DOI: 10.5061/dryad.v6wwpzgsq
title: Global patterns of the leaf economics spectrum in wetlands

description: The leaf economics spectrum (LES) describes consistent correlations among
 a variety of leaf traits that reflect a gradient from conservative to
 acquisitive plant strategies. So far, whether the LES holds in wetland
 plants at a global scale has been unclear. Using data on 365 wetland
 species from 151 studies, we find that wetland plants in general show a
 shift within trait space along the same common slope as observed in
 non-wetland plants, with lower leaf mass per area, higher leaf nitrogen
 and phosphorus, faster photosynthetic rates, and shorter leaf life span
 compared to non-wetland plants. We conclude that wetland plants tend to
 cluster at the acquisitive end of the LES. The presented global
 quantifications of the LES in wetland plants enhance our understanding of
 wetland plant strategies in terms of resources acquisition and allocation,
 and provide a stepping-stone to developing trait-based approaches for
 wetland ecology.
description: We defined wetland plants
 as plants that mainly occur in (or are exposed to) wetland habitats as
 described by the Ramsar Convention <sup>17</sup>. We
 summarized the 3 major groups including 42 sub-groups wetland habitat
 types in Ramsar Convention to be 12 categories (as estuary, intertidal
 wetland, mangrove swamps, rivers and lakes, brackish and saline inland
 wetlands, permanent non-forested wetlands, temporary non-forested
 wetlands, permanent forested wetlands, artificial waterbodies, marsh, bog,
 fen). We collected leaf economics traits for wetland plants on a global
 scale including those plants exposed to intermittent/permanent wetland
 conditions (waterlogged or flooded) from both field and experiment
 measurements. The wetland plant leaf economics trait dataset was compiled
 based on a systematic search in Web of Science and Google Scholar (last
 updated on the 5th June 2018). The literature search included permutations
 of the following keywords: wetland plants, marsh plant, bog plant,
 isoetid, aquatic plants, macrophytes, submerged plants, floating-leaved
 plants, emergent plants, mangroves, leaf economics traits, leaf economics
 spectrum, leaf nitrogen, leaf phosphorus, SLA, LMA, leaf life span,
 photosynthetic rate, underwater photosynthetic rate, dark respiration
 rate. Additionally, our network of wetland experts from around the world
 contributed recommendations for possible literature that we had
 overlooked. Finally, we added unpublished data of our own and of our
 network. We did not include data from other trait databases that are
 dominated by terrestrial records, including TRY, because the few records
 available for wetland plants in these databases do not have a sufficiently
 detailed habitat description that would allow the differentiation between
 waterlogged and submerged required for our analysis. We followed the nomination system
 in The Plant List (http://www.theplantlist.org) to unify all plant
 synonyms names from the original references to a unique and consistent
 accepted name. We
 supplemented the trait observations in our database with Ellenberg
 moisture indicator values. The Ellenberg moisture indicator is a classic
 index which generally reflects the plants’ adaptation/acclimation to
 habitat wetness. Plant species can be categorized into 12 levels from
 those occupying very dry habitats (level 1) to strictly aquatic plants
 (level 12) <sup>40</sup>. For the current meta-analysis, we
 selected plant species with Ellenberg moisture value &gt; 7 to
 represent wetland plants, as described in detail in Supplementary Methods.
 For these species, we selected records of the six LES traits (leaf
 nitrogen, leaf phosphorus, leaf dry mass per unit area, leaf life span,
 photosynthetic rate, and dark respiration rate). We took trait values for
 the same six traits for non-wetland plant traits (of 1569 species) from
 the GLOPNET database for comparison <sup>3</sup>. For a
 consistent analysis of trait-trait trade-offs, we expressed all leaf
 economics traits on a mass basis. Mass-based and area-based traits can be
 interconverted via a division by LMA. The mean value for each trait of
 each species was used (using the median did not alter the interpretation
 of the results, data not shown). We used species-mean values to attain a
 sufficient number of trait-trait combinations for a given species. We
 assume that the trait observations used for calculating the species-mean
 values were representative for the environmental/growth conditions in
 which the species occurs. Possible uncertainty in species trait mean
 values (for example due to intra-specific variation) will then result in
 noise in trait-trait relationships. In total, 365 wetland species of 184
 families from 151 studies were compiled and analyzed, comprising the
 largest dataset on wetland plant traits to our knowledge. A map of the
 sampling sites with accurate spatial location information can be found in
 Supplementary Figure 1. The species are from varied life forms, including
 grasses, sedges, seagrasses, shrubs/trees, emergent, floating-leaved,
 isoetid, and submerged plants. Traits of most (308) species had been
 measured at waterlogged conditions, with submerged measurements being
 available for 75 species.
description: The study is a meta-analysis of literature data. We designed a
 database in which for a given species observations on traits were
 compiled. For each species record, we thus noted the species, study
 system, environmental conditions (if available), and for each trait
 average, sample size, standard deviation and unit. We also documented the
 reference from which the record had been derived. We only compiled data
 for species normally occurring in wetlands, or measured at wetland
 conditions. We collected leaf economics traits for
 wetland plants on a global scale including those individuals exposed to
 intermittent/permanent wetland conditions (waterlogged or flooded) from
 both field and experiment measurements. The wetland plant leaf economics
 trait dataset was compiled based on a systematic search in Web of Science
 and Google Scholar (last updated on the 5th June 2018). The literature
 search included permutations of the following keywords: wetland plants,
 marsh plant, bog plant, isoetid, aquatic plants, macrophytes, submerged
 plants, floating-leaved plants, emergent plants, mangroves, leaf economics
 traits, leaf economics spectrum, leaf nitrogen, leaf phosphorus, SLA, LMA,
 leaf life span, photosynthetic rate, underwater photosynthetic rate, dark
 respiration rate. Additionally, our network of wetland experts from around
 the world contributed recommendations for possible literature that we had
 not retrieved. Finally, we added unpublished data of our own and of our
 network. In combination, we aimed to be as complete as possible without
 predetermined sample size. Any constraint because of the sample size
 obtained were accounted for in the statistical analysis.
 The data in the database refer to publications of which the
 oldest are from the 1960s and the most recent from publications from the
 year 2018. We did not restrict our search to specific time periods, as we
 considered the observed trait values to be representative of the plant
 species involved. Data are meant to represent global patterns, with most
 data coming from Europe, United states, China and Australia/New
 Zealand.