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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. A systematic review and meta-analyses of seed-based ecological restoration experiments identify native priority as a promising mechanism for controlling invasion of alien plant species, which can reduce the performance of invasive species by more than 50%. [ABSTRACT FROM AUTHOR]

Invasion of alien species is one of the main drivers of land degradation threatening both natural and managed ecosystems. Ecological restoration is crucial in controlling invasion to improve biotic resistance and avoid further land degradation. We investigated the possibility of controlling the establishment of invasive alien species (IAS) by native seed addition. We tested if trait similarity or increased propagule pressure of native species results in the suppression of IAS at the early stage of development. We set up a sowing experiment with three widespread IAS in Hungary of different life forms and functional groups (Asclepias syriaca, Conyza canadensis, Tragus racemosus) and four Pannonic sand grassland species (Festuca vaginata, Galium verum, Gypsophila paniculata, Saponaria officinalis). We found no significant differences in germination ability and seedling emergence between native species and IAS, despite the differences in thousand‐seed weight. Using univariate general linear models, we found that the seedling establishment of IAS can be reduced by adding native species at high densities but also depending on the species identity. Instead of species of similar traits, the seeding of a competitor perennial grass of sand grasslands (F. vaginata) reduced the seedling emergence of all studied IAS the most. Our results confirm that IAS can be effectively controlled by native seed addition in the early establishment stage, especially applying higher densities and competitive species. We conclude that invasion‐resistant restoration can be achieved by the combination of several factors, including high‐density sowing of native species that match IAS in the early stage of development. [ABSTRACT FROM AUTHOR]

To help upscale ecological restoration of degraded lands, landscape factors and longer time scales should be considered when assessing restoration efforts. We evaluated the impact of initial restoration intervention, landscape composition, and elapsed time since the restoration began on the long-term progress of Pannonic sand grassland restoration. Treatments (seeding, mowing, and carbon amendment) were implemented for 6–7 years and monitoring lasted up to 23 years after the first treatment applications in eight experimental blocks belonging to three field experiments. The abundance of target/neophyte species, and distance from primary grasslands and plantations (as major source of target/neophyte species) were estimated in 500 m landscape buffers around each block to characterize landscape composition. Restoration progress was calculated as the difference between the relative cover of target/neophyte species in treatment and control plots. Restoration intervention and neophyte abundance in the landscape had a significant effect on the restoration progress, but time did not. Seeding had the highest positive effect on target species and also prevented invasion by neophyte species. Higher abundance of neophytes in the landscape and the proximity to plantations increased the cover of neophytes in treatment plots. We conclude that restoration interventions may have a greater impact on restoration progress in the longer term than landscape factors or elapsed time. Seeding proved to be the best method in restoring sand grasslands by both favoring target species and controlling invasion. From the landscape factors, the abundance of neophyte species and distance to plantations should be considered when prioritizing areas and efforts for restoration. [ABSTRACT FROM AUTHOR]

To preserve the natural genetic pattern of species and to avoid the introduction of nonadapted ecotypes during restoration, seed transfer should be spatially restricted. Instead of applying administrative borders in the absence of species‐specific empirical data, biogeographical knowledge can be used as a proxy. Hungary was used as a suitable test region for this approach. The aims of the study were (1) to produce an evidence‐based seed transfer zone (STZ) map applying the Multiple Potential Natural Vegetation model; (2) to assess the uncertainty of the resulting STZ map; and (3) to compare the present seed transfer regulation based on administrative regions with the evidence‐based STZ map. The analysis was based on a floristic map, a vegetation map, and a landscape map of Hungary. Intersected polygons of the three maps were filled with Multiple Potential Natural Vegetation data and clustered to produce seven contiguous units that can serve as STZs. The uncertainty analyses provided a numerical comparison between the two approaches and demonstrated the inadequacy of defining administrative regions as STZs. The practical result of the study is the production of an evidence‐based STZ map that could replace the administrative map currently used for regulation in Hungary. Moreover, this map helps to develop native seed propagation and to enhance ecological restoration. We conclude that field‐based potential vegetation models, similar to the Multiple Potential Natural Vegetation, are suitable for STZ development in countries lacking an evidence‐based system for seed transfer. [ABSTRACT FROM AUTHOR]

