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Abstract

Aim: Plant trait databases often contain traits that are correlated, but for whom direct
(undirected statistical dependency) and indirect (mediated by other traits) connections
may be confounded. The confounding of correlation and connection hinders
our understanding of plant strategies, and how these vary among growth forms and
climate zones. We identified the direct and indirect connections across plant traits
relevant to competition, resource acquisition and reproductive strategies using a
global database and explored whether connections within and between traits from
different tissue types vary across climates and growth forms.
Location: Global.
Major taxa studied: Plants.
Time period: Present.
Methods: We used probabilistic graphical models and a database of 10 plant traits
(leaf area, specific leaf area, mass‐ and area‐based leaf nitrogen and phosphorous
content, leaf life span, plant height, stem specific density and seed mass) with
16,281 records to describe direct and indirect connections across woody and nonwoody
plants across tropical, temperate, arid, cold and polar regions.
Results: Trait networks based on direct connections are sparser than those based on
correlations. Land plants had high connectivity across traits within and between tissue
types; leaf life span and stem specific density shared direct connections with all
other traits. For both growth forms, two groups of traits form modules of more highly
connected traits; one related to resource acquisition, the other to plant architecture
and reproduction. Woody species had higher trait network modularity in polar compared
to temperate and tropical climates, while non‐woody species did not show
significant differences in modularity across climate regions.
Main conclusions: Plant traits are highly connected both within and across tissue
types, yet traits segregate into persistent modules of traits. Variation in the modularity
of trait networks suggests that trait connectivity is shaped by prevailing environmental
conditions and demonstrates that plants of different growth forms use
alternative strategies to cope with local conditions.