Native Plant Establishment Research Articles

Legacy effects of Phragmites australis and herbicide treatments can reduce survival but do not prevent native plant establishment

Introduced Phragmites australis represents a widespread threat to North American wetlands. Management agencies invest millions of dollars annually to manage the species, mostly by applying herbicides, to mitigate and prevent negative impacts. The often temporary reduction of P. australis rarely increases native diversity, and long‐term legacy effects of P. australis and repeat herbicide treatments are unknown. We used a coordinated management program targeting mostly small P. australis populations in the Adirondack Park in New York State, United States, to assess the potential for such legacy effects. We planted individuals of three native species as sentinels into treated and untreated, uninvaded reference wetlands after unassisted succession had occurred in treatment areas. Sentinel plants survived and grew in treated areas, suggesting legacy of P. australis and its management did not permanently limit establishment of native plants. However, responses were variable among sentinel species, with negative or neutral impacts on survival rates and neutral or positive effects on growth. Species‐specific responses and large variation in survival rates between sites and sentinels indicate that site factors are a dominant influence on survival and growth. Importantly, as treatment frequency increased, survival of one sentinel species decreased significantly, indicating a potential for long‐term negative impacts of repeated herbicide applications. Additional replanting after P. australis treatment and initial unassisted plant succession may enable more diverse plant communities to return, including species not able to recruit from local seed banks or seed sources. However, it remains unclear if active transplanting will enable more long‐term suppression of P. australis.

Impact of species selection on plant community, sod tensile strength, and translocation rooting of a pollinator‐garden sod

AbstractInterest in pollinator gardens is increasing to address pollinator decline. The establishment of perennial native plants often takes a few years and establishment projects are often lost to competition from unwanted weedy vegetation. Mature sod of pollinator‐serving, native plants that is free of weeds would be highly desirable to conventional turfgrass sod consumers, thus offering a new revenue stream for traditional sod producers. The objective of this study is to evaluate the influence of four foundational species treatments on 3‐year floral biodiversity of pollinator‐serving plants, sod tensile strength, and transplant rooting strength. Results suggest that polycultures of pollinator‐serving forbs can produce a marketable sod with sufficient tensile strength for lifting and translocating and sufficient ability to establish once relocated. Sod tensile strength, however, is insufficient for lifting when the plant community is not grown over plastic or does not contain a high‐shoot density or rhizomatous foundation species such as hard fescue (Festuca longifolia Thuill.) or common yarrow (Achillea millefolium L.). Unfortunately, adding hard fescue or common yarrow markedly reduces the Shannon diversity index and species richness. The force needed to lift transplanted sod after 3 months was 5553 to 6969 N m−2 regardless of foundation species treatment and was numerically higher than the force reported by previous researchers to lift sod of various turfgrass species. Collectively, the data suggest that the best balance between preserving floral biodiversity and maximizing sod handling integrity would be approached by establishing pollinator‐serving forbs alone or with a blend of native grasses over plastic.

The effects of native seed mix composition and sowing density on plant community reassembly in wetlands

AbstractSeed‐based restoration of wetlands is often necessary to improve important ecosystem functions (e.g., invasion resistance and habitat provisioning) and meet society's need for wetland ecosystem services such as supporting recreational activities and improving water quality. However, persistent questions remain about the composition and sowing density of seed mixes needed to restore robust native wetland plant communities. In Great Salt Lake wetlands (Utah, USA), the revegetation of native species is crucial to recovering critical habitat and preventing reinvasion of the invasive, non‐native grass Phragmites australis and other invasive species (e.g., Typha spp.). In greenhouse and field experiments, we investigated the effects of seed mix composition and sowing density on plant community reassembly. We predicted that seed mixes containing native forb species with resource‐preempting traits (e.g., rapid seedling emergence and high aboveground growth rate) and high sowing densities (>5500 pure live seed m−2), would increase native plant light acquisition and establishment, thereby limiting invasive species. To our surprise, the effect of seed mix composition on native plant performance (cover and biomass) varied among the experiments, with distinct differences between plant functional groups arising. Native forb species had the highest performance in the greenhouse, but native grasses performed better in the field. Although multiple seed mix compositions show promise for establishing high native cover and biomass, these mixes may not always suppress invasive species. Interestingly, seed mix composition most often affected plant performance independent of sowing density. However, in one greenhouse experiment, we found that only slow‐growing mixes required a high sowing density to maximize native cover, an indication that the ideal sowing density may depend on the seed mix composition. Our research also supports the idea that in addition to reducing propagules of invasive species via appropriate management strategies, the application of higher sowing densities (>5500 pure live seed m−2) may lead to more favorable outcomes when a high density of invasive plant seeds remains or stressful field conditions are present. This research contributes to knowledge of plant community reestablishment in wetlands and demonstrates how seed‐based restoration strategies can catalyze native species revegetation and, in some situations, reduce the cover of invasive species.

