Autumn is not just a beautiful season in which multicolored leaves fall to the ground from their branches. It is also a good time for all kinds of microbes to flourish with the new addition of delicious leaf litter nutrients. A new paper from Irga et al studies the connection between the fungi found on leaf litter and the potential for airborne species of these fungi to cause allergies in humans.
Samples were collected from five distinct species of deciduous trees in Sydney, Australia from late fall to early winter. In addition, different humidities were used on the sampled leaves in the lab to simulate varied rainfall. Air samples were also taken to complement the leaf data.
Leaves were found to be more diverse than air samples, and the air samples contained easily aerosolized spores that originated from the leaves. Many of the fungi found directly on the leaves were commensal and saprophytic. There were no serious human pathogens found in the samples, only low amounts of the human pathogen Aspergillus fumigatus. The different humidities had an effect on the fungal communities as well – the higher humidity samples had more plant pathogens on them. Diversity was also lower on the low humidity samples. Based on their research, the authors were able to say that leaf litter makes a big contribution to urban air quality, with no noteworthy pathogen risks.