scholarly journals Shifting States, Altered Fates: Divergent Fuel Moisture Responses after High Frequency Wildfire in an Obligate Seeder Eucalypt Forest

Forests ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 436 ◽  
Author(s):  
Jamie Burton ◽  
Jane Cawson ◽  
Philip Noske ◽  
Gary Sheridan
Keyword(s):  
High Frequency ◽  
Alternative Stable States ◽  
Stable State ◽  
Fuel Moisture ◽  
Stable States ◽  
Alternative Stable State ◽  
Obligate Seeder ◽  
Time Since Fire ◽  
Mountain Ash ◽  
Moisture Dynamics

High frequency wildfires can shift the structure and composition of obligate seeder forests and initiate replacement with alternative vegetation states. In some forests, the alternative stable state is drier and more easily burned by subsequent fires, driving a positive feedback that promotes further wildfire and perpetuates alternative stable states. Mountain Ash (Eucalyptus regnans (F.Muell.)) forests are highly valued for their biodiversity, water, timber and carbon. Fires are a natural part of the lifecycle of these forests, but too frequent fires can eliminate Mountain Ash and trigger a transition to lower stature, non-eucalypt forests which are dominated by understorey species. This study sought to better understand the fuel moisture dynamics of alternative stable states resulting from high frequency wildfires. A vegetation mosaic in the Central Highlands, Victoria created a unique opportunity to measure fuel moisture in adjacent forest stands that differed in overstorey species composition and time since fire. Specifically, we measured fuel moisture and microclimate at two eucalypt sites (9 and 79 years old) and three non-eucalypt sites (two 9 year old and one 79 year old). Fuel availability, defined here as the number of days surface fuels were below 16% and dry enough to ignite and sustain fire, was calculated to estimate flammability. Fuel availability differed between sites, particularly as a function of time since fire, with recently burnt sites available to burn more often (4–17 versus 0–3 days). There were differences in fuel availability between non-eucalypt sites of the same age, suggesting that high frequency fire does not always lead to the same vegetation condition or outcome for fuel availability. This indicates there is potential for both positive and negative flammability feedbacks following state transition depending on the composition of the non-eucalypt state. This is the first study to provide empirical insight into the fuel moisture dynamics of alternative stable states in Mountain Ash forests.

scholarly journals Path-dependent institutions drive alternative stable states in conservation

2018 ◽  
Vol 116 (2) ◽  
pp. 689-694 ◽  
Author(s):  
Edward W. Tekwa ◽  
Eli P. Fenichel ◽  
Simon A. Levin ◽  
Malin L. Pinsky
Keyword(s):  
Renewable Resources ◽  
Path Dependence ◽  
Alternative Stable States ◽  
Stable State ◽  
Empirical Support ◽  
Stable States ◽  
Alternative Stable State ◽  
Important Challenge ◽  
Quantitative Analyses ◽  
Path Dependent

Understanding why some renewable resources are overharvested while others are conserved remains an important challenge. Most explanations focus on institutional or ecological differences among resources. Here, we provide theoretical and empirical evidence that conservation and overharvest can be alternative stable states within the same exclusive-resource management system because of path-dependent processes, including slow institutional adaptation. Surprisingly, this theory predicts that the alternative states of strong conservation or overharvest are most likely for resources that were previously thought to be easily conserved under optimal management or even open access. Quantitative analyses of harvest rates from 217 intensely managed fisheries supports the predictions. Fisheries’ harvest rates also showed transient dynamics characteristic of path dependence, as well as convergence to the alternative stable state after unexpected transitions. This statistical evidence for path dependence differs from previous empirical support that was based largely on case studies, experiments, and distributional analyses. Alternative stable states in conservation appear likely outcomes for many cooperatively managed renewable resources, which implies that achieving conservation outcomes hinges on harnessing existing policy tools to navigate transitions.

scholarly journals Transient invaders can induce shifts between alternative stable states of microbial communities

2020 ◽  
Vol 6 (8) ◽  
pp. eaay8676 ◽  
Author(s):  
Daniel R. Amor ◽  
Christoph Ratzke ◽  
Jeff Gore
Keyword(s):  
Environmental Changes ◽  
Alternative Stable States ◽  
Stable State ◽  
Natural Soil ◽  
Stable States ◽  
Alternative Stable State ◽  
Community Shift ◽  
Invader Species ◽  
Potential Impact ◽  
And Function

