Soil variables
Thirty-two soil variables were measured for each sampling location,
including a number of macro- and micronutrients and variables associated
with soil textural properties (Table S1). Details about soil variables
measurements are described in Table S2. Preliminary analysis showed that
most micronutrients, excepting for soil copper (Cu), had weak
associations with fine root trait plasticity and biomass accumulation.
Consequently, we selected 13 soil variables previously identified in the
literature (Kesanakurti et al. 2011; Valverde-Barrantes et
al. 2015a; Luo et al. 2020) to frequently influence root growth
and trait variation for the present study, including soil pH, electrical
conductivity, total organic carbon, total nitrogen, total phosphorus,
total potassium, hydrolysable nitrogen, available phosphorus, available
potassium, sand content, silt content, clay content and available Cu.