Short-term responses of root exudation C and functional traits to
drought of five temperate tree species
Abstract
Plant fine root exudation carbon (C) and mycorrhizal colonization are
two critical “outsourcing” strategies for water and nutrient
exploitation. Quantifying the plasticity of multiple fine root traits
under water stress is important for understanding plant adaptations to
drought. Here, we carried out a short-term rainfall exclusion experiment
in a common garden with five temperate tree species in northeast China,
and quantified the co-variation of root exudation C, mycorrhizal
colonization, and four morphological and four chemical traits in
response to drought. Root exudation C was positively correlated with
“fast” root morphological traits (specific root length and area), but
negatively correlated with “slow” ones (root diameter and tissue
density). Percentage of mycorrhizal colonization decreased as increasing
root non-structural carbon concentration, but was weakly correlated with
the “fast-slow” morphological traits. Drought increased root diameter,
tissue density, nitrogen concentration, exudation C, and mycorrhizal
colonization, but decreased non-structural carbon concentration, and
specific root length and area. Our findings suggest that fine roots
investment in rhizosphere microorganisms through exudation C, together
with fungal collaboration and “fast-slow” gradient would encompass a
whole root economics space. Drought promotes “slow” root traits for
hydraulic safety, but increases root resource acquisition by
“outsourcing” processes, i.e., increased C investments in rhizosphere
microbes (through root exudation C) and mycorrhizal collaboration.