Two species of clonal
(native) and
(exotic) hybridize to form the highly invasive, heterotic (high vigor)
in North American wetlands leading to increased primary production, litter accumulation, and ...biodiversity loss. Conservation of
has become critical as invasive
has overwhelmed wetlands. In the field,
taxa identification is difficult due to subtle differences in morphology, and molecular identification is often unfeasible for managers. Furthermore, improved methods to non-destructively estimate
biomass is imperative to enhance ecological impact assessments. To address field-based
ID limitations, our study developed a predictive model from 14
characters in 7 northern Michigan wetlands to accurately distinguish
taxa (n = 33) via linear discriminant analysis (LDA) of molecularly identified specimens. In addition, our study developed a partial least squares regression (PLS) model to predict
biomass from field collected measurements (n = 75). Results indicate that two field measurements
,
can accurately differentiate the three
taxa and advanced-generation hybrids. The LDA model had a 100% correct prediction rate of
. The selected PLS biomass prediction model (
) improved upon existing simple linear regression (SLR) height-to-biomass predictions. The rapid field-based
identification and biomass assessment tools presented in this study advance targeted management for regional conservation of
and ecological restoration of wetlands impacted by invasive
taxa.
Invasive species management typically aims to promote diversity and wildlife habitat, but little is known about how management techniques affect wetland carbon (C) dynamics. Since wetland C uptake is ...largely influenced by water levels and highly productive plants, the interplay of hydrologic extremes and invasive species is fundamental to understanding and managing these ecosystems. During a period of rapid water level rise in the Laurentian Great Lakes, we tested how mechanical treatment of invasive plant Typha × glauca shifts plant-mediated wetland C metrics. From 2015 to 2017, we implemented large-scale treatment plots (0.36-ha) of harvest (i.e., cut above water surface, removed biomass twice a season), crush (i.e., ran over biomass once mid-season with a tracked vehicle), and Typha-dominated controls. Treated Typha regrew with approximately half as much biomass as unmanipulated controls each year, and Typha production in control stands increased from 500 to 1500 g-dry mass m−2 yr−1 with rising water levels (~10 to 75 cm) across five years. Harvested stands had total in-situ methane (CH4) flux rates twice as high as in controls, and this increase was likely via transport through cut stems because crushing did not change total CH4 flux. In 2018, one year after final treatment implementation, crushed stands had greater surface water diffusive CH4 flux rates than controls (measured using dissolved gas in water), likely due to anaerobic decomposition of flattened biomass. Legacy effects of treatments were evident in 2019; floating Typha mats were present only in harvested and crushed stands, with higher frequency in deeper water and a positive correlation with surface water diffusive CH4 flux. Our study demonstrates that two mechanical treatments have differential effects on Typha structure and consequent wetland CH4 emissions, suggesting that C-based responses and multi-year monitoring in variable water conditions are necessary to accurately assess how management impacts ecological function.
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•Five-year, large-scale study of biomass and carbon response to wetland management.•We measured in-situ plant-mediated CH4 flux and dissolved surface water CH4.•Crushing and harvesting Typha reduced biomass, even under high water levels.•We found a positive correlation between floating mats and surface water CH4.•Harvested stands had total in-situ CH4 flux rates twice as high as controls.
In Laurentian Great Lakes coastal wetlands (GLCWs), dominant emergent invasive plants are expanding their ranges and compromising the unique habitat and ecosystem service values that these ecosystems ...provide. Herbiciding and burning to control invasive plants have not been effective in part because neither strategy addresses the most common root cause of invasion, nutrient enrichment. Mechanical harvesting is an alternative approach that removes tissue‐bound phosphorus and nitrogen and can increase wetland plant diversity and aquatic connectivity between wetland and lacustrine systems. In this study, we used data from three years of Great Lakes‐wide wetland plant surveys, published literature, and bioenergy analyses to quantify the overall areal extent of GLCWs, the extent and biomass of the three most dominant invasive plants, the pools of nitrogen and phosphorus contained within their biomass, and the potential for harvesting this biomass to remediate nutrient runoff and produce renewable energy. Of the approximately 212,000 ha of GLCWs, three invasive plants (invasive cattail, common reed, and reed canary grass) dominated 76,825 ha (36%). The coastal wetlands of Lake Ontario exhibited the highest proportion of invasive dominance (57%) of any of the Great Lakes, primarily from cattail. A single growing season's biomass of these invasive plants across all GLCWs was estimated at 659,545 metric tons: 163,228 metric tons of reed canary grass, 270,474 metric tons of common reed, and 225,843 metric tons of invasive cattail, and estimated to contain 10,805 and 1144 metric tons of nitrogen and phosphorus, respectively. A one‐time harvest and utilization for energy of this biomass would provide the gross equivalent of 1.8 million barrels of oil if combusted, or 0.9 million barrels of oil if converted to biogas in an anaerobic digester. We discuss the potential for mitigating non‐point source nutrient pollution with invasive wetland plant removal, and other potential uses for the harvested biomass, including compost and direct application to agricultural soils. Finally, we describe the research and adaptive management program we have built around this concept, and point to current limitations to the implementation of large‐scale invasive plant harvesting.
