Bannister 110

The risks we face from a changing climate result from a combination of human-caused and natural variability. We can better prepare for future conditions if we fully understand natural patterns of climate variation and how those patterns have behaved in the recent past. Yet the instrumental record of climate variation is sparse and short – inadequate to characterize, for example, the multidecadal processes associated with megadroughts and fluctuations in global temperature, or the intrinsic variability in remote regions of the tropical Pacific critical to the El Niño system.

Here, we use annually resolved δ13C tree rings measurements across a NE-USA forest network to derive intercellurar CO2 (ci) response caused by increasing atmospheric CO2 (ca) trends and climate change over the past two decades, concurrent with direct long-term measurements of ecosystem carbon and water exchange. We find a substantial increase in ci suggesting that for each one 1 ppm increase in ca, ci increased proportionally or at the same rate. This response corresponds to static or moderate increase in water use efficiency-the ratio of carbon gain to water loss, respectively.

For a century, dendrochronology has provided Southwestern archaeology with the most precise and accurate prehistoric chronological controls available in the world. Being accurate to the calendar year, lacking statistical uncertainty, and having seasonal resolution, tree-ring dating provides the backbone of Southwestern chronology, especially on the Colorado Plateau. In addition, comprehensive dendroarchaeological data illuminate important aspects of the behavior of the people who produced the structures with which the wood specimens are associated.