Enhancing Native Plant Establishment in Mine Tailings under Drought Stress Conditions through the Application of Organo-Mineral Amendments and Microbial Inoculants

The implementation of phytoremediation strategies under arid and semiarid climates requires the use of appropriate plant species capable of withstanding multiple abiotic stresses. In this study, we assessed the combined effects of organo-mineral amendments and microbial inoculants on the chemical and biological properties of mine tailings, as well as on the growth of native plant species under drought stress conditions. Plants were cultivated in pots containing 1 kg of a mixture of mine tailings and topsoil (i.e., pre-mined superficial soil) in a 60:40 ratio, 6% marble sludge, and 10% sheep manure. Moreover, a consortium of four drought-resistant plant growth-promoting rhizobacteria (PGPR) was inoculated. Three irrigation levels were applied: well-watered, moderate water deficit, and severe water deficit, corresponding to 80%, 45%, and 30% of field capacity, respectively. The addition of topsoil and organo-mineral amendments to mine tailings significantly improved their chemical and biological properties, which were further enhanced by bacterial inoculation and plants’ establishment. Water stress negatively impacted enzymatic activities in amended tailings, resulting in a significant decrease in acid and alkaline phosphatases, urease, and dehydrogenase activities. Similar results were obtained for bacteria, fungi, and actinomycete abundance. PGPR inoculation positively influenced the availability of phosphorus, total nitrogen, and organic carbon, while it increased alkaline phosphatase, urease (by about 10%), and dehydrogenase activity (by 50%). The rhizosphere of Peganum harmala showed the highest enzymatic activity and number of culturable microorganisms, especially in inoculated treatments. Severe water deficit negatively affected plant growth, leading to a 40% reduction in the shoot biomass of both Atriplex halimus and Pennisetum setaceum compared to well-watered plants. P. harmala showed greater tolerance to water stress, evidenced by lower decreases observed in root and shoot length and dry weight compared to well-watered plants. The use of bioinoculants mitigated the negative effects of drought on P. harmala shoot biomass, resulting in an increase of up to 75% in the aerial biomass in plants exposed to severe water deficit. In conclusion, the results suggest that the combination of organo-mineral amendments, PGPR inoculation, and P. harmala represents a promising approach to enhance the phytoremediation of metal-polluted soils under semiarid conditions.

A Rooftop Agrivoltaic System: Pollinator Plant Establishment

In a time of rapid habitat removal in favor of urbanization, green roofs have been recognized as a means to increase biodiversity while emulating native habitats in urban ecosystems. There is often competition over roof space for use as solar energy generation, or green roof space. Here we explore the inclusion of both green roof and photovoltaic (PV) energy generation systems stacked vertically in a rooftop system to better understand the impacts of PV arrays on six species of pollinator plants native to Colorado’s Front Range and Great Plains Regions. We conducted randomized and replicated plant establishment and growth studies in a simulated rooftop system in full sun and under a fixed mounted PV array over the course of the initial growing season. Additionally, we measured the plant growing environment, including air temperature, substrate temperature, and substrate moisture to quantify the differences in the conditions in full sun compared to conditions under the PV arrays. Light conditions were modeled. We find plant establishment and overwinter survivability is greater under the PV array, while the seasonal plant growth index varies depending on the plant species. Substrate moisture was significantly higher under the PV while substrate temperature trended towards lower daytime temperatures and slightly raised nighttime temperatures under the PV. Based on this study, the microclimate under the PV array is amenable to plant growth, and differences in plant response to the shade may closely resemble ecotones found in nature. The combination of rooftop agrivoltaics and traditional full sun green roof plantings may lead to greater native plant establishment, and therefore greater diversity of habitat niches in the built environment.

