# Mountain grassland restoration using hay and brush material transfer combined with temporary wheat cover

Aure Durbecq, Léo Rocher, Renaud Jaunatre, Alice Dupré La Tour, Elise

Buisson, Armin Bischoff

► To cite this version:

Aure Durbecq, Léo Rocher, Renaud Jaunatre, Alice Dupré La Tour, Elise Buisson, et al. Mountain grassland restoration using hay and brush material transfer combined with temporary wheat cover. *Ecological Engineering*, 2022, pp.1-38. 10.1016/j.ecoleng.2021.106447. hal-03454196

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Distributed under a Creative Commons Attribution 4.0 International License
1 Mountain grassland restoration using hay and brush material transfer combined with temporary wheat cover

2 wheat cover

3 *Aure Durbecq¹,², Léo Rocher¹, Renaud Jaunatre³, Alice Dupré la Tour³, Elise Buisson¹, Armin Bischoff¹

4 Bischoff¹

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6 ¹ Mediterranean Institute of Biodiversity and Ecology (IMBE), Avignon University, CNRS, IRD, Aix Marseille University, Avignon, FR

7 Marseille University, Avignon, FR

8 ² Environmental consultancy ECO-MED, Marseille, FR

9 ³ Univ. Grenoble Alpes, INRAE, LESSEM, F-38402 St-Martin-d'Hères, FR

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11 Correspondence: Aure Durbecq, IMBE, Avignon University, CNRS, IRD, Aix Marseille University,

12 IUT, Avignon, FR.

13 Email: aure.durbecq@gmail.com

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15 Short title: Restoring mountain grasslands by propagule transfer

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21 Abstract

Mountain grassland restoration success may be hampered by limited seed dispersal and poor soil seed banks of many grassland species. These constraints can be overcome by actively introducing propagules from nearby non-degraded communities. We tested different restoration techniques in order to understand the mechanisms favouring target species seedling recruitment and establishment. In five degraded mountain grasslands, we analysed (i) the effect of two techniques increasingly used in ecological restoration to overcome low seed dispersal: transfer of brush-harvested seed material and hay transfer, and (ii) the potentially facilitative effect of a temporary plant cover (common wheat) on the recruitment of transferred brush-harvested propagules. We found that both propagule transfer techniques were successful in establishing plant species of the donor community with an increase of plant species richness, cover and abundance of transferred species. Hay transfer was more efficient in transferring species of the donor grassland than brush-harvested material transfer. Brush-harvested material transfer only increased abundance and cover of donor grassland species when sown together with wheat. The results indicated that hay mulch favoured seedling recruitment of target species, and that propagule transfer without hay mulch needs to be compensated by additional temporary plant cover in order to create favourable conditions for seedling recruitment. A comparison with best reference communities for each restoration grassland confirmed that hay transfer and brush material transfer with wheat sowing were successful in driving plant community composition towards the desired reference state. In conclusion, restoration of mountain grasslands with shallow and stony soils clearly benefits from a facilitative effect of dead (hay) or living (wheat) vegetation cover.

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Keywords

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Semi-natural montane grasslands, Seedling recruitment, Nurse crop, Erosion control, Mulch

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effect, Facilitation

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64 **1. Introduction**

65 Grassland ecosystems represent 25% of terrestrial biomes (Blair et al., 2014; Wilsey, 2020) and
66 are essential habitats for the conservation of biodiversity and associated ecosystem services
67 (Stoate et al., 2009; Amiaud & Carrère, 2012; Valkó et al., 2016). Since the 1980ies, the
68 conservation of species-rich semi-natural grasslands has become a major concern in Europe.

69 Most European semi-natural grasslands were integrated in the habitat management Natura
70 2000 network in order to stop habitat degradation and to re-establish grassland species
71 diversity using ecological restoration approaches (Wilsey, 2020).

72 Successful grassland restoration may be primarily hampered by limited dispersal
73 capacity and/or poor soil seed banks of many grassland species, and by a grazing management
74 favouring clonal reproduction over sexual reproduction (Halassy et al., 2016; Török et al., 2018).

75 These constraints are well documented and can be overcome by actively introducing
76 propagules (Kiehl et al., 2010; Scotton et al., 2012; Hölzel et al., 2012). The use of native plant
77 species of local origin is recommended to assure adaption to local environmental conditions
78 and to maintain genetic diversity (Vander Mijnsbrugge et al., 2010; Bucharova et al., 2019).

79 Consequently, transferring local seeds from nearby non-degraded communities is increasingly
80 used in ecological restoration (Scotton, 2019). Diverse techniques are currently applied
81 depending on specific environmental conditions at restoration and donor sites (Kiehl et al.,
82 2010; Hedberg & Kotowski, 2010). The increasing number of studies illustrates the scientific
83 interest in comparing restoration effectiveness of various seed harvesting and transfer
84 techniques (Scotton & Ševčíková, 2017), such as hay transfer vs. sowing of seed mixtures
85 (Auestad et al., 2015; Kövendi-Jakó et al., 2019), brush material vs. green hay transfer (Albert
86 et al., 2019), or sowing combined with various additional treatments (Török et al. 2012; Pawluśkiewicz et al., 2019; Havrilla et al., 2020).

88 In our study, we compared the restoration effectiveness of two mechanical harvesting techniques increasingly used in mountain grassland restoration: the transfer of brush-harvested seed material and the transfer of dry hay both collected from the same donor site located close to the degraded grasslands. The brush harvester strips and aspirates the plant material without cutting (Scotton et al., 2012). The harvested brush material comprises seeds but also vegetative parts of fruits and, to a lesser degree, other vegetative material. Low-growing and less abundant species may be under-represented in this material (Edwards et al., 2007; Scotton et al., 2009; Wagner et al., 2020), but brush harvesting allows concentrating seeds thus reducing humidity and facilitating storage. It also reduces the mulch layer that may hamper germination (Mollard et al., 2014). Dry hay transfer involves cutting of plant material close to the soil surface, drying it on the field before storage and spreading it on the restoration site. The higher vegetative biomass compared with brush material may hamper germination but protects seedlings against high solar radiation, drought and soil erosion (Eckstein & Donath, 2005; Graiss & Krautzer, 2011; Havrilla et al., 2020).

102 As seedling recruitment and establishment are important constraints in semi-natural grassland restoration (Öster et al., 2009), we also tested whether simultaneous transfer of brush material and sowing of an annual plant species may compensate for the absence of a protecting mulch layer. Such annuals provide temporary living cover that may facilitate seedling recruitment and establishment (Padilla et al., 2006; Wright et al., 2014). Similarly to hay mulch, a living cover may, however, increase root and light competition (Donath et al., 2006). We tested a mix of two lowland varieties of common wheat *Triticum aestivum* as a facilitative species. These varieties were expected to disappear within a couple of years since climatic
conditions of our mountain study sites limit their seed production and self-sowing. *Triticum*
cover may reduce soil erosion, an important criterion for the functionality of restoration
measures. Such soil stabilisation and erosion control are particularly important in mountain
grasslands on slopes facing a high risk of soil loss and propagule run-off (Huc et al., 2018;
Scotton, 2019).