Microbial dispersal often leads to the arrival of outsider organisms into ecosystems. When their arrival gives rise to successful invasions, outsider species establish within the resident community, which can markedly alter the ecosystem. Seemingly less influential, the potential impact of unsuccessful invaders that interact only transiently with the community has remained largely ignored. Here, we experimentally demonstrate that these transient invasions can induce a lasting transition to an alternative stable state, even when the invader species itself does not survive the transition. First, we develop a mechanistic understanding of how environmental changes caused by these transient invaders can drive a community shift in a simple, bistable model system. Beyond this, we show that transient invaders can also induce switches between stable states in more complex communities isolated from natural soil samples. Our results demonstrate that short-term interactions with an invader species can induce lasting shifts in community composition and function.

scholarly journals Transient invaders can induce shifts between alternative stable states of microbial communities

2019 ◽  
Author(s):  
Daniel R. Amor ◽  
Christoph Ratzke ◽  
Jeff Gore
Keyword(s):  
Community Composition ◽  
Environmental Changes ◽  
Alternative Stable States ◽  
Stable State ◽  
Natural Soil ◽  
Stable States ◽  
Alternative Stable State ◽  
Community Shift ◽  
Invader Species ◽  
And Function

AbstractMicrobial dispersal often leads to the arrival of outsider organisms into ecosystems. When their arrival give rise to successful invasions, outsider species establish within the resident community, which can dramatically alter the ecosystem. Seemingly less influential, the potential impact of unsuccessful invaders that interact only transiently with the community has remained largely ignored. Here, we experimentally demonstrate that such transient invasions can perturb the stability of microbial ecosystems and induce a lasting transition to an alternative stable state, even when the invader species itself does not survive the transition. First, we develop a mechanistic understanding of how environmental changes caused by such transient invaders can drive a community shift in a simple, bistable model system. Beyond this, we show that transient invaders can also induce switches between stable states in more complex communities isolated from natural soil samples. Our results demonstrate that short-term interactions with an invader species can induce lasting shifts in community composition and function.One Sentence SummaryTransient invaders can cause lasting shifts in community composition and function.

scholarly journals Successional dynamics and alternative stable states in a saline activated sludge microbial community over 9 years

Microbiome ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Yulin Wang ◽  
Jun Ye ◽  
Feng Ju ◽  
Lei Liu ◽  
Joel A. Boyd ◽  
...  
Keyword(s):  
Microbial Community ◽  
Activated Sludge ◽  
Alternative Stable States ◽  
Treatment Plant ◽  
Stable State ◽  
Comparative Genomic ◽  
Operational Parameters ◽  
Stable States ◽  
Alternative Stable State ◽  
Analysis Of Dynamics

Abstract Background Microbial communities in both natural and applied settings reliably carry out myriads of functions, yet how stable these taxonomically diverse assemblages can be and what causes them to transition between states remains poorly understood. We studied monthly activated sludge (AS) samples collected over 9 years from a full-scale wastewater treatment plant to answer how complex AS communities evolve in the long term and how the community functions change when there is a disturbance in operational parameters. Results Here, we show that a microbial community in activated sludge (AS) system fluctuated around a stable average for 3 years but was then abruptly pushed into an alternative stable state by a simple transient disturbance (bleaching). While the taxonomic composition rapidly turned into a new state following the disturbance, the metabolic profile of the community and system performance remained remarkably stable. A total of 920 metagenome-assembled genomes (MAGs), representing approximately 70% of the community in the studied AS ecosystem, were recovered from the 97 monthly AS metagenomes. Comparative genomic analysis revealed an increased ability to aggregate in the cohorts of MAGs with correlated dynamics that are dominant after the bleaching event. Fine-scale analysis of dynamics also revealed cohorts that dominated during different periods and showed successional dynamics on seasonal and longer time scales due to temperature fluctuation and gradual changes in mean residence time in the reactor, respectively. Conclusions Our work highlights that communities can assume different stable states under highly similar environmental conditions and that a specific disturbance threshold may lead to a rapid shift in community composition.

