scholarly journals A palaeolimnological perspective to understand regime-shift dynamics in two Yangtze-basin lakes

2019 ◽  
Vol 15 (11) ◽  
pp. 20190447 ◽  
Author(s):  
Min Xu ◽  
Rong Wang ◽  
Xuhui Dong ◽  
Xiangdong Yang
Keyword(s):  
Regime Shift ◽  
Nutrient Loading ◽  
Stable State ◽  
Regime Shifts ◽  
Alternative Stable State ◽  
Human Disturbances ◽  
Environmental Forcing ◽  
Ecological Threshold ◽  
Yangtze Basin ◽  
Shift Dynamics

Natural and human disturbances have caused widespread regime shifts in shallow lakes of the lower Yangtze basin (LYB, China) resulting in a severe decline of ecosystem services. Improved understanding of the relationship between environmental forcing and ecosystem response, and the mechanisms behind regime shifts has significant implications for management. However, the patterns of these regime shifts and the underlying internal mechanisms are less known. In this study, two typical lakes (Chaohu and Zhangdu) from the LYB were selected to determine the trajectories of ecological regime shifts, both of which transitioned from vegetation- to plankton-dominated states several decades ago. Ecological trajectories since the 1900s in both lakes were reconstructed using palaeolimnological proxies, mainly diatom assemblages. Although results show that regime shifts occurred in both lakes in the 1970s and the 1950s, respectively, their inherent mechanisms were different. In Lake Zhangdu, altered hydrological conditions pushed the ecosystem across an ecological threshold, providing an example of a driver-mediated regime shift. In Lake Chaohu, ongoing nutrient loading influenced ecosystem processes and drove the lake to an alternative stable state, potentially presenting an example of a critical transition after a loss of resilience. This research indicates that palaeolimnological perspectives can provide insights into regime shift changes, as well as important information regarding which restoration methods should be tailored to individual lakes.

Recruitment and survival of Northeast Pacific Ocean fish stocks: temporal trends, covariation, and regime shifts

2007 ◽  
Vol 64 (6) ◽  
pp. 911-927 ◽  
Author(s):  
Franz J Mueter ◽  
Jennifer L Boldt ◽  
Bernard A Megrey ◽  
Randall M Peterman
Keyword(s):  
Bering Sea ◽  
Regime Shift ◽  
Temporal Trends ◽  
Gulf Of Alaska ◽  
Regime Shifts ◽  
Environmental Forcing ◽  
Fish Stocks ◽  
Large Marine Ecosystems ◽  
Decadal Scale ◽  
Climatic Regime

Two measures of productivity for fish stocks (recruitment and stock–recruit residuals) within two large marine ecosystems (Gulf of Alaska and eastern Bering Sea – Aleutian Islands) showed significant positive covariation within several groups of species and significant negative covariation between certain others. For example, stock–recruit residuals of gadids (Gadidae) in the Bering Sea were inversely related to those of shelf flatfishes (Pleuronectidae), suggesting that environmental forcing affects these groups in opposite ways. Salmon (Oncorhynchus spp.), Pacific herring (Clupea pallasii), and groundfish stocks each showed strong patterns of covariation within these taxonomic groups and within ecosystems, and both salmon and groundfish stocks showed positive covariation between the two ecosystems. However, we found little evidence of covariation between salmon and herring stocks or between these stocks and demersal stocks. Recruitment and stock–recruit residuals in individual stocks did not show a consistent response to known climatic regime shifts. However, combined indices of productivity across stocks showed decadal-scale variability (regime-like patterns), suggesting that both pelagic productivity (mostly salmon) and demersal productivity increased in response to the well-documented 1976–1977 climatic regime shift, whereas the 1988–1989 regime shift produced inconsistent or short-lived responses.

scholarly journals Fast environmental change and eco-evolutionary feedbacks can drive regime shifts in ecosystems before tipping points are crossed

2021 ◽  
Vol 288 (1955) ◽  
pp. 20211192
Author(s):  
P. Catalina Chaparro-Pedraza
Keyword(s):  
Environmental Change ◽  
Environmental Changes ◽  
Phenotypic Diversity ◽  
Stable State ◽  
Regime Shifts ◽  
Tipping Points ◽  
Evolutionary Processes ◽  
Alternative Stable State ◽  
Management Measures ◽  
The Difference