In order to understand the underlying mechanisms of seedling recruitment and
establishment, we analysed first-year seedling abundance and second-year cover, respectively.
To determine which technique is the most appropriate in mountain grassland restoration, we
addressed the following questions: (1) Which method of plant material transfer is most
successful in establishing species transferred from the donor community? (2) Does sowing of
wheat improve the seedling establishment of brush material? (3) Do transfer techniques and
wheat sowing increase the similarity between restored and reference communities? (4) What
is the influence of these treatments on soil erosion?

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125 2. Material and methods

126 2.1. Study area

127 The study area was the upper Durance valley in the Southern French Alps. The five selected
128 restoration sites were degraded by the construction of a high-voltage transmission line
129 involving the creation of access tracks and working platforms. The construction work locally
130 destroyed the vegetation and affected the soil structure. The study zone extends over about
131 100 km, from L'Argentière-la-Bessée in the north to La-Bâtie-Neuve in the south (44°78'78"N,
132 6°59"41'E; 44°57'93"N, 6°20"77'E). The study sites are located on slopes above the Durance
133 valley, at an elevation of 1060 m to 1320 m above sea level. They are characterised by a
subcontinental climate, with an average annual temperature of 8.7°C and an annual rainfall of 740 mm (Embrun meteorological station, annual temperature corrected for an altitudinal difference of roughly 2°C). Dry to mesophilic grasslands occur at sites managed by grazing or mowing. Most of these surrounding non-degraded grasslands are priority habitats of Natura 2000: "Semi-natural dry grasslands of Festuco-Brometalia and scrubland facies on limestone" (N6210, European habitat directive 92/43/EEC; Calaciura & Spinelli, 2008). The five restoration sites used for the experiments were former access tracks and working platforms, and restoration goal was the re-establishment of typical Festuco-Brometalia grasslands. Traditional management by grazing was re-introduced.

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## 2.2. Donor and reference sites

One typical non-degraded Mesobromion grassland of the study area was chosen as donor site for harvesting plant material. The site was located in Freissinières (44°73'61"N; 6°56'72"E) at an elevation of 1100 m and a 3° south-west-facing slope. Two harvest techniques were applied, brush harvesting and traditional haymaking. The brush material was harvested on 13 July 2018 using a brush harvester mounted on a quad and equipped with an integrated vacuum system. On a surface of 4000 m², 2.6 kg of brush material was obtained. The harvested material comprised seeds (60 % of total mass) and vegetative parts (40 %). Seeds were counted in 10 subsamples of 0.5 g harvested material revealing an average density of 887 seeds/g. Hay was cut at 15 July 2018 on an additional area of 800 m² at the same donor site using a rotary mower. Harvest conditions were dry and warm without rainfall during the previous days. The hay was dried for two days on the harvested grassland and was baled in five bales of 7.5 kg (45 × 30 × 75 cm) for a total of 37.5 kg, with approximately 1 % of seeds in the total raw material. Brush
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material and hay were kept for three months at room temperature under dry and dark conditions.

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Although the donor site reflected the medium environmental conditions of the five restoration sites we identified “best references” for each site to evaluate restoration success.

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Since best reference sites are not always the closest ones (Durbecq et al., 2020), we surveyed eighteen non-degraded grasslands along the new electricity line. These potential references included the donor site and were located at the same altitudinal belt as restoration sites (1000 – 1400 m). Soil and microclimatic conditions measured at restoration sites and potential reference communities were used to identify the best references of each restoration site according to Durbecq et al., (2020, methodology).

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## 2.3. Experimental design

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At the five restoration sites, we repeated the following five treatments in 4 m × 4 m plots: control without hay or brush material transfer ('Control'), hay transfer ('Hay'), brush material transfer ('Seed'), wheat sowing ('Triticum') and both brush material and wheat seed addition together ('Triticum + Seed'). The restoration sites that were already colonized by spontaneous vegetation (mainly *Chenopodium album* L. and *Atriplex patula* L.) were mown before the set-up of the experiments and they were then extensively grazed in spring and autumn. The position of the five treatments was randomised within sites.

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In October 2018, 6.5 g/m² of harvested brush material was spread in the brush material treatments, corresponding to 3.75 g/m² of seed and 5765 seeds/m². The chosen seed density is a little higher than recommended for lowland grasslands and lower than usually sown in alpine grasslands (Kiehl et al., 2010; Scotton et al., 2012; Koch et al., 2015). The brush material

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180 was pressed to the ground using a lawn roller. In the hay transfer treatment, a bale of hay of 181 7.5 kg was spread (0.5 kg/m²) on each plot. The amount of hay was adjusted to an estimated 182 seed content of 1% (Scotton et al., 2012) corresponding to roughly 5 g/m² of seeds. The hay 183 was pressed to the ground by the wheels of tractor in order to maintain hay on the ground. The 184 sown wheat treatment was a mixture of two local lowland winter wheat (Triticum aestivum) 185 varieties, "Meunier d'Apt" and "Saissette de Provence". These early lowland varieties are not 186 well adapted to high altitude resulting in low seed production and a rapid decline during 187 mountain grassland succession. The seed density was adjusted to 9 g/m². Like for the brush 188 material transfer, a lawn roller was used to improve seed adhesion to the ground. Controls 189 were not sown but they were also rolled.

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## 2.4. Data collection

### 2.4.1. Vegetation surveys in donor and reference grasslands

193 In the donor grassland, vegetation surveys were conducted on 29 June 2018, and the 194 occurrence of mature seeds was evaluated for each plant species at the harvest date. Surveys 195 were used to establish a list of 37 potentially transferred species (hereafter: transferred 196 species). The vegetation surveys of the eighteen potential reference sites were conducted 197 between 21 June and 5 July 2018 by visual estimation of plant cover for each species in quadrats 198 of 2 m × 2 m. In the donor grassland, five quadrats were sampled, and three in each of the 199 other potential reference grasslands. Additionally, we monitored seed maturity in each plant 200 species at the day of harvest.

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### 2.4.2. Germination test in a greenhouse
203 In November 2018, brush material and hay were spread in an unheated greenhouse to evaluate
204 and compare the germination potential of seeds in brush material and hay. Harvested brush
205 material and dry hay were sown to ten trays (0.03 m²) filled with standard potting soil substrate
206 (mixture of 1/3 vermiculite and 2/3 of sterile peat). Five trays received 0.54 g of brush material
207 corresponding to 18g/m² of seeds, and five trays received 12.5 g of hay corresponding to 4
208 g/m² of seed material according to an estimated seed content of 1%. The trays were regularly
209 watered, and germinations identified and removed until April 2019.

