Self-organization Of Ecosystems Research Articles

Power-law productivity of highly biodiverse agroecosystems supports land recovery and climate resilience

Transformative change in primary food production is urgently needed in the face of climate change and biodiversity loss. Although there are a growing number of studies aimed at global policymaking, actual implementations require on-site analyses of social feasibility anchored by ecological rationale. This article reports the in-depth characterizations of low-input mixed polyculture of highly diverse crops managed on the self-organization of ecosystems, which performed better compared to conventional monoculture methods in Japan and Burkina Faso. Analyses on crop productivity and diversity showed that the primary production of ecosystems followed a power law, and through the underlying mechanisms excelled in (1) promoting diversity and total quantity of products along with the rapid increase of in-field biodiversity, especially useful for the recovery of local regime shift in a semi-arid environment; (2) a fundamental reduction of inputs and environmental load; and (3) ecosystem-based autonomous adaptation of the crop portfolio to climatic variability. The overall benefits imply substantial possibilities of a new typology of sustainable farming for smallholders sensitive to climate change, which could overcome the historical trade-off between productivity and biodiversity based on the human-guided augmentation of ecosystems.

Self-organization of ecosystems to exclude half of all potential invaders

Species-rich Lotka-Volterra competition models of ecosystem dynamics transition with increasing species pool size from a phase with well-defined stable equilibrium to a dynamic phase that remains incompletely understood. We analytically describe the statistical mechanics of the steady state deep inside this dynamic phase, characterized by incessant turnover in species composition, and extract the distribution of invasion fitness of random invaders. We find that steady state invasion probability universally equals 1/2. This striking result agrees well with observations in plants and animals. Published by the American Physical Society 2024

The hidden order of Turing patterns in arid and semi‐arid vegetation ecosystems

Vegetation Turing patterns play a critical role in the ecological functioning of arid and semi-arid ecosystems. However, the long-range spatial features of these patterns have been neglected compared to short-range features like patch shape and spatial wavelength. Drawing inspiration from hyperuniform structures in material science, we find that the arid and semi-arid vegetation Turing pattern exhibits long-range dispersion similar to hyperuniformity. As the degree of hyperuniformity of the vegetation Turing pattern increases, so does the water-use efficiency of the vegetation. This finding supports previous studies that suggest that Turing patterns represent a spatially optimized self-organization of ecosystems for water acquisition. The degree of hyperuniformity of Turing-type ecosystems exhibits significant critical slowing down near the tipping point, indicating that these ecosystems have non-negligible transient dynamical behavior. Reduced rainfall not only decreases the resilience of the steady state of the ecosystem but also slows down the rate of spatial optimization of water-use efficiency in long transient regimes. We propose that the degree of hyperuniformity indicates the spatial resilience of Turing-type ecosystems after strong, short-term disturbances. Spatially heterogeneous disturbances that reduce hyperuniformity lead to longer recovery times than spatially homogeneous disturbances that maintain hyperuniformity.

Phase-separation physics underlies new theory for the resilience of patchy ecosystems.

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.

Metabolic evolution and the self-organization of ecosystems

Metabolism mediates the flow of matter and energy through the biosphere. We examined how metabolic evolution shapes ecosystems by reconstructing it in the globally abundant oceanic phytoplankter Prochlorococcus To understand what drove observed evolutionary patterns, we interpreted them in the context of its population dynamics, growth rate, and light adaptation, and the size and macromolecular and elemental composition of cells. This multilevel view suggests that, over the course of evolution, there was a steady increase in Prochlorococcus' metabolic rate and excretion of organic carbon. We derived a mathematical framework that suggests these adaptations lower the minimal subsistence nutrient concentration of cells, which results in a drawdown of nutrients in oceanic surface waters. This, in turn, increases total ecosystem biomass and promotes the coevolution of all cells in the ecosystem. Additional reconstructions suggest that Prochlorococcus and the dominant cooccurring heterotrophic bacterium SAR11 form a coevolved mutualism that maximizes their collective metabolic rate by recycling organic carbon through complementary excretion and uptake pathways. Moreover, the metabolic codependencies of Prochlorococcus and SAR11 are highly similar to those of chloroplasts and mitochondria within plant cells. These observations lead us to propose a general theory relating metabolic evolution to the self-amplification and self-organization of the biosphere. We discuss the implications of this framework for the evolution of Earth's biogeochemical cycles and the rise of atmospheric oxygen.

