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Dong X, Richter DD, Thompson A, Wang J. The primacy of temporal dynamics in driving spatial self-organization of soil iron redox patterns. Proc Natl Acad Sci U S A 2023; 120:e2313487120. [PMID: 38096416 PMCID: PMC10742380 DOI: 10.1073/pnas.2313487120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 11/13/2023] [Indexed: 12/24/2023] Open
Abstract
This study investigates mechanisms that generate regularly spaced iron-rich bands in upland soils. These striking features appear in soils worldwide, but beyond a generalized association with changing redox, their genesis is yet to be explained. Upland soils exhibit significant redox fluctuations driven by rainfall, groundwater changes, or irrigation. Pattern formation in such systems provides an opportunity to investigate the temporal aspects of spatial self-organization, which have been heretofore understudied. By comparing multiple alternative mechanisms, we found that regular iron banding in upland soils is explained by coupling two sets of scale-dependent feedbacks, the general principle of Turing morphogenesis. First, clay dispersion and coagulation in iron redox fluctuations amplify soil Fe(III) aggregation and crystal growth to a level that negatively affects root growth. Second, the activation of this negative root response to highly crystalline Fe(III) leads to the formation of rhythmic iron bands. In forming iron bands, environmental variability plays a critical role. It creates alternating anoxic and oxic conditions for required pattern-forming processes to occur in distinctly separated times and determines durations of anoxic and oxic episodes, thereby controlling relative rates of processes accompanying oxidation and reduction reactions. As Turing morphogenesis requires ratios of certain process rates to be within a specific range, environmental variability thus modifies the likelihood that pattern formation will occur. Projected changes of climatic regime could significantly alter many spatially self-organized systems, as well as the ecological functioning associated with the striking patterns they present. This temporal dimension of pattern formation merits close attention in the future.
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Affiliation(s)
- Xiaoli Dong
- Department of Environmental Science and Policy, University of California, Davis, CA95616
| | - Daniel D. Richter
- Earth and Climate Sciences Division, Nicholas School of the Environment, Duke University, Durham, NC27708
| | - Aaron Thompson
- Department of Crop and Soil Sciences, University of Georgia, Athens, GA30602
| | - Junna Wang
- Department of Environmental Science and Policy, University of California, Davis, CA95616
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Zhang K, Yan J, He Q, Xu C, van de Koppel J, Wang B, Cui B, Liu QX. Self-organized mud cracking amplifies the resilience of an iconic "Red Beach" salt marsh. SCIENCE ADVANCES 2023; 9:eabq3520. [PMID: 37134167 DOI: 10.1126/sciadv.abq3520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 03/30/2023] [Indexed: 05/05/2023]
Abstract
Self-organized patterning, resulting from the interplay of biological and physical processes, is widespread in nature. Studies have suggested that biologically triggered self-organization can amplify ecosystem resilience. However, if purely physical forms of self-organization play a similar role remains unknown. Desiccation soil cracking is a typical physical form of self-organization in coastal salt marshes and other ecosystems. Here, we show that physically self-organized mud cracking was an important facilitating process for the establishment of seepweeds in a "Red Beach" salt marsh in China. Transient mud cracks can promote plant survivorship by trapping seeds, and enhance germination and growth by increasing water infiltration in the soil, thus facilitating the formation of a persistent salt marsh landscape. Cracks can help the salt marsh withstand more intense droughts, leading to postponed collapse and faster recovery. These are indications of enhanced resilience. Our work highlights that self-organized landscapes sculpted by physical agents can play a critical role in ecosystem dynamics and resilience to climate change.
