Forest top canopy bacterial communities are influenced by elevation and host tree traits

Area of Science:

• Microbiology
• Ecology
• Forest Science

Background:

• The phyllosphere microbiome is vital for plant health and ecosystem function.
• Host species significantly influences phyllosphere microbiome, but environmental factors cause intra-specific variation.
• Understanding phyllosphere microbiome variation across forest landscapes is crucial.

Purpose of the Study:

• To assess variations in top canopy phyllosphere bacterial communities within and between European beech (Fagus sylvatica) and Norway spruce (Picea abies) in temperate European forests.
• To identify the driving factors behind these variations.
• To understand the implications for host plant functioning and ecosystem processes.

Main Methods:

• Bacterial diversity and composition profiling of the top canopy phyllosphere of 211 trees across two temperate forests (Netherlands and Germany).
• Analysis of environmental factors including elevation, tree diameter at breast height, and leaf-specific traits (chlorophyll, P content).
• Correlation analysis between driving factors and bacterial community composition, including discriminant taxa.

Main Results:

• Bacterial communities were primarily shaped by host species, with significant intra-specific variation observed in both beech and spruce.
• Community composition varied with elevation, tree diameter, and leaf traits like chlorophyll and P content.
• Specific bacterial families' relative abundance correlated with these driving factors.

Conclusions:

• Host species is important, but substantial intra-specific variation in phyllosphere bacterial communities exists.
• Tree traits and landscape-level factors drive these variations, linking canopy microbiome to ecosystem processes.
• Close associations between forest canopy phyllosphere bacteria and host trees are critical for host plant functioning.