Native and non‐native mulch resulted in increased soil moisture and reduced plant recruitment in container plant restoration of coastal sage scrub

One challenge of habitat restoration is establishing healthy native plants that survive, grow, and reproduce. The addition of mulch after initial planting is thought to enhance native plant establishment. In our efforts to restore degraded sites at Crystal Cove State Park in Southern California, we compared two experimental mulch treatments made from native and non‐native plant material to unmulched plots. We planted four different native shrub species: Eriogonum fasciculatum, Malosma laurina, Isocoma menziesii, and Diplacus aurantiacus, and measured plant size, soil moisture, and plant density in the first year. In the second year, the same measurements were taken for I. menziesii and D. aurantiacus, which had greater survivorship in the first year. Our results showed significant differences in plant height, length, and width among the species but not between mulch treatments. However, soil moisture significantly varied between treatments, with native mulch plots having the greatest volumetric water content. In addition, mulch treatments had a significant effect on naturally recruiting plant density, with both mulch treatments having fewer native and non‐native seedling densities compared to control plots. Regarding survivorship, significant differences between species and treatment were observed only in the first year. Our results confirmed that mulch effectively helped retain higher soil moisture. Both locally sourced native and non‐native mulch had this benefit, although native mulch resulted in greater increases in soil moisture. While mulch reduced non‐native plant establishment, it also limited native recruitment, leading us to recommend that mulch be used only during the initial establishment of container plants.

Competition between pink muhly grass and native plant species: Is it really a harmful invasive species?

AbstractPink muhly grass (Muhlenbergia capillaris Trin.) is an exotic species in South Korea and is popular worldwide as an ornamental grass for landscaping purposes. The Ministry of Environment in South Korea has categorized this species as an “Ecosystem Hazard Class 2” plant, requiring long‐term monitoring to assess its ecological impacts on native species and communities. In this study, a 2‐year greenhouse experiment was conducted using M. capillaris and 17 native plant species (6 annuals, 8 nonwoody perennials, and 3 woody perennials) to test the hypothesis that if M. capillaris is an invasive species, it will negatively affect the establishment and growth of native plants in competitive pairings compared with controls (native species grown in monoculture). Results showed that the mean canopy cover of native plants in competition with M. capillaris was not significantly different from monocultures of the corresponding native species. There were also no significant differences in mean aboveground biomass production between native species growing with M. capillaris compared to corresponding native monocultures. Results indicate that M. capillaris did not significantly affect the establishment and growth of the 17 native species investigated. The minimal impacts suggest that M. capillaris may not be a harmful invasive species, but further monitoring of its spread will be required to test these findings under natural conditions.

Method for controlling invasive Ammophila arenaria in coastal dunes alters restoration trajectory

Coastal dune restoration often focuses on weed removal to reestablish native vegetation communities. Point Reyes National Seashore (PRNS) initiated large‐scale dune restoration after becoming concerned about loss of dune and rare species habitat from spread of non‐native Ammophila arenaria (European beachgrass). Two projects removed beachgrass from 146 ha of heavily invaded dunes using either mechanical removal or herbicide treatment. PRNS conducted pre‐ and post‐restoration vegetation monitoring for 10 years post‐implementation, evaluating success in (1) eradicating beachgrass and (2) reestablishing vegetation communities similar to native dunes in cover, diversity, and species composition. Both methods eradicated beachgrass with annual retreatment. However, they were less successful in rebuilding vegetation communities with comparable native species cover and/or richness. Mechanical removal areas remained largely barren expanses of sand that struggled to support native plants except for a rare perennial, Tidestrom's lupine (Lupinus tidestromii). Tidestrom's lupine and other rare plants now number in the hundreds of thousands. Conversely, herbicide‐treated backdunes were dominated by standing dead beachgrass that resisted decomposition even after 7 years, which hampered native and rare plant establishment. Delayed decomposition was less of an issue in herbicide‐treated foredunes, because sand overwash buried necromass. Restored areas also contended with subsequent invasion by secondary plant invaders. By 2021, only older herbicide‐treated backdunes, and to a lesser extent, mechanical backdunes, showed signs of convergence with native dunes. Successful convergence may be hindered by lingering physical and microbial legacy effects of beachgrass invasion and treatment method. Adaptive restoration may be needed to counter effects and improve project success.

