1 Supplementary Information for Invasive Grasses Increase

Home , Achnatherum, Agrostis, Bromus, Bromus tectorum, Gastridium, Lolium temulentum

Supplementary Information For

Invasive grasses increase fire occurrence and frequency across U.S. ecoregions

Emily J. Fusco1*, John T. Finn2, Jennifer K. Balch3,4, R. Chelsea Nagy3, Bethany A. Bradley1,2

Affiliations:

1 Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts- Amherst, Amherst, Massachusetts, 01003, USA

2 Department of Environmental Conservation, University of Massachusetts- Amherst, Amherst, Massachusetts, 01003, USA

3 Earth Lab, University of Colorado- Boulder, Boulder, Colorado, 80309, USA

4 Department of Geography, University of Colorado-Boulder, Boulder, Colorado, 80309, USA

Correspondence to: [email protected]

This PDF file includes: Figure S1 Tables S1 to S4 SI References

1 www.pnas.org/cgi/doi/10.1073/pnas.1908253116 Supplemental Table S1: A list of 176 non-native invasive grass and other graminoid species as listed by the Invasive Plant Atlas of the United States (1). For each species, we conducted a Web of Science (WOS) search and recorded whether there was literature suggesting the species altered fire regimes (Yes/No). For each fire promoting species in WOS, we supplemented our determination of whether that species was a fire promoter using the Fire Effects Information System (FEIS; 2). For each species designated as a fire promoter, we searched for available spatial data, and kept only species that were both fire-promoting with spatial data for our analysis. Final species used are highlighted in yellow.

WOS FEIS Fire Data Keep for Scientific Name Common Name(s) Search Database Promoter Available Analysis Achnatherum punagrass No - No - No brachychaetum Godr. Barkworth Aegilops cylindrica Host jointed goatgrass No - No - No Aegilops ovate goatgrass No - No - No geniculata Roth Aegilops triuncialis L. barb goatgrass No - No - No Agropyron cristatum L. crested wheatgrass No - No - No Gaertn. Agropyron desert wheatgrass Yes Yes Yes No No desertorum Fisch. ex Link J.A. Schultes Agropyron fragile Roth Siberian wheatgrass No - No - No P. Candargy Agrostis avenacea J.F. Pacific bentgrass No - No - No Gmel. Agrostis capillaris L. colonial bentgrass No - No - No Agrostis gigantea Roth redtop No - No - No Agrostis stolonifera L. creeping bentgrass No - No - No Aira caryophyllea L. silver hairgrass No - No - No Alopecurus creeping meadow No - No - No arundinaceus Poir. foxtail Alopecurus water foxtail No - No - No geniculatus L. Alopecurus slender meadow No - No - No myosuroides Huds. foxtail Alopecurus pratensis L. meadow foxtail No - No - No Ammophila arenaria L. European No - No - No Link beachgrass Anthoxanthum sweet vernalgrass Yes No No - No odoratum L. Arrhenatherum tall oatgrass Yes No No - No elatius L. Beauv. ex J.& K. Presl

Arthraxon small carpetgrass, No - No - No hispidus Thunb. Makino joint-head grass Arundo donax L. giant reed Yes Yes Yes Yes Yes Avena barbata Pott ex slender oat No - No - No Link Avena fatua L. wild oat No - No - No Avena sativa L. oat No - No - No Bambusa common bamboo Yes No Yes No No vulgaris Schrad. ex J.C. Wendl. Brachypodium annual false-brome No - No - No distachyon L. Beauv. Brachypodium perennial false- Yes No No - No sylvaticum Huds. brome Beauv. Briza maxima L. big quakinggrass No - No - No Briza minor L. little quakinggrass No - No - No Bromus arvensis L. field brome No - No - No Bromus rattlesnake brome No - No - No briziformis Fisch. & C.A. Mey. Bromus rescuegrass No - No - No catharticus Vahl Bromus diandrus Roth ripgut brome No - No - No Bromus hordeaceus L. soft brome No - No - No Bromus inermis Leyss. smooth brome No - No - No Bromus Japanese brome No - No - No japonicus Thunb. Bromus racemosus L. bald brome No - No - No Bromus rubens L. red brome Yes Yes Yes Yes Yes Bromus secalinus L. rye brome No - No - No Bromus sterilis L. poverty brome No - No - No Bromus tectorum L. cheatgrass Yes Yes Yes Yes Yes Carex kobomugi Ohwi Japanese sedge No - No - No Carex pendula Huds. hanging sedge No - No - No Cenchrus crimson No - No - No setaceus Forssk. fountaingrass Morrone Coix lacryma-jobi L. Job's tears No - No - No Cortaderia jubata Lem. purple pampasgrass No - No - No Stapf Cortaderia Uruguayan pampas No - No - No selloana Schult. & grass

