Composition of Plant Functional Traits of some Dominant Species along Altitudinal Gradients at the Doi Suthep-Pui National Park, Chiang Mai Province, Thailand

Dokrak Marod, Sarawood Sungkaew, Panida Kachina, Jakkaphong Thongsawi, Nathawat Khlangsap, and Prapawadee Nutiprapun



Plant functional traits are important in a forest ecosystem as they play an essential role in the plant response to various environmental factors. This study aimed to detect plant traits like specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness (Lth), leaf toughness (Lto), and wood density (WD) of woody species along altitudinal gradients between 900 – 1,040 m above sea level (a.s.l.). Fifteen species from a deciduous dipterocarp forest (DDF) and lower montane forest (LMF) were selected. Functional traits were calculated based on a community weighted mean (CWM) by the trait value weighted by the relative abundance of each species in the community. The differences in CMW traits among various forest types were tested using ANOVA. Regression analysis was performed between the altitudinal gradients and CWM for functional traits to evaluate trend of the functional traits as a function of the altitudinal gradient. The results showed that CWM traits varied with the altitudinal gradient. SLA and Lth were found to be higher in LMF (981–1,040 m. a.s.l.) compared to the forest ecotone, which is a common area between the two forests (FE, 941–980 m. a.s.l.) and DDF (900–940 m. a.s.l.), whereas LDMC and Lto were found to be higher at FE and WD was found to be higher at DDF compared to FE and LMF. This indicates that the establishment of woody tree species needed different traits depending on the gradient . There were significant correlations between the CWM of traits and altitudinal gradients. For example SLA and Lth increased with increasing altitudinal gradients while traits of WD decreased with increasing altitude. However, no significant correlation between CWM and Lto of LDMC with altitudinal gradients was found. Moreover, SLA, Lth, and WD varied along altitudinal gradients but only a small change was observed in LDMC and Lto. This indicates that the plant functional traits may be resilient to gradual altitudinal gradient changes.