Climate change amplifies the interactions between wind and bark beetle disturbances in forest landscapes

Abstract in dt. Sprache nicht verfügbarContext Growing evidence suggests that climate change could substantially alter forest disturbances. Interactions between individual disturbance agents are a major component of disturbance regimes, yet how interactions contribute to their climate sensitivity remains largely unknown. Objectives Here, our aim was to assess the climate sensitivity of disturbance interactions, focusing on wind and bark beetle disturbances. Methods We developed a process-based model of bark beetle disturbance, integrated into the dynamic forest landscape model iLand (already including a detailed model of wind disturbance). We evaluated the integrated model against observations from three wind events and a subsequent bark beetle outbreak, affecting 530.2 ha (3.8 %) of a mountain forest landscape in Austria between 2007 and 2014. Subsequently, we conducted a factorial experiment determining the effect of changes in climate variables on the area disturbed by wind and bark beetles separately and in combination. Results iLand was well able to reproduce observations with regard to area, temporal sequence, and spatial pattern of disturbance. The observed disturbance dynamics was strongly driven by interactions, with 64.3 % of the area disturbed attributed to interaction effects. A +4 C warming increased the disturbed area by +264.7 % and the area-weighted mean patch size by +1794.3 %. Interactions were found to have a ten times higher sensitivity to temperature changes than main effects, considerably amplifying the climate sensitivity of the disturbance regime. Conclusions Disturbance interactions are a key component of the forest disturbance regime. Neglecting interaction effects can lead to a substantial underestimation of the climate change sensitivity of disturbance regimes.(VLID)164896

Will forest dynamics continue to accelerate throughout the 21st century in the Northern Alps?

Observational evidence suggests that forests in the Northern Alps are changing at an increasing rate as a consequence of climate change. Yet, it remains unclear whether the acceleration of forest change will continue in the future, or whether downregulating feedbacks will eventually decouple forest dynamics from climate change. Here we studied future forest dynamics at Berchtesgaden National Park, Germany by means of a process-based forest landscape model, simulating an ensemble of 22 climate projections until the end of the 21st century. Our objectives were (i) to assess whether the observed acceleration of forest dynamics will continue in the future, (ii) to analyze how uncertainty in future climate translates to variation in future forest disturbance, structure, and composition, and (iii) to determine the main drivers of future forest dynamics. We found that forest dynamics continue to accelerate in the coming decades, with a trend towards denser, structurally more complex and more species rich forests. However, changes in forest structure leveled off in the second half of the 21st century regardless of climate scenario. In contrast, climate scenarios caused trajectories of tree species change to diverge in the second half of the 21st century, with stabilization under RCP 2.6 and RCP 4.5 scenarios and accelerated loss of conifers under RCP 8.5. Disturbance projections were 3 to 20 times more variable than future climate, whereas projected future forest structure and composition varied considerably less than climate. Indirect effects of climate change via alterations of the disturbance regime had a stronger impact on future forest dynamics than direct effects. Our findings suggest that dampening feedbacks within forest dynamics will decelerate forest change in the second half of the 21st century. However, warming beyond the levels projected under RCP 4.5 might profoundly alter future forest disturbance and composition, challenging conservation efforts and ecosystem service supply. --Raw simulation outputs are extensive in size and can be requested from the corresponding author, Dominik Thom.Funding provided by: European Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000781Award Number: 101001905Funding provided by: Bavarian State Ministry of the Environment and Consumer ProtectionCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100010219Award Number: StMUV TKP01KPB-66747The data is based on simulations of Berchtesgaden National Park using iLand (https://iland-model.org/). Simulations include 22 climate change projections à 20 replicates from year 2020 - 2100. Presented here is the analysis of iLand outputs

Partizipation und Stakeholder-Beteiligung in der Pilotregion Mostviertel: WP3 Synthesebericht

