Supporting Information for Plant diversity in hedgerows and road verges across Europe This document contains Table S1

(1)

Supporting Information for

Plant diversity in hedgerows and road verges across Europe

This document contains Table S1

^–

S13 and Fig. S1

^–

S9

(2)

Supplementary tables

Table S1. List of the 56 study sites (28 forest-hedgerow transects and 28 grassland-road verge transects), including geographical position (latitude, longitude).

Site code

Region Corridor type Site

no.

Latitude (°N) Longitude (°E)

FRH1 France Forest-hedgerow 1 49.943 3.839

FRRV1 France Grassland-road verge 1 49.913 3.885

BEH1 Belgium Forest-hedgerow 1 50.928 3.742

BERV1 Belgium Grassland-road verge 1 50.943 3.731

PLRV1 Poland Grassland-road verge 1 50.174 18.273

EGH1 Eastern Germany Forest-hedgerow 1 53.185 11.911

EGRV1 Eastern Germany Grassland-road verge 1 53.281 12.004 EGRV2 Eastern Germany Grassland-road verge 2 53.199 11.876 EGRV3 Eastern Germany Grassland-road verge 3 53.164 11.926 EGRV4 Eastern Germany Grassland-road verge 4 53.237 12.015

WGH1 Western Germany Forest-hedgerow 1 54.026 10.394

SSH1 Southern Sweden Forest-hedgerow 1 55.768 13.607

CSRV1 Central Sweden Grassland-road verge 1 59.060 17.148 CSRV2 Central Sweden Grassland-road verge 2 59.101 17.223 CSRV3 Central Sweden Grassland-road verge 3 58.948 17.437 Table S1. (continued)

(3)

Site code Region Corridor type Site no. Latitude (°N) Longitude (° E) CSRV4 Central Sweden Grassland-road verge 4 58.989 17.661

ESH1 Estonia Forest-hedgerow 1 58.528 26.890

ESRV1 Estonia Grassland-road verge 1 58.788 25.753

NOH1 Norway Forest-hedgerow 1 63.370 10.086

NORV1 Norway Grassland-road verge 1 63.416 10.150

(4)

Table S2. Complete list of all vascular plant species recorded across 336 vegetation plots in the understorey of the forest-hedgerow and grassland-road verge transects. For forests and hedgerows (Category 1), species were classified as forest specialists (S) and generalists (G) following Heinken (2019). For grasslands and road verges (Category 2), species were classified as semi-natural grassland specialists (S) or grassland generalists (G) according Ellenberg et al. (1991). Nomenclature follows Flora Europaea – The Euro+Med Plantbase Euro+Med 2006.

Name Category 1 Category 2

Acer campestre L. G G

Acer platanoides L. G G

Acer pseudoplatanus L. G G

Achillea millefolium L. G S

Achillea ptarmica L. G G

Aconitum septentrionale Koelle S G

Actaea spicata L. S G

Adoxa moschatellina L. S G

Aegopodium podagraria L. G G

Agrostis capillaris L. G S

Agrostis sp. G G

Agrostis stolonifera L. G G

Ajuga reptans L. G G

Alchemilla sp. G S

Allium oleraceum L. G G

Allium scorodoprasum L. G G

Allium vineale L. G G

Alnus incana (L.) Moench G G

Alopecurus pratensis L. G G

Anemone ranunculoides L. S G

Anemone nemorosa L. G G

Angelica archangelica L. G G

Angelica sylvestris L. G S

Anthoxanthum odoratum L. G G

Anthoxanthum sp. G G

Anthriscus sylvestris (L.) Hoffm. G G

Arctium lappa L. G G

Arctium minus (Hill) Bernh. G G

Argentina anserina (L.) Rydb. G G

Armeria maritima (Mill.) Willd. NA G

Arrhenatherum elatius (L.) J. Presl & C. Presl subsp. elatius G S

Artemisia vulgaris L. G G

Arum maculatum L. S G

Athyrium filix-femina (L.) Roth S G

Avenula pratensis (L.) Dumort. G G

Avenula pubescens (Huds.) Dumort. G G

Berteroa incana (L.) DC. NA G

(5)

Table S2. (continued)

