Absorptive root-multidimension strategy links air temperature and species distribution in a montane forest

Air temperature affects absorptive root traits, which are closely related to species distribution. However, it is still unclear how air temperature regulates species distribution through changes in absorptive root traits. Seven functional traits of the absorptive roots of 240 individuals of 52 species, soil properties and air temperature were measured along an elevational gradient on Mt. Fanjingshan, Tongren City, Guizhou, and then the direct and indirect effects of these controls on species distribution were detected. Absorptive roots adapted to air temperature with two strategies. The first strategy was positively associated with the specific root area (SRA) and specific root length (SRL) and was negatively associated with the root tissue density (RTD), representing the classic root economics spectrum (RES). The second strategy was represented by the trade-off between root diameter, mycorrhizal fungi colonization (MF) and SRL, representing the collaboration gradient with “do it yourself” resource uptake ranging from “outsourcing” to mycorrhizal resource uptake. Air temperature regulated species distribution in six ways: directly reducing species importance value; indirectly increasing the species importance value by reducing soil nitrogen content or increasing soil pH by reducing soil moisture inducing absorptive roots to change from “do it yourself” resource absorption to “outsourcing” resource absorption; indirectly decreasing the species importance value by decreasing soil moisture to change from “outsourcing” resource absorption to “do it yourself” resource absorption; indirectly increasing the species importance value with increasing soil pH by reducing soil moisture resulting in absorptive root traits turning into nutrient foraging traits; and indirectly decreasing the species importance value by promoting absorptive root traits to nutrient conservation traits. Absorptive root traits play a crucial role in the regulation of species distribution through multi-approaches of air temperature.