Tiering on Land – Trees and Forests (Late Palaeozoic)

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Abstract Trees with woody trunks first appeared in Middle Devonian times (390 MYA). However, a number of other types of Palaeozoic plants also achieved large sizes, most notably the arborescent lycopsids. The tropical wetlands of late Carboniferous and early Permian age (320–280 MYA), often referred to as the coal swamps or coal forests, were dominated by the arborescent lycopsids. Because of the unusual growth and reproductive strategies of these plants, and the water‐logged and low pH substrates, the ecological structure of these forests was quite different from most modern‐day forests. Rather than there being a vertical stratification of the vegetation controlled by light availability, there was a lateral ecological partitioning of the habitats controlled mainly by substrate conditions. Key Concepts: The late Palaeozoic coal forests were relatively open habitats, and therefore, light levels were not significant in controlling their ecological partitioning. Substrate conditions were most important for controlling plant distribution in the coal forests, resulting in a lateral ecological partitioning, rather than a vertical tiering as is typical in most modern‐day forests. The rapid determinate growth of the arborescent lycopsids that dominated the coal forests meant that huge amounts of peat were generated, which are now preserved as coal. The coal forests were a major carbon sink during the late Palaeozoic times and had a significant impact on levels of atmospheric carbon dioxide and global climates.