Functioning Of Natural Systems Research Articles

Low functional diversity and no redundancy in British avian assemblages

1. Spatial and temporal patterns in functional diversity can reveal the patterns and processes behind community assembly and whether ecological redundancy exists. Here, we analyse functional diversity in British avian assemblages over a period of about 20 years. 2. Functional diversity is generally lower than expected by chance, indicating that assemblages contain species with relatively similar functional traits. One potential explanation is filtering for traits suitable to particular habitats, though other explanations exist. 3. There was no evidence of ecological redundancy over the 20 years. In fact, changes in functional diversity were almost exactly proportional to changes in species richness. 4. The absence of functional redundancy results from little redundancy intrinsic to the species' functional relationships and also because compositional change was nonrandom. Observed extinction and colonization events caused greater changes in functional diversity than if these events were random. 5. Our findings suggest that community assembly is influenced by the traits of species and that observed changes in functional diversity provide no reason to believe that the functioning of natural systems is buffered against change by ecological redundancy.

Nutrient Addition Differentially Affects Ecological Processes of Avicennia germinans in Nitrogen versus Phosphorus Limited Mangrove Ecosystems

Nutrient over-enrichment is a major threat to marine environments, but system-specific attributes of coastal ecosystems may result in differences in their sensitivity and susceptibility to eutrophication. We used fertilization experiments in nitrogen (N)- and phosphorus (P)-limited mangrove forests to test the hypothesis that alleviating different kinds of nutrient limitation may have different effects on ecosystem structure and function in natural systems. We compared a broad range of ecological processes to determine if these systems have different thresholds where shifts might occur in nutrient limitation. Growth responses indicated N limitation in Avicennia germinans (black mangrove) forests in the Indian River Lagoon (IRL), Florida, and P limitation at Twin Cays, Belize. When nutrient deficiency was relieved, A. germinans grew out of its stunted form by increasing wood relative to leaf biomass and shoot length relative to lateral growth. At the P-limited site, P enrichment (+P) increased specific leaf area, N resorption, and P uptake, but had no effect on P resorption. At the N-limited site, +N increased both N and P resorption, but did not alter biomass allocation. Herbivory was greater at the P-limited site and was unaffected by +P, whereas +N led to increased herbivory at the N-limited site. The responses to nutrient enrichment depended on the ecological process and limiting nutrient and suggested that N- versus P-limited mangroves do have different thresholds. +P had a greater effect on more ecological processes at Twin Cays than did +N at the IRL, which indicated that the P-limited site was more sensitive to nutrient loading. Because of this sensitivity, eutrophication is more likely to cause a shift in nutrient limitation at P-limited Twin Cays than N-limited IRL.

Differentiating dilution and retention processes in mine effluent remediation within a natural wetland on the Zambian Copperbelt

The use of wetlands to treat mine effluent has grown in popularity over the past two decades, although the processes by which the natural systems function are often poorly understood. This field-scale investigation utilises daily data over a 9-month period in assessing the processes leading to the remediation of mine effluent within a natural wetland on the Zambian Copperbelt. The study differentiates effluent remediation through dilution from pollutant retention. Decreased wetland outflow concentrations of SO 4 and Na are due to dilution only, while Co (50%) and especially Cu (83%) are retained within the wetland. Retention was linked to adsorption onto new or primed surfaces during an initial period of effluent release into the system and to processes related to pH buffering to 7.5. The wetland’s acid buffering capacity was largely the result of carbonate-rich groundwater discharge into the wetland. Although this buffering capacity likely shows little seasonal fluctuation (20–80 kmol/day), the impact of acidic effluent input on the wetland itself probably varies markedly between seasons, owing to the temporal and spatial characteristics of discharge from the catchment’s aquifers. Assessment of other natural wetlands in the region indicated that some (circa 15%) showed similar catchment size, hydrochemical and hydrogeological characteristics as those of the New Dam wetland, likely demonstrating a similar effluent remediation potential as that described here.

