Moss functional trait ecology: Trends, gaps, and biases in the current literature

Functional traits are critical tools in plant ecology for capturing
organism-environment interactions based on trade-offs as well as making
links between organismal and ecosystem processes. While broad frameworks
for functional traits have been developed for vascular plants, we lack the
same for bryophytes, despite an escalation in the number of bryophyte
functional trait studies conducted in the last 45 years and an increased
recognition of the ecological roles bryophytes play across ecosystems. In
this review, we compiled data from 282 published articles (10005 records)
focusing on functional traits measured in mosses, and sought to (a)
examine trends in types of traits measured, (b) capture taxonomic and
geographic breadth of trait coverage, (c) reveal biases in coverage in the
current literature, and (d) develop a bryophyte-function index (BFI) to
describe completeness of current trait coverage and identify global gaps
to focus research efforts. The most commonly measured response traits
(those related to growth/reproduction in individual organisms) and effect
traits (those that directly affect community/ecosystem scale processes)
fell into the categories of morphology (e.g. leaf area, shoot height) and
nutrient storage/cycling, and our BFI revealed that these data were most
commonly collected from temperate and boreal regions of Europe, North
America and east Asia. However, fewer than 10% of known moss species have
available functional trait information. Our synthesis revealed that there
is a need for research on traits related to ontogeny, sex, and
intraspecific plasticity, and on co-measurement of traits related to
water-relations and bryophyte-mediated soil processes.