Soil Fertility and Tropical Forest Productivity — a Q&A with YCNCC Faculty Affiliate Michelle Wong

YCNCC Faculty Affiliate and Yale Ecology & Evolutionary Biology (EEB) Assistant Professor Michelle Wong was first author of “Soil fertility controls on tropical forest productivity and mortality: synthesis and roadmap,” published June 29, 2026, in New Phytologist and based on research funded by the YCNCC.  

YCNCC Science Communications Fellow Samantha Tracy recently sat down with Wong to discuss the influence of soil fertility on tropical forests and their global change responses.

YCNCC:  Can you define soil fertility, and explain how it relates to forest heath?

MW: Soil fertility describes the capacity for soil to sustain plant growth by supplying essential resources (i.e. nutrients). It’s a term adopted from agricultural science, but what we’ve realized is that the effects of soil fertility on forest growth and biomass are highly complex. Compared to agricultural systems, forests have many more plant species, and they are much  longer-lived. In agriculture, measuring soil fertility can tell you which fertilizers and in what quantities will support crop production, but adding nutrients to forest ecosystems does not always impact production in the same way. Measuring soil fertility in forest systems is also much more challenging – different elements can limit growth, plant species vary in their nutrient demands, and measuring nutrient  availability to plants is still limited by methodology. Overall soil fertility can tell us a lot about agricultural field health, but is highly variable and challenging to directly apply to measures of forest health. 

YCNCC:  What motivated this research, and what are the key findings? 

MW: Tropical forests play a major role in the global carbon cycle: they store about 50-60% of the world’s biomass carbon. However, what drives this biomass carbon and how it will respond to global change is less clear. Because tropical forests are often situated on highly weathered, nutrient-poor soils, we would expect that soil fertility would drive this biomass carbon. However, from past studies, soil fertility (despite all the complexities in how it is measured) seems to consistently  increase plant growth, but not biomass. Some studies have found that tree mortality rates increase with soil fertility; however, there are currently no clear mechanisms to explain this relationship. For this project, we decided to organize scientists from all over the world, working across  different tropical regions, to come together to better understand current and future forest carbon cycling and how this is related to soil fertility.

YCNCC:  This work was highly collaborative–how did you merge various expertises to fill this knowledge gap?

MW: A lot of the discussions about key knowledge gaps came out organically by bringing in over 20 people from around the world! We are so grateful for the funding from the YCNCC Workshop Grants Program, otherwise I don’t think the discussions would have moved the way that they did. For example, one of the big challenges we realized during the workshop is that how we measure and define soil fertility is a huge hindrance to large-scale syntheses across the tropics. You can’t find a clear X-Y relationship when the X  isn’t clearly defined. 

For writing the manuscript, we realized one person couldn’t write the whole draft on their own due to the wide topic ranges, so we had the core workshop organizers write the earlier drafts, and had a few Zoom meetings and rounds of feedback from the rest of the coauthors. 

YCNCC:  How does this soil fertility roadmap help us anticipate potential threats from global changes?

MW: We had a lofty vision in mind prior to the workshop with a major aim  to understand how global change would impact tropical forest carbon cycling via feedback through soil fertility. However, what we realized is that before we can even start understanding these relationships,  we need to understand the basic soil fertility-productivity and soil fertility-mortality relationships first. Rising atmospheric carbon dioxide, climate stress, and land-use change are altering both nutrient availability and forest responses and some of the responses are quite complex.

YCNCC:  Any final thoughts?

MW: We highlighted a few major knowledge gaps in advancing our understanding of tropical forest soil fertility and carbon cycling relationships, such as how soils can influence mortality mechanisms, how much carbon is allocated above vs. belowground, how plant traits and species composition shift across soil gradients, and how soil fertility is defined. Because these patterns are often context dependent, we need more networks and network studies to consistently measure these patterns across a range of sites. Collaborative and network science is needed more than ever!