A CANON FOR EARLY PALEOZOIC CONTINENTAL ECOSYSTEMS

Knowledge of early Paleozoic continental ecosystems has increased sufficiently to allow reconstruction of the ecological dialectic across the vital conjunction of air, light, water, and earth. On the side of circumstances, the air contained about the same concentration of N2 and O2 as at present but much more CO2 and -- possibly -- rather more dust and less water vapor. Such abundance of O2 would have facilitated aerobic metabolism and reduced penetration of UV radiation. The relatively high CO2/O2 ratio favored photoproduction as it induced a mild climate and minimized the losses of photoproduction to photorespiration and of water during the uptake of CO2. Though solar output was rather less than at present but the energy reaching the earth's surface was considerable except where attenuated by surficial water. Water would have been variously available as liquid sandwiched between air and earth, as water vapor above the surface, and as vapor and liquid below it. Chemical reactions involving N2, O2, CO2, H2O, wind-borne dust, and surface minerals at and just below the surface provided the mineral nutrients for photoproduction. Finally, the impact of raindrops, running water, and wind induced erosion, transport, and deposition that both damaged and benefited resident life. On the organismal side, the phototrophs probably included cyanobacteria, green algae, and 'eoembryophytes;' the heterotrophs, bacteria, protists, fungi (including lichen and mycorrhizal ones), nematodes, rotifers, and tardigrades, collembolids, mites, millipedes, and even enchytraeids centipeds, scorpions, spiders, aptergotes. The ecological dialectic emphasized the acquisition of light, CO2, water, and nutrients for green-plant photoproduction and the use of these in primary, secondary, and tertiary consumption (along with the recycling of CO2, water, and nutrients). It also stressed regulation by producers and consumers of radiation, photorespiration, and dehydration. Conversely the limited capabilities of the phototrophs restricted production to relatively low levels and ecosystem to mats, crusts, and turfs. The various consumers were similarly limited in their capabilities. These constraints limited bioengineering of physical circumstances.