Introduction
Southeast Asia rainforests are usually considered to be the oldest ones on Earth, being traced back at least to the Pleistocene (Morley, 2000), and amazingly they are also the tallest ones: highest trees reach about 55 m in South America, 70 m in Africa, while several trees exceed 80 m in Southeast Asia (Richard, 1952). This yet unexplained biogeographical pattern has, however, never been placed in a time perspective. Fossilization is unfortunately unlikely in tropical rainforests, as organic matter rapidly degrades in such an environment, and tall trees are moreover rarely fossil- ized complete. We report here giant fossil logs from the Middle Pleistocene of north-western Thailand, several of them being over 35 m long, one reaching 72.2 m. Architectural analysis of these logs suggests that some of the original trees towered to more than 100 m, well above the canopy of a lowland rainforest, at about 50 m. This characterizes a tall rainforest, a fact that is relevant to the interpretation of the palaeoclimate, contemporaneous assemblages of pebble tools and the evolution of mammals in Southeast Asia.
IntroductionSoutheast Asia rainforests are usually considered to be the oldest ones on Earth, being traced back at least to the Pleistocene (Morley, 2000), and amazingly they are also the tallest ones: highest trees reach about 55 m in South America, 70 m in Africa, while several trees exceed 80 m in Southeast Asia (Richard, 1952). This yet unexplained biogeographical pattern has, however, never been placed in a time perspective. Fossilization is unfortunately unlikely in tropical rainforests, as organic matter rapidly degrades in such an environment, and tall trees are moreover rarely fossil- ized complete. We report here giant fossil logs from the Middle Pleistocene of north-western Thailand, several of them being over 35 m long, one reaching 72.2 m. Architectural analysis of these logs suggests that some of the original trees towered to more than 100 m, well above the canopy of a lowland rainforest, at about 50 m. This characterizes a tall rainforest, a fact that is relevant to the interpretation of the palaeoclimate, contemporaneous assemblages of pebble tools and the evolution of mammals in Southeast Asia.
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