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Building a chronology of climate change in a region today was first simply a matter of matching overlapping tree ring patterns in older and older trees; but such efforts are no longer based solely on tree-ring widths.
Features such as wood density, the elemental composition (called dendrochemistry) of its makeup, the anatomical features of the wood, and stable isotopes captured within its cells have been used in conjunction with traditional tree ring width analysis to study air pollution effects, the uptake of ozone, and changes in soil acidity over time.
The downslope parts of the rings grow wider than the upslope ones, and in studies carried out in Poland, Malgorzata Wistuba and colleagues found that those tilts are in evidence between three and fifteen years prior to catastrophic collapse.
It had long been known that three 9th century Viking period boat-grave mounds near Oslo, Norway (Gokstad, Oseberg, and Tune) had been broken into at some point in antiquity.
How large the cambium's cells grow in each year, measured as the width of each ring, depends on temperature and moisture—how warm or cool, dry or wet each year's seasons were.
Environmental inputs into the cambium are primarily regional climatic variations, changes in temperature, aridity, and soil chemistry, which together are encoded as variations in the width of a particular ring, in the wood density or structure, and/or in the chemical composition of the cell walls.
At its most basic, during dry years the cambium's cells are smaller and thus the layer is thinner than during wet years.