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Affiliation(s)
- Kang Zhang
- Center for Global Change and Complex Ecosystems, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China
- Department of Estuarine and Delta Systems, Royal Netherlands Institute of Sea Research, Yerseke 4401 NT, The Netherlands
| | - Jiaguo Yan
- Department of Estuarine and Delta Systems, Royal Netherlands Institute of Sea Research, Yerseke 4401 NT, The Netherlands
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China
- Wuxi Research Institute of Applied Technologies, Tsinghua University, Wuxi 214072, China
- Division of Oilfield Chemicals, China Oilfield Services Limited (COSL), Beijing, China
| | - Qiang He
- Coastal Ecology Lab, National Observation and Research Station for Shanghai Yangtze Estuarine Wetland Ecosystems, School of Life Sciences, Fudan University, 2005 Songhu Road, Shanghai 200438, China
| | - Chi Xu
- School of Life Sciences, Nanjing University, Nanjing 210023, China
- Breeding Base for State Key Laboratory of Land Degradation and Ecological Restoration in northwestern China; Key Laboratory of Restoration and Reconstruction of Degraded Ecosystems in northwestern China of Ministry of Education, Ningxia University, Yinchuan 750021, China
| | - Johan van de Koppel
- Department of Estuarine and Delta Systems, Royal Netherlands Institute of Sea Research, Yerseke 4401 NT, The Netherlands
- Groningen Institute for Evolutionary Life Sciences, Conservation Ecology Group, University of Groningen, Groningen 9700 CC, The Netherlands
| | - Bo Wang
- School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Baoshan Cui
- State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China
| | - Quan-Xing Liu
- Center for Global Change and Complex Ecosystems, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China
- School of Mathematical Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
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Phase-separation physics underlies new theory for the resilience of patchy ecosystems. Proc Natl Acad Sci U S A 2023; 120:e2202683120. [PMID: 36595670 PMCID: PMC9926271 DOI: 10.1073/pnas.2202683120] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Spatial self-organization of ecosystems into large-scale (from micron to meters) patterns is an important phenomenon in ecology, enabling organisms to cope with harsh environmental conditions and buffering ecosystem degradation. Scale-dependent feedbacks provide the predominant conceptual framework for self-organized spatial patterns, explaining regular patterns observed in, e.g., arid ecosystems or mussel beds. Here, we highlight an alternative mechanism for self-organized patterns, based on the aggregation of a biotic or abiotic species, such as herbivores, sediment, or nutrients. Using a generalized mathematical model, we demonstrate that ecosystems with aggregation-driven patterns have fundamentally different dynamics and resilience properties than ecosystems with patterns that formed through scale-dependent feedbacks. Building on the physics theory for phase-separation dynamics, we show that patchy ecosystems with aggregation patterns are more vulnerable than systems with patterns formed through scale-dependent feedbacks, especially at small spatial scales. This is because local disturbances can trigger large-scale redistribution of resources, amplifying local degradation. Finally, we show that insights from physics, by providing mechanistic understanding of the initiation of aggregation patterns and their tendency to coarsen, provide a new indicator framework to signal proximity to ecological tipping points and subsequent ecosystem degradation for this class of patchy ecosystems.
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Ge Z, Liu QX. Foraging behaviours lead to spatiotemporal self-similar dynamics in grazing ecosystems. Ecol Lett 2021; 25:378-390. [PMID: 34808693 PMCID: PMC9299242 DOI: 10.1111/ele.13928] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/21/2021] [Accepted: 10/29/2021] [Indexed: 12/29/2022]
Abstract
Biological behaviour‐driven self‐organized patterns have recently been confirmed to play a key role in ecosystem functioning. Here, we develop a theoretical phase‐separation model to describe spatiotemporal self‐similar dynamics, which is a consequence of behaviour‐driven trophic interactions in short‐time scales. Our framework integrates scale‐dependent feedback and density‐dependent movement into grazing ecosystems. This model derives six types of selective foraging behaviours that trigger pattern formation for top‐down grazing ecosystems, and one of which is consistent with existing foraging theories. Self‐organized patterns nucleate under moderate grazing intensity and are destroyed by overgrazing, which suggests ecosystem degradation. Theoretical results qualitatively agree with observed grazing ecosystems that display spatial heterogeneities under variable grazing intensity. Our findings potentially provide new insights into self‐organized patterns as an indicator of ecosystem transitions under a stressful environment.
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Affiliation(s)
- Zhenpeng Ge
- Center for Global Change and Complex Ecosystems, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China
| | - Quan-Xing Liu
- Center for Global Change and Complex Ecosystems, School of Ecological and Environmental Sciences, East China Normal University, Shanghai, China.,State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, China
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