An example of isostatic rebound is the rise in sea level of Hudson Bay. The last 100,000 years are called the Holocene Period. In permafrost soils only moisture is frozen. The Younger Dryas Period was a warm interstadial. The outer coat of the pollen grain is resistant to bacterial decomposition.
Acidic conditions slow the rate of decomposition in bogs.
Lake sediments and bogs are water-logged and deficient in available oxygen. Moss remains have antibiotic properties that check bacterial growth. All of the above. Glacial-Interglacial cycles of climate change result in the disassembly of existing communities followed by their reassembly. Environmental gradients are not constant in time and space.