Schult. f. Asch. & Graebn. Cynodon dactylon L. bermudagrass No - No - No Pers Cynosurus echinatus L. hedgehog Yes No Yes No No dogtailgrass Cyperus deeprooted sedge No - No - No entrerianus Boeckl. Cyperus esculentus L. yellow nutsedge No - No - No Cyperus umbrella plant No - No - No involucratus Rottb Cyperus prolifer Lam miniature flatsedge No - No - No Cyperus rotundus L. purple nutsedge No - No - No Dactylis glomerata L. orchardgrass No - No - No Dactyloctenium crowfootgrass No - No - No aegyptium L. Willd Digitaria eriantha Steud. pangolagrass No - No - No Digitaria smooth crabgrass No - No - No ischaemum Schreb. Schreb. ex Muhl. Digitaria sanguinalis L. large crabgrass No - No - No Scop Digitaria setigera Roth East Indian No - No - No ex Roemer & J.A. crabgrass Schultes Digitaria violascens Link violet crabgrass No - No - No Echinochloa colona L. junglerice No - No - No Link Echinochloa crus- barnyardgrass No - No - No galli L. Beauv Ehrharta calycina Sm. perennial veldtgrass Yes No Yes No No Ehrharta erecta Lam. panic veldtgrass No - No - No Ehrharta longiflora Sm. longflowered No - No - No veldtgrass Eleusine indica L. goosegrass No - No - No Gaertn. Elymus repens L. Gould quackgrass No - No - No Elymus sibiricus L. Siberian wildrye No - No - No Eragrostis stinkgrass No - No - No cilianensis All. Vign. ex Janchen Eragrostis Cuming's lovegrass No - No - No cumingii Steud. Eragrostis weeping lovegrass Yes Yes Yes No No curvula Schrad. Nees 4

Eragrostis Lehmann lovegrass Yes Yes No - No lehmanniana Nees Eriochloa tropical cupgrass No - No - No fatmensis Hochst. & Steud. W.D. Clayton Festuca tall fescue No - No - No arundinacea Schreb. Festuca hard fescue No - No - No brevipila Tracey Festuca meadow fescue No - No - No pratensis Huds. Festuca sheep fescue No - No - No trachyphylla Hack. Krajina nom. illeg. Festuca Volga fescue No - No - No valesiaca Schleich. ex Gaudin Garnotia stricta Brongn. blue lawngrass No - No - No Gastridium nit grass No - No - No phleoides Nees & Meyen C.E. Hubbard Glyceria waxy mannagrass No - No - No declinata Brébiss. Glyceria rough mannagrass No - No - No maxima Hartman Holmb. Hemarthria limpograss No - No - No altissima Poir. Stapf & C.E. Hubbard Holcus lanatus L. common velvetgrass No - No - No Holcus mollis L. German velvetgrass No - No - No Hordeum smooth barley, No - No - No marinum Huds. leporinum barley, mouse barley, hare barley, foxtail barley Hordeum vulgare L. barley No - No - No Hymenachne West Indian marsh No - No - No amplexicaulis Rudge grass Nees Hyparrhenia hirta L. thatching grass No - No - No Stapf Hyparrhenia rufa Nees jaraguagrass No - No - No Stapf Imperata cylindrica L. cogongrass Yes Yes Yes Yes Yes Beauv. Juncus planifolius R. Br. broadleaf rush No - No - No

Kyllinga nemoralis J.R. white kyllinga No - No - No Forst. & G. Forst. Dandy ex Hutch. & Dalziel Leymus angustus Trin. Altai wildrye No - No - No Pilg. Lolium multiflorum Lam. annual ryegrass No - No - No Lolium perenne L. perennial ryegrass No - No - No Lolium temulentum Darnel ryegrass No - No - No Luziola watergrass No - No - No subintegra Swallen Luzula luzuloides Lam. oakforest woodrush No - No - No Dandy & Wilmott Megathyrsus guineagrass Yes* - No - No maximus Jacq. R. Webster, Panicum maximum Melinis molassesgrass Yes Yes Yes No No minutiflora Beauv. Melinis repens Willd. natalgrass No - No - No Zizka Microlaena weeping grass No - No - No stipoides Labill. Microstegium Japanese stiltgrass Yes Yes Yes Yes Yes vimineum Trin. A. Camus Miscanthus Chinese silvergrass Yes Yes Yes Yes Yes sinensis Anderss. Nardus stricta L. matgrass No - No - No Nassella manicata E. No - No - No Desv. Barkworth Neyraudia burmareed Yes Yes Yes Yes Yes reynaudiana Kunth Keng ex A.S. Hitchc. Oplismenus wavyleaf No - No - No undulatifolius Ard. basketgrass Roem. & Schult. Panicum blue panicum No - No - No antidotale Retz. Panicum miliaceum L. wild-proso millet No - No - No Panicum repens L. torpedograss No - No - No Paspalum dallisgrass No - No - No dilatatum Poir. Paspalum tussock paspalum No - No - No quadrifarium Lam.