Spatial Self-Organization of Ecosystems: Integrating Multiple Mechanisms of Regular-Pattern Formation.

Large-scale regular vegetation patterns are common in nature, but their causes are disputed. Whereas recent theory focuses on scale-dependent feedbacks as a potentially universal mechanism, earlier studies suggest that many regular spatial patterns result from territorial interference competition between colonies of social-insect ecosystem engineers, leading to hexagonally overdispersed nest sites and associated vegetation. Evidence for this latter mechanism is scattered throughout decades of disparate literature and lacks a unified conceptual framework, fueling skepticism about its generality in debates over the origins of patterned landscapes. We review these mechanisms and debates, finding evidence that spotted and gapped vegetation patterns generated by ants, termites, and other subterranean animals are globally widespread, locally important for ecosystem functioning, and consistent with models of intraspecific territoriality. Because these and other mechanisms of regular-pattern formation are not mutually exclusive and can coexist and interact at different scales, the prevailing theoretical outlook on spatial self-organization in ecology must expand to incorporate the dynamic interplay of multiple processes.

Geodiversity, self-organization, and health of three-phase semi-arid rangeland ecosystems, in the Israeli Negev

Source–sink, two-phase mosaic-like ecosystems are widespread throughout the world's drylands. Such ecosystems are composed of woody vegetation patches and intershrub spaces and have been characterized as having high flexibility and survivability. Recent studies from the semi-arid Negev drylands of Israel reported that livestock grazing has resulted in the modification of two-phase mosaic-like shrublands into three-phase mosaic rangelands, with livestock trampling routes encompassing a separate, and the most degraded phase, while the shrubs encompass the most improved phase. The objective of this study was, therefore, to reassess this theory through the investigation of patch-scale (spatial scale of one to several decimeters) geodiversity and self-organization of these ecosystems. In terms of the effect of type of surface cover (microhabitat), the soil hygroscopic moisture content and stable aggregate content of the uppermost layer (0–5cm depth) were significantly affected by this factor, and revealed the highest, intermediate, and smallest values for the shrubby patches (3.06% and 77%), intershrub spaces (2.81% and 68%), and the trampling routes (2.63% and 55%), respectively. An opposite effect was recorded for the sand content, revealing 23.9%, 25.3%, and 26.0%, respectively. The clay dispersion index was also significantly affected by microhabitat, and revealed a higher value for the trampling routes (0.83) than for the intershrub spaces and shrub patches (0.37 for both). At the same time, other soil characteristics were not significantly affected by microhabitat. Overall, some differences were recorded between north- and south-facing hillslopes, proposing somewhat better soil quality in the northern aspects. A conceptual model is proposed, in which moderate livestock pressure increases ecosystem geodiversity at the patch scale, modifying the ecosystem's self-organization to encompass a new (dynamic) equilibrium of a tri-modal pattern, and increasing ecosystem health. Also, a simple numerical simulation is proposed, modeling the effect of livestock trampling routes on the redistribution of water at the patch scale, with the resultant modifications in distribution of vegetation cover. Yet, it is proposed that functioning of three-phase mosaic rangelands is more complex than previously suggested, encompassing several simultaneous effects, of which some may have offsetting impacts.

