In the paper we document changes in forest structure between historical (1930s) and contemporary (2000s) surveys of California vegetation. The shorthand is:
- Statewide, tree density in forested regions increased by 30% between the two time periods, and forest biomass declined by 19%.
- Larger trees (>60 cm diameter at breast height) declined, whereas smaller trees (<30 cm) have increased.
- Large tree declines were more severe in areas experiencing greater increases in climatic water deficit since the 1930s.
- Forest composition in California in the last century has also shifted toward increased dominance by oaks relative to pines, a pattern consistent with warming and increased water stress, and also with paleohistoric shifts in vegetation in California over the last 150,000 years.
About the data: We've got the plot data, plot maps, maps, photos and photo locations available for download. Check it out! Please check it out and think about how these data can be of use in your research. The journey from paper collection to digital data has been a long one, with several cases of almost accidental and purposeful destruction. As such it is a cautionary tale about the importance of rescued and shared historical data in ecological and geographical analysis. We owe much to all the people who have contributed to the preservation and digitization of this important collection. Thanks to so many people who have been working on this project since the early 2000s: Barbara Allen-Diaz, James Thorne, Ken-ichi Ueda, the late great Norma Kobzina, Ann Huber, Shruti Myukhtar, Falk Schuetzenmeister, Kelly Easterday and Shufei Lei, and all of my lab group who digitized the plot data for no reward, and many many others.
I've been collecting tidbits about the collection here, including examples of photo reshoots.