Mental disorders, network models, and dynamical systems

2017 ◽  
Author(s):  
Denny Borsboom
Keyword(s):  
Mental Disorders ◽  
Alternative Stable States ◽  
Stable State ◽  
Network Models ◽  
External Shocks ◽  
Stable States ◽  
Adverse Life Events ◽  
Healthy State ◽  
Strongly Connected ◽  
Network Approaches

Network approaches have been proposed as an alternative way of thinking about relations between symptoms of mental disorders. Unlike traditional psychometric approaches, network models view these associations as the result of direct interactions between symptoms. Disorders are defined as alternative stable states of a network due to increased connectivity between symptoms. This increased connectivity creates a pattern of reinforcement, so the system can get stuck in a state of prolonged activation. Mental health is defined as the stable state of a weakly connected network. Although symptomatology may be temporarily increased in a healthy network (e.g., due to adverse life events), as the influence of a shock wanes the network will spontaneously return to its healthy state. Strongly connected networks, however, may transition into disordered states upon similar external shocks, and may not naturally recover. Thus, the proposed definitions yield plausible conceptualizations of resilience and vulnerability.

scholarly journals At what spatial scales are alternative stable states relevant in highly interconnected ecosystems?

2019 ◽  
Author(s):  
Vadim A. Karatayev ◽  
Marissa L. Baskett
Keyword(s):  
Spatial Scales ◽  
Alternative Stable States ◽  
Stable State ◽  
Environmental Stochasticity ◽  
Rocky Reef ◽  
Alternative States ◽  
Stable States ◽  
Long Distance ◽  
Rocky Reefs ◽  
Model Predictions

AbstractWhether ecosystems recover from disturbance depends on the presence of alternative stable states, which are theoretically possible in simple models of many systems. However, definitive empirical evidence for this phenomenon remains limited to demographically closed ecosystems such as lakes. In more interconnected systems such as temperate rocky reefs, the local relevance of alternative stable states might erode as immigration overwhelms local feedbacks and produces a single stable state. At larger spatial scales, dispersal might counter localized disturbance and feedbacks to synchronize states throughout a region. Here, we quantify how interconnectedness affects the relevance of alternative stable states using dynamical models of California rocky reef communities that incorporate observed environmental stochasticity and feedback loops in kelp-urchin-predator interactions. Our models demonstrate the potential for localized alternative states despite high interconnectedness likely due to feedbacks affecting dispersers as they settle into local communities. Regionally, such feedbacks affecting settlement can produce a mosaic of alternative stable states that span local (10-20km) scales despite the synchronizing effect of long-distance dispersal. The specific spatial scale and duration of each state predominantly depend on the scales of environmental variation and on local dynamics (here, fishing). Model predictions reflect observed scales of community states in California rocky reefs and suggest how alternative states co-occur in the wide array of marine and terrestrial systems with settlement feedbacks.

scholarly journals Different coastal marsh sites reflect similar topographic conditions for bare patches and vegetation recovery

2020 ◽  
Author(s):  
Chen Wang ◽  
Lennert Schepers ◽  
Matthew L. Kirwan ◽  
Enrica Belluco ◽  
Andrea D'Alpaos ◽  
...  
Keyword(s):  
Stable State ◽  
Venice Lagoon ◽  
State Theory ◽  
Sediment Supply ◽  
Coastal Marsh ◽  
Tidal Range ◽  
Unstable State ◽  
Stable States ◽  
Alternative Stable State ◽  
Subsequent Loss

Abstract. The presence of bare patches within otherwise vegetated coastal marshes is sometimes considered to be a symptom of marsh die-back and the subsequent loss of important ecosystem services. Here we studied the topographical conditions determining the presence and revegetation of bare patches in three marsh sites with contrasting tidal range, sediment supply and plant species: the Scheldt Estuary (the Netherlands), Venice Lagoon (Italy), and Blackwater Marshes (Maryland, USA). We analyzed topographic properties of bare patches, including elevation, size, distance and connectivity to channels based on GIS analyses of aerial and LIDAR imagery. Our results demonstrate that across the different marsh sites, bare patches connected to channels occur most frequently at the lowest elevations and farthest distance from the main channels. Bare patches disconnected from channels occur most frequently at intermediate elevations and distances from channels, and vegetated marshes dominate at highest elevations and shortest distances from channels. Revegetation in bare patches is observed in only one site with the highest tidal range and highest sediment availability, and preferentially occurs from the edges of small unconnected bare patches at intermediate elevations and intermediate distances from channels. Our results are discussed within the alternative stable state theory. We suggest the existence of two stable states, a high-elevated vegetated state close to channels that tends to remain high and vegetated, and a low-elevated state of bare connected patches far from channels that tends to remain bare, with an unstable state at intermediate channel distances where bare patches may form and rapidly become revegetated.

