Restoration Of Plant Communities Research Articles

Assessing seed pellet formulations to improve native plant restoration under water‐limited conditions

Water scarcity, a challenge expected to worsen with climate change, significantly hinders native plant community restoration. Enhancing seed‐based restoration requires methods to increase the water availability for seeds and seedlings. Surfactants and superabsorbent polymers (SAPs) can improve soil water‐holding capacity and infiltration, but their use in seed enhancements remains underexplored. We investigated whether pellets containing surfactants or SAPs could improve seedling emergence of two native species (Rytidosperma caespitosum and Chrysocephalum apiculatum) common in temperate grasslands in south‐eastern Australia under different watering treatments. We used a randomized block design with five watering treatments to simulate predicted changes in precipitation for south‐eastern Australia: ambient, two reducing overall water volume, and two reducing watering frequency while increasing watering volume to maintain ambient treatment water volume. We explored four enhanced pellets (two containing surfactants and two containing SAPs) and non‐pelleted seeds. Our results showed that watering events with larger volumes but reduced frequency increased seedling emergence. Under these conditions, block co‐polymer surfactants further increased seedling emergence of C. apiculatum, while synthetic SAP pellets promoted emergence of R. caespitosum. Block co‐polymer surfactants decreased R. caespitosum emergence, and both SAPs reduced C. apiculatum emergence under reduced watering frequency. A 50% reduction in overall water volume significantly reduced seedling emergence for both species, regardless of seed enhancement. These findings suggest that surfactants and SAP pellets can improve the success of seed‐based restoration under ambient conditions and when rainfall events are larger in volume but reduced in frequency, but not when the overall volume of rainfall is reduced.

Suppression of reed canarygrass by assisted succession: A sixteen‐year restoration experiment

Abstract Assisted succession could enable long‐term restoration where successional trajectories stall due to competition from invasive plants. Many invasives are shade‐intolerant; therefore, interventions reducing light availability should suppress invasion and re‐establish successional processes. However, given how ubiquitous nonlinearities are in ecology, restoration success also depends on identifying critical system thresholds, for example invader abundances below which regeneration of desired species is possible. We report the successful use of assisted succession to restore a swamp forest invaded by Phalaris arundinacea (reed canarygrass; hereafter Phalaris), initiated by a high‐density planting of woody species to outcompete Phalaris by reducing light availability. We established five pre‐planting treatments in a Phalaris near‐monoculture in Wisconsin, USA: herbicide‐only, herbicide+plough, herbicide+burn, mow+herbicide and control. In 2003 we planted 22 tree and shrub species at high densities, then in 2019 we censused the site to: (1) screen for long‐term differences among treatments, (2) evaluate long‐term effects of our interventions on community composition and (3) characterize the critical thresholds that enable invader suppression and restoration success. Vegetation responses and light availability across our four pre‐planting invader removal treatments did not differ. Late fall glyphosate application suppressed Phalaris long enough that a dense canopy of native woody species could establish and eventually out‐shade it. Overstory tree and shrub densities of 0.071/m2 suppressed Phalaris to 50% cover, but, due to nonlinearities, much higher densities were needed to reduce light availability and thus Phalaris cover enough to shift the system from being invader‐dominated. Compositional similarities between juvenile woody species and the overstory suggest a long‐term restoration success. Synthesis and applications. Invasive species management and the restoration of target plant communities can be aided by assisting successional trajectories that have stalled. We document a restoration strategy for forests invaded by shade‐intolerant invaders that is both effective and economical, as only a simple site preparation and single planting effort is required. Establishing a dense canopy of woody species in this way can break the feedbacks maintaining invader dominance and re‐introduce feedbacks enabling long‐term ecosystem recovery. We also illustrate the value of identifying critical thresholds influencing the abundance and impact of key invasive species.