Predator diversity dampens trophic cascades.

Food web complexity is thought to weaken the strength of terrestrial trophic cascades in which strong impacts of natural enemies on herbivores cascade to influence primary production indirectly. Predator diversity can enhance food web complexity because predators may feed on each other and on shared prey. In such cases, theory suggests that the impact of predation on herbivores relaxes and cascading effects on basal resources are dampened. Despite this view, no empirical studies have explicitly investigated the role of predator diversity in mediating primary productivity in a natural terrestrial system. Here we compare, in a coastal marsh community, impacts of arthropod predators on herbivores and plant productivity between a simple food web with a single predator species and a complex food web with a diverse predator assemblage. We show that enhancing predator diversity dampens enemy effects on herbivores and weakens trophic cascades. Consequently, changes in diversity at higher trophic levels can significantly alter ecosystem function in natural systems.

Ecosystem implications of genetic variation in water-use of a dominant riparian tree.

Genetic variation in dominant species can affect plant and ecosystem functions in natural systems through multiple pathways. Our study focuses on how genetic variation in a dominant riparian tree ( Populus fremontii, P. angustifolia and their natural F(1) and backcross hybrids) affects whole-tree water use, and its potential ecosystem implications. Three major patterns were found. First, in a 12-year-old common garden with trees of known genetic makeup, hybrids had elevated daily integrated leaf-specific transpiration ( E(tl); P=0.013) and average canopy conductance ( G(c); P=0.037), with both E(tl) and G(c) approximately 30% higher in hybrid cross types than parental types. Second, delta(13)C values of leaves from these same trees were significantly more negative in hybrids ( P=0.004), and backcross hybrids had significantly more negative values than all other F(1) hybrid and parental types ( P<0.001). Third, in the wild, a similar pattern was found in leaf delta(13)C values where both hybrid cross types had the lowest values ( P<0.001) and backcross hybrids had lower delta(13)C values than any other tree type ( P<0.001). Our findings have two important implications: (1). the existence of a consistent genetic difference in whole-tree physiology suggests that whole-tree gas and water exchange could be another pathway through which genes could affect ecosystems; and (2). such studies are important because they seek to quantify the genetic variation that exists in basic physiological processes-such knowledge could ultimately place ecosystem studies within a genetic framework.

Conservation of endangered species and the patterns and propensities of biodiversity

It is commonly asserted in the ecological and economic literature that habitat loss is the main cause of loss of imperiled species. The evidence clearly shows that habitat loss is a common contributing factor, but there is little evidence that it is the most important factor. Studies that have focused on the mechanisms of species loss have failed to produce models capable of predicting patterns of loss as a function of human activities. I propose that this is because ecologists have employed an unrealistic conceptual model of the functioning of natural systems. Karl Popper's construct of the propensities of natural systems provides a more realistic view, and better potential to yield predictive models. I provide two examples of patterns of biodiversity and species loss in Canada where mechanistic reasoning is inconsistent with the observed propensities of species loss. To cite this article: D.J. Currie, C. R. Biologies 326 (2003).

