DOCSLIB.ORG

Integrating Dynamic and Statistical Modelling Approaches in Order to Improve Predictions for Scenarios of Environmental Change

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Integrating Dynamic and Statistical Modelling Approaches in Order to Improve Predictions for Scenarios of Environmental Change Institut für Erd- und Umweltwissenschaften Arbeitsgruppe Environmental Modelling Integrating dynamic and statistical modelling approaches in order to improve predictions for scenarios of environmental change Kumulative Dissertation zur Erlangung des akademischen Grades "doctor rerum naturalium" (Dr. rer. nat.) in der Wissenschaftsdisziplin "Geoökologie" eingereicht an der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Potsdam von Damaris Zurell aus Templin Potsdam, den 05.05.2011 Published online at the Institutional Repository of the University of Potsdam: URL http://opus.kobv.de/ubp/volltexte/2011/5684/ URN urn:nbn:de:kobv:517-opus-56845 http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-56845 if tha eva does owt for nowt do it for thi sen Yorkshire saying Contents Contents CONTENTS I SUMMARY V ZUSAMMENFASSUNG VII 1 GENERAL INTRODUCTION 1 1.1 Motivation and objectives 2 1.2 State of the art 6 1.2.1 Correlative species distribution models 6 1.2.2 Mechanistic models of species distributions 11 1.2.3 ‘Hybrid’ models of species distributions 15 1.3 Thesis structure 16 2 THE VIRTUAL ECOLOGIST APPROACH: SIMULATING DATA AND OBSERVERS 19 2.1 Abstract 20 2.2 Introduction 20 2.3 The virtual ecologist approach 23 2.4 Past use of VE 26 2.4.1 Testing and improving sampling schemes and methods 26 2.4.2 Testing and comparing models 28 2.5 Discussion 33 2.5.1 Limitations 34 2.5.2 The role of mechanistic models 35 2.5.3 Future directions 36 3 STATIC SPECIES DISTRIBUTION MODELS IN DYNAMICALLY CHANGING SYSTEMS: HOW GOOD CAN PREDICTIONS REALLY BE? 39 i Contents 3.1 Abstract 40 3.2 Introduction 40 3.3 Methods 42 3.3.1 Dynamic population model 42 3.3.2 Sampling by virtual ecologist 46 3.3.3 Statistical modelling 46 3.4 Results 48 3.4.1 Dynamic population model 48 3.4.2 Statistical models 49 3.5 Discussion 54 3.5.1 Prediction accuracies under climate change 54 3.5.2 Model comparison 55 3.5.3 Effects of ecological properties and processes 55 3.5.4 Limitations and extensions 57 3.5.5 Perspectives and research needs in species distribution modelling 57 3.5.6 Conclusion 59 4 UNCERTAINTY IN PREDICTIONS OF RANGE DYNAMICS: BLACK GROUSE CLIMBING THE SWISS ALPS 61 4.1 Abstract 62 4.2 Introduction 62 4.3 Methods 65 4.3.1 Species data 65 4.3.2 Environmental predictors 65 4.3.3 Climate change scenarios 66 4.3.4 Species distribution model 66 4.3.5 Individual-based model 67 4.3.6 Sensitivity analysis 69 4.4 Results 70 4.4.1 Statistical modelling and range predictions 70 4.4.2 Population dynamics 72 4.4.3 Sensitivity analysis 73 4.5 Discussion 76 4.5.1 Black grouse population and range dynamics 77 4.5.2 Robustness of range predictions 79 ii Contents 4.5.3 Challenges in species distribution modelling 81 4.5.4 Conclusions 83 5 PREDICTING TO NEW ENVIRONMENTS: TOOLS FOR VISUALISING MODEL BEHAVIOUR AND IMPACTS ON MAPPED DISTRIBUTIONS 85 5.1 Abstract 86 5.2 Introduction 86 5.3 Demonstrating prediction problems: simulated species 88 5.4 New tools for visualisation 89 5.5 Summary 94 6 SYNTHESIS 95 6.1 Summary of achievements 96 6.1.1 Virtual ecologists 96 6.1.2 Range predictions by correlative models 98 6.1.3 Range predictions by dynamic models 100 6.2 Challenges in dynamic range predictions 102 6.2.1 Niche conservatism 102 6.2.2 Circularity 103 6.2.3 Model specification 103 6.2.4 Model complexity 104 6.2.5 Response vs. effect traits 105 6.2.6 Data availability 106 6.3 Quo vadis? 