Invasive species removal increases species and phylogenetic diversity of wetland plant communities

Abstract

Plant invasions result in biodiversity losses and altered ecological functions, though quantifying loss of multiple ecosystem functions presents a research challenge. Plant phylogenetic diversity correlates with a range of ecosystem functions and can be used as a proxy for ecosystem multifunctionality. Laurentian Great Lakes coastal wetlands are ideal systems for testing invasive species management effects because they support diverse biological communities, provide numerous ecosystem services, and are increasingly dominated by invasive macrophytes. Invasive cattails are among the most widespread and abundant of these taxa. We conducted a three‐year study in two Great Lakes wetlands, testing the effects of a gradient of cattail removal intensities (mowing, harvest, complete biomass removal) within two vegetation zones (emergent marsh and wet meadow) on plant taxonomic and phylogenetic diversity. To evaluate native plant recovery potential, we paired this with a seed bank emergence study that quantified diversity metrics in each zone under experimentally manipulated hydroperiods. Pretreatment, we found that wetland zones had distinct plant community composition. Wet meadow seed banks had greater taxonomic and phylogenetic diversity than emergent marsh seed banks, and high‐water treatments tended to inhibit diversity by reducing germination. Aboveground harvesting of cattails and their litter increased phylogenetic diversity and species richness in both zones, more than doubling richness compared to unmanipulated controls. In the wet meadow, harvesting shifted the community toward an early successional state, favoring seed bank germination from early seral species, whereas emergent marsh complete removal treatments shifted the community toward an aquatic condition, favoring floating‐leaved plants. Removing cattails and their litter increased taxonomic and phylogenetic diversity across water levels, a key environmental gradient, thereby potentially increasing the multifunctionality of these ecosystems. Killing invasive wetland macrophytes but leaving their biomass in situ does not address their underlying mechanism of dominance and is less effective than more intensive treatments that also remove their litter.

Need to Seed? Ecological, Genetic, and Evolutionary Keys to Seed-Based Wetland Restoration

“…increase establishment of habitat-forming perennial speciessuch as completely breaking seed dormancy and improving germination and establishment conditions -may be as conducive to supporting biotic resistance as introducing fast growing annuals (Iannone and Galatowitsch, 2008;Lishawa et al, 2019;Rosbakh et al, 2019).…”

“…Alteration of salinity at the site can be addressed with hydrologic flooding, strategic seed sowing timing (section "Optimal Germination Safe Sites and Season"), and selection of species that are able to tolerate higher salinities while providing valuable ecosystem functions (Howard, 2010). Physical suppression and shading of native species should be addressed by removing undesirable vegetation and litter from the site prior to seeding (Lishawa et al, 2019).…”

Moso Bamboo Invasion Reshapes Community Structure of Denitrifying Bacteria in Rhizosphere of Alsophila spinulosa

“…Evidence has been found that bamboo invasion reduced mean tree height (11.7 m) compared with native broadleaved forest (13.1 m) [29]. Contrarily, certain invasive vegetation removal can increase basal diameter, tree height, and phylogenetic diversity of wetland plant communities [52]. Our Spearman correlation analysis showed that tree height and crown width of A. spinulosa were negatively correlated with two denitrifying bacteria, Chitinophaga and Sorangium, respectively.…”

Combined use of mowing and chemical control for the efficient control of the noxious invasive species Typha spp.

“…For instance, Lawrence et al (2016) suggested that combined treatment of biomass harvest and disking can add to cattail control and could be a positive economical perspective for farmers due to cattail biomass utilization as biofuel, while at the same time the native plant community will be boosted. Lishawa et al (2019) suggested that restoration techniques of cattail dominant areas should focus on periodic treatments including biomass removal, in order to preserve the native biodiversity. Vroom et al (2018) proposed that T. latifolia can be utilized for the restoration of peatlands after their rewetting, because of the species capacity to control nitrogen and phosphorus concentrations from surface and pore water, as well as regulate CH 4 and N 2 O emissions.…”