Sampling and experiment
The soils were sampled from Gongga Snow Mountain, on the eastern edge of
the Tibet plateau, Sichuan province, China. We selected five different
ecosystems, bare
soil (29°34’37”N, 101°59’25”E,
2961m), grass (29°34’48”N, 101°59’33”E, 2955m), shrub (29°34’60”N,
101°59’42”E, 2934m), deciduous forest (29°34’16”N, 101°59’55”E,
2924m), and coniferous forest (29°34’23”N, 102°00’06”E, 2893m) (Li &
Xiong 1995; Jiang et al. 2018). Three samples were taken in each
type ecosystem (total of 15). All samples were passed through 2mm sieves
with large plant litters and small animal bodies (like insects and
earthworms) picked out by hand. Samples were transported on ice to
Beijing as soon as possible. The main vegetation species and types of
the sampling sites were described in detail in previous studies (Li &
Xiong 1995; Jiang et al. 2018).
Fifteen incubations were set up for each ecosystem (5 per soil sample).
For each incubation, 5g (dry weight) of soil were incubated in 50ml
centrifuge tubes under 60% water holding capacity and at 20°C. Every
12h the lids of the tubes were opened to allow complete exchange of the
air and to adjust water content. Incubations were allowed to acclimate
for 3 days before beginning the experiment. At the beginning of the
incubation, we sacrificed 3 original samples (O) for each ecosystem, the
other incubations were divided into high temperature stress treatment
and control groups (6 incubation per group for each ecosystem). The high
temperature treatment groups were transferred to 35°C for 3 days while
the control groups were incubating under the original temperature
condition. We then sampled 3 incubations from each ecosystem for
treatment (T1) and control (U1) groups. The remaining temperature stress
treatment incubations were returned to the original temperature
condition (20°C) and the incubations for both treatment and control
groups were incubated an additional 9 days. Then we sampled both
treatment (T2) and control (U2) groups at the end 12thday.