Aichi Target 15 aims to enhance the resilience of ecosystems through the restoration of 15% of degraded land by 2020. Compliance with the target is still insufficient, partly due to the lack of appropriate baselines and knowledge of restoration efforts. The four-level model of ecosystem condition was suggested to set the baseline and support the estimation of progress. This study is the first to assess the condition of MAES ecosystem types at a country scale, using the suggested approach. Altogether 613,000 ha of land is in close to natural condition (Level 1), 893,000 ha in a slightly degraded state (Level 2), 1,907,000 ha in moderately degraded condition (Level 3), and 5,890,000 ha of land is in highly modified category (Level 4). An inventory of ecological restoration interventions was created based on the reports of the national park directorates and EU LIFE projects. The findings of the restoration database of 634 interventions were compared to the need for restoration of nine habitat types. Restoration efforts were focused at habitat types with the most extended degraded area, except for dry forest restoration and the fight against invasive species in all three forest types. This study provides a more reliable estimate of habitats in natural state than Habitat Directive reporting can achieve, and is therefore better suited for estimating compliance with the 15% target. Only 1% of degraded land was the target for restoration in the period of 2002–2016. The details of the survey regarding habitat and degradation types can support further restoration planning. [ABSTRACT FROM AUTHOR]

Community assembly theory is suggested as a guiding principle for ecological restoration to help understand the mechanisms that structure biological communities and identify where restoration interventions are needed. We studied three hypotheses related to propagule limitation, stress‐dominance, and limiting similarity concepts in community assembly in a restoration field experiment with a trait‐based null model approach. The experiment aimed to assist the recovery of sand grassland on former arable land in the Kiskunság, Pannonian biogeographic region, Europe. Treatments included initial seeding of five grassland species, carbon amendment, low‐intensity mowing, and combinations in 1 m by 1 m plots in three old fields from 2003 to 2008. The distribution of 10 individual plant traits was compared to the null model and the effect of time and treatments were tested with linear mixed effect models. Initial seeding had the most visible impact on species and trait composition confirming propagule limitation in grassland recovery. Reducing nutrient availability through carbon amendment strengthened trait convergence for length of flowering as expected based on the stress‐dominance hypothesis. Mowing changed trait divergence to convergence for plant height with a strengthening impact with time, supporting our hypothesis of increasing dominance of limiting similarity with time. Our results support the idea that community assembly is simultaneously influenced by propagule limitation and multiple trait‐based processes that act through different traits. The limited impact of manipulating environmental filtering and limiting similarity compared to seeding, however, supports the view that only targeting the dispersal and environmental filters in parallel would improve restoration outcome. [ABSTRACT FROM AUTHOR]

Question: What is the effect of invasive common milkweed (Asclepias syriaca L.) on the germination and early establishment of native grass species during open sand grassland vegetation recovery in old‐fields? Location: Fülöpháza Sand Dune Area, Hungary. Methods: A small‐scale experiment was carried out in a sandy old‐field infested with Asclepias. We designated 36 2 m × 2 m plots in patches of Asclepias. We seeded two native grass species Festuca vaginata and Stipa borysthenica in 12 plots each (a third of the plots was left unseeded). We applied repeated mechanical removal of Asclepias shoots on half of the plots for two growing seasons. The number and above‐ground cover of the two grass seedlings were evaluated for two growing seasons. Results: The number and above‐ground cover of Festuca and Stipa seedlings did not increase after applying Asclepias shoot removal during the 2 years of the study. We found lower seedling number and cover of Festuca in plots with Asclepias shoot removal in the second year, when a severe summer drought occurred at the study site. The number and cover of the Stipa seedlings did not differ between plots with Asclepias shoot removal and control plots throughout the experiment. Conclusions: We did not find any negative effects of the presence of the invasive Asclepias during open sand grassland regeneration in terms of germination and early establishment of the dominant grass species. We even detected a nurse effect of Asclepias on Festuca, where the shade of Asclepias may have mitigated the unfavourable abiotic conditions for Festuca caused by summer drought. This mitigation was not observed in the case of Stipa, which can better tolerate summer droughts. Our results suggest that Asclepias control is not required for a successful open sand grassland restoration in the early phase of vegetation recovery, and restoration efforts should focus on the mitigation of propagule limitation of native grasses. However, further information is needed about the effects of Asclepias on other elements of the biota and in later phases of secondary succession. We experimentally investigated the effect of the invasive herb common milkweed (Asclepias syriaca L.) on grassland recovery in terms of the establishment of two dominant grasses of the open sand grassland community. We observed that milkweed did not have any adverse effects on the early establishment of these species, and even had a nurse effect on one of them during summer drought. [ABSTRACT FROM AUTHOR]