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211 **2.4.3. Seedling abundance and vegetation surveys in grasslands under restoration**

212 To measure seedling abundance, plant number was counted in three quadrats of 40 x
213 40 cm placed along the diagonal of each plot in June 2019, at the five restoration sites. Since it
214 was not possible to distinguish seedlings and plants re-sprouting from belowground organs, the
215 seedling counts may include stems or ramets of vegetative regeneration. We considered all
216 reproducing plant species of the donor site as transferred although some of them also occurred
217 in the control plots of sites under restoration, indicating their presence in the soil seed bank or
218 seed rain. In June 2020, the cover of plant species was measured following the same protocol
219 as in the potential reference grasslands: in each plot, one quadrat of 2 m x 2 m was sampled.

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221 **2.4.4. Erosion monitoring**

222 To evaluate the effect of the different treatments on soil erosion, we measured erosion
223 according to Feret & Sarrailh (2005) at four restoration sites (at one site, the permanent points
224 were accidentally removed in autumn 2019 not allowing any analysis). The device comprised a
225 1.5 m long aluminium bar and two 0.5 m long iron poles fixed in the ground of each plot. These
226 iron poles were the permanent points of the measurements. They were adjusted to provide a
227 horizontal support for the aluminium bar before measurements. Vertical holes were drilled in
228 the centre of the aluminium bar every 10 cm resulting in a total of 13 regularly spaced holes
229 (Fig. S1). To take the erosion measurements, a graduated rod was introduced in each of the
230 holes. The scale of the graduated rods allowed a direct measurement of the space between the
231 aluminium bar and the ground. An increase in space between measurements indicates erosion
232 whereas a decrease suggests an accumulation of soil. Measurements were taken in June 2019,
233 October 2019, June 2020 and September 2020, in order to assess the effect of restoration
234 treatments on soil erosion.
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236 **2.5. Data analysis**

237 We used plant abundance, cover and richness of the entire plant community and of
238 transferred species to run statistical tests and to calculate restoration indices. Major soil and
239 microclimatic variables of restoration sites and potential reference sites were fitted to
240 multivariate models (NMDS) to identify the best references of each restoration site. The
241 identification was based on dissimilarity coefficients using Euclidean distances and is detailed
242 in Durbecq et al., (2020). We compared restoration sites and these best reference sites using
243 the restoration indices CSII<sub>norm</sub> (normalized Community Structure Integrity Index) and HAI
244 (Higher Abundance Index). The CSII allows measuring which proportion of the species
245 abundance of the reference communities is represented in the restored communities, and the
246 HAI evaluates the proportions of the species abundance in the restored communities that are
247 higher than in the reference communities (Jaunatre et al., 2013).
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We ran linear and generalized mixed models with transfer treatments as fixed effect and site as random effect to analyse response variables (including restoration indices) to the restoration treatments. In the analyses of plant abundance, quadrat within treatment was additionally included as a random effect. Plant cover, species richness and restoration indices were normally distributed and thus analysed using a Gaussian distribution with identity link. Plant abundance was fitted using a Poisson distribution with log-link function. In the case of a significant treatment effect, pairwise comparisons were used to compare differences between transfer techniques (glht function in multcomp package; Hothorn et al., 2008).

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A NMDS (Non-Metric Multidimensional Scaling) based on Bray-Curtis similarity was applied to compare plant species composition of the five restoration sites and their best reference sites. A Permutational Multivariate Analysis of Variance (PERMANOVA) was used to analyse whether the community composition was significantly different between treatments (R package "vegan"). All analyses were performed using R 3.5.3 (R Core Team 2019).

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## 3. Results

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The greenhouse tests revealed a mean density of 197.4 viable seeds/g in the brush harvest material and 2.4 viable seeds/g in the hay. This corresponds to a comparable density of 1283 viable seeds per m² and 1200 viable seeds per m² transferred with brush material and hay to the restoration sites, respectively.

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### 3.1. Effects of transfer techniques and wheat sowing on target species establishment
270 Seedling emergence of transferred species was only 50/m² (without wheat) to 65/m² (with wheat) in the brush material transfer and 200/m² in the hay transfer corresponding to 4%, 5% of the number of transferred viable seeds, respectively. Transferred species abundance was significantly different between the restoration treatments (χ² = 51.85, df = 4, P < 0.001; Fig. 1). We found the clearly highest density of transferred species in the 'Hay' treatment although seed density was similar to brush material according to germination tests.
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276 The 'Seed' treatment involving brush material transfer without wheat addition was neither significantly different to the control nor to the 'Triticum' treatment. Transferred seedling abundance in the combined 'Triticum + Seed' treatment was significantly higher than in the control but lower than in the 'Hay' treatment.
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<figure><img src="image_2.png" /></figure>

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281 **Fig. 1.** Effect of seed transfer techniques on the abundance of transferred species estimated in quadrats of 40 × 40 cm in 2019. Error bars represent ±SE and different letters indicate significant differences between treatments (P < 0.05).
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The treatments also had a significant effect on the second-year cover of transferred species ($\chi^2$ = 16.28, df = 4, P = 0.002; Fig 2.a). However, the strongly positive effect of the 'Hay' treatment vanished and the difference to the control was not significant any more. Transferred species cover was significantly higher in the combined 'Triticum + Seed' treatment than in the 'Seed' and 'Triticum' treatments whereas all other treatments were not significantly different.

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Similarly to transferred species cover (Fig. 2.a), richness of transferred species varied significantly between treatments ($\chi^2$ = 19.65, df = 4, P < 0.001; Fig. 2.b). The 'Seed' treatment was again only significantly different from the control if combined with wheat sowing ('Triticum + Seed'). Contrary to transferred species cover but in line with first-year abundance, species richness was significantly higher in the 'Hay' treatment than in the control. The 'Hay' and the combined 'Triticum + Seed' treatments comprised on average seven more transferred species (± 3 species) than the control. The 'Seed' treatment without wheat sowing was not significantly different from the control or the 'Triticum' treatment. Similar treatment effects were visible for the total species richness (Fig. S2). However, only the difference between the combined 'Triticum + Seed' treatment and the control was significant.

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<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Effect of seed transfer techniques on (a) transferred species cover, and (b) transferred species richness, both based on 2020 cover values and estimated in quadrats of 2 × 2 m. Error bars represent ±SE and different letters indicate significant differences between treatments (P < 0.05).</figcaption></figure>

**3.2. Comparison with best references of each restoration site**

The plant species composition of the restoration sites was very different from that of reference sites in all treatments (Fig. 3). Restoration and reference sites were particularly separated on the first axis. This axis represented a disturbance gradient with annual and ruderal species occurring on the left together with restoration sites (*Arctium minus* (Hill) Bernh., *Polygonum aviculare* L., *Anisantha sterilis* (L.) Nevski, etc.) and perennial grassland species on the right together with reference sites (*Stipa pennata* L., *Helianthemum nummularium* (L.) Mill., *Pilosella officinarum* F.W.Schultz & Sch.Bip., etc.). The differences between reference sites reflect the heterogeneity of plant communities according to different environmental conditions that are independent of degradation. They were particularly separated on the second NMDS
axis representing a productivity gradient from stony, xeric sites in the lower part of the biplot
to more humid, mesophilic sites in the upper part. There was a large overlap between the five
treatments within restoration sites, but the treatment effect was still significant (F = 1.432, df
= 4, P = 0.012). As expected, the unsown control showed the greatest distance to the
references. The ‘Hay’ and ‘Triticum + Seed’ treatments were closest to the reference sites,
followed by the ‘Seed’ treatment without wheat. However, the latter treatment was not much
closer to the reference communities than wheat sowing alone. The ‘Triticum’ treatment
showed the highest variation between sites resulting in a large NMDS polygon.