Festuca coelestis Increases Drought Tolerance and Nitrogen Use via Nutrient Supply-Demand Relationship on the Qinghai-Tibet Plateau.

Drought and nutrient deficiency pose great challenges to the successful establishment of native plants on the Qinghai-Tibet Plateau. The dominant factors and strategies that affect the adaptation of alpine herbs to dry and nutrient-deficient environments remain unclear. Three water gradients were established using two-factor controlled experiments: low water (WL), medium water (WM), and high water (WH). The field water-holding capacities were 35%, 55%, and 75%, respectively. Nitrogen fertilizer (N) was applied at four levels: control (CK), low (FL), medium (FM), and high (FH) at 0, 110, 330, and 540 mg/kg, respectively. The results revealed that N was the main limiting factor, rather than phosphorous (P), in Festuca coelestis under drought stress. Under water shortage conditions, F. coelestis accumulated more proline and non-structural carbohydrates, especially in the aboveground parts of the leaves and stems; however, the root diameter and aboveground nitrogen use efficiency were reduced. Appropriate N addition could mitigate the adverse effects by increasing the release of N, P, and enzyme activity in the bulk soil and rhizosphere to balance their ratio, and was mainly transferred to the aboveground parts, which optimized the supply uptake relationship. The effects of water and fertilizer on the physiological adaptability and nutrient utilization of F. coelestis were verified using structural equation modeling. Based on their different sensitivities to water and nitrogen, the WHFM treatment was more suitable for F. coelestis establishment. Our results demonstrated that the disproportionate nutrient supply ability and preferential supply aboveground compared to below ground were the main factors influencing F. coelestis seedling establishment under drought conditions. This study provides evidence for a better understanding of herbaceous plants living in high mountain regions and offers important information for reducing the risk of ecological restoration failure in similar alpine regions.

Native Microbes Amplify Native Seedling Establishment and Diversity While Inhibiting a Non-Native Grass.

Although several studies have shown increased native plant establishment with native microbe soil amendments, few studies have investigated how microbes can alter seedling recruitment and establishment in the presence of a non-native competitor. In this study, the effect of microbial communities on seedling biomass and diversity was assessed by seeding pots with both native prairie seeds and a non-native grass that commonly invades US grassland restorations, Setaria faberi. Soil in the pots was inoculated with whole soil collections from ex-arable land, late successional arbuscular mycorrhizal (AM) fungi isolated from a nearby tallgrass prairie, with both prairie AM fungi and ex-arable whole soil, or with a sterile soil (control). We hypothesized (1) late successional plants would benefit from native AM fungi, (2) that non-native plants would outcompete native plants in ex-arable soils, and (3) early successional plants would be unresponsive to microbes. Overall, native plant abundance, late successional plant abundance, and total diversity were greatest in the native AM fungi+ ex-arable soil treatment. These increases led to decreased abundance of the non-native grass S. faberi. These results highlight the importance of late successional native microbes on native seed establishment and demonstrate that microbes can be harnessed to improve both plant community diversity and resistance to invasion during the nascent stages of restoration.

Allelopathic potential of Leucaena leucocephala (Lam.) de Wit leaf extracts on native species.

Allelopathy is seen as one of the possible factors that favor the invasion of exotic plants in the environment, as these species, by releasing allelochemicals, can negatively interfere with the establishment of native plants, facilitating the growth and dissemination of invasive exotic plants. This study aimed to verify the possible allelopathic effects of Leucaena leucocephala (Lam.) de Wit (leucaena) on native tree species Pterogyne nitens Tul. and Peltophorum dubium (Spreng.) Taub., via laboratory bioassays. We used Petri dishes containing seeds of native species and aqueous extract of leucaena leaves with 2, 4, 8, 10 and 20% concentrations (m/v) for germination tests and estimated the percentage, mean time, and germination speed index at the end of the germination period. For initial growth, we kept the Petri dishes containing aqueous leucaena extract and germinated seeds of native species in a germination chamber at 25 °C, and after 48 hours we obtained the length of the primary root, hypocotyl, and fresh and dry biomass of the seedlings. We obtained the a, b, and total chlorophyll and carotenoid content of seedling leaves kept in the aqueous extract at different concentrations. We verified the content of total phenolic compounds in mg/L from the aqueous leucaena extracts. Both native species showed a reduction in the percentage and germination speed index when in contact with the aqueous leucaena extracts at the highest concentrations. The initial growth of native species was also negatively affected, and P. nitens showed a reduction of all growth parameters analyzed in all concentrations of the aqueous extract. P. dubium showed a reduction in growth, especially at the highest concentrations. The effects can be associated with phenolic compounds present in leucaena extracts, and we found the highest total phenolic content in the extract with the highest concentration. The results show the allelopathic potential of leucaena, which may contribute to this plant ability to settle in natural areas.