Betula pendula Roth G G

Betula pubescens Ehrh. G G

Blechnum spicant (L.) Roth S G

Brassica napus L. NA G

Brachypodium sylvaticum (Huds.) P. Beauv. S G

Briza media L. G S

Bromus inermis Leyss. NA G

Bromus racemosus L. S S

Calamagrostis angustifolia Kom. G G

Calamagrostis arundinacea (L.) Roth G G

Calamagrostis canescens (Weber) Roth G G

Calamagrostis epigejos (L.) Roth G G

Calystegia sepium (L.) R. Br. G G

Calystegia sp. G G

Calamagrostis stricta (Timm.) Koeler G G

Campanula latifolia L. S G

Campanula persicifolia L. S G

Campanula rotundifolia L. G S

Campanula trachelium L. S G

Capsella bursa-pastoris (L.) Medik. S G

Carpinus betulus L. S G

Carum carvi L. NA S

Carex digitata L. S G

Cardamine flexuosa With. S G

Carex hirta L. G G

Cardamine impatiens L. S G

Carex pilulifera L. G S

Cardamine pratensis L. G S

Carex remota L. S G

Carex sp. G G

Carex spicata Huds. G G

Carex sylvatica Huds. S G

Centaurea jacea L. G S

Centaurea scabiosa L. G S

Cerastium arvense L. NA S

Cerastium fontanum subsp. fontanum G S

Cerastium sp. NA G

Chaerophyllum temulum L. S G

Chamaepericlymenum suecicum (L.) Asch. & Graebn. G G

Chenopodium album L. S G

Chenopodium sp. G G

Chenopodium suecicum NA G

(6)

Cirsium arvense (L.) Scop. G G

Circaea lutetiana L. S G

Cirsium oleraceum (L.) Scop. G S

Cirsium palustre (L.) Scop. G S

Cirsium sp. NA G

Cirsium vulgare (Savi) Ten. G G

Circaea x intermedia Ehrh. S G

Compositaceae fam. NA G

Convolvulus arvensis L. S G

Conopodium majus (Gouan) Loret G G

Corylus avellana L. G G

Cornus sanguinea L. G G

Crataegus laevigata (Poir.) DC. G G

Crataegus monogyna Jacq. G G

Cardamine sp. S G

Crepis biennis L. G S

Crepis capillaris (L.) Wallr. G S

Crepis paludosa (L.) Moench G S

Dactylis glomerata L. G S

Daucus carota L. G G

Deschampsia cespitosa (L.) P. Beauv. G S

Deschampsia flexuosa (L.) Trin. G S

Dryopteris carthusiana (Vill.) H.P.Fuchs S G

Dryopteris dilatata (Hoffm.) A. Gray S G

Dryopteris expansa (C. Presl) Fraser-Jenk. & Jermy S G

Dryopteris filix-mas (L.) Schot S G

Dryopteris sp. S G

Duchesnea indica (Jacks.) Focke G G

Elymus caninus (L.) L. S G

Elytrigia repens (L.) Nevski G G

Empetrum nigrum L. G G

Epilobium angustifolium (L.) Scop. G G

Epipactis helleborine (L.) Crantz S G

Epilobium hirsutum L. G G

Epilobium montanum L. G G

Epilobium sp. G G

Equisetum arvense L. G G

Equisetum fluviatile L. G G

Equisetum palustre L. G G

Equisetum pratense Ehrh. S G

Equisetum sp. NA G

Equisetum sylvaticum L. S G

(7)

Equisetum telmateia Ehrh. G G

Eriophorum vaginatum L. G G

Euonymus europaea L. G G

Euphrasia sp. G G

Fagus sylvatica All. S G

Festuca altissima L. S G

Festuca arundinacea Schreb. G G

Festuca gigantea (L.) Vill. S G

Festuca pratensis Huds. G S

Festuca rubra L. G S

Festuca sp. NA G

Ficaria verna Huds. G G

Filipendula kamtschatica (Pall.) Maxim. NA G

Filipendula ulmaria (L.) Maxim. G S

Fraxinus excelsior L. G G

Fragaria moschata Weston S G

Fragaria vesca L. G G

Gagea lutea (L.) Ker Gawl. S G

Gagea spathacea (Hayne) Salisb. S G

Galanthus nivalis L. G G

Galium odoratum (L.) Scop. S G

Galega orientalis Lam. NA G

Galium parisiense L. G S

Galeopsis sp. G G

Galeopsis tetrahit L. G G

Galium aparine L. G G

Galium boreale L. G S

Galium mollugo L. G S

Galium verum L. G S

Geranium dissectum L. S G

Geranium molle L. S G

Geranium palustre L. G S

Geranium pratense L. NA G

Geranium pusillum L. NA G

Geranium robertianum L. G G

Geranium sp. NA G

Geranium sylvaticum L. G G

Geum rivale L. G S

Geum urbanum L. G G

Glechoma hederacea L. G G

Gymnocarpium dryopteris (L.) Newman S G

Hedera helix L. S G

Hepatica nobilis Schreb. S G

(8)

