Supplementary material Appendix S1 List of the 10 most common plant species found in the riparian vegetation patches (A) and adjacent habitats (B) surveyed for the current study classified according to the vegetation communities provided by Font (2014). All Arundo donax plots were monospecific, with the exception of a plot in the Vallvidrera stream where Brachypodium sylvaticum was marginally present.

(A) Riparian vegetation communities Deciduous forest communities Ruderal plant communities Alnion incanae Populion albae Silybo-Urticion Bidention tripartitae Alnus glutinosa Arum italicum Chenopodium album Apium nodiflorum Brachypodium sylvaticum Asparagus acutifolius Convolvulus arvensis Aster squamatus Carex pendula Brachypodium sylvaticum Galium aparine Chenopodium album Clematis vitalba Clematis vitalba Hordeum murinum Lythrum salicaria Corylus avellana Crataegus monogyna Malva sylvestris Paspalum distichum Crataegus monogyna Fraxinus angustifolia Rubus ulmifolius Polygonum persicaria Geranium robertianum Hedera helix Rumex crispus Rumex palustris Hedera helix Rubus ulmifolius Silybum marianum Sonchus oleraceus Rubus ulmifolius Ruscus aculeatus Sonchus oleraceus Veronica anagallis-aquatica Viola sylvestris Ulmus minor Urtica dioica Xanthium echinatum

(B) Adjacent plant species to the riparian areas Mediterranean oak forest Highly human-impacted areas (Rivers Ripoll and (Vallvidrera stream) Llobregat) Viburno-Quercetum ilicis Mixed Asparagus acutifolius Anagallis arvenis Asplenium adiantum-nigrum Capsella bursa-pastoris Hedera helix Chenopodium album Lonicera implexa Cynodon dactylon Quercus ilex Capsella bursa-pastoris Rubus ulmifolius Echium vulgare Ruscus aculeatus Foeniculum vulgare Smilax aspera Hordeum murinum Viburnum tinus Oryzopsis miliacea Viola alba Plantago major Appendix S2 List of arthropods provided by taxonomical level (class, order and family), trap method (P=pitfall trap, B=Berlese funnel) and soil layer for Berlese captures (O: organic layer and M: mineral layer) in the three types of riparian areas (D: deciduous forest, R: native ruderal plants, A: Arundo donax) surveyed in the three catchments (L: Llobregat, R: Ripoll, V: Vallvidera) of the north-eastern Spain. Trophic guilds are also shown for each family.

River Riparian area Sampling method Layer Cl. Arachnida O. Araneae F. Agelenidae L, R, V D, A P F. Dysderidae L, R, V D, R, A P, B O F. Gnaphosidae L, R, V D, R, A P, B O, M F. Lycosidae L, R, V D, R, A P, B O, M F. Salticidae V R P F. Tetragnathidae R, V R P F. Thomisidae L R B M F. Zodariidae L, R D, R P O. Opiliones F. Phalangiidae L, V D, A P, B M F. Trogulidae V R B O O. Pseudoscorpiones F. Chthoniidae L, R, V D, R, A P, B O, M Cl. Chilopoda O. Geophilomorpha F. Geophiliidae L, R, V D, R, A B O, M O. Lithobiomorpha F. Lithobiidae L, V D, A P, B M Cl. Diplopoda O. Chordeumatida F. Craspedosomatidae L, R, V D, R, A P, B O, M O. Glomerida F. Glomeridae L, R, V D, R, A P, B O, M O. Julida F. Julidae L, R, V D, R, A P, B O, M O. Polydesmida F. Polydesmidae L, R, V D, R, A P, B O Cl. Insecta O. Dictyoptera F. Blattidae L, R, V D, R, A P, B O, M O. Coleoptera F. Anobiidae L, V R, A B O, M F. Carabidae L, R, V D, R, A P, B O, M F. Coccinellidae L, S D P F. Corylophidae L, R, V D, R, A B O, M F. Curculiionidae L, R, V D, A B O, M F. Elateridae L, R D, R, A B O, M F. Silphidae L, R, V D, A P F. Staphilinidae L, D P River Riparian area Sampling method Layer O. Dermaptera F. Forficulidae V D, A B O, M O. Diptera F. Muscidae S, V D, A P F. Tachinidae S, V R P F. Fanniidae S R P F. Sciaridae S, V R, A B O O. Hemiptera F. Geocoridae L D P F. Rhyparochromidae L, S, V D, A P O. Hymenoptera F. Braconidae L, S, V D, R, A P, B O F. Eupelmidae S R P F. Formicidae L, S, V D, R, A P, B O, M O. Thysanoptera F. Phlaeothripidae L, S, V D, R, A B O, M Cl. Malacostraca O. Isopoda F. Armadillidae L, S, V D, R, A P, B O, M F. Porcellionidae S D, A P Appendix S3 Detrended correspondence analyses scores for macro-arthropod taxa captured either in pitfall traps or the Berlese funnels in the three types of riparian vegetation in Rivers Llobregat and Ripoll and the Vallvidrera stream.

