PS 45-3
The relationship between root foraging precision and other plant functional traits in heterogeneous soil
Plant interactions belowground occur in a heterogeneous environment, where nutrients are found in small patches. Foraging precision, preferentially growing roots in nutrient patches, may play a significant role in success in heterogeneous soil because plants with higher foraging precision will more efficiently take up resources. However, it has been suggested that foraging precision may correlate with other traits contributing to a fast-resource-use strategy, rather than varying independently. This experiment measures functional traits for 12 co-occurring species and examines how they relate to foraging precision. Individual plants were grown in pots with nutrient patches and eight functional traits reflecting an overall growth strategy were measured: foraging scale, foraging precision, specific leaf area, specific root length, root:shoot ratio, relative growth rate, shoot nitrogen concentration, and root nitrogen concentration. We calculated two measures of root foraging precision: precision based on mass (ln(root mass patch/root mass control)) and precision based on length (ln(root length patch/root length control)). PCA analysis was done to determine (a) if foraging precision is correlated with traits associated with a “fast-use” resource strategy, (b) if foraging precision was negatively correlated with foraging scale, or (c) if precision was not related to any of these traits.
Results/Conclusions
PCA analysis shows that foraging precision based on mass is positively correlated with specific leaf area and specific root length, and negatively correlated with root:shoot ratio. Species that allocate more biomass to shoots also produce very thin leaves, thin roots, and have higher root biomass in patches. Precision based on length was not correlated with these traits, but this may be due to small sample size. Foraging precision based on mass is not negatively correlated with foraging scale (measured as total root mass), indicating that precision and scale are not in a trade-off as has been suggested in the past. It seems that precision is correlated with some traits such as specific leaf area and specific root length that are suggested to be part of a “fast resource use” strategy, where plants grow very quickly, grow thin leaves and roots, and are able to get to nutrient patches sooner than slower growing plants. Precision therefore, should contribute to success in heterogeneous soils because plants with higher foraging precision can access nutrients quicker than their competitors.