Hepatica sp. S G

Heracleum sphondylium L. G G

Hieracium sp. G G

Holcus lanatus L. G S

Holcus mollis L. G G

Hordeum vulgare L. S G

Humulus lupulus L. S G

Hyacinthoides non-scripta (L.) Chouard ex Rothm. S G

Hypericum maculatum Crantz G S

Hypericum perforatum L. G G

Hypochaeris radicata L. G S

Hypericum sp. NA G

Ilex aquifolium L. S G

Ulex europaeus L. G G

Impatiens glandulifera Royle G G

Impatiens noli-tangere L. S G

Impatiens parviflora DC. S G

Jacobaea vulgaris Gaertn. G S

Juniperus communis L. subsp. communis G G

Juncus effusus L. G S

Juncus sp. G G

Knautia arvensis (L.) Coult. G S

Lactuca serriola L. S G

Lamium album L. G G

Lamium galeobdolon (L.) Crantz S G

Lamium purpureum L. G G

Lamium sp. NA G

Lapsana communis L. G G

Lathraea clandestina L. S G

Lathyrus pratensis L. G S

Lathyrus sp. NA G

Leontodon sp. NA S

Ligustrum sp. NA G

Ligustrum vulgare L. G G

Linnaea borealis L. S G

Lolium multiflorum Lam. NA G

Lolium perenne L. NA S

Lolium sp. NA G

Lonicera periclymenum L. G G

Lonicera sp. G G

Lotus corniculatus L. G S

Lunaria annua L. NA G

Luzula campestris (L.) DC. G S

(9)

Luzula pilosa (L.) Willd. S G

Lychnis flos-cuculi L. G S

Lychnis sp. NA G

Lysimachia nummularia L. G G

Lysimachia vulgaris L. G S

Lythrum salicaria L. G S

Maianthemum bifolium (L.) F. W. Schmidt S G

Matricaria chamomilla L. NA G

Matricaria discoidea DC. NA G

Matteuccia struthiopteris (L.) Tod. S G

Medicago lupulina L. G G

Medicago sativa L. G G

Medicago polymorpha L. NA G

Melica nutans L. S G

Melampyrum nemorosum L. S G

Melampyrum pratense L. G G

Melampyrum sp. NA G

Melampyrum sylvaticum L. S G

Melica uniflora Retz. S G

Mentha arvensis L. G G

Mercurialis perennis L. S G

Milium effusum L. S G

Moehringia trinervia (L.) Clairv. S G

Mycelis muralis (L.) Dumort. G G

Myosotis arvensis (L.) Hill G G

Myosotis decumbens Host G G

Myosotis sp. NA G

Myosotis sylvatica Hoffm. S G

Oxalis acetosella L. S G

Paris quadrifolia L. S G

Pastinaca sativa L. NA S

Persicaria hydropiper (L.) Delarbre G G

Persicaria lapathifolia (L.) Delarbre NA G

Persicaria maculosa Gray G G

Phalaroides arundinacea (L.) Rauschert G G

Phegopteris connectilis (Michx.) Wat S G

Phleum pratense L. G S

Phleum sp. NA G

Phragmites australis (Cav.) Steud. G G

Picea abies (L.) H. Karst. G G

Pimpinella saxifraga L. G S

Pinus sylvestris L. G G

Plantago lanceolata L. G S

(10)

