A. Block

Syndromes of Global Change: a qualitative modelling approach to assist global environmental management

A novel transdisciplinary approach to investigate Global Change (GC) is presented. The approach rests on the decomposition of the intrigue dynamics of GC into patterns of civilization–nature interactions (“syndromes”) by an iterative scientific process of observations, data and system theoretical analyses, and modelling attempts. We illustrate the approach by a detailed analysis of the Sahel Syndrome, which describes the rural poverty driven overuse of natural resources. The investigation is performed by (i) identifying relevant “symptoms” and interlinkages which are characteristics for this pattern, and (ii) a qualitative model representing the internal dynamics of the essential flywheel. The geographical patchwork of the regions affected by the syndrome which is obtained by global data analysis, proves the high global relevance of this pattern. The qualitative model is employed for an evaluation of basic policy strategies debated in the context of rural poverty driven environmental degradation. It turns out that a mixed policy of combating poverty and introducing soil preserving agricultural techniques and practices is most promising to tackle the syndrome dynamics.

Reduction of biosphere life span as a consequence of geodynamics

The long-term co-evolution of the geosphere’biospere complex from the Proterozoic up to 1.5 billion years into the planet’s future is investigated using a conceptual earth system model including the basic geodynamic processes. The model focusses on the global carbon cycle as mediated by life and driven by increasing solar luminosity and plate tectonics. The main CO2 sink, the weathering of silicates, is calculated as a function of biologic activity, global run-off and continental growth. The main CO2 source, tectonic processes dominated by sea-floor spreading, is determined using a novel semi-empirical scheme. Thus, a geodynamic extension of previous geostatic approaches can be achieved. As a major result of extensive numerical investigations, the “terrestrial life corridor”, i.e., the biogeophysical domain supporting a photosynthesis-based ecosphere in the planetary past and in the future, can be identified. Our findings imply, in particular, that the remaining life-span of the biosphere is considerably shorter (by a few hundred million years) than the value computed with geostatic models by other groups. The “habitablezone concept” is also revisited, revealing the band of orbital distances from the sun warranting earth-like conditions. It turns out that this habitable zone collapses completely in some 1.4 billion years from now as a consequence of geodynamics.

Habitable zone for Earth-like planets in the solar system

Abstract We present a new conceptual Earth system model to investigate the long-term co-evolution of geosphere and biosphere from the geological past upto 1.5 billion years into the planets future. The model is based on the global carbon cycle as mediated by life and driven by increasing solar luminosity and plate tectonics. As a major result of our investigations we calculate the “terrestrial life corridor”, i.e. the biogeophysical domain supporting a photosynthesis-based ecosphere during planetary history and future. Furthermore, we calculate the behavior of our virtual Earth system at various distances from the Sun, using different insolations. In this way, we can find the habitable zone as the band of orbital distances from the Sun within which an Earth-like planet might enjoy moderate surface temperatures and CO2-partial pressures needed for advanced life forms. We calculate an optimum position at 1.08 astronomical units for an Earth-like planet at which the biosphere would realize the maximum life span. According to our results, an Earth-like planet at Martian distance would have been habitable upto about 500 Ma ago while the position of Venus was always outside the habitable zone.

Multifractal analysis of the microdistribution of elements in sedimentary structures using images from scanning electron microscopy and energy dispersive X ray spectrometry

A novel method for the quantitative characterization of density distributions of elements in sedimentary geosystems is presented. This general technique is based on the multifractal analysis of image-processed elemental maps obtained by scanning electron microscopy combined with energy dispersive X ray spectrometry. Applications to microdistributions of Si, Fe, and Al in recent bioactive siliciclastic marine sediments are reported. Inhomogeneous scaling behavior of these elemental distributions is observed in all cases. Two main conclusions can be drawn: (1) The sedimentary matrix exhibits true fractal geometry and (2) the processes allocating and rearranging the elements are not of pure stochastic type. Therefore the identification of genetic processes may be possible on the basis of their “multifractal fingerprints”.

