Tree rings in Taxodium distichum wood (bald cypress) 4
Taxodium distichum (Linnaeus, 1753) - bald cypress, possibly from North Carolina, USA. (public display, North Carolina Museum of Natural Sciences, Rayleigh, North Carolina, USA)
Plants are multicellular, photosynthesizing eucaryotes. Most species occupy terrestrial environments, but they also occur in freshwater and saltwater aquatic environments. The oldest known land plants in the fossil record are Ordovician to Silurian. Land plant body fossils are known in Silurian sedimentary rocks - they are small and simple plants (e.g., Cooksonia). Fossil root traces in paleosol horizons are known in the Ordovician. During the Devonian, the first trees and forests appeared. Earth's initial forestation event occurred during the Middle to Late Paleozoic. Earth's continents have been partly to mostly covered with forests ever since the Late Devonian. Occasional mass extinction events temporarily removed much of Earth's plant ecosystems - this occurred at the Permian-Triassic boundary (251 million years ago) and the Cretaceous-Tertiary boundary (65 million years ago).
The most conspicuous group of living plants is the angiosperms, the flowering plants. They first unambiguously appeared in the fossil record during the Cretaceous. They quickly dominated Earth's terrestrial ecosystems, and have dominated ever since. This domination was due to the evolutionary success of flowers, which are structures that greatly aid angiosperm reproduction.
The bald cypress is not an angiosperm. It is a gymnosperm, but it is not an evergreen. Unusual for a conifer, the bald cypress sheds its foliage in the fall. Shown above is a cut cross-section through a bald cypress tree trunk. The numerous concentric lines are tree rings. During stressful years with harsh weather conditions, the tree has minimal growth, resulting in a narrow tree ring. During non-stressful years with pleasant weather, the tree grows more rapidly, resulting in wider tree rings. Rings can be used to date trees, modern wood, and historic wood. They can also be used to help pinpoint dates of large volcanic eruptions, which usually result in significant, but ephemeral, climate changes. Forest fire events can also be identified in tree ring records. The study of tree rings is called dendrochronology. A continuous record of tree rings goes back to the near-latest Pleistocene (~12,000 to 13,000 years ago).
From museum signage:
Cypress trees along North Carolina's Black River are among the oldest trees in eastern North America - some are at least 1,700 years old! Look at the tight growth rings of this cypress, which is approximately 700 years old. The compact rings are a result of the poor nutrient conditions common in blackwater swamps.
Classification: Plantae, Pinophyta, Pinopsida, Pinales, Cupressaceae / Taxodiaceae
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