<figure><img src="image_4.png" /><figcaption>Fig. 3. NMDS of plant species composition in the five transfer technique treatments compared to plant species composition in the best reference for each restoration site previously identified in Durbecq et al., (2020). Polygons indicate the position of the outmost plots in each treatment (stress = 0.20). Different symbols indicate the five different restoration sites and corresponding</figcaption></figure>
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references: ● and ○ for sites corresponding to reference n°16 (same reference for the two
restoration sites), ■ to reference n°12, ❌ to reference n°6, and ▲ to reference n°9.

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The CSII<sub>norm</sub> calculated for each restoration site compared with their respective best reference showed a significant difference between treatments (χ<sup>2</sup> = 18.02, df = 4, P < 0.01; Fig. 4.a and 5). CSII<sub>norm</sub> was significantly higher in the combined 'Triticum + Seed' treatment than in the control, the 'Triticum' and the 'Seed' treatments. The 'Hay' treatment was not significantly different from other treatments.

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The HAI was also significantly different between treatments (χ² = 11.44, df = 4, P < 0.05, Fig. 4.b and 5). The lowest HAI was found in the 'Seed' treatment being significantly lower than the control and the 'Triticum' treatment, indicating significantly lower non-target abundances in the 'Seed' treatment. Differences between other treatments were not significant.

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<figure><img src="image_5.png" /></figure>

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Fig. 4. (a) CSII<sub>norm</sub> and (b) HAI, comparing the plant communities of transfer technique treatments of each restoration site with their respective best reference site. Error bars

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347 represent ±SE and different letters indicate significant differences between treatments (P < 0.05).

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The significant differences in CSII<sub>norm</sub> were explained by a higher number of target species in the 'Hay' and in the combined 'Triticum + Seed' treatments compared to the other treatments. Target species were those occurring in the best references such as *Plantago media* L., *Festuca cinerea* Vill., *Teucrium chamaedrys* L., *Poa pratensis* L., *Hippocrepis comosa* L., *Lotus corniculatus* L., *Silene vulgaris* (Moench) Garcke, *Eryngium campestre* L., *Poterium sanguisorba* L. and *Trifolium pratense* L. (Fig. 5). In the 'Hay' and the 'Triticum + Seed' treatments, the cover of several target species was even higher than in the references, (e.g. *Poterium sanguisorba* L., *Medicago lupulina* L., *Trifolium repens* L., *Trifolium pratense* L., *Convolvulus arvensis* L.).

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Alyssum alyssoides *
Stachys recta *
Potentilla reptens *
Convolvulus arvensis
Melliflorus officinale
Lappula squarrosa
Polygonum aviculare
Echinops ritro
Trifolium pratense *
Lactuca serriola
Veronica arvensis
Onobrychis viciifolia *
Arenaria serpyllifolia *
Trifolium repens
Medicago lupulina
Galium mollugo agg.
Ranunculus bulbosus *
Schedonorus arundinaceus *
Plantago lanceolata *
Pimpinella saxifraga *
Taraxacum officinale agg. *
Poterium sanguisorba
Daucus carota
Achillea millefolium *
Eryngium campestre
Tragopogon pratensis
Silene vulgaris *
Lotus corniculatus *
Galium verum
Hippocrepis comosa
Knautia arvensis *
Festuca marginata *
Poa pratensis *
Teucrium chamaedrys
Festuca cinerea
Dactylis glomerata *
Salvia pratensis *
Anthyllis vulneraria
Plantago media *
Rhinanthus alectorolophus *
Bromopsis erecta *

Species Reference Control Hay Seed Triticum + Seed Triticum

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>
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Fig. 5. Mean target plant cover of abundant species (> 9 samples, 41 of 259 species in total) in restoration treatments and the best reference community. Different colours represent the mean cover proportion in references (black), the mean cover proportion in communities under restoration up to the mean cover in the reference communities (green), and the mean cover proportion exceeding that of the reference communities (orange). Asterisks indicate transferred species. For readability, the x-axis is limited to 10 % cover (only *Bromopsis erecta* (Huds.) Fourr., *Schedonorus arundinaceus* (Schreb.) Dumort. and *Galium molugo* agg. exceeded).

### 3.3. Ecosystem function: erosion control

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Erosion monitoring did not show significant treatment effects at the end of the observation period. Lowest erosion was observed in the 'Hay' treatment but due to high between-site variation the difference to other treatments was not significant (Fig. 6). Intermediate measurements demonstrated a high temporal variability of erosion and of treatment effects on erosion (Fig. S3).
<figure><img src="image_9.png" /><figcaption>Fig.6. Effect of seed transfer techniques on soil erosion. Error bars represent ±SE. Positive values show higher erosion, thus a lesser amount of material on the ground 14 months after the beginning of the experiment.</figcaption></figure>

## 4. Discussion

Both techniques, brush-harvested propagule transfer and hay transfer, allowed the introduction of high numbers of viable seeds. However, first-year seedling recruitment was much higher in hay transfer than in brush material transfer. Additional wheat sowing had a particularly positive effect on seedling establishment from brush material resulting in a second-year cover of transferred species similar to that of hay. Brush material transfer alone did neither increase transferred species cover nor plant species richness. According to transferred species abundance and cover, hay transfer and brush material transfer combined with wheat sowing were also most successful in restoring the plant species composition of the reference. Soil erosion was not affected by any restoration treatments.
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## 4.1. Effect of seed-addition techniques on transferred species recruitment

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Brush harvesting has many technical advantages compared to hay cutting allowing selection and cleaning of seeds, drying and particularly easy storage (lower volume than hay) under optimum temperature and humidity (Edwards et al., 2007; Vitis et al., 2020; Frischie et al., 2020). Contrary to hay cutting, it is possible to brush-harvest several times a season thus maximizing the number of transferred species (Edwards et al., 2007; Scotton & Ševčíková, 2017). The possibility to use grasslands for hay making after brush harvesting is another advantage reducing losses for livestock farmers. However, several studies obtained a low efficiency in plant establishment from brush material compared to hay transfer (Edwards et al., 2007; Sengl et al., 2017; Albert et al., 2019). Albert et al., (2019) explained the lower seed number per harvested area by the higher working height of brushes compared to mowing machinery missing the seeds of low-growing species.

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In our study, the brush material contained as many viable seeds as the hay suggesting that the low recruitment compared to hay transfer was due to lower germination and seedling survival. The mulch layer resulting from hay transfer may improve seedling recruitment of transferred species through an increase in soil moisture retention (Donath et al., 2007; Mollard et al., 2014; Havrilla et al., 2020). Soil moisture retention and temperature buffering are important factors influencing germination in our study region characterized by shallow soils, spring frosts and high solar radiation. Furthermore, hay mulch protects seeds from predation, and animal trampling (Scotton et al., 2012; Vanderburg et al., 2020) and limits competition of ruderal species in early stages of grassland restoration (Kiehl & Wagner, 2006). Additionally, a hay layer may reduce surface runoff (Graiss & Krautzer, 2011) and improve seed adherence to
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the soil (Chambers, 2000; Havrilla et al., 2020). High recruitment in the hay transfer treatment suggests that such positive effects prevailed in our study over negative effects of a mulch layer on transferred species establishment, such as light limitation (Eckstein & Donath, 2005). Such mulch effects are highly species-specific (Sonkoly et al., 2020), and in our study the mulch layer had most likely an indirect positive effect on target species by having a direct negative effect on ruderal species. Furthermore, a mulch layer may stronger limit light availability of seeds in the soil (spontaneous, mostly ruderal species) than of seeds of transferred species that remain at the soil surface or even in upper mulch layers.

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Effects of temporary wheat cover on seedling recruitment may be similar to hay mulch effects, such as protection against drought and solar radiation (Wright et al., 2014). Additionally, belowground effects may facilitate seedling recruitment and establishment since wheat roots stabilize the soil and foster the recolonization of the soil fauna (Faivre 2000). In modifying soil structure and composition (Pohl et al., 2009; Liu et al., 2018), wheat can be considered as a nurse crop (Padilla et al., 2006). Many high-altitude restoration studies aimed at improving recruitment conditions and reducing soil erosion using nurse species or wheat straw addition to stabilize the soil (Graiss & Krautzer, 2011; Kavian et al., 2018; Scotton, 2019).

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However, propagule run-off, germination and early survival are less likely affected by wheat sowing than by hay mulch since wheat cover develops later. In our study, this was probably the reason for an absence of a wheat sowing effect on first-year abundance of species transferred with brush material whereas the effect on second-year cover was strongly positive. Like hay transfer, facilitative effects of wheat sowing prevailed over negative effects of competition for light and water observed in other studies on additional sowing (Donath et al., 2006; Wright et al., 2014).
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Soil preparation before sowing has often been recommended to improve seedling recruitment in sowing of brush-harvested seeds or seed mixtures (Kiehl et al., 2010; Edwards et al., 2007; Klaus et al., 2017; Shaw et al., 2020). Similarly to hay mulch, soil preparation increases seed and water retention as well as seed adhesion (Chambers, 2000) and may thus compensate for the absence of a hay mulch layer limiting seed run-off. In our study area, a previous experiment testing soil preparation effects on seedling recruitment showed a strong increase in first-year abundance of transferred species (Durbecq et al., 2021). Thus, the plots that received brush material in our study may particularly benefit from previous soil tillage and a combination with additional wheat sowing may be the optimum strategy for seedling recruitment and establishment.

## 4.2. Successful restoration of reference communities and erosion protection

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Seed addition using brush material and hay of the donor site was successful in increasing the similarity to best references at plant community level. As in the analysis of cover and number of species transferred from the donor site, best restoration results were obtained for hay transfer and the combination of brush material with wheat sowing, showing highest similarity to references in plant species composition and highest target abundance (higher CSII<sub>norm</sub> = abundance of species occurring in the reference). This finding confirmed that a dead (hay) or living (wheat) "nurse cover" improves seedling establishment of target (reference communities) and transferred (donor community) species (Graiss & Krautzer, 2011; Kavian et al., 2018; Scotton, 2019). The brush material transfer without wheat sowing did not increase similarity to references nor target abundance. However, HAI (proportion of non-target abundances) of this treatment was lower compared to the control whereas the HAI of brush
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material with wheat and hay transfer were not significantly different from the control. These
results indicated that hay mulch and wheat cover did not only provide better conditions for
target species but also for non-target species recruitment.

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In mountain and alpine grasslands with more or less steep slopes, soil stabilization
processes are slow, which increases soil erosion (Wiesmair et al., 2017). Erosion control is thus
essential to restore these ecosystems (Pohl et al., 2009; Scotton, 2019; Löbmann et al., 2020).

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Without plant cover, erosion, depletion of organic matter and gully formation may compromise
restoration approaches (Dupin et al., 2019). Several authors have shown a negative linear
relationship between vegetation cover and soil runoff (Peratoner, 2003; Liu et al., 2018; Gu et
al., 2020). Hence, immediate revegetation by locally adapted propagules is widely

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recommended (Scotton et al., 2009; Wiesmair et al., 2017; Dupin et al., 2019). Using well-adapted temporary nurse crop may have a stronger positive effect on soil erosion control than dead plant material, such as hay or straw, since developing roots allow a belowground stabilisation of the soil (Pohl et al., 2009). According to Liu et al., (2018) and Gu et al. (2020), an average total vegetation cover of 60 % observed in our study may reduce soil erosion by up to 80 % compared to bare soil. However, our restoration treatments did not sufficiently influence total plant cover compared to control and thus the treatment effect on soil erosion was not significant. Run-off at several places may have been compensated by sediment accumulation in others without changing the overall erosion measurement. To analyse erosion and sediment accumulation within plots in detail combined sediment-runoff collection systems may be used with water collection and storage tanks being placed at the down slope side (Parsons et al., 2006; Phan Ha et al., 2012).

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Contrary to our results, Kavian et al. (2018) found a long-term reduction in soil runoff using wheat residual as agriculture mulch. Our restoration sites were not characterized by steep slopes, thus limiting soil run-off and the probability to find differences between treatments. Additionally, spontaneous vegetation emerging from the soil seed bank dominated in the beginning limiting the treatment effect.