Aufgabe eines Partizipativen Regional Integrierten Vulnerabilitätsassessments (PRIVAS) ist es, in Zusammenarbeit mit Stakeholdern die integrative Wissensproduktion bei einem komplexen Mensch-Umwelt-Problem wie dem Klimawandel zu optimieren. Dieses Ziel stellt jedes Projekt vor konzeptive, methodische, prozessuale und forschungspraktische Herausforderungen, denen sich RIVAS in der Testregion gestellt hat. Auf Basis der Analyse und Erfahrungen aus 14 nationalen und internationalen Vulnerabilitätsassessments und der einschlägigen wissenschaftlichen Literatur wurde ein experimentelles Ablaufdesign für ein PRIVAS erstellt, welches im Mostviertel in einer Laufzeit von über einem Jahr umgesetzt wurde. Den Kern der Stakeholderinteraktionen bildete eine Referenzgruppe, die sich aus Akteuren der Demosektoren Land-, Wasser- und Forstwirtschaft, dem Regionalmanagement und des Projektteams zusammensetzte. Die Referenzgruppe war zentraler Kommunikationsort, wo eine Dialog- und Konsensorientierung vorherrschte. Die partizipativen Anknüpfungspunkte der Personen aus der Referenzgruppe im Vulnerabilitätsassessment waren unterschiedlich ausgeformt und gewichtet, da in RIVAS einige innovative und konzeptive Überlegungen getestet werden sollten. Der Schwerpunkt dabei wurde auf die partizipative Problemformulierung und Eingrenzung der Untersuchungsfragen (Phase „zu Beginn“ eines Assessments) sowie auf die Methodenanwendung und Analyse (Phase „während“ eines Assessments) gelegt. Eines der zentralen Ergebnisse von RIVAS ist, dass nicht nur das Produkt und die Ergebnisse einer Vulnerabilitätsbewertung Wissen und Verständnis schaffen, sondern dass zumindest gleichberechtigt auch der strukturierte Prozess für die Verbreitung, Aufnahme und den Transfer von Informationen und Wissen verantwortlich ist. Der Prozesscharakter solcher Interaktionen optimiert nicht nur die Qualität und Nutzbarkeit der Projektergebnisse, sondern unterstützt auch ein soziales Lernen und begünstigt langfristige Wirkungen, die weit über die Projektlaufzeit hinausreichen. Neben den bereits in der Literatur vielfach beschrieben organisatorischen Rahmenbedingungen (Transparenz, Regelmäßigkeit, Langfristigkeit, Vertrauenswürdigkeit, Interaktionsregeln und -techniken, Zeitpläne, etc.) ist vor allem der Grad der Partizipation ein entscheidendes Kriterium, welches für den Erfolg oder Misserfolg eines PRIVAS verantwortlich ist. In welchen Bereichen des Vulnerabilitätsassessments eine Mitbestimmung von Stakeholdern auf der Ebene der Information, Konsultation oder Mitbestimmung stattfinden soll, muss nicht nur frühzeitig und entlang der Bedürfnisse der Stakeholder und WissenschafterInnen abgestimmt werden, sondern sollte insbesondere immer einer zielgerichteten Entscheidung unterliegen, die auf den Zweck der Partizipation fokussiert. Ein weiteres Attribut für das Gelingen eines PRIVAS ist eine regel- und gleichmäßige Partizipation der Stakeholder. Das Projekt zeigt auf, dass die Institutionalisierung der Beteiligung vor allem durch die Bildung der Referenzgruppe gewährleistet werden konnte. Darüber hinaus hat die Einbindung eines regionalen Prozessträgers – des Regionalmanagements Mostviertel – entscheidend zur Beteiligungsmotivation beigetragen. Die Partizipation an einem Prozess und nicht nur die punktuellen Beteiligung an einem Projekt stand damit im Vordergrund. Schlussendlich müssen sich alle Partizipationsverfahren in einem PRIVAS dahingehend rechtfertigen, ob der notwendige Aufwand an Kosten und Zeit in einem angemessenen Verhältnis zu den Ergebnissen steht, und ob die im Projekt angestrebten Ziele auch erreicht wurden. Beides kann mit Hilfe der nach Abschluss des regionalen Projektteils durchgeführten Evaluation der Stakeholderbeteiligung für RIVAS positiv bestätigt werden

Multi-scale Drivers of Spatial Variation in Old-Growth Forest Carbon Density Disentangled with Lidar and an Individual-Based Landscape Model