107 A THE VIRTUAL ECOLOGIST APPROACH: SIMULATING DATA AND OBSERVERS – SUPPLEMENTARY MATERIAL 113 B STATIC SPECIES DISTRIBUTION MODELS IN DYNAMICALLY CHANGING SYSTEMS: HOW GOOD CAN PREDICTIONS REALLY BE? – SUPPLEMENTARY MATERIAL 123 C UNCERTAINTY IN PREDICTIONS OF RANGE DYNAMICS: BLACK GROUSE CLIMBING THE SWISS ALPS – SUPPLEMENTARY MATERIAL 127 iii Contents D PREDICTING TO NEW ENVIRONMENTS: TOOLS FOR VISUALISING MODEL BEHAVIOUR AND IMPACTS ON MAPPED DISTRIBUTIONS – SUPPLEMENTARY MATERIAL 135 BIBLIOGRAPHY 153 DANKSAGUNG 173 iv Summary Summary Species respond to environmental change by dynamically adjusting their geographical ranges. Robust predictions of these changes are prerequisites to inform dynamic and sustainable conservation strategies. Correlative species distribution models (SDMs) relate species’ occurrence records to prevailing environmental factors to describe the environmental niche. They have been widely applied in global change context as they have comparably low data requirements and allow for rapid assessments of potential future species’ distributions. However, due to their static nature, transient responses to environmental change are essentially ignored in SDMs. Furthermore, neither dispersal nor demographic processes and biotic interactions are explicitly incorporated. Therefore, it has often been suggested to link statistical and mechanistic modelling approaches in order to make more realistic predictions of species’ distributions for scenarios of environmental change. In this thesis, I present two different ways of such linkage. (i) Mechanistic modelling can act as virtual playground for testing statistical models and allows extensive exploration of specific questions. I promote this ‘virtual ecologist’ approach as a powerful evaluation framework for testing sampling protocols, analyses and modelling tools. Also, I employ such an approach to systematically assess the effects of transient dynamics and ecological properties and processes on the prediction accuracy of SDMs for climate change projections. That way, relevant mechanisms are identified that shape the species’ response to altered environmental conditions and which should hence be considered when trying to project species’ distribution through time. (ii) I supplement SDM projections of potential future habitat for black grouse in Switzerland with an individual-based population model. By explicitly considering complex interactions between habitat availability and demographic processes, this allows for a more direct assessment of expected population response to environmental change and associated extinction risks. However, predictions were highly variable across simulations emphasising the need for principal evaluation tools like sensitivity analysis to assess uncertainty and robustness in dynamic range predictions. Furthermore, I identify data coverage of the environmental niche as a likely cause for contrasted range predictions between SDM algorithms. SDMs may fail to make reliable predictions for truncated and edge niches, meaning that portions of the niche are not represented in the data or niche edges coincide with data limits. v Summary Overall, my thesis contributes to an improved understanding of uncertainty factors in predictions of range dynamics and presents ways how to deal with these. Finally I provide preliminary guidelines for predictive modelling of dynamic species’ response to environmental change, identify key challenges for future research and discuss emerging developments. vi Zusammenfassung Zusammenfassung Das Vorkommen von Arten wird zunehmend bedroht durch Klima- und Landnutzungswandel. Robuste Vorhersagen der damit verbundenen Arealveränderungen sind ausschlaggebend für die Erarbeitung dynamischer und nachhaltiger Naturschutzstrategien. Habitateignungsmodelle erstellen statistische Zusammenhänge zwischen dem Vorkommen einer Art und relevanten Umweltvariablen und erlauben zügige Einschätzungen potentieller Arealveränderungen. Dabei werden jedoch transiente Dynamiken weitgehend ignoriert sowie demographische Prozesse und biotische Interaktionen. Daher wurden Vorschläge laut, diese statistischen Modelle mit mechanistischeren Ansätzen zu koppeln. In der vorliegenden Arbeit zeige