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 “habitable‐zone 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.
A novel transdisciplinary description of the mega-process called Global Change" in terms of functional patterns Syndromes" is presented. This approach to environmental analysis is inspired by medical sciences, where syndromes are perceived as typical combinations of pertinent co-factors. Sixteen main syndromes are identi ed as the subdynamics generating the worldwide environment and development process with all its negative aspects and impacts. The analysis relies on a speci c semi-qualitative methodology, which brings together elements from complex systems theory, fuzzy logic and expert-judgment e v aluations. The concept is illustrated by in-depth treatment and comparison of the syndromes Sahel" and Green Revolution". As a corollary of the syndrome approach, a simple operational de nition of Sustainable Development" is suggested.
A 2‐dimensional extension of the simple Lovelock‐Watson model for geosphere‐biosphere feedback is introduced and discussed. Our enriched version also takes into account various pertinent physical, biological, and civilisatory processes like lateral heat transport, species competition, mutation, germination, and habitat fragmentation. The model is used as a caricature of the Earth System, which allows potential response mechanisms of the biosphere to environmental stress (as generated, e.g., by global warming or anthropogenic land‐cover change) to be investigated qualitatively. Based on a cellular automaton representation of the system, extensive calculations are performed. They reveal a number of remarkable and, partially, counter‐intuitive phenomena: our model biosphere is able to control almost perfectly the geophysical conditions for its own existence. If the environmental stress exceeds certain thresholds, however, life breaks down on the artificial planet via a first‐order phase transition, i.e., in a non‐reversible way. There is a close connection between self‐stabilizing capacity, biodiversity and geometry of habitat fragmentation. It turns out, in particular, that unrestricted Darwinian competition, which reduces the number of co‐existing species, is the best guarantee for survival of the artificial ecosphere as a whole.
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.
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