Vegetation Dynamics in a Grazed Mulga Shrubland Community. I. The Mid-Storey Shrubs

1984 ◽  
Vol 32 (3) ◽  
pp. 239 ◽  
Author(s):  
RB Hacker
Keyword(s):  
Interspecific Competition ◽  
Seedling Survival ◽  
Alternative Stable States ◽  
Stable State ◽  
Grazing Pressure ◽  
Point Of View ◽  
Temporary Increase ◽  
Stable States ◽  
Winter Rainfall ◽  
Plant Remains

The dynamics of the major mid-storey shrub species in a grazed mulga shrubland community were studied on a senes of sites in the arid winter rainfall zone of Western Australia Of the major specles present, Eremophila leucophylla decreased with increasing grazing pressure while Maireana planifolia and Eremophila sp. declined after a temporary increase. All three species are strongly aggregated around old plant remains and under the canopies of existing trees and tall shrubs Their aggregation in this microenvironment results from enhanced seedling survival. Common preference for this restricted part of the total space apparently leads to an exclusion type of Interspecific competition and to species populations that are segregated relatwe to one another The importance of this microenvironment, and the apparent nature of interspecific competition within it, suggest that a stable state may develop under moderate levels of grazing in this community. The dynamics of the community are unlikely to be explained satisfactonly by traditional Clementsian concepts Rather, they would appear to be more consistent with the concept of alternative stable states. Any beneficial influence of management on community composition, from a pastoral point of view, is thus likely to be limited to dlscrete opportunities under specific seasonal conditions.

scholarly journals Biocrust as one of multiple stable states in global drylands

2020 ◽  
Vol 6 (39) ◽  
pp. eaay3763 ◽  
Author(s):  
Ning Chen ◽  
Kailiang Yu ◽  
Rongliang Jia ◽  
Jialing Teng ◽  
Changming Zhao
Keyword(s):  
Vascular Plants ◽  
Stable State ◽  
Aridity Index ◽  
Bare Soil ◽  
Biogeochemical Cycles ◽  
Stable States ◽  
Alternative Stable State ◽  
Bistable Region ◽  
Fold Bifurcation ◽  
Multiple Stable States

Biocrusts cover ~30% of global drylands with a prominent role in the biogeochemical cycles. Theoretically, biocrusts, vascular plants, and bare soil can represent multiple stable states in drylands. However, no empirical evidence for the existence of a biocrust stable state has been reported. Here, using a global drylands dataset, we found that biocrusts form an alternative stable state (biocrust cover, ~80%; vascular cover, ≤10%) besides bare soil (both biocrust and vascular cover, ≤10%) and vascular plants (vascular cover, >50%; biocrust cover, ~5%). The pattern of multiple stable states associated with biocrusts differs from the classic fold bifurcation, and values of the aridity index in the range of 0 to 0.6 define a bistable region where multiple stable states coexist. This study empirically demonstrates the existence and thresholds of multiple stable states associated with biocrusts along climatic gradients and thus may greatly contribute to conservation and restoration of global drylands.

scholarly journals A Matter of Life and Death: Alternative Stable States in Trees, From Xylem to Ecosystems

2020 ◽  
Vol 3 ◽  
Author(s):  
William M. Hammond
Keyword(s):  
Tree Mortality ◽  
Alternative Stable States ◽  
Physiological Mechanism ◽  
Stable State ◽  
Stable Condition ◽  
State Theory ◽  
Future Climate ◽  
Environmental Drivers ◽  
Stable States ◽  
Hydraulic Failure

Global forests are experiencing widespread climate-induced mortality. Predicting this phenomenon has proven difficult, despite recent advances in understanding physiological mechanisms of mortality in individual trees along with environmental drivers of mortality at broad scales. With heat and drought as primary climatic drivers, and convergence on hydraulic failure as a primary physiological mechanism, new models are needed to improve our predictions of Earth’s forests under future climate conditions. While much of ecology focuses on equilibrium states, transitions from one stable state to another are often described with alternative stable state theory (ASST), where systems can settle to more than one stable condition. Recent studies have identified threshold responses of hydraulic failure during tree mortality, indicating that alternative stable states may be present. Here, I demonstrate that the xylem of trees has characteristics indicative of alternative stable states. Through empirical evidence, I identify a catastrophic shift during hydraulic failure which prevents trees from returning to pre-droughted physiological states after environmental stressors (e.g., drought, heat) are relieved. Thus, the legacy of climate-induced hydraulic failure likely contributes to reduced resilience of forests under future climate. I discuss the implications and future directions for including ASST in models of tree mortality.

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