ich zwei verschiedene Möglichkeiten solcher Kopplung auf. (i) Ich beschreibe den sogenannten ‚Virtuellen Ökologen’-Ansatz als mächtiges Validierungswerkzeug, in dem mechanistische Modelle virtuelle Testflächen bieten zur Erforschung verschiedener Probenahmedesigns oder statistischer Methoden sowie spezifischer Fragestellungen. Auch verwende ich diesen Ansatz, um systematisch zu untersuchen wie sich transiente Dynamiken sowie Arteigenschaften und ökologische Prozesse auf die Vorhersagegüte von Habitateignungsmodellen auswirken. So kann ich entscheidende Prozesse identifizieren welche in zukünftigen Modellen Berücksichtigung finden sollten. (ii) Darauf aufbauend koppele ich Vorhersagen von Habitateignungsmodellen mit einem individuen-basierten Populationsmodell, um die Entwicklung des Schweizer Birkhuhnbestandes unter Klimawandel vorherzusagen. Durch die explizite Berücksichtigung der Wechselwirkungen zwischen Habitat und demographischer Prozesse lassen sich direktere Aussagen über Populationsentwicklung und damit verbundener Extinktionsrisiken treffen. Allerdings führen verschiedene Simulationen auch zu hoher Variabilität zwischen Vorhersagen, was die Bedeutung von Sensitivitätsanalysen unterstreicht, um Unsicherheiten und Robustheit von Vorhersagen einzuschätzen. Außerdem identifiziere ich Restriktionen in der Datenabdeckung des Umweltraumes als möglichen Grund für kontrastierende Vorhersagen verschiedener Habitateignungsmodelle. Wenn die Nische einer Art nicht vollständig durch Daten beschrieben ist, kann dies zu unrealistischen Vorhersagen der Art-Habitat-Beziehung führen. Insgesamt trägt meine Arbeit erheblich bei zu einem besseren Verständnis der Auswirkung verschiedenster Unsicherheitsfaktoren auf Vorhersagen von Arealveränderungen und zeigt Wege auf, mit diesen umzugehen. Abschließend erstelle ich einen vorläufigen Leitfaden für Vorhersagemodelle und identifiziere Kernpunkte für weitere Forschung
Load more

Recommended publications
  • Limiting Similarity? the Ecological Dynamics of Natural Selection Among Resources and Consumers Caused by Both Apparent and Resource Competition
    vol. 193, no. 4 the american naturalist april 2019 E-Article Limiting Similarity? The Ecological Dynamics of Natural Selection among Resources and Consumers Caused by Both Apparent and Resource Competition Mark A. McPeek* Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755 Submitted December 31, 2017; Accepted September 8, 2018; Electronically published January 17, 2019 Online enhancements: appendix, MATLAB code, video. abstract: 1959). Most explorations of this idea have focused on one Much of ecological theory presumes that natural selection — should foster species coexistence by phenotypically differentiating particular type of species interaction competition among competitors so that the stability of the community is increased, but consumers for shared resources. Resource competition is an whether this will actually occur is a question of the ecological dynamics indirect interaction between consumers that is mediated by of natural selection. I develop an evolutionary model of consumer- their effects on and responses to shared resources (Levene resource interactions based on MacArthur’s and Tilman’s classic works, 1976; Tilman 1980, 1982, 1987). If multiple resource species including both resource and apparent competition, to explore what are involved, the indirect interaction of apparent competition fosters or retards the differentiation of resources and their consumers. Analyses of this model predict that consumers will differentiate only between resources also occurs and is mediated by their effects on specific ranges of environmental gradients (e.g., greater productivity, on and responses to the consumers (Holt 1977). However, weaker stressors, lower structural complexity), and where it occurs, the MacArthur’s original exploration of these issues recast all of magnitude of differentiation also depends on gradient position.
