect-relationships between the mechanisms of succession

Dynamic modelling of silvopastoral landscape structure: Past reconstruction and scenarios for future climate and land use

International audienc

Establishment patterns in a secondary tree line ecotone

On semi-open pre-alpine fen pastures Alder encroachment creates a dynamic mosaic of grassland and woodland, which is rich in ecotones from fen to Carr. The structural diversity in colonisation patterns of Alder on fens suggests a dependency on multiple environmental drivers. Unidirectional progressive ecotone development provides an opportunity to address a current deficit in understanding successional patterns, i.e. process-pattern relationships in a multiple factor regime

Dynamic modelling of silvopastoral landscape structure: Scenarios for future climate and land use

International audienc

Integrating models across temporal and spatial scales to simulate landscape patterns and dynamics in mountain pasture-woodlands

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 ~198,000 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.ISSN:0921-2973ISSN:1572-976

Climate change simulations in Alpine summer pastures suggest a disruption of current vegetation zonation

Alpine summer grazing areas (high-altitude pastures) represent hotspots of biodiversity and high cultural heritage values. Low density forests (Alpine Larix decidua and/or Pinus cembra forests) and species-rich open land (Alpine and boreal heaths, siliceous Alpine and boreal grasslands) are protected according to the Flora-Fauna-Habitat-directive of the European Union. These habitats are threatened by the accelerated mountain climate warming and the expected upslope shift of vegetation zones. With climate change, tree growth accelerates and montane species spread to higher altitudes. The fate of low density larch forests, alpine heathlands and grasslands is unclear. We used the process-based wooded pasture model WoodPaM to simulate large-scale and long-term dynamics of the forest and tree line under several land-use scenarios and climate change. The simulation results for the central Alpine summer grazing area Furggtal (Canton Valais, Switzerland) showed a plausible projection of the upslope migration of vegetation zones due to climate warming in the very long-term. For the upcoming centuries however, the existing vegetation zonation was disrupted by the intermixing of tree species during the migration process. This unexpected result emerged from the process-based modelling of tree species specific dispersal and establishment in interaction with livestock grazing. This effect was most pronounced in simulations of grazing abandonment and current low intensity grazing of free ranging livestock, which failed to buffer climate change effects. The establishment of paddocks and thereby intensified grazing on the current pastures on the valley floor promised the conservation of valuable open habitats. We conclude that the ongoing rapid upslope shift of climate zones in mountain regions might not be followed by a similar shift of vegetation zones. Widespread colonisation processes might lead to a period dominated by very dynamic vegetation communities that might not zone along climatic gradients as it was in the past of comparable stable climate. Climate change may therefore impact more like disturbance on alpine ecosystems rather than to drive continuous range shifts. During this disruptive transformation, adapted grazing management in summer pastures can help to maintain continuity for valuable habitats but would require subsidies to establish infrastructure and to increase livestock numbers

Intermediate foraging large herbivores maintain semi-open habitats in wilderness landscape simulations

In the context of the rewilding Europe debate, the German national strategy on biodiversity aims to dedicate two percent of the German state area to wilderness development until 2020. Many of these potential large wilderness reserves harbor open habitats that require protection according to the Flora-Fauna-Habitat-directive of the European Union. As forests prevail in potential natural vegetation, research is required, to which extent wild large herbivores and natural disturbances may create semi-open landscape patterns in the long-term. We used the spatially explicit process-based model of pasture-woodland ecosystem dynamics WoodPaM, to analyze the long-term interactions between intermediate foraging large wild herbivores and vegetation dynamics in edaphically heterogeneous forest-grassland mosaic landscapes. We newly implemented a routine for intermediate foraging herbivores. We determined herbivore impact on vegetation from the quantitative balance between the demand and supply of herbaceous forage and woody browse. In abstract landscapes that represent the conditions in the established German wilderness area "Döberitzer Heide", we simulated potential future landscape dynamics on open land, in forest and along forest edges with and without intermediate foraging large herbivores and for a climate change scenario. In our simulations the currently open landscape was conserved and even more the opening of current oak and beech forest was promoted. Canopy thinning and patch-mosaics of oak, birch, poplar and pine stands increased the overall nature conservation value in the long-term. To the contrary, open habitats were lost in simulations without herbivores. Moreover, our simulations suggested that intermediate foraging herbivores are especially suitable to maintain semi-open landscapes in wilderness areas, because (i) no additional winter forage was required, the natural availability of browse was sufficient. (ii) Their grazing maintained open land and their browsing thinned tree canopies even on poor sites that were unattractive for foraging. Here, habitat was maintained for threatened species from dry grasslands

Integrating models across temporal and spatial scales to simulate landscape patterns and dynamics in mountain pasture-woodlands

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