Relationship between functional traits of woody species and elevation gradient: a case study from forest vegetation in Northern Taiwan

Master thesis

Author: Yen-Cheng Shen

Advisors: David Zelený, Wen-Yun Kao

Abstract:

Functional traits are used to describe how species interact with their environment and also to predict community species composition. In this study, I asked the following questions: (1) What is the interrelationship among traits, and how to define the plant strategy by these traits? (2) By which traits is the environment filtering the species into the vegetation community? To answer these questions, I set up plots along the transect from Badaoer Shan to Taman Shan, with elevation separated into six zones (850, 1100, 1350, 1600, 1850 and 2100 m a.s.l.). In each zone, I established three 400-m2 permanent plots and seven 100-m2 plots. The study focused on investigating leaf and wood traits of woody species in the plots. I combined data from this study with data previously collected by Vegetation Ecology lab. In total, I surveyed 465 individuals of 119 broadleaf tree species and measured the following traits of these individuals: leaf area (LA), specific leaf area (SLA), leaf dry-matter content (LDMC), leaf thickness (Lth), succulence, chlorophyll content (Chl), leaf water repellency, venation density (VD), wood density (WD), stable isotope ratio of leaf nitrogen and carbon (δ15N and δ13C) and content of nitrogen and carbon per leaf mass (Nmass and Cmass). For trait–trait relationships, I classified these traits into three main categories based on trait variability: leaf economic spectrum, mechanical support and nitrogen cycling. For trait–environment relationships, I conducted fourth-corner analysis between each trait and elevation. Results show that SLA, LA, δ15N and leaf water repellency are negatively related to elevation, while Chl, Lth, LDMC and δ13C are positively related to the elevation. The result implies that species growing in the high elevation cloud forest face water stress and nutrient limitation.

Key words: cloud forest, fourth-corner analysis, monsoon forest, trait-trait relationship, trait-environment relationship, water stress.