Plantago major L. G G

Plantago sp. G G

Poa angustifolia L. G S

Poa annua L. NA G

Poa nemoralis L. S G

Poa pratensis L. G S

Poa sp. NA G

Poa trivialis L. G G

Polygonum aviculare L. NA G

Polygonatum multiflorum (L.) All. S G

Polygonatum verticillatum (L.) All. S G

Polypodium vulgare L. G G

Populus sp. G G

Populus tremula L. G G

Potentilla erecta (L.) Räusch. G S

Potentilla reptans L. G G

Potentilla sterilis (L.) Garcke S G

Potentilla supina L. NA G

Primula elatior (L.) Hill S G

Primula sp. NA G

Prunus avium (L.) L. G G

Prunus padus L. G G

Prunus sp. G G

Prunus spinosa L. G G

Prunella vulgaris L. G S

Pteridium aquilinum (L.) Kuhn G G

Pulicaria dysenterica (L.) Bernh. NA G

Quercus petraea (Mat.) Liebl. G G

Ranunculus acris L. G S

Ranunculus auricomus coll. G S

Ranunculus cassubicus L. S G

Ranunculus repens L. G G

Ranunculus sp. NA G

Ranunculus tuberosus Lapeyr. NA G

Rhamnus frangula L. G G

Ribes rubrum L. S G

Ribes sp. S G

Rosa arvensis Huds. S G

Rosa canina L. G G

Rosa rubiginosa L. G G

Rosa sp. G G

Rubus caesius L. G G

Rubus chamaemorus L. G G

(11)

Rubus fruticosus agg. G G

Rubus idaeus L. S G

Rubus saxatilis L. S G

Rubus sp. G G

Rumex acetosa L. G S

Rumex acetosella L. G S

Rumex crispus L. NA G

Rumex obtusifolius L. G G

Salix aurita L. G G

Salix caprea L. G G

Salix sp. G G

Sambucus nigra L. G G

Sambucus nigra f. laciniata NA G

Sambucus sp. G G

Sanguisorba officinalis L. G S

Scirpus sp. NA G

Scirpus sylvaticus L. G S

Scrophularia umbrosa Dumort. G G

Scutellaria galericulata L. G G

Sedum sexangulare L. G S

Sedum spurium M. Bieb. NA G

Senecio ovatus (G. Gaertn. & al.) Hoppe S G

Setaria viridis (L.) P. Beauv. NA G

Silene dioica (L.) Clairv. G G

Silene latifolia Poir. G G

Sinapis arvensis L. NA G

Solidago virgaurea L. G S

Sonchus sp. G G

Sorbus aucuparia L. G G

Stachys palustris L. G G

Stachys sylvatica L. S G

Stellaria graminea L. G S

Stellaria holostea L. S G

Stellaria longifolia Willd. S G

Stellaria media (L.) Cirillo G G

Stellaria nemorum L. S G

Stellaria sp. NA G

Symphytum officinale L. G G

Tanacetum vulgare L. NA G

Taraxacum officinale F. H. Wigg. G G

Thalictrum aquilegiifolium L. G G

Thalictrum lucidum L. G S

Tilia cordata Mill. S G

(12)

Tilia platyphyllos Scop. S G

Tragopogon dubius Scop. NA G

Tragopogon pratensis L. NA S

Trifolium arvense L. NA S

Trifolium dubium Sibth. NA S

Trientalis europaea L. S G

Tripleurospermum inodorum (L.) Sch. Bip. NA G

Trifolium medium L. G G

Trifolium pratense L. G S

Trifolium repens L. G G

Trifolium sp. NA G

Tussilago farfara L. G G

Ulmus glabra Huds. S G

Ulmus sp. S G

Urtica dioica L. G G

Urtica urens L. NA G

Vaccinium myrtillus L. G G

Vaccinium uliginosum L. G G

Vaccinium vitis-idaea L. G G

Valeriana officinalis L. G S

Veronica agrestis L. NA G

Veronica arvensis L. NA G

Veronica chamaedrys L. G G

Veronica hederifolia L. G G

Veronica montana L. S G

Veronica sp. NA G

Veronica teucrium G S

Viburnum opulus L. G G

Vicia cracca L. G S

Vicia hirsuta (L.) Gray NA G

Vicia sepium L. G G

Vicia sp. NA G

Viola arvensis NA G

Viola biflora L. G G

Viola canina L. G S

Viola canina L. subsp. montana (L.) Hartm. G S

Viola mirabilis L. S G

Viola odorata L. G G

Viola palustris L. G G

Viola reichenbachiana Jord. ex Boreau S G

Viola riviniana Rchb. S G

Viola sp. NA G

(13)

(14)

