Elevation-related variation in leaf stomatal traits as a function of plant functional type: evidence from Changbai Mountain, China

Abstract

Understanding the variation in stomatal characteristics in relation to climatic gradients can reveal the adaptation strategies of plants, and help us to predict their responses to future climate changes. In this study, we investigated stomatal density (SD) and stomatal length (SL) in 150 plant species along an elevation gradient (540-2357 m) in Changbai Mountain, China, and explored the patterns and drivers of stomatal characteristics across species and plant functional types (PFTs: trees, shrubs, and herbs). The average values of SD and SL for all species combined were 156 mm(-2) and 35 µm, respectively. SD was higher in trees (224 mm(-2)) than in shrubs (156 mm(-2)) or herbs (124 mm(-2)), and SL was largest in herbs (37 µm). SD was negatively correlated with SL in all species and PFTs (P < 0.01). The relationship between stomatal characteristics and elevation differed among PFTs. In trees, SD decreased and SL increased with elevation; in shrubs and herbs, SD initially increased and then decreased. Elevation-related differences in SL were not significant. PFT explained 7.20-17.6% of the total variation in SD and SL; the contributions of CO2 partial pressure (P CO2), precipitation, and soil water content (SWC) were weak (0.02-2.28%). Our findings suggest that elevation-related patterns of stomatal characteristics in leaves are primarily a function of PFT, and highlight the importance of differences among PFTs in modeling gas exchange in terrestrial ecosystems under global climate change.

Figure 1. Histograms of the distribution of stomatal density (SD, a) and stomatal length (SL, b) for all species.

The fitted log-normal curves are indicated. N, species number; Max, maximum value; Min, minimum value; SE, standard error; CV, coefficient of covariance.

Figure 2. Relationship between stomatal density (SD) and stomatal length (SL) at the species (a) and plant functional type (PFT, b) level.

“Slope”, difference in standardized major axis (SMA) slopes; “Elevation”, difference in SMA elevations (y-intercept); NS, not significantly different; *, significantly different (P<0.05). All regression lines shown in each panel are significant (P<0.01).

Figure 3. Changes in stomatal density (SD) and stomatal length (SL) with elevation for all species (a, e), trees (b, f), shrubs (c, g), and herbs (d, h).

Data are means; bars represent standard error. Different lowercase letters in each panel indicate significant differences among altitudes (P<0.05).

Figure 4. Stomatal density (SD) and stomatal length (SL) in relation to CO₂ partial pressure (; a, c), and soil water content (SWC; b, d).

Only significant regression lines are shown in each panel (P<0.05).