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

Background: 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.Results: 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.Conclusions: Absorptive root traits play a crucial role in the regulation of species distribution through multiapproaches of air temperature.

Elevation gradient distribution of indices of tree population in a montane forest:The role of leaf traits and the environment

Background:To disentangle the controls on species distribution in the context of climate change is a central element in proposed strategies to maintain species diversity.However,previous studies have focused mainly on the roles of abiotic factors(e.g.,climate and soil properties),with much less attention given to the roles of biotic factors such as functional traits.Here,we measured eight leaf traits for 240 individual trees of 53 species and analyzed the variation in traits and population composition indices and their relationships with soil properties,climate factors,and leaf traits.Results:The tree density,frequency and species importance values of the overall species and saplings significantly increased with increasing elevation,while the same indices(except for species frequency)of adults did not significantly change.The largest percentage of variation of species importance value(greater than 50%)was explained by climate,but leaf traits played a critical role in driving elevation distribution patterns of both saplings and adults;the abundance of saplings significantly increased with elevation,with increased leaf carbon contents,while the abundance of adults did not change in accordance with a nutrient conservation strategy associated with the leaf economic spectrum.Conclusions:Our results suggest that the elevation gradient distribution of woody plant species is dependent on tree size and that local atmospheric humidity and leaf traits cause considerable variation in species distribution along subtropical mountain elevations.We provide evidence of which leaf traits play a key role in the elevation gradient distribution of different sizes of woody tree species.