Understanding self-organization of ecosystems under disturbance using a microcosm study

It is a key to success of ecological engineering to understand self-organization of a target ecosystem. Self-organizing patterns of ecosystems, however, become complicated due to a wide range of disturbance regimes in nature. We investigated how disturbances influence self-organization of ecosystems from energetic perspectives using 14 freshwater aquatic microcosms transplanted from lakes in Florida. We observed five different disturbance–productivity relationships from the microcosm tests and these variable relationships were attributed to the different initial states of the microcosms under the same input sequence of test plans and disturbance regimes. Through processes of self-organization, as the microcosms matured with time, resistance increased and resilience decreased. The microcosm study provided insights regarding restoration and management of ecosystems including the insight that initial seeds for restoration of an ecosystem should be carefully selected in consideration of typical disturbance regimes of the region. It is also suggested that consideration or manipulation of disturbance regimes in each successional stage is sometimes needed for maximum productivity or a designated goal of a restoration project because self-organizing patterns that result under disturbances vary depending on a system's maturity.

A putative mechanism for bog patterning.

The surface of bogs commonly shows various spatial vegetation patterning. Typical are "string patterns" consisting of regular densely vegetated bands oriented perpendicular to the slope. Here, we report on regular "maze patterns" on flat ground, consisting of bands densely vegetated by vascular plants in a more sparsely vegetated matrix of nonvascular plant communities. We present a model reproducing these maze and string patterns, describing how nutrient-limited vascular plants are controlled by, and in turn control, both hydrology and solute transport. We propose that the patterns are self-organized and originate from a nutrient accumulation mechanism. In the model, this is caused by the convective transport of nutrients in the groundwater toward areas with higher vascular plant biomass, driven by differences in transpiration rate. In a numerical bifurcation analysis we show how the maze patterns originate from the spatially homogeneous equilibrium and how this is affected by changes in rainfall, nutrient input, and plant properties. Our results confirm earlier model results, showing that redistribution of a limiting resource may lead to fine-scale facilitative and coarse-scale competitive plant interactions in different ecosystems. Self-organization in ecosystems may be a more general phenomenon than previously thought, which can be mechanistically linked to scale-dependent facilitation and competition.

Unifying the relationships of species richness to productivity and disturbance.

Although species richness has been hypothesized to be highest at 'intermediate' levels of disturbance, empirical studies have demonstrated that the disturbance-diversity relationship can be either negative or positive depending on productivity On the other hand, hypothesized productivity diversity relationships can be positive, negative or unimodal, as confirmed by empirical studies. However, it has remained unclear under what conditions each pattern is realized, and there is little agreement about the mechanisms that generate these diverse patterns. In this study, I present a model that synthesizes these separately developed hypotheses and shows that the interactive effects of disturbance and productivity on the competitive outcome of multispecies dynamics can result in these diverse relationships of species richness to disturbance and productivity The predicted productivity diversity relationship is unimodal but the productivity level that maximizes species richness increases with increasing disturbance. Similarly, the predicted disturbance diversity relationship is unimodal but the peak moves to higher disturbance levels with increasing productivity Further, these patterns are well explained by the opposite effects of productivity and disturbance on competitive outcome that are suggested by the change in community composition along these two environmental gradients: higher productivity favours superior competitors while higher disturbance levels favour inferior competitors.

Network integration of ecological extremal principles: exergy, emergy, power, ascendency, and indirect effects

Self organization in ecosystems has been postulated to be directed by a number of seemingly unrelated goal functions or extremal principles. These include exergy, the useful work content of energy, which measures distance from thermodynamic ground; emergy, which increases in proportion to the number of steps energy has taken away from its point of input to a system; power, which is work per unit time, and can be measured as the total energy flow in an ecosystem; ascendency, which combines a mutual information measure of the distribution of flows in a system network with the total flow; and indirect effects, which concern relationships at a distance in energy networks. S.E. Jørgensen recently obtained high correlations between exergy, emergy, ascendency, and the ratio of indirect to direct effects, in a set of ecosystem models. These results suggest that these optimality criteria may be formally related. This paper shows, for systems at macroscopic steady states, that they are. Exergy, emergy, power, ascendency, and indirect effects all have common origins in the path structure and associated microscopic dynamics of energy and matter flows and storages in ecosystem networks. Thus, these organizational measures, originally derived from different perspectives on ecosystems, are in fact related through a common basis.