Anthropogenic environmental changes are altering ecological and evolutionary processes of ecosystems. The possibility that ecosystems can respond abruptly to gradual environmental change when critical thresholds are crossed (i.e. tipping points) and shift to an alternative stable state is a growing concern. Here I show that fast environmental change can trigger regime shifts before environmental stress exceeds a tipping point in evolving ecological systems. The difference in the time scales of coupled ecological and evolutionary processes makes ecosystems sensitive not only to the magnitude of environmental changes, but also to the rate at which changes are imposed. Fast evolutionary change mediated by high trait variation can reduce the sensitivity of ecosystems to the rate of environmental change and prevent the occurrence of rate-induced regime shifts. This suggests that management measures to prevent rate-induced regime shifts should focus on mitigating the effects of environmental change and protecting phenotypic diversity in ecosystems.

Large herbivores suppress liana infestation in an African savanna

2021 ◽  
Vol 118 (41) ◽  
pp. e2101676118
Author(s):  
Tyler C. Coverdale ◽  
Ryan D. O’Connell ◽  
Matthew C. Hutchinson ◽  
Amanda Savagian ◽  
Tyler R. Kartzinel ◽  
...  
Keyword(s):  
Stable State ◽  
Life Forms ◽  
Tree Canopy ◽  
Alternative Stable State ◽  
African Savanna ◽  
Large Herbivore ◽  
Large Herbivores ◽  
Woody Vines ◽  
Plant Life Forms ◽  
Canopy Area

African savannas are the last stronghold of diverse large-mammal communities, and a major focus of savanna ecology is to understand how these animals affect the relative abundance of trees and grasses. However, savannas support diverse plant life-forms, and human-induced changes in large-herbivore assemblages—declining wildlife populations and their displacement by livestock—may cause unexpected shifts in plant community composition. We investigated how herbivory affects the prevalence of lianas (woody vines) and their impact on trees in an East African savanna. Although scarce (<2% of tree canopy area) and defended by toxic latex, the dominant liana, Cynanchum viminale (Apocynaceae), was eaten by 15 wild large-herbivore species and was consumed in bulk by native browsers during experimental cafeteria trials. In contrast, domesticated ungulates rarely ate lianas. When we experimentally excluded all large herbivores for periods of 8 to 17 y (simulating extirpation), liana abundance increased dramatically, with up to 75% of trees infested. Piecewise exclusion of different-sized herbivores revealed functional complementarity among size classes in suppressing lianas. Liana infestation reduced tree growth and reproduction, but herbivores quickly cleared lianas from trees after the removal of 18-y-old exclosure fences (simulating rewilding). A simple model of liana contagion showed that, without herbivores, the long-term equilibrium could be either endemic (liana–tree coexistence) or an all-liana alternative stable state. We conclude that ongoing declines of wild large-herbivore populations will disrupt the structure and functioning of many African savannas in ways that have received little attention and that may not be mitigated by replacing wildlife with livestock.

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 Approximating the Cost-of-Living Index for a Storable Good

2018 ◽  
Vol 10 (2) ◽  
pp. 286-314 ◽  
Author(s):  
Matthew Osborne
Keyword(s):  
Regime Shift ◽  
Structural Model ◽  
Regime Shifts ◽  
Cost Of Living ◽  
Product Categories ◽  
Dynamic Structural Model ◽  
Fixed Base ◽  
Retail Prices ◽  
The Cost ◽  
Cost Of Living Index

This paper estimates a cost-of-living index using a dynamic structural model for two storable product categories. In each category, regime shifts to higher or lower retail prices are observed. Fixed-base indexes do a poor job of capturing changes in welfare after a regime shift, and deviate from the dynamic index by as much as 300 percent. I evaluate the extent to which two recently proposed indexes can approximate the model-derived index. These indexes improve welfare measurement and are straightforward to compute. The category’s competitive structure and features of the regime shift determine which of the two provides a better approximation. (JEL C43, C51, E31, L11)

Uncertain ecosystems: the conceptual framework

2019 ◽  
pp. 27-42
Author(s):  
William J. Bond
Keyword(s):  
Trophic Ecology ◽  
Resource Constraints ◽  
Stable State ◽  
State Theory ◽  
Tree Cover ◽  
Top Down ◽  
Alternative Stable State ◽  
Positive Feedbacks ◽  
Vegetation Models ◽  
Global Vegetation