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## 5. Conclusions

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All applied transfer techniques were successful in establishing plant species of the donor community. However, the transfer of brush harvested seed material was only efficient together with wheat sowing. Our results demonstrated that restoration of grasslands of the mountain altitudinal belt with shallow and stony soils clearly benefit from dead (hay) or living (wheat) vegetation cover providing a nurse effect. Facilitation effects prevail over competition and/or reduction in resources such as light (Eckstein & Donath, 2005; Padilla et al., 2006; Wright et al., 2014). Hay transfer was the best method to increase germination and seedling recruitment but the difference to brush material transfer with wheat sowing vanished in the second year indicating higher seedling mortality in the hay mulch (Eckstein & Donath, 2005). The lower seedling recruitment in brush material transfer may be compensated by harrowing the soil before brush material transfer to improve recruitment conditions (Kiehl et al., 2010; Klaus et al., 2017; Durbecq et al., 2021). Propagule transfer did not improve the soil erosion control. Short-lived species spontaneously emerging from the soil seed bank dominated in the beginning reducing the magnitude of treatment effects. Long-term monitoring is required to evaluate the replacement of short-lived ruderals by the transferred perennial species often observed in restoration studies (Albert et al., 2019; Kiss et al., 2020; Shaw et al., 2020).
517

518

519 **Funding**

520 Financial support was provided by RTE (Electricity Transmission Network), the environmental

521 consultancy ECO-MED and ANRT (National Agency of Research and Technology) via a grant

522 CIFRE N° 2017 / 0478.

523

524 **Declaration of competing interest**

525 The authors declare that they have no competing interests.

526

527 **Acknowledgements**

528 We thank Alexandre Cluchier for accompanying and supporting the project. Many thanks to

529 Daniel Pavon for help in seedling identification. We also thank Tiago Toma and Christel Vidaller

530 for their precious comments on design and analyses as well as Margaux d'Ambly and Chloé

531 Malik for field assistance.

532

533 **Appendix 1. Supplementary material**

534

535 **ORCID**

536 Aure Durbecq https://orcid.org/0000-0002-9201-1916
537 Léo Rocher https://orcid.org/0000-0003-0122-1588

538 Renaud Jaunatre https://orcid.org/0000-0001-6970-8304

539 Alice Dupré la Tour http://orcid.org/0000-0001-8713-6514

540 Elise Buisson https://orcid.org/0000-0002-3640-8134

541 Armin Bischoff https://orcid.org/0000-0003-2865-8720

542

543 References

544 Albert, Á.-J., Mudrák, O., Jongepierová, I., Fajmon, K., Frei, I., Ševčíková, M., Klimešová, J., &
545 Doležal, J. (2019). Grassland restoration on ex-arable land by transfer of brush-harvested
546 propagules and green hay. Agriculture, Ecosystems & Environment, 272, 74–82.
547 https://doi.org/10.1016/j.agee.2018.11.008

548 Amiaud, B., & Carrère, P. (2012). Grassland multifunctionality in providing ecosystem services.
549 *Fourrages*, No. 211, 229–238. https://www.cabdirect.org/cabdirect/abstract/20123387519

550 Auestad, I., Austad, I., & Rydgren, K. (2015). Nature will have its way: local vegetation trumps
551 restoration treatments in semi-natural grassland. *Applied Vegetation Science*, 18(2), 190–196.
552 https://doi.org/10.1111/avsc.12138

553 Blair, J., Nippert, J., & Briggs, J. (2014). Grassland Ecology. In R. K. Monson (Ed.), *Ecology and
the Environment* (pp. 389–423). Springer. https://doi.org/10.1007/978-1-4614-7501-9_14

555 Bucharova, A., Bossdorf, O., Hölzel, N., Kollmann, J., Prasse, R., & Durka, W. (2019). Mix and
match: regional admixture provenancing strikes a balance among different seed-sourcing
557 strategies for ecological restoration. *Conservation Genetics*, 20(1), 7-17.
558 https://doi.org/10.1007/s10592-018-1067-6

559 Calaciura, B., & Spinelli, O. (2008). Management of Natura 2000 habitats. 6210 Semi-natural dry grasslands and scrubland facies on calcareous substrates (Festuco-Brometalia) (*important orchid sites). European Commission.
560
561
562 https://ec.europa.eu/environment/nature/natura2000/Seminatural_dry_grasslands.pdf

563 Chambers, J.-C. (2000). Seed movements and seedling fates in disturbed steppe ecosystems: implications for restoration. *Ecological Applications*, 10(5), 1400-1413.
564
565 https://doi.org/10.1890/1051-0761(2000)010[1400:SMASFI]2.0.CO;2

566 Donath, T.-W., Bissels, S., Hölzel, N., & Otte, A. (2007). Large scale application of diaspore transfer with plant material in restoration practice – Impact of seed and microsite limitation.
567
568 *Biological Conservation*, 138(1-2), 224-234. https://doi.org/10.1016/j.biocon.2007.04.020

569 Donath, T.-W., Hölzel, N., & Otte, A. (2006). Influence of competition by sown grass, disturbance and litter on recruitment of rare flood-meadow species. *Biological Conservation*, 130(3), 315-323. https://doi.org/10.1016/j.biocon.2005.12.022

572 Dupin, B., Malaval, S., Coueron, G., Cambecedes, J. et Largier, G. (2019). Restauration écologique de prairies et de pelouses pyrénéennes ? Un guide technique pour régénérer les sols et les végétations dégradés en montagne. Conservatoire botanique national des Pyrénées et de Midi-Pyrénées, Bagnères-de-Bigorre. 177p.
573
574
575
576 http://cbnmc.fr/pmb/opac_css/doc_num.php?explnum_id=5835
577 Durbecq, A., d'Ambly, M., Buisson, E., Jaunatre, R., Cluchier, A., & Bischoff, A. (2021). Seedling recruitment in mountain grassland restoration: Effects of soil preparation and grazing. *Applied Vegetation Science*. 24, e12564. https://onlinelibrary.wiley.com/doi/abs/10.1111/avsc.12564

580 Durbecq, A., Jaunatre, R., Buisson, E., Cluchier, A., & Bischoff, A. (2020). Identifying reference communities in ecological restoration: the use of environmental conditions driving vegetation composition. *Restoration Ecology*, 28(6), 1445-53. https://doi.org/10.1111/rec.13232

583 Eckstein, R.-L., & Donath, T.-W. (2005). Interactions between litter and water availability affect seedling emergence in four familial pairs of floodplain species. *Journal of Ecology*, 93(4), 807–816. https://doi.org/10.1111/j.1365-2745.2005.01015.x

586 Edwards, A.-R., Mortimer, S.-R., Lawson, C.-S., Westbury, D.-B., Harris, S.-J., Woodcock, B.-A., & Brown, V.-K. (2007). Hay strewing, brush harvesting of seed and soil disturbance as tools for the enhancement of botanical diversity in grasslands. *Biological Conservation*, 134(3), 372–382. https://doi.org/10.1016/j.biocon.2006.08.025

590 Faivre, P. (2000). Revégétalisation et sols reconstitués au niveau des pistes de ski. Bilan sommaire de 3 campagnes de terrain (97-99) et perspectives de recherche. Centre Interdisciplinaire Scientifique de la Montagne, Université de Savoie, Val Thorens, France.

