DOI: 10.5061/dryad.x0k6djhmg
title: Diversification and phylogenetic correlation of functional traits for co-occurring understory species in the Chinese boreal forest

description: Functional traits impact species interactions, community composition, and
 ecosystem functioning. However, few studies have focused on the
 diversification and phylogenetic correlation of multiple functional traits
 over geological time. We conducted phylogenetic comparative analysis for
 boreal forest understory species in northeast China to examine the
 diversification and phylogenetic correlation in several functional traits:
 leaf area (LA), leaf carbon content (LCC), leaf dry matter content (LDMC),
 leaf nitrogen content (LNC), plant height (PH), and specific leaf area
 (SLA). Phylogenetic signals showed that there were very low levels of
 phylogenetic niche conservatism (PNC) in understory leaf-related traits
 and plant height, suggesting divergence of functional traits for the
 co-occurring understory species. The disparity through time analyses (DTT)
 indicated that trait disparities mainly originated during recent
 divergence events and there were no differences in the observed trait
 disparities compared to that expected under Brownian motion. Furthermore,
 we found both positive and negative phylogenetic correlations among the
 measured functional traits. The very low levels of PNC suggests that these
 functional traits diverged among co-occurring understory species, and that
 those species are distantly phylogenetically related. The phylogenetic
 correlations among traits maybe caused by both positively and negatively
 correlated adaptions which correspond to resource acquisition strategies.
 This study provides evidence that divergence in functional traits may
 reflect understory adaptations to boreal conditions. 
description: Six functional traits (Table
 1) which are closely associated with understory growth, survival, and
 light capture were measured (Meers et al., 2010; Refsland &
 Fraterrigo, 2017):
 including leaf area (LA), leaf carbon content (LCC), leaf dry matter
 content (LDMC), leaf nitrogen content (LNC), specific leaf area (SLA), and
 plant height (PH). These
 six functional traits were measured according to Pérez-Harguindeguy et al.
 (2013). In each sampled plot, we selected at least five reproductively
 mature individuals for each observed species. We sampled the relatively
 young, fully expanded and hardened leaves from adult plants. As understory
 plants grow between the forest canopy and the forest floor, light is
 usually the most limiting resource, affecting the establishment and growth
 of the understory plant species. For the species that typically grow
 partly in sunlight, the sampled leaves were taken from the parts that are
 most exposed to sunlight. Wherever possible, we avoided selecting leaves
 with obvious symptoms of pathogen or herbivore attack, or with a
 substantial covering of epiphylls. We put the leaf samples in sealed
 plastic bags, stored the bags in a portable cooler container, and
 transported them to the laboratory. To measure leaf area, we scanned
 leaves individually at 300 dpi using a Canon LiDE 120 series scanner
 coupled with a microcomputer. Then we used the scanned images to measure
 LA with ImageJ (Collins, 2007). The additional details on image processing
 can be found in the protocol proposed by Glozer (2008). After measuring
 LA, the leaf fresh weight was obtained using a electronic balance. Each
 leaf sample was subsequently placed in a paper envelope and dried at 80
 ℃ for 48 h to determine
 the leaf dry weight with electronic balance. Other fresh leaf samples were
 dried at 80 ℃ for 48 h and
 ground until they would pass through a 2 mm sieve. LCC and LNC in ground
 leaf samples were measured using an automated elemental analyzer (EA1112
 coupled with Delta-XP, Thermo Fisher Scientific K.K., Yokohama, Japan). PH
 was measured to the nearest cm from the top of the plant to the ground
 using a measuring tape.