Aims
We examined how mechanical management of invasive macrophyte,
Typha × glauca
alters plant-soil interactions underlying carbon processes and nutrient cycling, which are important to wetland ...function but under-represented in restoration research.
Methods
In the northern Great Lakes, we compared plant biomass, light transmittance, soil nutrient availability and carbon mineralization rates of
Typha
-dominated controls with
Typha
stands harvested above the waterline (harvest) and at the soil surface (submerged harvest).
Results
Relative to controls, harvested stands had 50% less litter and twice as much light transmittance to the water surface after one year. However,
Typha
stems re-grew, and soil nutrient availability rates were similar to controls. Submerged harvest eliminated
Typha
litter and stems, and increased light transmittance through the water column. P and K soil availability rates were 70% greater with submerged harvest than in controls. Soil C mineralization rates were not affected by treatment (mean ± 1 SE; 40.11 ± 2.48 μg C-CO
2
and 2.44 ± 0.85 μg C-CH
4
g
−1
soil C hr.
−1
), but were positively correlated with soil Fe availability.
Conclusions
While submerged harvest effectively decreased invasive
Typha
biomass after one year, it increased soil nutrient availability, warranting further examination of macronutrient cycling and export during invasive plant management.
Coastal wetlands provide critical habitat for aquatic organisms and important ecosystem services for the terrestrial and aquatic landscapes that they bridge, but increasingly common invasive ...macrophytes disrupt plant communities, food webs, habitat structure and littoral–pelagic linkages. In Laurentian Great Lakes coastal wetlands, invasive cattails (Typha × glauca and T. angustifolia, hereafter Typha) homogenise ecosystem structure and reduce nearshore dissolved oxygen, and plant, fish and macroinvertebrate diversity. We hypothesised that management treatments which reduce Typha and its abundant litter promote structural heterogeneity and mitigate physicochemical and biodiversity impacts.
To test this hypothesis, we implemented a large‐scale (2,048 m2 treatment units), multi‐site (four coastal wetlands) experiment in northern Michigan (U.S.A.) to examine how invasive Typha mechanical harvesting treatments (biomass harvest, aquatic connectivity channels, Typha‐dominated control) altered fish, macroinvertebrate, plant, larval amphibian abundance and diversity, and water quality for 2‐year post‐treatment.
Both harvest and channel treatments reduced Typha biomass, cover and dominance; harvest increased multi‐taxa species richness, fish diversity and abundance; and channels altered plant, fish, and macroinvertebrate community structures. Dissolved oxygen was greater and litter was reduced by both treatments, indicating likely mechanisms for shifts in fish and macroinvertebrate use.
Our results suggest that harvesting invasive macrophytes can ameliorate biodiversity impacts and improve habitat quality, and that adding aquatic connectivity channels can increase community complexity.
Typha management that incorporates both harvesting and aquatic connectivity channels appears to provide the greatest benefit to several taxonomic groups, likely by reducing Typha and its litter, increasing dissolved oxygen availability, and increasing the connection between open water and wetland interiors. Increasing habitat complexity and aquatic connectivity of invaded wetlands can promote biodiversity and provides a more realistic management goal than the complete elimination of invasive macrophytes.
Invasive wetland plants are the primary targets of wetland management to promote native communities and wildlife habitat, but little is known about how commonly implemented restoration techniques ...influence nutrient cycling. We tested how experimental mowing, herbicide application, and biomass harvest (i.e., removal of aboveground biomass) treatments of Typha-invaded mesocosms altered porewater nutrient (NOâ â», NHâ âº, PO â â»Â³) concentration and supply rate, vegetation response, and light penetration to the soil surface. We found that while herbicide application eliminated the target species, it also reduced native plant density and biomass, as well as increased porewater nutrient concentration (PO â â»Â³ , NOâ â») and supply rates (N, P, K) up to a year after treatments were implemented. Because herbicide application promotes nutrient enrichment, it may increase the likelihood of reinvasion by problematic wetland invaders, as well as cause eutrophication and deleterious algal blooms in adjacent aquatic systems. Our data suggest that biomass harvest should be considered by managers aiming to reduce Typha abundance without eradicating native diversity, avoid nutrient leaching, as well as possibly utilizing biomass for bioenergy.