Multifractal characterization of microbially induced magnesian calcite formation in Recent tidal flat sediments

Abstract Structures resulting from biogenic carbonate cementation of microbial mats in Recent siliciclastic tidal flat sediments of the North Sea are analyzed quantitatively by a novel combination of scanning electron microscopy and energy-dispersive X-ray spectrometry (SEM/EDX) imaging and subsequent multifractal analysis. Evaluation of calcium distribution patterns and their links to sediment-intrinsic mineralization processes show that the applied geometrical technique is an efficient tool for detecting microscopic variations in elemental distributions and related minerals within sedimentary matrices. Two main conclusions can be drawn: (i) magnesian calcite is a rapidly formed product of the early diagenesis of organic matter in Recent bioactive marine sediments; and (ii) multifractal spectra are measures for the spatial inhomogeneity of authigenic calcification processes acting on the sedimentary structure. This implies that elemental distribution patterns in a sedimentary system are scale-independent phenomena. Processes causing such patterns have occurred over certain periods with varying rates and on different scales. The detection of multifractal measures also opens a way towards a systematic survey of dynamic processes occurring in sedimentary structures.

Tutorial Modelling of geosphere–biosphere interactions: the effect of percolation-type habitat fragmentation

A considerably extended two-dimensional version of the famous Lovelock–Watson model for geosphere–biosphere interactions (“Daisyworld”) is employed to investigate the impact of habitat fragmentation. The latter is dynamically modelled through the standard percolation process first introduced by solid state theory. It is found that the connectivity of the space accessible for life is crucial for ecological performance. In particular, the self-stabilizing capacity of the biosphere strongly depends on the fragmentation topology. An extremely rich and partially counter-intuitive eco-dynamics is observed when a simple community structure, consisting of plants and herbivores, is introduced. Quite remarkably, high herbivore vitality destroys the stability of the entire biosphere in a way reminiscent of “desertification”.

Fractal geometry and root system structures of heterogeneous plant communities

Above-ground plant growth is widely known in terms of structural diversity. Likewise, the below-ground growth presents a mosaic of heterogeneous structures of differing complexity. In this study, root system structures of heterogeneous plant communities were recorded as integral systems by using the trench profile method. Fractal dimensions of the root images were calculated from image files by the box-counting method. This method allows the structural complexity of such associations to be compared between plant communities, with regard to their potentials for soil resource acquisition and utilization. Distinct and partly significant differences are found (fractal dimension between 1.46 ± 0.09 and 1.71 ± 0.05) in the below-ground structural complexity of plant communities, belonging to different biotope types. The size of the heterogeneous plant community to be examined has an crucial influence on the fractal dimension of the root system structures. The structural heterogeneity becomes particularly evident (fractal dimensions between 1.32 and 1.77) when analysing many small units of a complex root system association. In larger plant communities, a broad variety of below-ground structures is recorded in its entirety, integrating the specific features of single sub-structures. In that way, extreme fractal dimensions are lost and the diversity decreases. Therefore, the analysis of larger units of root system associations provides a general knowledge of the complexity of root system structures for heterogeneous plant communities.

Aggregation by attractive particle-cluster interaction

A quasideterministic irreversible growth model is studied, where aggregates are generated by attractive cluster-particle forces proportional ro r- alpha . It is shown that fractal dimensions and growth site probability measures of the resulting fractal structures strongly depend on the parameter alpha . Comparison with experimental results indicates that this model represents a further step towards realistic simulations of growth processes.

Characteristic Multifractal Element Distributions in Recent Bioactive Marine Sediments

It is shown that SEM/EDX imaging is a powerful tool for detecting the spatial distribution of different elements and minerals in recent bioactive sediments. The evaluation of these distribution patterns by multifractal analysis provides a quantitative assessment of the characteristic inhomogeneities.

“Active Planetary Cover” Concept and Long-Term Evolution of Planetary Climate

At the beginning of XIX. century J.-B. Lamarque had introduced the term “biosphere”. In accordance with his definition the biosphere is a “scope of life” and it is an external cover for the Earth. In 1875 E. Suss, who also distinguished the biosphere as one of the Earth covers, introduced the same term in geology. But V. Vernadsky was the person who first created the modern concept of the biosphere as an active planetary cover, which does not only passively reflects its geological and geochemical environment but also transforms it. So that Lovelock (1979) has done only a next step when he has postulated that this transformation is an act of self-regulation creating optimal conditions for the biosphere existence.