Beyond TQM implementation: the new paradigm of TQM sustainability

The concept of sustainable development has been touted as a new planning agenda (Beatley & Manning, 1998). As such, it becomes a fundamental concept that should be an important aspect of all further policy developments (Loffler, 1998). Sustainable development is based on a perceived need to address environmental deterioration and to maintain the vital functions of natural systems for the well being of present and future generations. Sustainability is defined as ‘the ability of an organization to adopt to change in the business environment to capture contemporary best practice methods and to achieve and maintain superior competitive performance’ (Zairi & Liburd 2001). This concept implies that sustainability is a mean for an organization to maintain its competitiveness. Quinn (2000) has a similar idea on sustainability. He describes it as the development that meets present needs without compromising the ability of future generations to meet their own needs. Gladwin et al. (1995), on the other hand, define it as ‘development, which meets the needs of the present, without compromising the ability of future organizations to meet their own needs’. Total Quality Management (TQM) represents an integrative approach for the pursuit of customer satisfaction (Chin et al., 2001). However, facing intense pressure of global competition, organizations need to consider incorporating the idea of sustainability in TQM in order to sustain their competitive advantage and performance improvement. In addition, the interest of organizational survival, growth and prosperity has therefore got to be concerned with not just the present but also the future. The concept of sustainability does however remain unclear and it is therefore worth exploring further how it can be applied. It is the purpose of this paper to highlight some of the key issues of sustainable TQM, to trace transformational evolutions that bring different orientations over time. The paper will then describe how various critical factors can create a sustainable competitive advantage, when working in harmony. Finally, a wide range of best practices will be illustrated to support a proposed model for TQM sustainability.

Louis Sander and Contemporary Psychoanalysis An Introduction

Louis Sander's bold and ambitious theoretical synthesis deserves careful attention from psychoanalysts of all persuasions. Sander's cutting-edge approach draws on infant observation research, nonlinear dynamic systems theories, and current biology, physics, and other “hard” sciences. He is rethinking the psychoanalytic approach to psychic structure, motivation, and therapeutic action. In so doing, he updates Freud's project of linking psychoanalysis with scientific paradigms, but without reductionism, epistemological naivete, or an implicit antipsychological attitude. Sander emphasizes the dynamic relationships between elements in systems. His method draws parallels between the different levels of the functioning of natural systems, starting with the basic “biological” level of cells and organs and moving toward the psychic and interpersonal phenomena that are of greatest interest to psychoanalysts. In this way, he opens a window for a broad and inclusive “relational metapsychology.”

Setting ecological restoration goals for technical feasibility and scientific validity

Major ecological restoration will not be undertaken unless human society approves the goals and objectives of restoration. In addition, restoration will not persist unless human society has sufficient esteem for the restored ecosystem to protect its integrity. Linking ecological restoration to sustainable use of the planet seems a promising way to foster society’s interest in and acknowledgment of human dependence on natural systems. An increase in environmental and ecological literacy is essential to achieving this end, as is an awareness of the goals and conditions of sustainability. If the science and technology underlying ecological restoration are not understood by the general public, implementation will fail for lack of public support. Ecosystem services, those functions of natural systems perceived as beneficial to human society, are likely to be understood and accepted if their value in the life support system of human society is explained. Emphasis in ecological restoration must shift from reestablishing a naturalistic community of plants and animals in the damaged ecosystems to restoring ecological functions, particularly those perceived as ecosystem services. Most restoration projects thus far have emphasized structure rather than function, although both are doubtless important to sustainable use of the planet. Nevertheless, support for ecological restoration may be enhanced by emphasizing the restoration of ecological services. An essential third consideration beyond technically feasible and scientifically valid goals is whether the goals are socially feasible. This manuscript will explore aspects of social feasibility because neither technically feasible goals nor scientifically valid goals will be possible in the absence of societal acceptance.

Nature's Services: Societal Dependence on Natural Ecosystems

Life itself as well as the entire human economy depends on goods and services provided by earth's natural systems. The processes of cleansing, recycling, and renewal, along with goods such as seafood, forage, and timber, are worth many trillions of dollars annually, and nothing could live without them. Yet growing human impacts on the environment are profoundly disrupting the functioning of natural systems and imperiling the delivery of these services.Nature's Services brings together world-renowned scientists from a variety of disciplines to examine the character and value of ecosystem services, the damage that has been done to them, and the consequent implications for human society. Contributors including Paul R. Ehrlich, Donald Kennedy, Pamela A. Matson, Robert Costanza, Gary Paul Nabhan, Jane Lubchenco, Sandra Postel, and Norman Myers present a detailed synthesis of our current understanding of a suite of ecosystem services and a preliminary assessment of their economic value. Chapters consider: major services including climate regulation, soil fertility, pollination, and pest control philosophical and economic issues of valuation case studies of specific ecosystems and services implication of recent findings and steps that must be taken to address the most pressing concerns Nature's Services represents one of the first efforts by scientists to provide an overview of the many benefits and services that nature offers to people and the extent to which we are all vitally dependent on those services. The book enhances our understanding of the value of the natural systems that surround us and can play an essential role in encouraging greater efforts to protect the earth's basic life-support systems before it is too late. -- publisher's description