Climate sets the potential biomass of trees and physiologists have made considerable progress in understanding and predicting that potential and applying it in global vegetation models. The problem is in understanding and predicting tree cover where it is far from the climate potential. Vast areas of non-forested vegetation occur where climates are suitable for forests. Arguments over why forests are absent, ongoing for over a century, are generally polarized between favouring bottom-up factors (resource constraints) or top-down factors (herbivory, predation, fire). There is increasing support for hypotheses invoking the interaction between the two. This chapter introduces the key hypotheses, their assumptions and predictions. Trophic ecology is a useful framework for exploring departures from the climate potential for trees, focussing explicitly on regulation by consumers, including fire. Alternative stable state theory is emerging as particularly appropriate for explaining forest/non-forest mosaics with each state maintained by positive feedbacks to the preferred environment.

scholarly journals Identification of Regime Shifts and Their Potential Drivers in the Shallow Eutrophic Lake Yilong, Southwest China

2020 ◽  
Vol 12 (9) ◽  
pp. 3704
Author(s):  
Lei Zhao ◽  
Mingguo Wang ◽  
Zhongyao Liang ◽  
Qichao Zhou
Keyword(s):  
Regime Shift ◽  
Eutrophic Lake ◽  
Regime Shifts ◽  
Nutrient Reduction ◽  
Eutrophic Lakes ◽  
Test Analysis ◽  
Key Drivers ◽  
High Possibility ◽  
Cage Fish

Regime shifts in shallow lakes can lead to great changes in ecosystem structures and functions, making ecosystem management more complicated. Lake Yilong, located in Yunnan Province, is one of the most eutrophic lakes in China. Although there is a high possibility that this lake has undergone regime shift one or more times, the presence of regime shifts and their drivers remain unknown. Here, we employed the sequential t-test analysis of regime shifts to detect the regime shifts based on the long-term (1989–2018) dataset of the lake. We further determined their potential drivers, and explored the nutrient thresholds of regime shifts and hysteresis. The results showed that during the testing period, three regime shifts occurred in 1996 (restorative type), 2009 (catastrophic type) and 2014 (restorative type). The potential key drivers for the first two regime shifts (1996 and 2009) were both related to aquaculture. The abolition of cage fish culture may have led to the restorative regime shift in 1996, and the stocking of crabs and excessive premature releasing of fry possibly caused the catastrophic regime shift in 2009. However, the third regime shift, which occurred in 2014, was possibly related to the drought and succedent hydration. These results indicate that adjustments of aquaculture strategy and hydrological conditions are critical for the lake ecosystem’s recovery. Moreover, the total phosphorus thresholds were identified to be lower than 0.046 mg/L (restorative type) and higher than 0.105 mg/L (catastrophic type), respectively. In addition, an obvious hysteresis was observed after 2014, suggesting that nutrient reduction is important for this lake’s management in the future.

scholarly journals Cascading regime shifts within and across scales

Science ◽  
2018 ◽  
Vol 362 (6421) ◽  
pp. 1379-1383 ◽  
Author(s):  
Juan C. Rocha ◽  
Garry Peterson ◽  
Örjan Bodin ◽  
Simon Levin
Keyword(s):  
Regime Shift ◽  
Regime Shifts ◽  
Control Case ◽  
Scale Interactions ◽  
Cascading Effects ◽  
Critical Transitions ◽  
Structural Interdependence

Regime shifts are large, abrupt, and persistent critical transitions in the function and structure of ecosystems. Yet, it is unknown how these transitions will interact, whether the occurrence of one will increase the likelihood of another or simply correlate at distant places. We explored two types of cascading effects: Domino effects create one-way dependencies, whereas hidden feedbacks produce two-way interactions. We compare them with the control case of driver sharing, which can induce correlations. Using 30 regime shifts described as networks, we show that 45% of regime shift pairwise combinations present at least one plausible structural interdependence. The likelihood of cascading effects depends on cross-scale interactions but differs for each type. Management of regime shifts should account for potential connections.

The alternative stable state concept and the management of Apennine mountain ponds

2005 ◽  
Vol 15 (6) ◽  
pp. 625-634 ◽  
Author(s):  
Antonio Ruggiero ◽  
Angelo G. Solimini ◽  
Gianmaria Carchini
Keyword(s):  
Stable State ◽  
Alternative Stable State
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