Seeding Density Alters the Assembly of a Restored Plant Community after the Removal of a Dam in Southern Wisconsin, USA

Recently exposed reservoir sediments, prone to colonization by invasive species, provide novel settings to test hypotheses related to soil conditions and propagule supply as potential drivers of plant assembly in disturbed ecosystems. We used a dam removal site in southwestern Wisconsin to examine the relationship between the physiochemical properties of dewatered sediments, seeding density, and plant community assembly. The plant communities from five seed densities (1000, 500, 250, 125, and 0 seed m−2) were annually assessed over four years. We hypothesized (1) that the native aboveground biomass and the proportion of native to invasive (non-seeded species) aboveground biomass would increase with the seeding density and (2) that the diversity of seeded native species would increase with a higher seeding density. We found evidence that sowing at least 500 seeds m−2 of prairie species increased their abundance, establishment, and plot diversity compared to non-seeded plants that persisted four years after seeding (p < 0.05). The seeding density treatments led to the assembly of two distinct communities: “native” and “invasive”. The “native” community, assembled in plots seeded with at least 500 seeds m−2, had a greater aboveground biomass and diversity (i.e., richness) of seeded plants compared to plots with lower seed densities, and its productivity was positively related to this richness. In the “weedy” community, the diversity of invasive species had no relationship to their aboveground biomass, likely because these species share similar traits (i.e., redundancy) and may have performed similar functions within the plant community. These findings suggest that the seeding density interacted with the disturbed soil resources to increase the diversity and productivity of seeded native species and may serve as a positive feedback mechanism for the establishment of native communities in dewatered sediments.

Prairie restoration promotes the abundance and diversity of mutualistic arbuscular mycorrhizal fungi.

Predicting how biological communities assemble in restored ecosystems can assist in conservation efforts, but most research has focused on plants, with relatively little attention paid to soil microbial organisms that plants interact with. Arbuscular mycorrhizal (AM) fungi are an ecologically significant functional group of soil microbes that form mutualistic symbioses with plants and could therefore respond positively to plant community restoration. To evaluate the effects of plant community restoration on AM fungi, we compared AM fungal abundance, species richness, and community composition of five annually cultivated, conventionally managed agricultural fields with paired adjacent retired agricultural fields that had undergone prairie restoration 5-9 years prior to sampling. We hypothesized that restoration stimulates AM fungal abundance and species richness, particularly for disturbance-sensitive taxa, and that gains of new taxa would not displace AM fungal species present prior to restoration due to legacy effects. AM fungal abundance was quantified by measuring soil spore density and root colonization. AM fungal species richness and community composition were determined in soils and plant roots using DNA high-throughput sequencing. Soil spore density was 2.3 times higher in restored prairies compared to agricultural fields, but AM fungal root colonization did not differ between land use types. AM fungal species richness was 2.7 and 1.4 times higher in restored prairies versus agricultural fields for soil and roots, respectively. The abundance of Glomeraceae, a disturbance-tolerant family, decreased by 25% from agricultural to restored prairie soils but did not differ in plant roots. The abundance of Claroideoglomeraceae and Diversisporaceae, both disturbance-sensitive families, was 4.6 and 3.2 times higher in restored prairie versus agricultural soils, respectively. Species turnover was higher than expected relative to a null model, indicating that AM fungal species were gained by replacement. Our findings demonstrate that restoration can promote a relatively rapid increase in the abundance and diversity of soil microbial communities that had been degraded by decades of intensive land use, and community compositional change can be predicted by the disturbance tolerance of soil microbial taxonomic and functional groups.

Equivalent mating system parameters in post‐mining and undisturbed native plant populations confirms restitution of bird‐pollinator function

Abstract The restoration of diverse self‐sustaining ecosystems requires re‐establishment of functional interactions among species. For plant communities, pollinators are usually essential for pollination, seed set and seed quality. A common assumption in ecological restoration for plants pollinated by animals is one of ‘build it and they will come’, which is rarely tested. Beyond seed set, there may be negative genetic consequences for seed quality if pollinators and their behaviour do not reflect those in reference populations. Here, we conduct an ecological genetic assessment of seed quality via mating system parameters in Lambertia multiflora (Proteaceae), a species dependent on nectar‐feeding birds for pollination. Four populations of L. multiflora in disturbed sites that were rehabilitated following mineral sands mining were compared with four native reference populations, near Eneabba, Western Australia. In each population, approximately 10 offspring from each of 10 maternal plants were genotyped with 11 highly polymorphic microsatellite markers. From these data, genetic diversity and mating system parameters were assessed, and found to be equivalent across all populations. Mean allelic diversity and heterozygosity across loci were very high. All populations were completely outcrossing with no bi‐parental inbreeding. Mean correlated paternity, sibship and effective population size estimates for restored and natural populations were not significantly different and reflected uniformly high paternal diversity and wide outcrossing. Equivalent genetic results for restored and natural reference populations indicate successful restitution of bird‐pollinator services for L. multiflora in these post‐mining rehabilitation sites. Synthesis and applications. Reviewing our results with other published studies to date suggests a resilience of bird‐pollinator services in restored plant communities. These findings provide some reassurance to restoration practitioners working in these global south systems where bird pollination is a feature, at least for similar landscape scenarios. Our study also highlights the global contribution of ecological genetics to the objective assessment of functional species interactions in ecological restoration, an increasingly important goal of land managers and regulators seeking to improve restoration standards.

