Résumé
Global climate change is increasing pest and pathogen pressures on plant
communities, deteriorating optimal plant functioning. In plant
communities, root functional trait expression and microbial communities
are important indicators of plant functioning belowground, and, when
confronted with pathogens aboveground, can simultaneously reflect plant
defence strategies. Yet, while research is continuing to emerge on the
response of root functional traits and microbial processes to pathogens
aboveground, little work has investigated these interactions in
tree-crops, or the role organic amendments play in moderating
these relationships. The main objective of this study is
to disentangle the dynamic effects of pathogens and amendments on
root functional traits (i.e., specific root length and area, root
diameter, root length density, root nitrogen, and root carbon to nitrogen
ratio) and root endophytic fungal communities. As a model, we use Coffea
arabica (coffee) variety Caturra along a gradient of
Coffee Leaf Rust – a foliar disease prominent in coffee systems – under
contrasting but widespread amendment regimes in
biodiverse agroforestry systems. We found that root trait
expression varies along established conservation and collaboration
gradients, where fungal endophyte community composition varies
significantly as a function of root traits. Belowground resource
acquisition strategies do not change with foliar disease incidence,
suggesting they may be decoupled. Rather, amendment regimes differentially
shape root trait expression and microbial communities, where coffee plants
under organic amendments, regardless of foliar disease incidence,
expressed greater acquisitive traits and enhanced collaboration with
symbiotic fungi. This is an important first step in disentangling the
dynamic inter-relationships between plant traits, endophytes, and
pathogens, generating new questions on the role of amendments in
sustainable pathogen management in biodiverse agroecosystems.