    [Show full text]
  • Range and Variation in Landscape Patch Dynamics: Implications for Ecosystem Management
    Range and Variation in Landscape Patch Dynamics: Implications for Ecosystem Management Robert E. Keane Janice L. Garner Casey Teske Cathy Stewart Paul Hessburg Abstract—Northern Rocky Mountain landscape patterns are shaped example, the range of patch sizes on a landscape over time primarily by fire and succession, and conversely, these vegetation could be used to design the size of a prescribed fire so that it patterns influence burning patterns and plant colonization pro- is not bigger, or smaller, than what would have occurred cesses. Historical range and variability (HRV) of landscape pattern historically (Cissel and others 1999; Swetnam and others can be quantified from three sources: (1) historical chronosequences, 1999; Mladenoff and others 1993). Current landscape condi- (2) spatial series, and (3) simulated chronosequences. The last two tions could also be compared with summarized historical sources were used to compute HRV for this study. Spatial series landscape conditions to detect ecologically significant change, were characterized from aerial photographs of 10 similar land- such as that brought on by fire exclusion and timber harvest- scapes on the Bitterroot National Forest, Montana. The LANDSUM ing (Baker 1992, 1995; Cissel and others 1999; Hessburg and model was used to simulate landscape patterns for three landscapes others 1999b; Landres and others 1999). on the Flathead National Forest. Landscape metrics were computed Landscape structure and composition are usually charac- using FRAGSTATS. Results can be used (1) to describe landscape terized from the spatial distribution of patches—a term characteristics, (2) to develop baseline threshold values, and (3) to synonymous with stands or polygons. Many types of spatial design treatment guidelines for ecosystem management.
    [Show full text]
  • Broadly Inflicted Stressors Can Cause Ecosystem Thinning
    Theoretical Ecology https://doi.org/10.1007/s12080-019-0417-4 ORIGINAL PAPER Broadly inflicted stressors can cause ecosystem thinning Matthew G. Burgess1,2 & Alexa Fredston-Hermann3 & David Tilman3,4 & Michel Loreau5 & Steven D. Gaines3,6 Received: 11 July 2018 /Accepted: 12 February 2019 # Springer Nature B.V. 2019 Abstract Many anthropogenic stressors broadly inflict mortality or reduce fecundity, including habitat destruction, pollution, climate change, invasive species, and multispecies harvesting. Here, we show—in four analytical models of interspecies competition—that broadly inflicted stressors disproportionately cause competitive exclusions within groups of ecologically similar species. As a result, we predict that ecosystems become progressively thinner—that is, they have progressively less functional redundancy—as broadly inflicted stressors become progressively more intense. This may negatively affect the temporal stability of ecosystem functions, but it also buffers ecosystem productivity against stress by favoring species less sensitive to the stressors. Our main result follows from the weak limiting similarity principle: species with more similar ecological niches compete more strongly, and their coexistence can be upset by smaller perturbations. We show that stressors can cause indirect competitive exclusions at much lower stressor intensity than needed to directly cause species extinction, consistent with the finding of empirical studies that species interactions are often the proximal drivers of local extinctions. The excluded species are more sensitive to the stressor relative to their ecologically similar competitors. Moreover, broadly inflicted stressors may cause hydra effects—where higher stressor intensity results in higher abundance for a species with lower sensitivity to the stressor than its competitors. Correlations between stressor impacts and ecological niches reduce the potential for indirect competitive exclusions, but they consequently also reduce the buffering effect of ecosystem thinning on ecosystem productivity.