Table S3. Univariate statistical relationships between the total, generalist and specialist species richness in forests and hedgerows, on the one hand, and the additional environmental variables, on the other hand. Values and symbols are χ²-values and significances, respectively, from a likelihood ratio test of generalized linear mixed-effect models with Poisson distribution (Species richness ~ Predictor + Habitat + Predictor × Habitat). The direction of the effect is given as “↑” for a positive effect of the predictor or a higher species richness in hedgerows than in forests, and “↓” for a negative effect of the predictor or a lower species richness in hedgerows than in forests. Significances are indicated as “***” for P < 0.001, “**” for P < 0.01, “*” for P < 0.05 “.” for P < 0.1 and

“n.s.” for P ≥ 0.1.

Total Generalist Specialist

Predictor Habitat

Predictor ×

Habitat Predictor Habitat

Predictor ×

Predictor × Habitat Maximum

temperature of the

warmest month n.s. ↑18.667*** n.s. n.s. ↑72.447*** n.s. n.s. ↓14.122*** n.s.

Minimum

coldest month ↓4.63* ↑18.69*** n.s. n.s. ↑72.596*** n.s. ↓6.568* ↓14.024*** n.s.

Precipitation of the

wettest quarter n.s. ↑18.672*** n.s. n.s. ↑72.437*** n.s. n.s. ↓14.124*** n.s.

driest quarter n.s. ↑18.677*** n.s. n.s. ↑72.636*** n.s. n.s. ↓14.116*** n.s.

Total canopy cover n.s. ↑19.624*** n.s. n.s. ↑72.745*** n.s. n.s. ↓12.703*** n.s.

Minimum annual

temperature offset n.s. ↑15.27*** n.s. ↓16.752*** ↑55.838*** n.s. n.s. ↓12.277*** 3.047.

Mean annual

temperature offset n.s. ↑15.598*** n.s. ↑13.287*** ↑63.105*** 3.311. n.s. ↓12.976*** n.s.

Maximum annual

temperature offset ↑3.216. ↑9.959** 3.052. ↑34.403*** ↑47.029*** 4.725* n.s. ↓13.107*** n.s.

Mean summer

temperature offset ↑2.971. ↑15.96*** 3.235. n.s. ↑60.792*** 7.041** ↓3.945* ↓10.97*** n.s.

Mean winter

temperature offset n.s. ↑18.284*** n.s. n.s. ↑71.651*** n.s. n.s. ↓13.99*** n.s.

(15)

Table S4. Univariate statistical relationships between the total, generalist and specialist species richness in grasslands and road verges, on the one hand, and the additional environmental variables, on the other hand. Values and symbols are χ²-values and significances, respectively, from a likelihood ratio test of generalized linear mixed-effect models with Poisson distribution (Species richness ~ Predictor + Habitat + Predictor × Habitat). The direction of the effect is given as “↑” for a positive effect of the predictor or a higher species richness in road verges than in grasslands, and “↓” for a negative effect of the predictor or a lower species richness in road verges than in grasslands. Significances are indicated as “***” for P < 0.001, “**” for P < 0.01, “*” for P < 0.05 “.”

for P < 0.1 and “n.s.” for P ≥ 0.1.

Total Generalist Specialist

Predictor Habitat

Predictor ×

Predictor × Habitat Maximum

warmest month n.s. ↑3.621. n.s. n.s. ↑6.603* n.s. n.s. n.s. n.s.

Minimum

coldest month n.s. ↑3.583. 8.056** n.s. ↑6.469* 6.829** n.s. n.s. n.s.

wettest quarter n.s. ↑3.586. 4.062* n.s. ↑6.603* 3.382. n.s. n.s. n.s.

driest quarter n.s. ↑3.557. 9.527** n.s. ↑6.451* 6.152* n.s. n.s. 3.781.

Minimum annual

temperature offset n.s. ↑3.621. n.s. n.s. ↑6.603* n.s. n.s. n.s. n.s.

Mean annual

Maximum annual

Mean summer

Mean winter

5 3

Sorbus aucuparia

3 2

(17)

4 3

(18)

Table S6. Location of the weather stations used to extract free-air (macroclimate) temperature data for each of the study regions.

Region Weather station Elevation (m a.s.l.)