Forest ecosystems are the most important terrestrial carbon (C) storage globally, and presently mitigate anthropogenic climate change by acting as a large and persistent sink for atmospheric CO₂. Yet, forest C density varies greatly in space, both globally and at stand and landscape levels. Understanding the multi-scale drivers of this variation is a prerequisite for robust and effective climate change mitigation in ecosystem management. Here, we used airborne light detection and ranging (Lidar) and a novel high-resolution simulation model of landscape dynamics (iLand) to identify the drivers of variation in C density for an old-growth forest landscape in Oregon, USA. With total ecosystem C in excess of 1 Gt ha⁻¹ these ecosystems are among the most C-rich globally. Our findings revealed considerable spatial variability in stand-level C density across the landscape. Notwithstanding the distinct environmental gradients in our mountainous study area only 55.3% of this variation was explained by environmental drivers, with radiation and soil physical properties having a stronger influence than temperature and precipitation. The remaining variation in C stocks was largely attributable to emerging properties of stand dynamics (that is, stand structure and composition). Not only were density- and size-related indicators positively associated with C stocks but also diversity in composition and structure, documenting a close link between biodiversity and ecosystem functioning. We conclude that the complexity of old-growth forests contributes to their sustained high C levels, a finding that is relevant to managing forests for climate change mitigation.Keywords: old-growth forests, functional diversity, iLand, forest carbon storage, forest stand dynamics, ecosystem structure and functioning, individual-based modeling, airborne Lidar, climate change mitigationKeywords: old-growth forests, functional diversity, iLand, forest carbon storage, forest stand dynamics, ecosystem structure and functioning, individual-based modeling, airborne Lidar, climate change mitigatio

Influence of Canopy Disturbances on Runoff and Landslide Disposition after Heavy Rainfall Events

As protective forests have a major control function on runoff and erosion, they directly affect the risk from hydrogeomorphic processes such as sediment transport processes or debris flows. In this context, future scenarios of climate-related canopy disturbances and their influence on the protective effect remain, however, an unsolved problem. With the individual-based forest landscape and disturbance model iLand, an ensemble of forest landscape simulations was carried out and the effects of future changes in natural disturbance regimes were evaluated. To determine peak runoff, hydrological simulations have been conducted, using the conceptual hydrological model ZEMOKOST as well as the deterministic model GEOtop. Effects of forest disturbances on hillslope stability were investigated, based on a modified Coulomb landslide model. Our results suggest no influence of the disturbance regime on the runoff. The climate-related increase in the frequency of disturbances is not reflected in increased runoff during the period under consideration. Contrary, slope stability analyses indicate that the availability of shallow landslides in steep forested torrent catchments might be decreased by the occurrence of disturbances – especially for a warm and dry climate projection. Canopy disturbances seem to accelerate the adaptation of tree species to future climate conditions, which is likely to be accompanied by a change in root systems away from flat roots that currently predominate in torrential catchments. In terms of managing the protective effect of forests against shallow landslides, such natural disturbances can thus be considered as positive interventions in the existing forest ecosystem by promoting natural succession

Tree mortality submodels drive simulated long-term forest dynamics: assessing 15 models from the stand to global scale

Models are pivotal for assessing future forest dynamics under the impacts of changing climate and management practices, incorporating representations of tree growth, mortality, and regeneration. Quantitative studies on the importance of mortality submodels are scarce. We evaluated 15 dynamic vegetation models (DVMs) regarding their sensitivity to different formulations of tree mortality under different degrees of climate change. The set of models comprised eight DVMs at the stand scale, three at the landscape scale, and four typically applied at the continental to global scale. Some incorporate empirically derived mortality models, and others are based on experimental data, whereas still others are based on theoretical reasoning. Each DVM was run with at least two alternative mortality submodels. Model behavior was evaluated against empirical time series data, and then, the models were subjected to different scenarios of climate change. Most DVMs matched empirical data quite well, irrespective of the mortality submodel that was used. However, mortality submodels that performed in a very similar manner against past data often led to sharply different trajectories of forest dynamics under future climate change. Most DVMs featured high sensitivity to the mortality submodel, with deviations of basal area and stem numbers on the order of 10–40% per century under current climate and 20–170% under climate change. The sensitivity of a given DVM to scenarios of climate change, however, was typically lower by a factor of two to three. We conclude that (1) mortality is one of the most uncertain processes when it comes to assessing forest response to climate change, and (2) more data and a better process understanding of tree mortality are needed to improve the robustness of simulated future forest dynamics. Our study highlights that comparing several alternative mortality formulations in DVMs provides valuable insights into the effects of process uncertainties on simulated future forest dynamics

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter