This repository provides the R script and data that was used in the study "Viscum album in French forests: distribution, environmental drivers and impacts on tree health and growth" by William Marchand, Jean-Baptiste Daubrée and Claire Depardieu. It allows the users to re-draw the main figures.

Mistletoe infestation was monitored between 2008 and 2022 on more than 80,000 sample plots (more than 700,000 trees) belonging to the French NFI temporary sample plot network, along with dendrometric, environmental and ecological data. We analyzed this data (together with the relationships with MeteoFrance and WorldClim climate variables) using binomial generalized additive mixed models.

Main findings are:

• The spatial distribution of mistletoe depends on environmental and tree-level factors;
• Isothermality, temperature and soil factors are key drivers of mistletoe distribution;
• In the case of pine and fir mistletoe, species-diverse stands display lower occurrences of the parasite;
• Trees with a high level of canopy dieback are more susceptible to mistletoe infestation;
• Mistletoe induces growth reductions of 22-32 % in Scots pine and Silver fir.