Archived code that was developed for a research project at WSL Birmensdorf, Switzerland. The original study was conducted by Prof. Fritz Schweingruber and Patrick Züst in 2015/16, supervisioned by Prof. Ulf Büntgen. The approach was later used in several dendrochronlogy research groups around the world.
Plant lignification has been an important research topic for years. Our assumption was that the amount of lignin in xylem structures can serve as an indicator for a plant's living condition. The more mechanical stress a plant experiences, the more lignin is produced.
We took pictures of hundreds of double-stained cross-sections. The samples came from wildly different vegetation zones and taxonomic groups. We analyzed the color ratios in the samples and examined the result based on several factors.
The data clearly shows that a plant's taxonomic group and living condition can serve as an indicator for its grade of lignification. The corresponding tables and charts can be found in this repository.
The workflow uses the public domain image processing program «ImageJ» to analyze the color ratios in the xylem. The resulting data was processed both with «R» and «Excel».
Examples for microscopic pictures and the resulting analysis can be found in the folder Example_Pictures. Included are as well a Powerpoint-presentation and a concise handout summarizing the basic concept.
Disclaimer: The scripts were written when I still had little programming experience, so use them with caution.
Fritz Schweingruber, who initiated and led this study, passed away in January 2020. It was an honor working with him on this project, and presenting it on several occasions. He was a pioneer in the field of dendrochronolgy, an author of 35 books, and an important mentor for me and many others. This article says it all:
"As well as being a brilliant scientist, Fritz Schweingruber was also endowed with great personal charisma. He impressed many colleagues and friends with his near-perfect memory as well as qualities including determination, creativity and a flair for innovation. His expertise and personal commitment combined with tenacity and perseverance always made him a force to be reckoned with. [...] His scientific and educational achievements are virtually impossible to quantify."