Location (°N, °E)

Average distance to study sites (km)

Source

France Fontaine-les-Vervins 186 49.8372, 3.87778 11.5 Meteo France (htp://www.meteofrance.com/) Poland Racibórz 195 50.0920, 18.2193 9.53 Instytut Meteorologii i Gospodarki Wodnej (IMGW)

(htp://dane.imgw.pl)

Belgium Melle 8 50.9804, 3.81594 11.2 Royal Meteorological Institute

Eastern Germany

Marnitz 87 53.3167, 11.9333 12.9 Deutscher Weterdienst (www.dwd.de)

Western Germany

Lübeck-Blankensee 16 53.8025, 10.6988 26.7 Deutscher Weterdienst (www.dwd.de) Souther

n Sweden

Hörby 81 55.8524, 13.6609 7.86 Swedish Meteorological and Hydrological Institute (htps://www.smhi.se/)

Central Sweden

Södertalje 23 59.2142, 17.6289 28.8 Swedish Meteorological and Hydrological Institute (htps://www.smhi.se/)

Estonia Jõgeva

Tartu-Tõravere Tiirikoja

79 39 34

58.7467, 26.3939 58.3806, 26.7251 58.8653, 26.9522

39.5 38.8 44.8

Estonian Weather Service (htps://www.ilmateenistus.ee/)

Norway Trondheim 8 64.4305, 10.3951 20.2 Norwegian Meteorological Institute (htps://www.yr.no/)

(19)

Table S7. List of explanatory variables (including abbreviation) used in the models relating species richness in the original habitat-ecological corridor transects to environmental factors varying both locally and along the continental-scale environmental gradient.

Variable Unit Range

Nitrogen deposition and macroclimatic variables

Nitrogen deposition (NDEP) kg N ha⁻¹ 1.34–15.78

Annual mean temperature (BIO1) °C 5.12–10.5

Max temperature of warmest month (BIO5) °C 15.0–21.8 Min temperature of coldest month (BIO6) °C -11.7–-0.988

Annual precipitation (BIO12) mm 575–1215

Precipitation of wetest quarter (BIO16) mm 184–392 Precipitation of driest quarter (BIO17) mm 86.0–205 Landscape variables

Forest cover in 500-m buffer (F500) % 5.82–59.9

Grassland cover in 500-m buffer (G500) % 8.49–70.1 Variables related to canopy structure and composition

Canopy cover (CANOPY) % 1.2–100

Height of shrub layer (SHRUB_H) m 1.5–13.8

Height of tree layer (TREE_H) m 6.6–36.6

Total number of woody species (WOODY_N) - 0–10

Total cover of shrub layer (SHRUB_C) % 0–205

Total cover of tree layer (TREE_C) % 0–220

Cover-weighted average liter quality (LQ) - 1–5 Cover-weighted average shade-casting ability (SCA) - 1.08–5 Soil variables

pH-H20 - 3.68–8.27

Ca mg kg⁻¹ 80.4–16863.0

K mg kg⁻¹ 26.8–974.8

Mg mg kg⁻¹ 20.0–2538.2

Ctot % 1.05–46.11

Ntot % 0.104–2.595

POlsen mg kg⁻¹ 3.95–136.41

Microclimatic buffering

Minimum annual temperature (MIN_Ty) °C -0.677–1.93

Mean annual temperature (MEAN_Ty) °C -0.789–0.964

Maximum annual temperature (MAX_Ty) °C -1.97–2.52 Minimum summer temperature (MIN_Ts) °C -0.807–3.15

Mean summer temperature (MEAN_Ts) °C -1.54–1.08

Maximum summer temperature (MAX_Ts) °C -3.22–2.95 Minimum winter temperature (MIN_Tw) °C -0.759–2.85

Mean winter temperature (MEAN_Tw) °C -0.790–1.82

Maximum winter temperature (MAX_Tw) °C -1.28–2.40

(20)

Table S8. Total number of herbaceous species, forest generalists end specialists in the hedgerows (H) and adjacent forests (F).

Region Habitat Total Generalist Specialist

France (FR) F 51 16 26

H 70 38 21

Belgium (BE) F 56 27 20

H 37 22 10

Eastern Germany (EG) F 53 26 17

H 69 44 15

Western Germany (WG) F 50 17 26

H 50 23 21

Southern Sweden (SS) F 65 31 26

H 56 36 14

Estonia (ES) F 71 34 29

H 94 57 23

Norway (NO) F 90 51 33

H 94 61 22

Table S9. Percentage of species from the total species pool (Total), forest generalists end specialists shared among hedgerows and adjacent forests.