Mapping Foliar C, N, and P Concentrations in An Ecological Restoration Area with Mixed Plant Communities Based on LiDAR and Hyperspectral Data

Interactions between carbon (C), nitrogen (N), and phosphorus (P), the vital indicators of ecological restoration, play an important role in signaling the health of ecosystems. Rapidly and accurately mapping foliar C, N, and P is essential for interpreting community structure, nutrient limitation, and primary production during ecosystem recovery. However, research on how to rapidly map C, N, and P in restored areas with mixed plant communities is limited. This study employed laser imaging, detection, and ranging (LiDAR) and hyperspectral data to extract spectral, textural, and height features of vegetation as well as vegetation indices and structural parameters. Causal band, multiple linear regression, and random forest models were developed and tested in a restored area in northern China. Important parameters were identified including (1), for C, red-edge bands, canopy height, and vegetation structure; for N, textural features, height percentile of 40–95%, and vegetation structure; for P, spectral features, height percentile of 80%, and 1 m foliage height diversity. (2) R2 was used to compare the accuracy of the three models as follows: R2 values for C were 0.07, 0.42, and 0.56, for N they were 0.20, 0.48, and 0.53, and for P they were 0.32, 0.39, and 0.44; the random forest model demonstrated the highest accuracy. (3) The accuracy of the concentration estimates could be ranked as C > N > P. (4) The inclusion of LiDAR features significantly improved the accuracy of the C concentration estimation, with increases of 22.20% and 47.30% in the multiple linear regression and random forest models, respectively, although the inclusion of LiDAR features did not notably enhance the accuracy of the N and P concentration estimates. Therefore, LiDAR and hyperspectral data can be used to effectively map C, N, and P concentrations in a mixed plant community in a restored area, revealing their heterogeneity in terms of species and spatial distribution. Future efforts should involve the use of hyperspectral data with additional bands and a more detailed classification of plant communities. The application of this information will be useful for analyzing C, N, and P limitations, and for planning for the maintenance of restored plant communities.

Successful restoration of alpine plant communities depends on habitat type

Alpine ecosystems are under increasing pressure from land‐use change and road construction, resulting in habitat fragmentation and declines in biodiversity and ecosystem function. Ecosystem restoration can mitigate the impacts from human land‐use change by assisting the recovery of natural ecosystems. We developed an assessment framework using established international standards and monitored alpine vegetation recovery within restored zones along a hydropower‐dam road built in 2013 in the Knutshø landscape protected area, Norway. Using data collected in 2016, 2018 and 2021, we compared abiotic variables and vegetation indicators (cover, and community composition) in restored zones against directly adjacent intact zones within three different habitat types. After eight years, wetland habitat had similar cover of plant functional types and abiotic variables within restored and intact zones, while ridge and willow‐heath habitats had more cover of graminoids and less cover of shrubs in restored compared to intact zones. In addition, community composition in restored wetland habitat zones was similar to intact zones, while the community composition of restored zones in ridge and willow‐heath habitats was significantly different from adjacent intact zones. This suggests that restored wetland habitat in our study system is on a trajectory of recovery, but that recovery of other plant community types may require longer periods of time or, in some cases, may not be possible without further intervention because of alternative stable states. Our results underscore the need for long‐term monitoring and adaptive management to insure restoration success in alpine environments.

Success in restoring native plant communities on kimberlite mining dumps in the Afro-alpine Drakensberg region of Lesotho.

Rehabilitation strategies for degraded mine dumps have generally seen limited success due to different complications associated with mining biophysical disturbance. In this study, we tested a combination of two methods to expedite revegetation of kimberlite tailings at Letseng Diamond Mine (i.e., in the Afro-alpine areas of Lesotho). We ran trials on different growth media located on fine and coarse kimberlite tailings (i.e. sites) mixed with different substrate combinations and topsoil and sowing a seed mix comprised of native plant species. Overall, as predicted, fine kimberlite tailings displayed significantly higher plant abundance than coarse kimberlite tailings, and sown seeds performed significantly better than spontaneous colonisation by emerging species. Kimberlite tailings mixed with topsoil (100 mm) showed significantly greater plant abundance, and similarly, when coarse kimberlite tailings were introduced to fine tailings. Physicochemical analyses of growth media components suggested that topsoil provided additional nutrients and that plants could readily access available nutrients in the fine kimberlite tailings. We noted a gradual significant increase in plant abundance over 5 years, enhanced by new plant species emerging from the topsoil seed bank or by natural seed dispersal. Although plant abundance differed significantly, both fine and coarse kimberlite tailings displayed high plant species diversity (H = 3.4 and D = 0.95 and H = 3.5 and D = 0.95, respectively). Out of 36 emerging plant species, 15 species spontaneously colonised both growth media. The significant variation in abundance among plant species between treatments was mostly attributed to dominant forb species, namely Chrysocoma ciliata, Glumicalyx montanus, Oxalis obliquifolia, Senecio inaequidens and Trifolium burchellianum. We have identified suitable growth media for plant community restoration on kimberlite tailings in the Drakensberg alpine area using a seed mix of native plant species in combination with natural seed dispersal from the surrounding pristine environment. We provide evidence for using two complementary approaches to optimise native plant community development during restoration in the Drakensberg alpine area.

Mixed sowing improves plant and soil bacterial community restoration in the degraded alpine meadow

Mixed sowing improves plant and soil bacterial community restoration in the degraded alpine meadow

Scales of Diversity Affecting Ecosystem Function across Agricultural and Forest Landscapes in Louisiana

Current land use and extensive modifications of natural ecosystems across the state of Louisiana are generally similar to those across the southeastern USA where rainfall supports forest ecosystems. Both intentional and unintentional consequences of ecosystem modifications from the scales of water and sediment movement across a field edge to state-wide loss of functional grasslands are legacies from previous development across the state. While major investments and large-scale, long-term plans are aspects of some continuing ecological issues across the state, small-scale, volunteer-led restoration of native grassland plant communities in the Louisiana Coastal Prairie illustrates the value associated with the restoration of natural ecosystem function in drastically disturbed environments. As is now becoming increasingly recognized, Louisiana grasslands represent less obvious components of forest, woodland, and wetland landscapes across the state, where they have contributed essential wildlife habitat, and ecosystem functions. These are now largely missing from many landscapes across the state and region. The strategic restoration of grassland functions combining novel native grass pastures and fully functional native grassland plant communities as landscape components could provide both economic and ecosystem benefits. Specific native grassland seed resources are needed for various restoration activities to enhance ecosystem function at a range of scales across the state and region.

Long-term interactive impacts of the invasive shrub Lonicera maackii and white-tailed deer (Odocoileus virginianus) on a deciduous forest understory

AbstractWhite-tailed deer (Odocoileus virginianus) (hereafter, ‘deer’) and invasive plants affect forest understories, but few studies have investigated their interaction. We investigated long-term (11-yr) effects of excluding deer and removing the invasive shrub, Amur honeysuckle [Lonicera maackii (Rupr.) Herder], on plants in southwest Ohio. Deer exclusion enhanced tree seedling richness and density, but reduced annual and bare ground cover. Vine density was reduced by Lonicera, especially where deer were excluded. Seedlings of several tree species, the invasive shrub, burning bush [Euonymus alatus (Thunb.) Siebold], and the invasive vine, winter creeper [Euonymous fortunei (Turcz.) Hand.-Maz.], were indicator species of the deer exclosure by Lonicera removal treatment combination. The effect of deer on cover of native species depended on Lonicera treatment: where shrubs were removed, cover was higher where deer were excluded, but where shrubs were present, cover was higher where deer had access. We attribute these interactions to the reduced growth of, and shading by, Lonicera where deer had access and browsed this invasive shrub. Some of these effects were evident in the first 6 yr, but are now larger. Other effects were not evident in the earlier evaluation. These findings inform management of areas with high densities of deer and invasive shrubs palatable to deer. Control of only invasive shrubs will reduce native cover and not improve tree regeneration. Managing only deer will increase woody plants but reduce native cover. Management of both stressors is needed to promote tree regeneration and restoration of plant communities.

