The rise of trees and how they changed paleozoic at- mospheric co2, climate, and geology. in

Arge vascular plants with deep, extensive root systems arose and spread over the continents starting about 380 million years ago during the Devonian Period. Previously there were only bryophytes, algae, and small vascular plants restricted to the edges of water courses (Gensel and Edwards 2001). Large plants are important because their vast root systems produce a larger interface between the geosphere and the biosphere than do the more primitive species, where the plant/mineral interface is greatly reduced. This large interface allows plants to take up nutrients more rapidly, to grow bigger and faster (Algeo and Scheckler 1998), and to accelerate mineral weathering (Berner 1998). In addition, the larger plants, upon death, supply a much greater mass of organic matter for burial in sediments. Because of these effects, the rise of large vascular plants brought about a dramatic change in the level of atmospheric CO2, the climate, and the formation of carbon-rich deposits (coal) during the late Paleozoic.
The Rise of Trees and How They Changed Paleozoic Atmospheric CO 2 , Climate, and Geology. Available from: https://www.researchgate.net/publication/251145868_The_Rise_of_Trees_and_How_They_Changed_Paleozoic_... [accessed Nov 25 2017].

Covalent bond is the correct answer

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