Population viability and spatial fish reproductive strategies in constant and changing environments: an individual-based modelling approach

A spatially explicit individual-based model (IBM) helps to explain how two reproductive strategies, described as obstinate and opportunist, may be acting at the population level. Factors such as the spatial structure and the dynamics of the environment, the shape of the reproductive function, and spawning season duration are considered. Five simulations are presented to explore the importance of these factors in the success of two reproductive strategies experiencing in a first step, a constant, and in a second step, a changing environment. Simulations show that the obstinate strategy is characterized by high inertia and mainly selects optimal environmental conditions in the long term, whereas the opportunist strategy maintains diversity in site choice and allows the individual to explore environmental variability. Under drastic environmental changes, only a population combining both strategies avoids extinction. A low percentage of opportunists (about 1%) coupled with a high proportion of obstinates (about 99%) ensure population viability. Similar percentages have been observed in nature for philopatric species. The respective percentages of inertia and innovation that are needed in the functioning of natural systems are discussed.

Leadership at the edge of CHAOS: From control to creativity

“A new breed of companies is emerging that seems to thrive on chaos. These companies — which I call ‘Quantum Organizations’ — operate on an organic model that closely mirrors the functioning of natural systems.”

Are we lost in the vale of ignorance or on the mountain of principle?

Making progress in understanding global and long-run problems raised by human perturbations of ecological systems, and in making that understanding relevant to policy formulation, will require intense collaboration between, at least, ecologists and economists. There is far too little of this now and far too much fairly fruitless argument and lecturing—in part because each side seems embarrassed by its lack of ability to do what it claims needs to be done. Ecological models cannot predict the long-run changes in the multiple functions of natural systems that might follow from human actions such as land clearance or waste storage. Economists' valuation techniques cannot convincingly deal with multiple dimensions of change in the environment or with the non-use values of any changes. An ecological-economic modeling project of 20 years ago reveals a few lessons for those who would like to see progress on collaborative research ultimately aimed at correcting these deficiencies. For example, real collaboration requires investment of substantial up-front time, investment best made in the context of a mathematical model of the problem to be investigated. The model forces participants to fit their ideas together rather than to string them out independently. It also will likely force compromise from disciplinary purity. There is much to be said for using such projects to train a small group of Ph.D.s who will have observed and participated in the collaboration. The existence of such a group will do more for “eco-system valuation” than ad hoc and episodic forums involving old dogs, even though some of these would be happy to learn new tricks.

The role of habitat selection in landscape ecology

Landscape ecology - whether it is defined as the fragmentation of habitats into insular or weakly coupled subpopulations or by the interaction of scale-dependent processes among ecological communities (or species, or populations) - involves forms of spatial analysis. Habitat selection analyses how organisms become distributed in response to spatial heterogeneity. Thus, processes associated with habitat selection should be central to landscape ecology. Insofar as the individuallevel activity of habitat selection has predictable population and community level consequences, habitat selection can form a mechanistic basis for understanding landscape ecology. A survey of any major ecological journal reveals considerable confusion and disagreement on the roles of spatially-dependent processes in the evolution, structure and function of natural systems. Part of the confusion is due, no doubt, to the complexity of spatial interactions. Processes responsible for spatial patterns may themselves be dependent upon spatial, temporal and even organizational scales. Some processes such as density-dependence (dependence on population size) operate across a spectrum of spatial and temporal scales. Assumptions of density-dependence are central to our views of natural selection, to our understanding of population dynamics and community structure and to our management of natural resources. Once again, habitat selection provides a natural forum for considering this central role of density-dependent and scale-interdependent processes. Within the conceptual framework of habitat selection, we feel it is possible to develop a set of inter-related theories that explain observed patterns of distribution and abundance at several ecological scales. (A similar claim can be made for a central role of habitat selection in evolutionary processes; see Evolutionary Ecology, 1987, Vol. 1, No. 4).