Local site conditions, not landscape context, influence restored plant communities within urban contexts

Restoration outcomes are variable, which impairs our ability to plan projects, meet goals, and predict restoration outcomes. Understanding the drivers of this variation is an important research need, especially within urban ecosystems, which support altered abiotic and biotic conditions and face higher rates of loss and degradation than non‐urban areas. Despite the importance of urban areas for restoration, research and practice have largely focused on non‐urban areas. It is unclear if we can extend current knowledge from restoration ecology to urban systems. Here, we surveyed 30 urban prairie restoration plantings across southern Michigan. We collected plant community and site condition data (e.g. soil attributes) and we quantified landscape context as the percentage of urban land surrounding each site. Variation in plant community composition among restorations was related primarily to site‐level factors, such as soil compaction, texture, and water‐holding capacity, rather than landscape context. Non‐prairie species were structured primarily by the local site conditions. There was an increase in non‐prairie richness for sites that experienced warmer local climate conditions, while there was a decrease in non‐prairie richness for sites where soils were less compacted, sandier, and had elevated water‐holding capacity. Prairie species richness responded oppositely. Overall, our study revealed specific factors structuring restoration outcomes in urban contexts and illustrated the importance of local site conditions, not surrounding landscape context, for shaping plant community composition. Restoration practices developed in non‐urban areas should be extended to urban contexts to better understand the impact of local site conditions on plant community development.

Agricultural land-use legacies affect soil bacterial communities following restoration in a global biodiversity hotspot

Ecosystem restoration in post-agricultural landscapes is a critical response to agricultural land abandonment, climate change, and the escalating biodiversity crisis. However, effective restoration of these landscapes can be hampered by land-use legacies that create biotic and abiotic barriers to ecosystem recovery, particularly in ancient Tertiary landscapes where vegetation is adapted to nutrient deficient soils. While our understanding of how to overcome these barriers when restoring plant communities is improving, there is limited knowledge of how these legacies impact on recovery of soil microbiota – the biodiverse and functionally-important communities of soil microbes. Here, we used amplicon sequencing of the bacterial 16S rRNA gene extracted from soils across a restoration project in southwest Western Australia, a global biodiversity hotspot, to examine recovery of soil microbiota following post-agricultural restoration. We sampled soils at six sites under four land conditions – degraded post-agriculture, actively revegetated post-agriculture, passively regenerated, and remnant bushland – generating 1,609,618 sequences corresponding to 15,009 unique bacterial taxa. We show that soil bacterial communities in revegetated and degraded samples were similar across sites but strongly dissimilar to adjoining remnant samples. We show that limited recovery of bacterial communities was linked to elevated soil phosphorus levels. Together, our results indicate soil microbiota have not recovered despite revegetation taking place up to 17 years ago, and this lack of recovery is likely driven by soil nutrient legacies from past agricultural practices. Our study highlights a key challenge faced by conservation practitioners when integrating soil microbiota into ecosystem restoration in post-agricultural landscapes in ancient, nutrient-poor landscapes.

Soil nutrients drive changes in the structure and functions of soil bacterial communities in a restored forest soil chronosequence

The restoration of plants is effective for restoring ecosystems in eroded areas. Soil bacterial communities play an important role in nutrient cycling. High-throughput sequencing technology was used to determine the changes in soil bacteria in different restored plant communities and years of restoration. The FAPROTAX database and random forest model were also used to analyze the changes in soil bacterial carbon (C), nitrogen (N), and phosphorus (P) metabolic functions and their influencing factors. The results showed that the bacterial community diversity, soil texture, physicochemical properties, and multifunctionality improved substantially with the increments and years of restoration. These changes, in turn, altered the nutrient metabolic functions in soils by increasing the fixation of bacterial C, decreasing the fixation of N, and gradually relieving the limitations on N. However, these changes also increased the limitation of P during the late stage of restoration. The pH values and soil nutrients were crucial and exerted a large influence on the nutrients and metabolic functions of the bacteria. These findings facilitate the restoration of plants in subtropical areas of eroded soil.