Identifying and Remediating Soil Microbial Legacy Effects of Invasive Grasses for Restoring California Coastal Sage Scrub Ecosystems

As invasive grasses encroach upon native ecosystems, they have the potential to transform intact California coastal sage scrub (CSS) into non-native grasslands. This occurs—in part—due to legacy effects: changes in soil microbial composition elicited by grass invasions with long-term impacts on soil and native vegetation. Along with direct effects on CSS vegetation, legacy effects may alter microbial communities which may in turn impact native plant growth. To tease apart these factors, we monitored growth in three CSS species inoculated with either uninvaded soil or sterilized uninvaded soil that were subsequently planted into a site characterized by observed microbial legacy effects. Our findings indicate native plant growth can be explained by changes in soil microorganisms. Specifically, native Artemisia californica and Baccharis pilularis grew larger in plots with unsterilized uninvaded soil inoculum, which contained a larger abundance of Gemmatimonadetes and Glomus, compared to the sterilized soil inoculum plots. Therefore, microbial augmentation may not only improve restoration in post-invasive sites but long-term changes in soil microbial communities may be linked to native plant growth. Furthermore, adding uninvaded soil replete with native microbes has the potential to support restoration of invaded sites by promoting native plant survival and establishment in these restored ecosystems.

Planting time, first‐year mowing, and seed mix design influence ecological outcomes in agroecosystem revegetation projects

The conversion of tallgrass prairie to agriculture has negatively affected provisioning of ecosystem services. Successful restoration of ecosystem services could depend on management decisions applied during revegetation projects. We examined the effects of three management decisions (seed mix design, planting time, and first‐year mowing) on targeted ecosystem services (erosion control, weed resistance, and pollinator resources). We tested three seed mixes of varying diversity and grass‐to‐forb seeding ratios: Economy mix (21 species, 3:1 grass:forb), Pollinator mix (38 species, 1:3), and Diversity mix (71 species, 1:1). We established plots at two planting times (dormant‐season and spring) with or without first‐year mowing. To assess ecosystem services, we measured stem density, canopy cover, and floral density and richness of sown species in the second year after planting. The Economy mix had the highest stem density and cover but lowest floral density and richness. The Pollinator mix had the lowest stem density and cover but highest floral density. The Diversity mix had comparable stem density and cover to the Economy mix and comparable floral density and richness to the Pollinator mix. Mowing accelerated native plant establishment in all seed mixes. Dormant‐season planting improved establishment of spring and fall forbs and favored cool‐season graminoids over warm‐season grasses. All three management decisions influenced ecosystem outcomes, and comparison to a previous study revealed these effects to be robust to variation in site and climatic conditions. We recommend a diverse, balanced seed mix design, first‐year mowing, and dormant‐season planting to improve multifunctionality of conservation projects.

N Addition Mitigates Water Stress via Different Photosynthesis and Water Traits for Three Native Plant Species in the Qinghai–Tibet Plateau

Reseeding with native plants to rebuild alpine meadow has become a popular way of ecological restoration. However, the harsh environment poses a great challenge to the establishment of native plants due to poor management of water and nutrients. How water–fertilizer interaction influences dominant grass species is still unclear, and reasonable water and fertilizer conditions are still not determined. Our results showed that addition of nitrogen could mitigate the photosynthetic and water-use traits caused by water stress, i.e., a reduction in Pn and water use results from fewer and thinner leaves, weak stomatal traits, etc. Compared to the control, the peak Pn values of Poa crymophila, Festuca coelestis, and Stipa purpurea increased significantly (71.2%, 108.4%, and 25.4%, respectively). Under drought stress, Pn tended to decrease due to reduced stomatal conductance (Gs). However, appropriate fertilization buffered against Pn decreases by altering the stomatal size and regulating the Gs. Based on reduced water consumption, the water-use efficiency of P. crymophila and F. coelestis decreased whereas that of S. purpurea increased. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea growth were suitable for the alpine region. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea were suitable for their establishment in the alpine region. A reasonable water–fertilizer combination could effectively reduce the risk of establishment failure in ecological restoration.

