Objective In this study, we explored the responses of leaf functional traits of Pinus tabuliformis to altitude gradients and quantified the contribution of topography and soil to intraspecific trait variation. This work aims to provide a basis for predicting the spatial-temporal variations and its mechanism of leaf functional trait caused by climate change in the future.
Method Leaves of Pinus tabuliformis on the southern slope of Songshan Mountain area in Beijing at an altitude of 789−1106 m were collected to measure 8 leaf functional traits, including leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), nitrogen concentration per unit mass (MN), phosphorous concentration per unit mass (MP), nitrogen concentration per unit of area (AN), phosphorous concentration per unit of area (AP) and leaf nitrogen to phosphorus ratio (LN:P). Correlation between these traits and its response to altitude gradients were analyzed. The responses of these traits to topography and soil were also examined in this study.
Result (1) LA, SLA and MP showed a decreasing trend with the altitude gradient, while LDMC, MN, AN and LN:P showed an increasing trend along the altitude gradient. AP did not respond to the altitude. The leaf functional traits of Pinus tabuliformis showed significant intraspecific variations and the variation coefficient was between 10.33% and 27.59%. The order of variation was LA > AN > AP > SLA > LN:P > MN > MP > LDMC. (2) A significant synergy or trade-off was observed among some functional traits as the altitude changed, where SLA of Pinus tabuliformis was negatively correlated with LDMC (P < 0.05) and it was extremely negatively correlated with AN and AP (P < 0.001). (3) The variation of leaf functional traits was affected by various environmental factors. We found that LA, SLA and LN:P of Pinus tabuliformis were mainly affected by altitude and soil phosphorus content (TP), while LDMC was mainly affected by soil nitrogen to phosphorus ratio and soil water content. Both MN and AN were mainly affected by soil pH and TP, and MP was mainly affected by altitude and slope. (4) Altitude and soil could only explain 6.28%−41.1% of the variation in leaf functional traits of Pinus tabuliformis.
Conclusion In the study area, leaf functional traits of Pinus tabuliformis adapt to altitude gradient change by certain character variation and combination, among which the dominant factors and extent of the character variation were different.