    [Show full text]
  • Natural Disturbance and Stand Development Principles for Ecological Forestry
    United States Department of Agriculture Natural Disturbance and Forest Service Stand Development Principles Northern Research Station for Ecological Forestry General Technical Report NRS-19 Jerry F. Franklin Robert J. Mitchell Brian J. Palik Abstract Foresters use natural disturbances and stand development processes as models for silvicultural practices in broad conceptual ways. Incorporating an understanding of natural disturbance and stand development processes more fully into silvicultural practice is the basis for an ecological forestry approach. Such an approach must include 1) understanding the importance of biological legacies created by a tree regenerating disturbance and incorporating legacy management into harvesting prescriptions; 2) recognizing the role of stand development processes, particularly individual tree mortality, in generating structural and compositional heterogeneity in stands and implementing thinning prescriptions that enhance this heterogeneity; and 3) appreciating the role of recovery periods between disturbance events in the development of stand complexity. We label these concepts, when incorporated into a comprehensive silvicultural approach, the “three-legged stool” of ecological forestry. Our goal in this report is to review the scientific basis for the three-legged stool of ecological forestry to provide a conceptual foundation for its wide implementation. Manuscript received for publication 1 May 2007 Published by: For additional copies: USDA FOREST SERVICE USDA Forest Service 11 CAMPUS BLVD SUITE 200 Publications Distribution NEWTOWN SQUARE PA 19073-3294 359 Main Road Delaware, OH 43015-8640 November 2007 Fax: (740)368-0152 Visit our homepage at: http://www.nrs.fs.fed.us/ INTRODUCTION Foresters use natural disturbances and stand development processes as models for silvicultural practices in broad conceptual ways.
    [Show full text]
  • Equilibrium Theory of Island Biogeography: a Review
    Equilibrium Theory of Island Biogeography: A Review Angela D. Yu Simon A. Lei Abstract—The topography, climatic pattern, location, and origin of relationship, dispersal mechanisms and their response to islands generate unique patterns of species distribution. The equi- isolation, and species turnover. Additionally, conservation librium theory of island biogeography creates a general framework of oceanic and continental (habitat) islands is examined in in which the study of taxon distribution and broad island trends relation to minimum viable populations and areas, may be conducted. Critical components of the equilibrium theory metapopulation dynamics, and continental reserve design. include the species-area relationship, island-mainland relation- Finally, adverse anthropogenic impacts on island ecosys- ship, dispersal mechanisms, and species turnover. Because of the tems are investigated, including overexploitation of re- theoretical similarities between islands and fragmented mainland sources, habitat destruction, and introduction of exotic spe- landscapes, reserve conservation efforts have attempted to apply cies and diseases (biological invasions). Throughout this the theory of island biogeography to improve continental reserve article, theories of many researchers are re-introduced and designs, and to provide insight into metapopulation dynamics and utilized in an analytical manner. The objective of this article the SLOSS debate. However, due to extensive negative anthropo- is to review previously published data, and to reveal if any genic activities, overexploitation of resources, habitat destruction, classical and emergent theories may be brought into the as well as introduction of exotic species and associated foreign study of island biogeography and its relevance to mainland diseases (biological invasions), island conservation has recently ecosystem patterns. become a pressing issue itself.