Categorical system theory and the phenomenological calculus

The mathematical theory of categories is used as a tool in the description of the structure and function of natural systems. The connections between the category of natural systems, with observables and dynamics, and the phenomenological calculus of response tensors, duality- and adjoint-invariance diagrams are established. The unified theory is applied to the analysis of hierarchies, pattern generation and the structure and dynamics of proteins.

Synthesis and oxygenation studies of monomolecular hemoprotein models

The preparation and properties of molecules modeling the active site of natural oxygen carriers have received considerable attention in recent years for the elucidation of the factors that control the binding reactions of molecular oxygen and carbon monoxide in some hemoproteins. Such compounds have been synthesized following three requirements which seem necessary in the biological functions of natural systems: 1. pentacoordination of the iron(II) ion by a nitrogenous base on the proximal site; 2. steric protection of the heme in order to prevent it from irreversible oxidation into μ-oxo iron(III) dimers; 3. control of the dioxygen environment on the distal site. Several groups have investigated these three problems separately [1]. As part of our studies of the stereochemical influences on the formation and stability of oxygenated model compounds, we have prepared two series of porphyrin derivatives which correspond to the three structural conditions mentioned above. ▪ ▪ All the compounds were synthesized following the concept of both face hindered tetraphenylporphyrins (‘basket handle’ porphyrins) in which two opposite mesophenyl rings are bridged by a convenient chain [2,3]. The proximal base (pyridine or imidazole) was inserted into one of the handles. The size and polarity of the cage on the distal side can be modified to some extent by suitable chemical changes of the second handle. The newly ‘hanging base’ porphyrins were prepared either from 5,10,15,20-tetrakis( o-hydroxyphenyl)porphyrin (series A, compounds 1–4) or from 5,10,15,20-tetrakis( o-aminophenyl)porphyrin (series B, compounds 5–8). Thus the main structural difference between the two series lies in the presence of non polar ether groups in the former and of polar amide linkage in the latter [4]. Their iron(II) complexes have a magnetic high spin state (S = 2) characteristic of deoxymyoglobins and hemoglobins. Addition of O 2 and CO to these complexes results in the formation of hexacoordinated diamagnetic species (S = O), as in oxy and carbooxyhemoproteins, without any paramagnetic perturbations by low lying thermally excited states. A systematic study of the O 2 and CO rates and equilibrium binding constants has been carried out in toluene by laser flash photolysis using a modified exchange rate law [5]. This clearly establishes the important role of factors such as the distal steric hindrance, the proximal base constraint and the polarity of the dioxygen environment in the control of the O 2 binding and the stability of oxygenated complexes. The association rate constants of O 2 and CO are of the same order of magnitude in the two series, but a large variation in the dissociation rate constants is observed. The smaller dissociation rate constants are observed for the compounds having amide linkages as compared with their analogous ether bearings linkages. This results in an increase of the intrinsic stability of the oxygenated derivatives up to the values observed in the natural compounds. The proton magnetic resonance spectra of the oxygenated complexes indicate that the bound dioxygen molecule lies preferentially in a plane oriented toward the distal amide groups in the B series, in contrast with series A in which four nearly equivalent orientations are observed. This preferential orientation of the oxygen molecule results from an hydrogen bonding interaction with the amide groups as shown by the chemical shift of the corresponding protons. The role of this bond in the stability and the bent geometry of the oxygenated complex is of the same type as those proposed for hemoproteins involving distal histidine [6, 7].