593 Feret, J.-B., & Sarrailh J.-M. (2005). Utilisation d'un appareil de mesure simple, et précis, pour l'étude de l'érosion à Mayotte. *BOIS ET FORÊTS DES TROPIQUES*, 286(4), 29-40. https://agritrop.cirad.fr/528996/1/document_528996.pdf

596 Frischie, S., Miller, A.-L., Pedrini, S., & Kildisheva, O.-A. (2020). Ensuring seed quality in ecological restoration: Native seed cleaning and testing. *Restoration Ecology*, 28(S3), S239–S248. https://doi.org/10.1111/rec.13217
599

Graiss, W., & Krautzer, B. (2011). Soil Erosion and Surface Runoff on Slopes in Mountain

600

Environment Depending on Application Technique and Seed Mixture – A Case-Study. Soil

601

Erosion Studies. https://doi.org/10.5772/25124

602

Gu, C., Mu, X., Gao, P., Zhao, G., Sun, W., & Tan, X. (2020). Distinguishing the effects of

603

vegetation restoration on runoff and sediment generation on simulated rainfall on the

604

hillslopes of the loess plateau of China. *Plant and Soil*, 447, 393–412.

605

https://doi.org/10.1007/s11104-019-04392-4

606

Halassy, M., Singh, A.-N., Szabó, R., Szili-Kovács, T., Szitár, K., & Török, K. (2016). The application

607

of a filter-based assembly model to develop best practices for Pannonian sand grassland

608

restoration. *Journal of Applied Ecology*, 53(3), 765–773. https://doi.org/10.1111/1365-

609

2664.12618

610

Havrilla, C.-A., Munson, S.-M., McCormick, M.-L., Laushman, K.-M., Balazs, K.-R., & Butterfield,

611

B.-J. (2020). RestoreNet: An emerging restoration network reveals controls on seeding success

612

across dryland ecosystems. *Journal of Applied Ecology*, 57(11), 2191-2202.

613

https://doi.org/10.1111/1365-2664.13715

614

Hölzel, N., Buisson, E., & Dutoit, T. (2012). EDITORIAL: Species introduction -a major topic in

615

vegetation restoration. *Applied Vegetation Science*, 15(2), 161–165. JSTOR.

616

https://www.jstor.org/stable/41410183

617

Hothorn, T., Bretz, F., & Westfall, P. (2008). Simultaneous Inference in General Parametric

618

Models. *Biometrical Journal* 50(3), 346–363. https://doi.org/10.1002/bimj.200810425
619 Huc, S., Arlandis, J., Dupre la Tour, A., Rouillon, A., & Spiegelberger, T. (2018). SEM'LESALPES - Des semences d'origine locale pour la restauration de milieux ouverts en montagne alpine, Conservatoire Botanique National Alpin, Gap, 106p. https://hal.inrae.fr/hal-02608278

622 Jaunatre, R., Buisson, E., Muller, I., Morlon, H., Mesléard, F., & Dutoit, T. (2013). New synthetic indicators to assess community resilience and restoration success. *Ecological Indicators*, 29, 468-477. https://doi.org/10.1016/j.ecolind.2013.01.023

625 Kavian, A., Gholami, L., Mohammadi, M., Spalevic, V., & Soraki, M. F. (2018). Impact of Wheat Residue on Soil Erosion Processes. *Notulae Botanicae Horti Agrobotanici Cluj-Napoca*, 46(2), 553-562. https://doi.org/10.15835/nbha46211192

628 Kiehl, K., Kirmer, A., Donath, T.-W., Rasran, L., & Hölzel, N. (2010). Species introduction in restoration projects – Evaluation of different techniques for the establishment of semi-natural grasslands in Central and Northwestern Europe. *Basic and Applied Ecology*, 11(4), 285-299. https://doi.org/10.1016/j.baae.2009.12.004

632 Kiehl, K., & Wagner, C. (2006). Effect of Hay Transfer on Long-Term Establishment of Vegetation and Grasshoppers on Former Arable Fields. *Restoration Ecology*, 14(1), 157-166. https://doi.org/10.1111/j.1526-100X.2006.00116.x

635 Kiss, R., Deák, B., Tóthmérész, B., Miglécz, T., Tóth, K., Török, P., Lukács, K., Godó, L., Körmöczi, Z., Radócz, S., Kelemen, A., Sonkoly, J., Kirmer, A., Tischew, S., Švamberková, E., & Valkó, O. (2020). Establishment gaps in species-poor grasslands: artificial biodiversity hotspots to support the colonization of target species. *bioRxiv* 2020.01.23.916155. https://doi.org/10.1101/2020.01.23.916155
640

Klaus, V.-H., Schäfer, D., Kleinebecker, T., Fischer, M., Prati, D., & Hölzel, N. (2017). Enriching

641

plant diversity in grasslands by large-scale experimental sward disturbance and seed addition

642

along gradients of land-use intensity. *Journal of Plant Ecology*, 10(4), 581–591.

643

https://doi.org/10.1093/jpe/rtw062

644

Kövendi-Jakó, A., Halassy, M., Csecserits, A., Hülber, K., Szitár, K., Wrbka, T., & Török, K. (2019).

645

Three years of vegetation development worth 30 years of secondary succession in urban-

646

industrial grassland restoration. *Applied Vegetation Science*, 22(1), 138–149.

647

https://doi.org/10.1111/avsc.12410

648

Koch, E.-M., Spiegelberger, T., Barrel, A., Bassignana, M., & Curtaz, A. (2015). Les semences

649

locales dans la restauration écologique en montagne. Production et utilisation de mélanges

650

pour la préservation. Institut Agricole Régional, Rég. La Rochère 1/A, I-11100 Aoste.

651

http://www.iaraosta.it/wp-content/uploads/2017/08/Manuale-AlpGrain_FRA-EC.pdf

652

Liu, J., Gao, G., Wang, S., Jiao, L., Wu, X., & Fu, B. (2018). The effects of vegetation on runoff

653

and soil loss: Multidimensional structure analysis and scale characteristics. *Journal of*

654

*Geographical Sciences*, 28(1), 59–78. https://doi.org/10.1007/s11442-018-1459-z

655

Löbmann, M.-T., Tonin, R., Stegemann, J., Zerbe, S., Geitner, C., Mayr, A., & Wellstein, C. (2020).

656

Towards a better understanding of shallow erosion resistance of subalpine grasslands. *Journal*

657

*of Environmental Management*, 276, 111267. https://doi.org/10.1016/j.jenvman.2020.111267

658

Mollard, F.-P.-O., Naeth, M.-A., & Cohen-Fernandez, A. (2014). Impacts of mulch on prairie

659

seedling establishment: Facilitative to inhibitory effects. *Ecological Engineering*, 64, 377–384.