Molecular Mechanisms Underlying Mimosa acutistipula Success in Amazonian Rehabilitating Minelands.

Mimosa acutistipula is endemic to Brazil and grows in ferruginous outcrops (canga) in Serra dos Carajás, eastern Amazon, where one of the largest iron ore deposits in the world is located. Plants that develop in these ecosystems are subject to severe environmental conditions and must have adaptive mechanisms to grow and thrive in cangas. Mimosa acutistipula is a native species used to restore biodiversity in post-mining areas in canga. Understanding the molecular mechanisms involved in the adaptation of M. acutistipula in canga is essential to deduce the ability of native species to adapt to possible stressors in rehabilitating minelands over time. In this study, the root proteomic profiles of M. acutistipula grown in a native canga ecosystem and rehabilitating minelands were compared to identify essential proteins involved in the adaptation of this species in its native environment and that should enable its establishment in rehabilitating minelands. The results showed differentially abundant proteins, where 436 proteins with significant values (p < 0.05) and fold change ≥ 2 were more abundant in canga and 145 in roots from the rehabilitating minelands. Among them, a representative amount and diversity of proteins were related to responses to water deficit, heat, and responses to metal ions. Other identified proteins are involved in biocontrol activity against phytopathogens and symbiosis. This research provides insights into proteins involved in M. acutistipula responses to environmental stimuli, suggesting critical mechanisms to support the establishment of native canga plants in rehabilitating minelands over time.

La depredación de semillas nativas y no-nativas varía en plantaciones de pino del noroeste de la Patagonia

Human disturbances can cause functional alterations in ecosystems, affecting key interactions such as those between plants and animals. For example, post-seed dispersal predation determines plant establishment in many terrestrial ecosystems and can have positive or negative effects on plant community composition, which can, then, influence ecosystem structure and functionality. However, seed predation can be altered in modified environments, with consequences on the establishment and dispersal of native and non-native plants. The objective of this study was to evaluate the post-dispersal predation of native and non-native seeds at different spatial scales in modified environments: pine plantations, clearcut areas and native forests in Isla Victoria, northwestern Patagonia (Argentina). We used a cafeteria-type experiment offering native and non-native seed species in each habitat and measured the vegetation cover around each seed offering area to assess the effect of microsite characteristics. After evaluating predation in the three environments, we only found that there is a greater preference for predation of native seeds in pine forest plantations. On the other hand, we identified that vegetation cover at ground level (strongly correlated with the type of environment) keeps a positive relationship with seed predation. This study shows that seed predation of native and non-native plants could be driven in part by microsite characteristics (greater plant cover = greater seed predation), perhaps through generating refuge (safe site) for the main seed predators of these forests (i.e., rodents). Forest conservation, management and restoration strategies must consider the short- and long-term dynamics of a post-intervention restoration site with the aim of creating an environment conducive to native forest regeneration.

Invasive Alien Plant Species for Use in Paper and Packaging Materials

Invasive plant species can impede the establishment and growth of native plants and affect several ecosystem properties. These properties include soil cover, nutrient cycling, fire regimes, and hydrology. Controlling invasive plants is therefore a necessary, but usually expensive, step in restoring an ecosystem. The sustainability of materials with an emphasis on the use of local resources plays an important role in the circular economy. The use of alternative fibers from invasive plants promotes local production in smaller paper mills that offer the protection of local species and the reduction of waste and invasive plants. A synthesis of the literature is needed to understand the various impacts of invasive plants and their practical control in the context of papermaking applications and to identify associated knowledge gaps. To improve our understanding of the practical application of invasive species in the paper industry, we reviewed the existing literature on invasive plant species in the area of fiber production, printability, coating solution production, dyes, and extracts, and collected information on the major invasive plant species in Europe and the methods used for various applications.