On the issue of studying the anthropogenic impact on the vegetation of the Zabaikalsky National Park

On the territory of the Zabaikalsky National Park, core zone in the Karga area has been allocated, where observations are made of the vegetation restoration under the anthropogenic influence. This core zone was allocated in 2021 by the Department of Science of the «Reserved Podlemorya». During two years under study, monitoring plots were organized, where seasonal observations of the state of plant communities are carried out. The article presents materials for 2022. These are primary data that serve as the foundation for subsequent analysis of the progress of the restoration of plant communities. Work is carried out in places open to tourists, as well as on the territory of the core zone. A total of six trial plots were established. The collection and analysis of the material was carried out using the methods and approaches of conventional geobotanical, floristic and cenopopulation studies. About 100 herbarium sheets were collected, 20 geobotanical releves were made. A comparative analysis showed that the vegetation in the core zone is in a rather depressed state. Vegetation in an area with a tourist load can also be characterized as regressive. This state is evidenced by low indicators of the total projective cover, poor species composition both in the herbaceous layer and in the shrub-tree layer.

PLANT COMPOSITION AND SOIL PROPERTIES DURING POSTAGROGENIC EVOLUTION IN THE CIS-BAIKAL FOREST-STEPPE ZONE

Purpose. The purpose of the study was to examine the features of the restoration of plant communities and some properties of gray forest soils, including the humus state, during their post-agrogenic transformation in the conditions of the Cis-Baikal forest-steppe zone.
 Materials and methods. The study was carried out using the post-agrogenic chronosequences, including arable land, abandoned soils of different ages, and natural cenoses (meadow and forest). Traditional methods of phytocenology were applied to study the plant composition. Mixed soil samples from three trenches were collected from the former arable layer of 0–20 cm. The content of organic carbon (Corg), total nitrogen (N), and the C/N ratio, the pH(H2O) and pH(KCL) values, as well as soil density and the reserves of Corg were determined. The statistical processing of data was performed using One Way ANOVA (Sigma Plot from Windows Version 14.0).
 Results. It was shown that plant vegetation being typical for the Baikal forest-steppe zone was recovering after the cessation of plowing. At the same time, the several ruderal species were preserved in the plant composition during a long period. This specific phenomenon could be the cause for inhibition of terminal phytocenoses formation. Along with the change in the vegetation, a significant increase in the organic carbon content was revealed in the soils of chronosequences. At the later stages of post-agrogenic succession the carbon reserves in soil were 1.5 times higher than those in arable soil. The humus content in the soils increased with age of the abandoned lands, but no cardinal changes in its qualitative composition were observed. The data indicated the stable functioning of the system of humus substances in the gray forest soils of the Baikal forest-steppe zone during their post-agrogenic evolution.
 Conclusion. The results can be used for the forecast of post-agrogenic soil changes under various scenarios of land use in conditions of the Baikal region.

Meta-analysis identifies native priority as a mechanism that supports the restoration of invasion-resistant plant communities

The restoration of invasion-resistant plant communities is an important strategy to combat the negative impacts of alien invasions. Based on a systematic review and meta-analysis of seed-based ecological restoration experiments, here we demonstrate the potential of functional similarity, seeding density and priority effect in increasing invasion resistance. Our results indicate that native priority is the most promising mechanism to control invasion that can reduce the performance of invasive alien species by more than 50%. High-density seeding is effective in controlling invasive species, but threshold seeding rates may exist. Overall seeding functionally similar species do not have a significant effect. Generally, the impacts are more pronounced on perennial and grassy invaders and on the short-term. Our results suggest that biotic resistance can be best enhanced by the early introduction of native plant species during restoration. Seeding of a single species with high functional similarity to invasive alien species is unpromising, and instead, preference should be given to high-density multifunctional seed mixtures, possibly including native species favored by the priority effect. We highlight the need to integrate research across geographical regions, global invasive species and potential resistance mechanisms.

Do seeding and seedling planting result in similar restored plant communities?