    [Show full text]
  • Patch Dynamics and Metapopulation Theory: the Case of Successional Species
    Journal of Theoretical Biology (2001) 209 (3): 333-344. http://dx.doi.org/10.1006/jtbi.2001.2269 Patch Dynamics and Metapopulation Theory: The Case of Successional Species a a,b Priyanga Amarasekare and Hugh Possingham a National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara, 735 State Street, Suite 300, Santa Barbara, CA, 93101-5504, U.S.A. b Departments of Zoology and Mathematics, The University of Queensland, St Lucia, QLD 4072, Australia Abstract We present a mathematical framework that combines extinction–colonization dynamics with the dynamics of patch succession. We draw an analogy between the epidemiological categorization of individuals (infected, susceptible, latent and resistant) and the patch structure of a spatially heterogeneous landscape (occupied–suitable, empty–suitable, occupied–unsuitable and empty– unsuitable). This approach allows one to consider life-history attributes that influence persistence in patchy environments (e.g., longevity, colonization ability) in concert with extrinsic processes (e.g., disturbances, succession) that lead to spatial heterogeneity in patch suitability. It also allows the incorporation of seed banks and other dormant life forms, thus broadening patch occupancy dynamics to include sink habitats. We use the model to investigate how equilibrium patch occupancy is influenced by four critical parameters: colonization rate, extinction rate, disturbance frequency and the rate of habitat succession. This analysis leads to general predictions about how the temporal scaling of patch succession and extinction–colonization dynamics influences long- term persistence. We apply the model to herbaceous, early-successional species that inhabit open patches created by periodic disturbances. We predict the minimum disturbance frequency required for viable management of such species in the Florida scrub ecosystem.
    [Show full text]
  • Resource Partitioning Among African Savanna Herbivores in North Cameroon: the Importance of Diet Composition, Food Quality and Body Mass
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Wageningen University & Research Publications Journal of Tropical Ecology (2011) 27:503–513. © Cambridge University Press 2011 doi:10.1017/S0266467411000307 Resource partitioning among African savanna herbivores in North Cameroon: the importance of diet composition, food quality and body mass H. H. de Iongh∗,1,C.B.deJong†, J. van Goethem∗,E.Klop∗, A. M. H. Brunsting†, P. E. Loth∗ and H. H. T. Prins† ∗ Institute of Environmental Sciences, Leiden University, P.O. Box 9518, 2300 RA Leiden, the Netherlands † Resource Ecology Group, Wageningen University, Droevendaalsesteeg 3a, 6708 PB Wageningen, the Netherlands (Accepted 20 June 2011) Abstract: The relationship between herbivore diet quality, and diet composition (the range of food plants consumed) and body mass on resource partitioning of herbivores remains the subject of an ongoing scientific debate. In this study we investigated the importance of diet composition and diet quality on resource partitioning among eight species of savanna herbivore in north Cameroon, with different body mass. Dung samples of four to seven wild herbivore and one domesticated species were collected in the field during the dry and wet period. Diet composition was based on microhistological examination of herbivore droppings, epidermis fragments were identified to genus or family level. In addition, the quality of the faecal droppings was determined in terms of phosphorus, nitrogen and fibre concentrations. The results showed that there was no significant correlation between body mass and (differences in) diet composition for wet and dry season. When all species are considered, only significant relationships are found by the Spearman rank correlation analyses during the wet season between body mass and phosphorus and nitrogen, but this relationship did not exist during the dry season.
    [Show full text]
  • Competitive Exclusion and Limiting Similarity: a Unified Theory
    International Institute for Tel: +43 2236 807 342 Applied Systems Analysis Fax: +43 2236 71313 Schlossplatz 1 E-mail: [email protected] A-2361 Laxenburg, Austria Web: www.iiasa.ac.at Interim Report IR-05-040 Competitive Exclusion and Limiting Similarity: A Unified Theory Géza Meszéna ([email protected]) Mats Gyllenberg ([email protected]) Liz Pásztor ([email protected]) Johan A. J. Metz ([email protected]) Approved by Ulf Dieckmann Program Leader, ADN August 2005 Interim Reports on work of the International Institute for Applied Systems Analysis receive only limited review. Views or opinions expressed herein do not necessarily represent those of the Institute, its National Member Organizations, or other organizations supporting the work. IIASA STUDIES IN ADAPTIVE DYNAMICS NO. 101 The Adaptive Dynamics Network at IIASA fosters the develop- ment of new mathematical and conceptual techniques for under- standing the evolution of complex adaptive systems. Focusing on these long-term implications of adaptive processes in systems of limited growth, the Adaptive Dynamics Network brings together scientists and institutions from around the world with IIASA acting as the central node. Scientific progress within the network is collected in the IIASA ADN Studies in Adaptive Dynamics series. No. 1 Metz JAJ, Geritz SAH, Meszéna G, Jacobs FJA, van No. 11 Geritz SAH, Metz JAJ, Kisdi É, Meszéna G: The Dy- Heerwaarden JS: Adaptive Dynamics: A Geometrical Study namics of Adaptation and Evolutionary Branching. IIASA of the Consequences of Nearly Faithful Reproduction. IIASA Working Paper WP-96-077 (1996). Physical Review Letters Working Paper WP-95-099 (1995).
