Silurian-Devonian Terrestrial Revolution

The Silurian-Devonian Terrestrial Revolution, also known as the Devonian Plant Explosion (DePE)^[1] and the Devonian explosion, was a period of rapid colonization, diversification and radiation of land plants and fungi on dry lands that occurred 428 to 359 million years ago (Mya) during the Silurian and Devonian periods,^[2][3][4] with the most critical phase occurring during the Late Silurian and Early Devonian.^[5]

This diversification of terrestrial photosynthetic florae had vast impacts on the biotic composition of the Earth's surface, especially upon the Earth's atmosphere by oxygenation and carbon fixation. Their roots also eroded into the rocks, creating a layer of water-holding and mineral/organic matter-rich soil on top of Earth's crust known as the pedosphere, and significantly altering the chemistry of Earth's lithosphere and hydrosphere. The floral activities following the Silurian-Devonian plant revolution also exerted significant influences on changes in the water cycle and global climate, as well as driving the biosphere by creating diverse layers of vegetations that provide both sustenance and refuge for both upland and wetland habitats, paving the way for all terrestrial and aquatic biomes that would follow.^[6]

Through fierce competition for sunlight, soil nutrients and available land space, phenotypic diversity of plants increased greatly during the Silurian and Devonian periods, comparable in scale and effect to the explosion in diversity of animal life during the Cambrian explosion,^[7] especially in vertical growth of vascular plants, which allowed for expansive canopies to develop, and forever altering the plant evolutions that followed. As plants evolved and radiated, so did arthropods, who became the first established terrestrial animals and some formed symbiotic coevolution with plants.^[8] Herbivory, granivory and detritivory subsequently evolved independently among terrestrial arthropods (especially hexapods such as insects, as well as myriapods), molluscs (land snails and slugs) and tetrapod vertebrates, causing plants to in turn develop defenses against foraging by animals.

The Silurian and Devonian terrestrial florae were largely spore-bearing plants (ferns) and significantly different in appearance, anatomy and reproductive strategies to most modern florae, which are dominated by fleshy seed-bearing angiosperms that evolved much later during the Early Cretaceous. Much of these Silurian-Devonian florae had died out in extinction events including the Kellwasser event, the Hangenberg event, the Carboniferous rainforest collapse, and the End-Permian extinction.^[9][10]