The mechanisms by which invasive plants displace native species are often not well elucidated, limiting knowledge of invasion dynamics and the scientific basis for management responses. ...Typha × glauca Godr. invades wetlands throughout much of North America. Like other problematic wetland invaders, Typha is large, grows densely, and leaves behind copious litter. It thus has the potential to impact wetlands both in life and after death. We assessed patterns in field settings and used simulated wetland-plant communities to experimentally test abiotic and community responses to live Typha, Typha litter, and water-level differences (confounded in the field) using a full-factorial design. In general, litter was a stronger driver of change than live Typha. The greatest impacts were seen where, as in nature, live and dead Typha co-occurred. Live-Typha treatments did not differ from controls in light or temperature conditions but did reduce community biomass and alter community composition. Litter strongly affected light, temperature and its variability, community and species-level plant biomass, and community composition. Interactions between live Typha and litter affected aspects of plant-community composition. Advantageously for Typha, interspecific litter effects were not mirrored by intraspecific suppression of live Typha. These findings clarify how Typha is such an effective invader. Similar mechanisms are likely involved in invasions by other plant species, particularly in wetlands. Managers should respond quickly to new Typha invasions and, when dealing with established stands, remove litter in addition to eradicating live plants.
The ecological impacts of invasive plants increase dramatically with time since invasion. Targeting young populations for treatment is therefore an economically and ecologically effective management ...approach, especially when linked to post-treatment monitoring to evaluate the efficacy of management. However, collecting detailed field-based post-treatment data is prohibitively expensive, typically resulting in inadequate documentation of the ecological effects of invasive plant management. Alternative approaches, such as remote detection with unmanned aerial vehicles (UAV), provide an opportunity to advance the science and practice of restoration ecology. In this study, we sought to determine the plant community response to different mechanical removal treatments to a dominant invasive wetland macrophyte (
spp.) along an age-gradient within a Great Lakes coastal wetland. We assessed the post-treatment responses with both intensive field vegetation and UAV data. Prior to treatment, the oldest
stands had the lowest plant diversity, lowest native sedge (
spp.) cover, and the greatest
cover. Following treatment, plots that were mechanically harvested below the surface of the water differed from unharvested control and above-water harvested plots for several plant community measures, including lower
dominance, lower native plant cover, and greater floating and submerged aquatic species cover. Repeated-measures analysis revealed that above-water cutting increased plant diversity and aquatic species cover across all ages, and maintained native
spp. cover in the youngest portions of
stands. UAV data revealed significant post-treatment differences in normalized difference vegetation index (NDVI) scores, blue band reflectance, and vegetation height, and these remotely collected measures corresponded to field observations. Our findings suggest that both mechanically harvesting the above-water biomass of young
stands and harvesting older stands below-water will promote overall native community resilience, and increase the abundance of the floating and submerged aquatic plant guilds, which are the most vulnerable to invasions by large macrophytes. UAV's provided fast and spatially expansive data compared to field monitoring, and effectively measured plant community structural responses to different treatments. Study results suggest pairing UAV flights with targeted field data collection to maximize the quality of post-restoration vegetation monitoring.
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.
We conducted a 3‐year study in two Laurentian Great Lakes wetlands, testing the effects of dominant invasive plant removal techniques within two vegetation zones on plant taxonomic and phylogenetic diversity. Removal of invasive cattails and their litter increased phylogenetic diversity and species richness across water levels, more than doubling richness compared to unmanipulated controls, thereby potentially increasing the multifunctionality of these ecosystems.
Ecological and financial constraints limit restoration efforts, preventing the achievement of desired ecological outcomes. Harvesting invasive plant biomass for bioenergy has the potential to reduce ...feedback mechanisms that sustain invasion, while alleviating financial limitations. Typha × glauca is a highly productive invasive wetland plant that reduces plant diversity, alters ecological functioning, its impacts increase with time, and is a suitable feedstock for bioenergy. We sought to determine ecological effects of Typha utilization for bioenergy in a Great Lakes coastal wetland by testing plant community responses to harvest‐restoration treatments in stands of 2 age classes and assessing community resilience through a seed bank study. Belowground harvesting increased light penetration, diversity, and richness and decreased Typha dominance and biomass in both years post‐treatment. Aboveground harvesting increased light and reduced Typha biomass in post‐year 1 and in post‐year 2, increased diversity and richness and decreased Typha dominance. Seed bank analysis revealed that young stands (<20 years) had greater diversity, richness, seedling density, and floristic quality than old stands (>30 years). In the field, stand‐age did not affect diversity or Typha dominance, but old stands had greater Typha biomass and slightly higher richness following harvest. Harvesting Typha achieved at least 2 desirable ecological outcomes: reducing Typha dominance and increasing native plant diversity. Younger stands had greater potential for native recovery, indicated by more diverse seed banks. In similar degraded wetlands, a single harvest of Typha biomass would likely result in significant biodiversity and habitat improvements, with the potential to double plant species richness.
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