    [Show full text]
  • Disturbance Management - Application of Ecological Knowledge to Habitat Restoration - A
    BIODIVERSITY: STRUCTURE AND FUNCTION – Vol. II - Disturbance Management - Application of Ecological Knowledge to Habitat Restoration - A. Jentsch DISTURBANCE MANAGEMENT - APPLICATION OF ECOLOGICAL KNOWLEDGE TO HABITAT RESTORATION A. Jentsch Department of Conservation Biology, Helmholtz - Centre for Environmental Research UFZ, Permoserstr. 15, D-04318 Leipzig, and Dept. of Disturbance Ecology and Vegetation Dynamics, Bayreuth University, D-95440 Bayreuth, Germany Keywords: disturbance, ecosystem dynamics, succession, plant functional type, resources, grassland Contents 1. Part A: Concepts and Theory - Relating Disturbance Ecology to Restoration 1.1 The general role of disturbance in restoration 1.2 Continuous versus discrete processes in ecosystem dynamics 1.3 Significance of disturbance for ecosystem dynamics 1.4 Disturbance definition 1.5 The patch and multi-patch concept 1.6 Disturbance as a filter in community assembly and a tool in restoration 1.7 Dynamic equilibrium as a restoration goal 2. Part B: For Practitioners - Application of Ecological Knowledge to Habitat Restoration 2.1 Effective restoration goals and practices 3. Part C: Case Study - Conservation Action For Substitution of Missing Dynamics 3.1 Dry acidic grasslands on former military training areas in central Europe 3.2 Conclusion Acknowledgements Bibliography Biographical Sketch Summary Disturbance plays a roll in ecology so important that it is arguably the cause, condition, and solution to conservation measures. Discrete disturbances are described in many spatial andUNESCO temporal terms, but their importa – nceEOLSS to ecological systems is dependant on their timing during succession. Understanding this dynamic role is the task of restorationists who need to know that ecosystems evolve to be resilient to a particular set of historical SAMPLEdisturbances.
    [Show full text]
  • The Metacommunity Concept: a Framework for Multi-Scale Community Ecology
    Ecology Letters, (2004) 7: 601–613 doi: 10.1111/j.1461-0248.2004.00608.x REVIEW The metacommunity concept: a framework for multi-scale community ecology Abstract M. A. Leibold,1* M. Holyoak,2 The metacommunity concept is an important way to think about linkages between N. Mouquet,3,4 P. Amarasekare,5 different spatial scales in ecology. Here we review current understanding about this J. M. Chase,6 M. F. Hoopes,7 concept. We first investigate issues related to its definition as a set of local communities 8 9 10 R. D. Holt, J. B. Shurin, R. Law, that are linked by dispersal of multiple potentially interacting species. We then identify D. Tilman,11 M. Loreau12 and 13 four paradigms for metacommunities: the patch-dynamic view, the species-sorting view, A. Gonzalez the mass effects view and the neutral view, that each emphasizes different processes of potential importance in metacommunities. These have somewhat distinct intellectual histories and we discuss elements related to their potential future synthesis. We then use this framework to discuss why the concept is useful in modifying existing ecological thinking and illustrate this with a number of both theoretical and empirical examples. As ecologists strive to understand increasingly complex mechanisms and strive to work across multiple scales of spatio-temporal organization, concepts like the metacommunity can provide important insights that frequently contrast with those that would be obtained with more conventional approaches based on local communities alone. Keywords Mass effects, metacommunity, neutral model, patch dynamics, species sorting. Ecology Letters (2004) 7: 601–613 2002). Remarkably, however, much of formal community INTRODUCTION theory is focused on a single scale, assuming that local Community ecology as a field is concerned with explaining communities are closed and isolated.
