Flash 2000 ea ht

The labeled, whole samples of current-year leaves, one-year leaves, branches, stems, and roots were dried to a constant weight at 65 °C. The samples were ground into powders, the δ¹³C and C allocations were determined using an isotope ratio mass spectrometer (Delta V Advantage) coupled with an elemental analyzer (Flash 2000 EA-HT) (Thermo Fisher Scientific Inc., Waltham, MA, USA), and the corresponding analyses were performed, as described in our previous report [46 (link)].

Leaves, branches, shoot, root, and soil samples were collected on the labeling day before (coded as 0 day) and the following 1, 5, 10, 21, and 30 days after labeling. Plant aboveground parts of all species were harvested and pooled as shoot samples by clipping at the soil surface. Soil cores (5 cm in diameter) were taken to 15-cm depth. All roots and soil in the cores were carefully extracted and sieved with a 2-mm sieve. Soil samples passed through the sieve were air-dried for total C and ¹³C analysis. The sampled roots were carefully washed by wet sieving through a 0.5-mm sieve to remove attached soil and debris. Shoot and root samples were oven-dried at 65°C for 48 h. The δ¹³C and C contents were determined using an isotope ratio mass spectrometer (Delta V Advantage) coupled with an elemental analyzer (Flash 2000 EA-HT) (Thermo Fisher Scientific Inc., Waltham, MA, United States).
NaOH was used to absorb CO₂ produced by soil respiration in a certain period of time (Deng et al., 2019 ). At the end of labeling, a closed breathing chamber containing NaOH solution (1 mol L^–1) (7.5 cm in diameter and 9 cm in height) was inserted into the basin soil to absorb CO₂ produced by soil respiration on the 1st, 4th, 5th, 11th, and 9th day after labeling, and the amount of CO₂ uptake was determined by HCl (1 mol L^–1).