Region Total (%) Generalists (%) Specialists (%)

FR 37.5 25.6 51.6

BE 36.8 38.2 36.4

EG 58.4 54.5 68.4

WG 56.3 48.1 62.1

SS 42.4 47.7 37.9

ES 42.2 40.3 48.6

NO 44.9 54.3 44.7

All 54.6 52.1 72.7

Table S10. Percentage of herbaceous species (Total), forest generalists end specialists shared among paired combinations of hedgerows and adjacent forests.

FR 4.55 4.65 3.23

BE 4.41 8.82 0.00

EG 2.60 0.00 10.5

WG 4.69 3.70 6.90

SS 4.71 9.09 0.00

ES 1.72 1.61 2.86

NO 3.94 1.43 10.5

All 4.80 4.86 7.79

(21)

Table 11. Total number of herbaceous species, semi-natural grassland generalists and specialists in the road verges (RV) and adjacent grasslands (G).

Region Habita

t

Total Generalists Specialists

France (FR) G 35 21 14

RV 49 35 14

Belgium (BE) G 35 22 13

RV 54 34 20

Poland (PL) G 36 18 18

RV 54 37 17

Eastern Germany (EG) G 53 33 20

RV 58 40 18

Central Sweden (CS) G 49 29 20

RV 41 28 13

Estonia (ES) G 67 40 27

RV 49 30 19

Norway (NO) G 55 34 21

RV 45 29 16

Table S12. Percentage of species from the total species pool, semi-natural grassland specialists and generalists shared among road verges and adjacent grasslands.

FR 40.0 36.6 47.4

BE 48.3 47.4 50.0

PL 38.5 27.9 59.1

EG 54.2 49.0 65.2

CS 45.1 46.2 43.5

ES 40.2 34.5 50.0

NO 46.9 37.2 66.7

All 51.5 50.4 54.1

Table S13. Percentage of herbaceous species, semi-natural grassland specialists and generalists shared among paired combinations of road verges and adjacent grasslands.

FR 1.67 0.00 5.26

BE 3.33 0.00 9.09

PL 3.08 2.33 4.55

EG 12.5 12.2 13.0

CS 6.45 2.56 13.0

ES 6.90 7.27 6.25

NO 6.25 0.00 19.0

All 9.79 6.02 18.0

(22)

Supplementary figures

Fig. S1. Canopy cover (a), height of shrub layer (b), height of tree layer (c), overstorey species richness (d), total cover of shrub layer (e), total cover of tree layer (f), liter quality (g) and shade- casting ability (h) in forests (F) and hedgerows (H) across all regions. The difference between both groups was tested using a linear mixed-effect model (LMM) with ‘region’ and ‘site’ (nested within

‘region’) as random effect terms. Different letters denote significant differences (P < 0.05).

(23)

Fig. S2. Principal component analysis (PC) on all soil variables measured in 168 sites spread across forests and hedgerows. The soil variables included in this analysis were soil pH, Calcium (Ca), Magnesium (P), Potassium (K), total nitrogen (N), total carbon (C), plant-available phosphorus (P) and C:N ratio.

(24)

Fig. S3. Principal component analysis (PC) on all soil variables measured in 168 sites spread across grasslands and road verges. The soil variables included in this analysis were soil pH, Calcium (Ca), Magnesium (P), Potassium (K), total nitrogen (N), total carbon (C), plant-available phosphorus (P) and C:N ratio.

(25)

Fig. S4. (a) Non-metric multidimensional scaling (NMDS) plot showing 84 forest sites (red circles) and 84 hedgerow sites (blue circles). Only the 5 % most abundant understorey plant species are indicated in the plot. The necessary distance matrices were constructed using the Bray-Curtis dissimilarity index. Species abbreviations: Adomos = Adoxa moschatellina, Aegpod = Aegopodium podagraria, Anenem = Anemone nemorosa, Dacglo = Dactylus glomerata, Ficver = Ficaria verna, Glehed = Glechoma hederacea, Hedhel = Hedera helix, Lamgal = Lamium galeobdolon, Milleff = Millium effusum, Oxaace = Oxalis acetosella, Poanem = Poa nemoralis, Stehol = Stellaria holostea, Rubsp = Rubus sp., Urtdio = Urtica dioica. (b) NMDS plot showing 84 semi-natural grassland sites (red circles) and 84 road verge sites (blue circles) as well as the 5 % most abundant plant species. Species abbreviations: Alopra = Alopercurus pratensis, Arrela = Arrhenatherum elatior, Dacglo = Dactylis glomerata, Desfle = Deschampsia flexuosa, Elyrep = Elytrigia repens, Fesrub = Festuca rubra, Hollan = Holcus lanatus, Lolper = Lolium perenne, Tarsp = Taraxacum sp., Tripra = Trifolium pratense.

