generate questions: There is evidence that there have been significant changes in Amazon rainforest vegetation over the last 21,000 years through the Last Glacial Maximum (LGM) and subsequent deglaciation. Analyses of sediment deposits from Amazon basin paleolakes and from the Amazon Fan indicate that rainfall in the basin during the LGM was lower than for the present, and this was almost certainly associated with reduced moist tropical vegetation cover in the basin. There is debate, however, over how extensive this reduction was. Some scientists argue that the rainforest was reduced to small, isolated refugia separated by open forest and grassland; other scientists argue that the rainforest remained largely intact but extended less far to the north, south, and east than is seen today. This debate has proved difficult to resolve because the practical limitations of working in the rainforest mean that data sampling is biased away from the center of the Amazon basin, and both explanations are reasonably well supported by the available data.
What does LGM stands for? {sep_token} What did the analysis from the sediment deposits indicate? {sep_token} What are some of scientists arguments? {sep_token} How has this debate been proven? {sep_token} How are the explanations supported? {sep_token} There have been major changes in Amazon rainforest vegetation over the last how many years? {sep_token} What caused changes in the Amazon rainforest vegetation? {sep_token} What has been analyzed to compare Amazon rainfall in the past and present? {sep_token} What has the lower rainfall in the Amazon during the LGM been attributed to? {sep_token} Many changes in the vegetation of the amazon rainforest took place since the  Last Glacial Maximum, which was how many years ago? {sep_token} Analysis of what kind of deposits from the Amazon Fan indicates a change in rainfall in the Amazon basin? {sep_token} Changes in rainfall reduced what kind of vegetation cover in the Amazon basin? {sep_token} Scientists disagree with how the Amazon rainforest changed over time with some arguing that it was reduced to isolated refugia seperated by what? {sep_token} Why is it difficult to resolve disagreements about the changes in the Amazon rainforest?