A framework for fine‐root trait syndromes: syndrome coexistence may support phosphorus partitioning in tropical forests.

Fine roots balance multiple essential plant functions that ultimately fuel plant productivity. The coordination of root functional traits is multidimensional, meaning that some traits are correlated while others can vary independently. This leads to a large variety of adaptive trait combinations and thus functional diversity in plant belowground morphology, anatomy, physiology and symbioses with soil biota. Within forest communities, co‐occurrence of such belowground trait combinations may be especially prevalent in tropical forests, not only due to their immense biodiversity but also because their soils are frequently weathered and limited in phosphorus. Phosphorus occurs in different forms (that differ in their mobility and accessibility) that may select for different trait combinations on relatively small spatial scales. While evidence accumulates of the myriad viable nutrient acquisition strategies on poor tropical soils, they are not well conceptualized. In this study, we outline criteria for the identification and investigation of fine‐root trait syndromes. We then apply these criteria to a case study of tropical tree species adapted to phosphorus‐poor soil and synthesize a range of traits. Five potentially coexisting syndromes are presented that are distinguished by root morphology, mycorrhizal association type, their interactions and implications for fine‐root functioning. We connect the functional variation of these species‐level syndromes in tropical communities to an established phosphorus partitioning hypothesis. The co‐occurrence of fine‐root trait syndromes could have implications for root sampling design, species coexistence, community structure and biogeochemical cycling. [ABSTRACT FROM AUTHOR]