Environmental factors
Snow
fences and resulting thicker snow cover significantly increased winter
soil temperature from -5.6±0.6 °C to
-3.7±0.9 °C (Table S1, P< 0.01), and exerted legacy effects on soil and plants in the
subsequent growing season. For instance, soil moisture significantly
increased from 47.8±4.9% to 52.7±2.0% (P = 0.03), and thaw
depth significantly increased from 35.3±0.8 cm to 38.4±2.6 cm (P= 0.03). Gross primary productivity (GPP) significantly increased from
394.5±7.0 g m-2 to 514.7±7.4 g m-2(P = 0.01), mainly attributed to the increase in graminoid
biomass (146.7±38.7 g m-2 in control plots vs.
231.0±86.5 g m-2 in warmed plots, P = 0.05).
As high plant biomass usually
leads to more plant respiration, R eco, the sum of
aboveground plant and soil respiration, was significantly enhanced from
363.3±3.7 g m-2 to 449.2±4.4 g m-2(P < 0.01). There were no significant changes of soil C
and N pools, including LCP (P = 0.94), RCP (P = 0.94),
NH4+-N (P = 0.47), and
NO3--N (P = 0.59).