Tipping the balance: The role of seed density, abiotic filters, and priority effects in seed-based wetland restoration.

Sowing native seeds is a common approach to reintroduce native plants to degraded systems. However, this method is often overlooked in wetland restoration despite the immense global loss of diverse native wetland vegetation. Developing guiding principles for seed-based wetland restoration is critical to maximize native plant recovery, particularly in previously invaded wetlands. Doing so requires a comprehensive understanding of how restoration manipulations, and their interactions, influence wetland plant community assembly. With a focus on the invader Phragmites australis, we established a series of mesocosm experiments to assess how native sowing density, invader propagule pressure, abiotic filters (water and nutrients), and native sowing timing (i.e., priority effects) interact to influence plant community cover and biomass in wetland habitats. Increasing the density of native seeds yielded higher native cover and biomass, but P. australis suppression with increasing sowing densities was minimal. Rather, community outcomes were largely driven by invader propagule pressure: P. australis densities of ≤500 seeds/m2 maintained high native cover and biomass. Low-water conditions increased the susceptibility of P. australis to dominance by native competitors. Early sowing of native seeds showed a large and significant benefit to native cover and biomass, regardless of native sowing density, suggesting that priority effects can be an effective restoration manipulation to enhance native plant establishment. Given the urgent wetland restoration need combined with the limited studies on seed-based wetland restoration, these findings provide guidance on restoration manipulations that are grounded in ecological theory to improve seed-based wetland restoration outcomes.

Native arbuscular mycorrhizal fungi promote native grassland diversity and suppress weeds 4 years following inoculation

Restoration quality of native prairie can be improved by reintroducing key organisms from the native plant microbiome such as arbuscular mycorrhizal (AM) fungi. Here, we assess whether the positive effects of a native mycorrhizal inoculation observed during the first growing season remained at the end of the fourth growing season. In 2016, an experiment was initiated that assessed the response of a restored tallgrass prairie to an inoculation density gradient of native mycorrhizal fungi ranging from 0 to 8,192 kg/ha. First year results indicated that native plant establishment benefited from high but not low densities of native mycorrhizal inocula, resulting in improvements in native plant abundance, richness, and diversity. To assess whether these effects persist in later growing seasons, we resampled the prairie restoration in 2020 and analyzed the data similarly. Results from the fourth growing season indicated that the pattern of responses had persisted; the positive effects of inoculation observed during the first growing season remained after four growing seasons as demonstrated by improvements in total and native plant diversity and reduced non‐native abundance. Additionally, the low densities of mycorrhizal amendment that were not initially effective were found to reduce non‐native abundance in the fourth growing season, suggesting that low densities of mycorrhizal amendment can be amplified via positive plant‐AM fungal feedback to suppress weeds following the introduction of lesser amounts of AM fungi.

Plant growth ability, rather than phylogenetic relatedness, predicts the effect of soil biota from an abandoned field on native and exotic plants

Abstract Soil biota, as legacy effects of previous species in natural ecosystems, profoundly affects plant performance in new habitats and, in turn, plant community. However, how soil biota, as legacy effects of agricultural crops, affects the likelihood of establishment of exotic and native plants in newly abandoned farmland remains poorly understood, which may hinder effective management of agricultural weeds. Here, we grew 58 plant species (28 exotic species and 30 native species) common in Central China in sterilized vs. nonsterilized soils collected from a newly abandoned maize field. We (i) estimated the effects of soil biota on plant shoot, root and total mass, (ii) explored the dependence of soil effects on the plants’ phylogenetic distance to maize, origin (native vs. exotic) and life history (annual vs. perennial) and (iii) tested which plant traits could predict soil effects. Soil biota, in general, decreased plant mass, suggesting a dominant role of enemies. The effect of the soil biota on plant total mass was unrelated to the phylogenetic distance of the plants to maize and decreased linearly with increasing plant intrinsic growth ability. Moreover, the soil biota on average had greater negative impacts on the total mass of exotic plants, particularly perennial species, than on that of native plants. Our results suggest that plant intrinsic growth ability, rather than phylogenetic relatedness, is a reliable predictor of soil effects. Additionally, native plants can benefit from plant–soil interactions in competing with exotic perennial plants when initially established in newly abandoned farmlands.