Scaling-up ecological restoration demands the involvement of private sector actors. Experience regarding science-based habitat restoration programs in the sector should be made available to support further joint projects. In our case, hierarchical restoration prioritization was applied to select best target for habitat reconstruction at a Hungarian industrial area. Multiple potential natural vegetation model, a novel approach, supported restoration prioritization satisfying both ecological (sustainability and nature conservation value) and other needs (feasibility, rapid green surface, amenity, and education value). The target that met all priorities was the open steppe forest that has a mosaic arrangement with open and closed sand steppes. The potential area of this xero-thermophile oak wood is expected to expand in Hungary with climate change, therefore the selected target has a likelihood of long-term sustainability, if established. A matrix of sand steppes was created first at the factory area in 2014-2015, and tree and shrub saplings were planted in this matrix. The seeding induced rapid changes in vegetation composition: the second year samples became close to reference sand steppes in the principal component analysis ordination space. Tree and shrub survival was species dependent, reaching a maximum of 52 and 73% for tree and shrub species, respectively. One tree and 2 shrub species did not survive at all. Altogether 53 of 107 target species have established. So far, restored vegetation development confirmed the suitability of the applied hierarchical prioritization framework at factory scale. [ABSTRACT FROM AUTHOR]

The application of a filter-based assembly model is a promising concept to support ecological restoration. The filters illustrate dispersal, abiotic and biotic constraints that narrow down the species pool and determine the realized species composition. The aim of restoration interventions is the manipulation of filters to achieve a restoration target., We tested the applicability of a filter-based assembly model in the restoration of endemic Pannonian sandy grassland on old-fields. We report the results of a six-year experiment to identify key filters and find possible interactions. Treatments included the following: (i) seeding (dispersal filter), (ii) carbon amendment to lower nitrogen availability (abiotic filter) and (iii) mowing (biotic filter). Treatments were carried out in 1 m2 plots following the same Latin square design in three old-fields., Seeding was the most important treatment increasing species richness, vascular cover and enhancing target species composition. Mowing played a secondary role, acting primarily in interaction with the other treatments. Carbon amendment significantly reduced soil mineral nitrogen, but played a subordinate role in determining vegetation composition. Significant interactions were found between the biotic and dispersal and the biotic and abiotic filters determining primarily the structural characteristics of the vegetation in terms of vascular cover, moss cover, litter and bare ground. Regarding species composition, synergistic links between the dispersal and biotic filters for seeded species and long-lived forbs, and antagonistic interaction between the dispersal and abiotic filters for seeded species were found., Synthesis and applications. Based on the impact and interactions of filters uncovered in this experiment, we propose a scheme for Pannonian grassland restoration, which can be validated and also used for other oligotrophic systems. In the proposed conceptual model, the dispersal filter plays a key role in determining the outcome of restoration measures followed by the biotic filter if manipulated by mowing, while the abiotic filter altered by nitrogen immobilization proved to have a weak effect. Based on our results, targeting several filters in parallel would improve restoration outcome. We propose that filter interactions should form an integral part of filter-based assembly models and should be taken into account in restoration decisions. [ABSTRACT FROM AUTHOR]