RESULTS

Effects of warming on dew formation

The multiple measurement methods showed decreased dew amounts under warming conditions. Warming resulted in average decreases of 91.7%, 83.9% and 41.6% in dew amount by the artificial condensation surface method, the in situ dew formation on plants and the leaf wetness sensors, respectively (linear mixed-effects model: P < 0.001; Fig. 1). From 2015 to 2017, warming significantly decreased the dew duration by an average of 10.3% (linear mixed-effects model:P < 0.001; Fig. 2a). Therefore, warming reduced the total dew formation by not only reducing the daily dew amounts (mm/day) but also the dew duration (days). The results also showed that warming significantly increased the temperature differences (Ta-Tdew) by 3.8% (P < 0.001; Fig. 2b), which made dew formation more difficult. Furthermore, the differences in the dew amount between the control and warming treatments (Dcontrol-Dwarming) showed significant differences at the seasonal scale (Fig. 2c). The dew amounts under the warming treatment decreased by an average of 0.05 mm (up to 64.5%) during the growing seasons and only decreased by an average of 0.006 mm (only 27.5%) in nongrowing seasons (Fig. 2c).

Effects of warming on dew amount among different functional groups

The total aboveground biomass and dew amounts among each functional group were measured as the in situ dew formation on plants in this study. The results showed that different plant functional groups significantly differed in dew formation, and warming significantly decreased the dew amount among each functional group (a reduction of 83.5%, 71.6%, 97.6% and 87.0% for sedges, forbs, grasses and all species combined, respectively, Fig. 3a), while it slightly changed the aboveground biomass of different functional groups (Fig. 3b).

Effects of warming on the relationships between plant height and dew amount

Compared with the control treatment, the warming treatment significantly affected the relationship between plant height and dew amount (P< 0.001, n=60; Fig. 4). In the control treatment, linear regression revealed that the dew amount was significantly positively correlated with plant height (R2 = 0.35, P< 0.001; Fig. 4a). However, dew amount was significantly negatively correlated with plant height (R2 = 0.34,P < 0.001; Fig. 4b) in the warming treatment.