Understanding mechanisms that underlie plant community diversity and structure remains a central concern in ecology, particularly in highly diverse tropical forests. Recent work suggests that feedbacks between plants and soil microbial communities may drive patterns of density-dependent seedling recruitment and tropical plant community structure (e.g. relative abundances, spatial distributions), as well as productivity. Nevertheless, understanding of the mechanisms by which feedbacks operate remains poor. Plant-soil feedbacks  are hypothesized to form as parent plants influence the local assembly of soil microbes, which in turn may either favor or suppress subsequent local recruitment of conspecifics. Negative feedbacks involving species-specific pathogens are thought to produce distance/density-dependent recruitment, thereby maintaining plant diversity, whereas positive feedbacks involving soil mutualists are generally thought to lead to declines in diversity. 

 

Plants may experience different strengths of feedback due to variation in benefit conferred by mycorrhizal fungal mutualists, including Arbuscular- and Ecto-Mycorrhizal Fungi . AMF and EMF may vary in contribution to plant-soil feedbacks, owing to differences in host specificity, dispersal, host benefit (EMF appear to confer greater benefit to their hosts than do AMF), and differences in interaction with soil pathogens. However, a majority of work on tropical plant soil feedback has taken place in Neotropical forests where AMF dominate as soil mutualists, and EMF are rare & associated chiefly with monodominant stands.

 

I am explored plant-soil feedback in a South East Asian forest characterized by codominance of AM and EM soil communities. Using a potted plant experiment at Lambir Hills National Park, Malaysia, I tested the generality of negative soil feedbacks in tropical forests, examining the role of fungal association strategy in determining patterns of feedback.