(26)

Fig. S5. Correlation matrix for the explanatory variables used in the generalized linear mixed model (GLMM) analysis of species diversity in forests and hedgerows. The values inside the cells represent the Pearson’s r correlation coefficient for each combination of explanatory variables. The colour intensity of the cells denotes the relative strength of the correlations, with blue and red indicating highly negative and highly positive correlations, respectively (Student’s t test, P < 0.05).

(27)

Fig. S6. Correlation matrix for the explanatory variables used in the generalized linear mixed model (GLMM) analysis of species diversity in grasslands and road verges. The values inside the cells represent the Pearson’s r correlation coefficient for each combination of explanatory variables. The colour intensity of the cells denotes the relative strength of the correlations, with blue and red indicating highly negative and highly positive correlations, respectively (Student’s t test, P < 0.05).

(28)

Fig. S7. Total, generalist and specialist species richness in forests (black) and hedgerows (white) of each region (FR = France, BE = Belgium, EG = eastern Germany, WG = western Germany, SS = southern Sweden, ES = Estonia, NO = Norway).

(29)

Fig. S8. Total, generalist and specialist species richness in grasslands (black) and road verges (white) of each region (FR = France, PL = Poland, BE = Belgium, EG = eastern Germany, CS = central Sweden, ES = Estonia, NO = Norway).

(30)

Fig. S9. Relationship between total species richness in grasslands (full circles) and road verges (open circles), on the one hand, and the first principal component axis (PCA1) of soil variables (a), on the other hand. Relationship between generalist species richness in grasslands (full circles) and road verges (open circles), on the one hand, and the proportion of grassland in a 500-m radius (G500) (b), the second principal component axis (PCA2) of soil variables (c) and the maximum winter temperature (TMAX_W) offset (d), on the other hand. Relationship between specialist species richness in grasslands (full circles) and road verges (open circles), on the one hand, and the first principal component axis (PCA1) of soil variables (e), on the other hand. Fited regression lines are from generalized linear mixed-effect models (GLMM) with Poisson distribution, including ‘species richness’ as response variable, ‘habitat’, the environmental variable and their interaction as fixed effects, and ‘region’ and ‘site’ (nested within ‘region’) as random intercept terms. If the interaction term was significant in the models, two regression lines were ploted, i.e. one for forests (dark coloured line) and one for hedgerows (light coloured line).

(31)

References

Ellenberg, H., Weber, H.E., Düll, R., Wirth, V., Werner, W. & Paulissen, D. (1991) Zeigerwerte von Pflanzen in Mitteleuropa. Scripta Geoboanica, Goltze, Gottingen.

Euro+Med (2006) Euro+Med PlantBase - the information resource for Euro-Mediterranean plant diversity. Published on the Internet htp://ww2.bgbm.org/EuroPlusMed/.

Heinken, T. (2019) European forest vascular plant species list. figshare. doi:

10.6084/m9.figshare.8095217.v1.

Maes, S.L., Blondeel, H., Perring, M.P., Depauw, L., Brūmelis, G., Brunet, J., . . . Verheyen, K. (2019) Liter quality, land-use history, and nitrogen deposition effects on topsoil conditions across European temperate deciduous forests. Forest Ecology and Management, 433, 405-418. doi:

htps://doi.org/10.1016/j.foreco.2018.10.056.

Verheyen, K., Baeten, L., De Frenne, P., Bernhardt-Römermann, M., Brunet, J., Cornelis, J., . . . Verstraeten, G. (2012) Driving factors behind the eutrophication signal in understorey plant communities of deciduous temperate forests. Journal of Ecology, 100, 352-365. doi:

10.1111/j.1365-2745.2011.01928.x.