660

https://doi.org/10.1016/j.ecoleng.2014.01.012
661 Öster, M., Ask, K., Cousins, S.-A.-O., & Eriksson, O. (2009). Dispersal and establishment limitation reduce the potential for successful restoration of semi-natural grassland communities on former arable fields. *Journal of Applied Ecology*, 46(6), 1266–1274.
https://doi.org/10.1111/j.1365-2664.2009.01721.x

665 Padilla, F.-M., & Pugnaire, F.-I. (2006). The role of nurse plants in the restoration of degraded environments. *Frontiers in Ecology and the Environment, 4(4)*, 196–202.
https://doi.org/10.1890/1540-9295(2006)004[0196:TRONPI]2.0.CO;2

668 Parsons, A.-J., Brazier, R.-E., Wainwright, J. and Powell, D.-M. (2006). Scale relationships in hillslope runoff and erosion. *Earth Surf. Process. Landforms*, 31, 1384-1393.
https://doi.org/10.1002/esp.1345

671 Pawluśkiewicz, B., Janicka, M., & Piekut, K. (2019). Effects of Different Introduction Methods on Plant Species Establishment Success in Wet Grassland Restoration. *Polish Journal of Environmental Studies*, 28(3), 1857–1867. https://doi.org/10.15244/pjoes/81293

674 Peratoner, G. (2003). Organic seed propagation of alpine species and their use in ecological restoration of ski runs in mountain regions. PhD thesis. Kassel University Press, Kassel, Germany. 240 pp.

677 Phan Ha, H.-A., Huon, S., des Tureaux, T.-H., Orange, D., Jouquet, P., Valentin, C., De Rouw, A., & Duc, T.-T. (2012). Impact of fodder cover on runoff and soil erosion at plot scale in a cultivated catchment of North Vietnam. *Geoderma*, 177–178, 8-17,
https://doi.org/10.1016/j.geoderma.2012.01.031
681 Pohl, M., Alig, D., Körner, C., & Rixen, C. (2009). Higher plant diversity enhances soil stability in disturbed alpine ecosystems. *Plant and Soil*, 324(1), 91–102. https://doi.org/10.1007/s11104-009-9906-3

684 R Core Team (2019). R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria https://www.Rproject.org/

686 Scotton, M. (2019). Mountain grassland restoration: Effects of sowing rate, climate and soil on plant density and cover. *Science of The Total Environment*, 651, 3090–3098. https://doi.org/10.1016/j.scitotenv.2018.10.192

689 Scotton, M., Kirmer, A., & Krautzer, B. (2012). Practical handbook for seed harvest and ecological restoration of species-rich grasslands. Cooperativa Libraria Editrice Università di Padova. https://agris.fao.org/agris-search/search.do?recordID=US201300010888

692 Scotton, M., Piccinin, L., Dainese, M., & Sancin, F. (2009). Seed Harvesting for Ecological Restoration: Efficiency of Haymaking and Seed-Stripping on Different Grassland Types in the Eastern Italian Alps. *Ecological Restoration*, 27(1), 66–75. https://doi.org/10.3368/er.27.1.66

695 Scotton, M., & Ševčíková, M. (2017). Efficiency of mechanical seed harvesting for grassland restoration. *Agriculture, Ecosystems & Environment*, 247, 195–204. https://doi.org/10.1016/j.agee.2017.06.040

698 Sengl, P., Magnes, M., Weitenthaler, K., Wagner, V., Erdős, L., & Berg, C. (2017). Restoration of lowland meadows in Austria: A comparison of five techniques. *Basic and Applied Ecology*, 24, 19–29. https://doi.org/10.1016/j.baae.2017.08.004
701 Shaw, N., Barak, R.-S., Campbell, R.-E., Kirmer, A., Pedrini, S., Dixon, K., & Frischie, S. (2020).

702 Seed use in the field: Delivering seeds for restoration success. *Restoration Ecology*, 28(S3),

703 S276-S285. https://doi.org/10.1111/rec.13210

704 Sonkoly, J., Valkó, O., Balogh, N., Godó, L., Kelemen, A., Kiss, R., Miglécz, T., Tóth, E., Tóth, K.,

705 Tóthmérész, B., & Török, P. (2020). Germination response of invasive plants to soil burial depth

706 and litter accumulation is species-specific. *Journal of Vegetation Science*, 31, 1081–1089.

707 https://doi.org/10.1111/jvs.12891

708 Stoate, C., Báldi, A., Beja, P., Boatman, N.-D., Herzon, I., van Doorn, A., de Snoo, G.-R., Rakosy,

709 L., & Ramwell, C. (2009). Ecological impacts of early 21st century agricultural change in Europe

710 – A review. *Journal of Environmental Management*, 91(1), 22–46.

711 https://doi.org/10.1016/j.jenvman.2009.07.005

712 Török, P., Helm, A., Kiehl, K., Buisson, E., & Valkó, O. (2018). Beyond the species pool:

713 modification of species dispersal, establishment, and assembly by habitat restoration.

714 *Restoration Ecology*, 26, S65–S72. https://doi.org/10.1111/rec.12825

715 Török, P., Miglécz, T., Valkó, O., Kelemen, A., Tóth, K., Lengyel, S., & Tóthmérész, B. (2012). Fast

716 restoration of grassland vegetation by a combination of seed mixture sowing and low-diversity

717 hay transfer. *Ecological Engineering*, 44, 133-138.

718 https://doi.org/10.1016/j.ecoleng.2012.03.010.

719 Valkó, O., Zmihorski, M., Biurrun, I., Loos, J., Labadessa, R., & Venn, S. (2016). Ecology and

720 Conservation of Steppes and Semi-Natural Grasslands. *Hacquetia*, 15(2), 5–14.

721 https://doi.org/10.1515/hacq-2016-0021
722 Vanderburg, K.-L., Steffens, T.-J., Lust, D.-G., Rhoades, M.-B., Blaser, B.-C., Peters, K., & Ham, M.-J. (2020). Trampling and Cover Effects on Soil Compaction and Seedling Establishment in Reseeded Pasturelands Over Time. *Rangeland Ecology & Management, 73*(3), 452-461.
https://doi.org/10.1016/j.rama.2020.01.001

726 Vitis, M.-D., Hay, F.-R., Dickie, J.-B., Trivedi, C., Choi, J., & Fiegener, R. (2020). Seed storage: Maintaining seed viability and vigor for restoration use. *Restoration Ecology, 28*(S3), S249-S255.
https://doi.org/10.1111/rec.13174

729 Wagner, M., Hulmes, S., Hulmes, L., Redhead, J.-W., Nowakowski, M., & Pywell, R.-F. (2020). Green hay transfer for grassland restoration: species capture and establishment. *Restoration Ecology, n/a*(n/a).
https://doi.org/10.1111/rec.13259

732 Wiesmair, M., Otte, A., & Waldhardt, R. (2017). Relationships between plant diversity, vegetation cover, and site conditions: Implications for grassland conservation in the Greater Caucasus. *Biodiversity and Conservation, 26*(2), 273-291.
https://doi.org/10.1007/s10531-016-1240-5

736 Wilsey, B. (2020). Restoration in the face of changing climate: importance of persistence, priority effects, and species diversity. *Restoration Ecology, n/a*(n/a).
https://doi.org/10.1111/rec.13132

739 Wright, A., Schnitzer, S.-A., & Reich, P.-B. (2014). Living close to your neighbors: the importance of both competition and facilitation in plant communities. *Ecology, 95*(8), 2213-2223.
https://doi.org/10.1890/13-1855.1