AbstractAimsRestoration practitioners often face a tradeoff between low cost but risky seeding vs expensive but more reliable seedling planting to meet revegetation goals. Knowing under what environmental and management conditions direct seeding vs seedling planting benefit different species could improve restoration practice.MethodsWe compared seed emergence to planted‐seedling survival among perennial herbaceous species commonly used in restoration across eight experimental restoration sites on the Colorado Plateau, USA. We used linear models to assess relationships between emergence and survival among species, and to assess the effects of site climate and seeding pre‐treatments on those relationships.ResultsWe found that among species, emergence was positively correlated with survival in the cooler sites, meaning that species with high emergence also had high survival and vice versa, but had no relationship in the hottest sites. Furthermore, pre‐treatments to enhance soil moisture in seeded plots, specifically microtopography (pits) and mulch, also resulted in positive relationships between emergence and survival among species, while seeding without additional soil pre‐treatments did not. Seedling planting cost 14 times as much as direct seeding alone, dropping to nine times as much when pre‐treatments were combined with seeding.ConclusionsTaken together, these results suggest that investments in seedling planting at hotter dryland sites, or in creating microtopography or mulching prior to seeding across sites, are likely to promote establishment success compared to simple seeding methods in degraded dryland ecosystems. These findings also identify opportunities for hybrid seeding and planting approaches that balance tradeoffs between risk and cost, respectively.

A nontarget, disturbance‐resilient native species influences post‐fire recovery and multiphasic herbicide‐seeding outcomes in drylands threatened by exotic annual grasses

Native species that are abundant and persistent across disturbance‐succession cycles can affect recovery and restoration of plant communities, especially in drylands. In the sagebrush‐steppe deserts of North America, restoring deep‐rooted perennial bunchgrasses (DRPBGs) is key to the strategy for breaking an increasingly problematic cycle of wildfire promoted by exotic annual grasses (EAGs) and displacement of perennials by post‐fire increases in EAGs. We asked how Sandberg bluegrass (Poa secunda, POSE)—a common native grass that shares traits with EAGs such as resilience to disturbance and rapid, shallow‐rooted, early season growth—(1) recovered after wildfire, (2) responded to different combinations of native‐plant seedings of DRPBGs and EAG‐targeting herbicides; and (3) in turn, related to DRPBG recovery. In repeated sampling of up to approximately 2,000 plots spanning 113,000 burned hectares, POSE was initially more abundant than DRPBGs until POSE began to decline 5 years post‐fire, and POSE was marginally affected or unaffected by restoration treatments targeting DRPBGs or EAGs. In comparison, EAG cover decreased 8–16% where preemergent herbicide was sprayed and DRPBG cover increased 3–9% where they were drill‐seeded, and the greatest EAG reductions and DRPBG increases were seen where seeding and herbicides were combined in a time‐staggered fashion. Treatments had less target effects where POSE cover was high (>18%), which is also where EAG cover was scarcer and DRPBG cover greater, regardless of post‐fire interventions. Consideration of the ecological role of disturbance‐resilient species with ruderal characteristics that match traits of key invaders may improve the efficiency and effectiveness of restoration interventions.

Seedling responses to moderate and severe herbivory: a field-clipping experiment with a keystone Mediterranean palm.

Plant-ungulate interactions are critical in shaping the structure of Mediterranean plant communities. Nevertheless, there is a dearth of knowledge on how plant intrinsic and extrinsic factors mediate the sign and strength of plant-ungulate interactions. This is most relevant when addressing natural or assisted restoration of plant communities in human-disturbed areas. We conducted field-clipping experiments simulating how different intensities of ungulate herbivory may affect the natural regeneration and establishment of the Mediterranean dwarf palm (Chamaerops humilis), a keystone species in Mediterranean ecosystems. We quantified seedling survival and size in two human-disturbed sites (SW Spain) where wild and domestic ungulates exert high herbivory pressure on vegetation. Severe clipping and seedling aging reduced rates of seedling survival. In contrast, moderate clipping did not affect seedling survival, suggesting a certain degree of C. humilis tolerance to herbivory. Severe clipping reduced seedling height strongly but not seedling diameter, and these effects seem to have decreased seedling survival. Nurse shrubs increased seedling size, which likely improved seedling survival. We also found seedling compensatory growth which varied between study sites. Field-clipping experiments can help disentangle effects of plant extrinsic and intrinsic factors on the sign and strength of plant-ungulate interactions and their ecological consequences on the dynamics of human-disturbed ecosystems. We call attention to the importance of appropriately managing scenarios of severe herbivory and summer droughts, particularly frequent in Mediterranean ecosystems, as synergic effects of such key drivers can negatively affect the structure and dynamics of plant communities and endanger their conservation.