Pitfall traps Berlese funnels DCA 1 DCA 2 DCA 1 DCA 2 Agelenidae -0.58 -1.48 nd nd Anobiidae nd nd -2.34 3.39 Armadillidae 1.75 -0.22 0.27 -0.79 Blattidae -0.79 -1.42 -1.34 -0.99 Braconidae -2.12 -0.81 1.24 -1.09 Carabidae -0.45 -1.16 -0.34 1.21 Chthoniidae 1.67 1.38 1.99 -0.24 Coccinellidae -2.48 -2.09 nd nd Corylophidae nd nd 0.79 -1.41 Craspedosomatida e 0.85 1.83 -2.39 -2.55 Curculionidae nd nd 0.10 -1.76 Dysderidae -0.19 1.53 -4.00 0.82 Elateridae nd nd -1.27 -1.33 Eupelmidae 2.54 0.15 nd nd Faniidae -2.53 2.48 nd nd Forficulidae nd nd -0.42 2.12 Formicidae 0.27 0.32 -0.07 0.58 Geocoridae -2.75 -2.39 nd nd Geophiliidae nd nd 1.48 0.07 Glomeridae -0.83 -0.91 0.49 -0.55 Gnaphosidae -1.59 -2.17 1.60 0.26 Julidae 2.84 0.15 -0.24 1.27 Lithobiidae 1.78 -0.81 3.40 0.34 Lycosidae 0.91 0.11 -1.66 0.47 Muscidae 1.71 1.00 nd nd Phalangiidae 1.66 -1.05 2.12 1.38 Phlaeothripidae nd nd -0.96 0.86 Polydesmidae -0.24 1.71 2.85 0.99 Porcellionidae 0.08 -0.04 nd nd Rhyparochromidae -1.15 2.04 nd nd Salticidae 3.78 0.15 nd nd Sciaridae nd nd 0.25 1.29 Silphidae -0.72 1.09 nd nd Staphilinidae 0.79 -1.97 nd nd Tachinidae 3.78 0.15 nd nd Tetragnathidae -1.79 1.32 nd nd Thomisidae 1.85 1.22 nd nd Trogulidae nd nd 1.91 -0.52 Zodariidae -1.52 1.19 nd nd nd = not captured Appendix S4 GLM outputs for abundances of representatives of all families captured in pitfall traps (A) and Berlese funnels (B) in the three types of vegetation in Rivers Llobregat and Besòs and the Vallvidrera stream. In all significant treatments (NS = not significant), P-values are provided and trends in abundance are also shown for A. donax plots (D = decrease and I = increase).

(A) Pitfall trap captures Family Trophic guild River Vegetation type River x Vegetation type Trend in A. donax plots Armadillidae Detritivorous NS NS NS NS Craspedosomatida e Detritivorous NS NS NS NS Faniidae Detritivorous 0.001 0.001 NS D Glomeridae Detritivorous 0.004 0.01 NS D Julidae Detritivorous <0.001 <0.001 NS D Polydesmidae Detritivorous NS NS NS NS Porcellionidae Detritivorous NS NS NS NS Silphidae Detritivorous <0.001 <0.001 <0.001 D Blattidae Omnivorous NS NS NS NS Formicidae Omnivorous NS 0.004 NS D Muscidae Omnivorous NS NS NS NS Staphilinidae Omnivorous NS NS NS NS Braconidae Parasitoids 0.04 0.02 NS D Eupelmidae Parasitoids NS NS NS NS Tachinidae Parasitoids NS NS NS NS Rhyparochromidae Phytophagous NS 0.02 NS D Agelenidae Predators NS NS NS NS Carabidae Predators 0.001 0.001 0.001 D Chthoniidae Predators <0.001 <0.001 NS D Coccinellidae Predators NS NS NS NS Dysderidae Predators NS NS NS NS Geocoridae Predators NS NS NS NS Gnaphosidae Predators 0.002 0.002 NS NS Lithobiidae Predators 0.02 0.02 NS D Lycosidae Predators NS NS NS NS Phalangiidae Predators NS NS NS NS Salticidae Predators NS NS NS NS Tetragnathidae Predators NS NS NS NS Thomisidae Predators NS NS NS NS Zodariidae Predators NS NS NS NS

See also the next page (B) Berlese funnels captures

Family Trophic guild River Vegetation type River x Vegetation type Trend in A. donax plots Armadillidae Detritivorous NS NS NS NS Craspedosomatida e Detritivorous <0.001 <0.001 NS D Forficulidae Detritivorous NS NS 0.02 I (Only Vallvidrera) Glomeridae Detritivorous NS 0.004 0.01 D (Except Llobregat) Julidae Detritivorous NS NS NS NS Polydesmidae Detritivorous 0.001 NS NS NS Corylophidae Mycophagous NS 0.01 NS D Phlaeothripidae Mycophagous NS 0.02 0.05 D Sciaridae Mycophagous NS NS NS NS Blattidae Omnivorous NS NS NS NS Formicidae Omnivorous NS NS 0.04 D (Except Vallvidrera) Braconidae Parasitoids 0.004 0.004 NS D Anobiidae Phytophagous NS NS NS NS Curculionidae Phytophagous NS 0.01 NS D Elateridae Phytophagous NS NS 0.03 D (Except Vallvidrera) Carabidae Predators NS NS 0.02 D (Except Vallvidrera) Chthoniidae Predators <0.001 <0.001 NS D Dysderidae Predators NS NS 0.03 I (Except Llobregat) Geophiliidae Predators 0.04 <0.001 NS D Gnaphosidae Predators 0.01 NS NS NS Lithobiidae Predators NS NS NS NS Lycosidae Predators 0.001 0.001 0.003 I/D/NS Phalangiidae Predators NS NS 0.02 D (Only Vallvidrera) Trogulidae Predators <0.001 <0.001 NS NS Appendix S5 Spearman rank correlation coefficients between riparian vegetation attributes and soil properties. The table only contains the pair-wise correlations that were highly correlated (|rho| ≥ 0.7).

Local native plant richness Leaf litter deposition r=-0.81 P<0.001 Mean herbaceous height r=0.85 P<0.001 Herbaceous cover r=0.84 P<0.001 pH r=0.70 P=0.001 Soil moisture r=0.71 P=0.002

Soil porosity Soil carbon stock r=0.74 P<0.001 Herbaceous cover r=-0.70 P<0.001

Soil carbon stock Leaf litter deposition r=0.70 P<0.001 Herbaceous cover r=-0.75 P<0.001