    [Show full text]
  • Assessing the Impacts of Habitat Fragmentation on Biodiversity Across Scales: the Case of Thousand Island Lake, China by Maxwel
    Assessing the Impacts of Habitat Fragmentation on Biodiversity Across Scales: The Case of Thousand Island Lake, China by Maxwell Christopher Wilson A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved March 2018 by the Graduate Supervisory Committee Jianguo Wu, Chair Andrew Smith Sharon Hall Lin Jiang Arianne Cease ARIZONA STATE UNIVERSITY May 2018 ABSTRACT Habitat fragmentation, the loss of habitat in the landscape and spatial isolation of remaining habitat patches, has long been considered a serious threat to biodiversity. However, the study of habitat fragmentation is fraught with definitional and conceptual challenges. Specifically, a multi-scale perspective is needed to address apparent disagreements between landscape- and patch-based studies that have caused significant uncertainty concerning fragmentation’s effects on biological communities. Here I tested the hypothesis that habitat fragmentation alters biological communities by creating hierarchically nested selective pressures across plot-, patch-, and landscape-scales using woody plant community datasets from Thousand Island Lake, China. In this archipelago edge-effects had little impact on species-diversity. However, the amount of habitat in the surrounding landscape had a positive effect on species richness at the patch-scale and sets of small islands accumulated species faster than sets of large islands of equal total size at the landscape-scale. In contrast, at the functional-level edge-effects decreased the proportion of shade-tolerant trees, island-effects increased the proportion of shade- intolerant trees, and these two processes interacted to alter the functional composition of the regional pool when the total amount of habitat in the landscape was low.
    [Show full text]
  • Patch Dynamics of Eelgrass Zostera Marina
    MARINE ECOLOGY PROGRESS SERIES Vol. 106: 147-156, 1994 Published March 17 Mar. Ecol. Prog. Ser. Patch dynamics of eelgrass Zostera marina Birgit Olesen, Kaj Sand-Jensen* Department of Plant Ecology, University of Aarhus, Nordlandsvej 68, DK-8240 Risskov, Denmark ABSTRACT: Eelgrass has declined extensively during the last decades following eutrophication of coastal regions of western Europe and the USA. Recent efforts have been taken to reduce nutrient loading, with the hope of restoring the former widespread populations. We studied fine-scale patch dynamics of eelgrass Zostera marina L, in permanent plots outside the continuous vegetation in a pro- tected embayrnent in Limfjorden, Denmark, to evaluate means of recruitment and rates of expansion and mortality of patches. The size distribution was dominated by small patches which were formed by seedlings at high rates during spring (0.16 to 0.76 m-'). Mortality was high and only low proportions (0 to 24 %) of the studied cohorts remained as individual patches 1.5 and 2.5 yr later. Patch mortality was restricted to small patches containing <32 shoots with a mean age of < 5 yr. The sharply declining mortality with increasing patch age and size is presumably due to improved anchoring, mutual physi- cal protection and physiological integration among the shoots. The lateral expansion of established patches by centrifugally growing horizontal rhizomes averaged 16 cm yr-l and was independent of patch size With this lateral growth the possible annual areal expansion will be faster in systems with many small patches (260% in 0.1 m' patches) and slower in systems with few large patches (19% in 10 m2patches).
    [Show full text]