Paspalum ricegrass paspalum No - No - No scrobiculatum Linnaeus Paspalum urvillei Steud. vaseygrass No - No - No Pennisetum kikuyugrass No - No - No clandestinum Hochst. ex Chiov. Pennisetum glaucum L. pearl millet No - No - No R. Br. Pennisetum mission grass No - No - No polystachion L. Schultes Pennisetum No - No - No purpureum Schumacher Pennisetum ciliare, buffelgrass Yes Yes Yes Yes Yes Cenchrus ciliaris Pennisetum setaceum crimson Yes* - No - No Forssk. Chiov. fountaingrass Pennisetum villosum R. feathertop No - No - No Br. ex Fresen. Phalaris aquatica L. bulbous canarygrass No - No - No Phalaris arundinacea L. reed canarygrass No - No - No Phalaris canariensis L. canarygrass No - No - No Phalaris minor Retz. littleseed No - No - No canarygrass Phleum pratense L. timothy No - No - No Phragmites common reed Yes Yes Yes Yes Yes australis Cavanilles Trinius ex Steudel Phyllostachys golden bamboo No - No - No aurea Carr. ex A.& C. Rivière Phyllostachys yellow groove No - No - No aureosulcata McClure bamboo Phyllostachys black bamboo No - No - No nigra Lodd. Munro Poa annua L. annual bluegrass No - No - No Poa compressa L. Canada bluegrass No - No - No Poa pratensis Lindm. H. spreading No - No - No Lindb. bluegrass, kentucky bluegrass Poa trivialis L. roughstalk bluegrass No - No - No Polypogon rabbitfoot polypogon No - No - No monspeliensis L. Desf. Polypogon water-bent No - No - No viridis Gouan Breistr.

Psathyrostachys Russian wildrye No - No - No juncea Fisch. Nevski Pseudosasa arrow bamboo No - No - No japonica Sieb. & Zucc. ex Steud. Makino ex Nakai Puccinellia weeping alkaligrass No - No - No distans Jacq. Parl. Rottboellia itchgrass No - No - No cochinchinensis Lour. W.D. Clayton Rytidosperma Tasmanian wallaby No - No - No biannulare Zotov grass Connor & Edgar Rytidosperma tufted wallaby grass No - No - No caespitosum Gaudich. Connor & Edgar Rytidosperma hairy wallaby grass No - No - No penicillatum Labill. Connor & Edgar Saccharum ravennae L. ravennagrass No - No - No Sacciolepis indica L. glenwoodgrass No - No - No Chase Schismus Arabian schismus Yes No Yes Yes Yes arabicus Nees Schismus common Yes No Yes Yes Yes barbatus Loefl. ex L. mediterraneangrass Thellung Schoenoplectiella ricefield bulrush No - No - No mucronata L. J. Jung & H. K. Choi Scleria lacustris C. lakeshore nutrush No - No - No Wright Secale cereale L. cereal rye No - No - No Setaria faberi Herrm. giant foxtail No - No - No Setaria italica L. Beauv. foxtail millet No - No - No Setaria palmgrass No - No - No palmifolia Koenig Stapf Setaria pumila Poir. yellow foxtail No - No - No Roemer & J.A. Schultes Setaria verticillata L. bristly foxtail No - No - No Beauv. Setaria viridis var. green bristlegrass, No - No - No viridis L. P. Beauv. green foxtail Sorghum bicolor L. sudangrass No - No - No Moench

Sorghum halepense L. johnsongrass No - No - No Pers. Spartina anglica C.E. common cordgrass No - No - No Hubbard Spartina denseflower No - No - No densiflora Brongn. cordgrass Sporobolus tussock dropseed No - No - No diandrus Retz. P. Beauv. Sporobolus indicus rat-tail grass No - No - No Engelm. Stipa capensis Thunb. Mediterranean No - No - No needlegrass Stipa miliacea L. smilo grass No - No - No Hoover Taeniatherum caput- medusahead Yes Yes Yes Yes Yes medusae L. Nevski Thinopyrum intermediate No - No - No intermedium Host wheatgrass Barkworth & D.R. Dewey Thinopyrum tall wheatgrass No - No - No ponticum Podp. Z.-W. Liu & R.-C. Wang Tripidium ravennae L. ravennagrass No - No - No H. Scholz Triticum aestivum L. common wheat No - No - No Urochloa mutica Forsk. paragrass No - No - No T.Q. Nguyen Ventenata dubia Leers ventenata No - No - No Coss. & Durieu Vulpia bromoides L. squirreltail fescue No - No - No S.F. Gray Vulpia myuros L. K.C. rattail fescue No - No - No Gmel.

*Species was listed as fire promoting in Hawaii, but not in the conterminous United States study area.

Supplemental Table S2: Available spatial data and affected ecoregions for each grass species. The extents of invaded pixels within affected Level III Ecoregions (3) were used to define each study area.

Location of Suspected Number of Scientific Name Fire Impacts Level III Ecoregion(s) Invaded Pixels Arundo donax southern California California Coastal /Sage Chaparral and 35 Oak Woodlands (11.1.1) Bromus rubens Mojave Desert, Sonoran Arizona/ New Mexico Mountains (13.1.1), 286 Desert, California Arizona/ New Mexico Plateau (10.1.7), chaparral Madrean Archipelago (12.1.1), Mojave Basin and Range (10.2.1), Sonoran Basin and Range (10.2.2)

Bromus tectorum Great Basin, Mojave Central Basin and Range (10.1.5), 9,388 Desert Columbia Plateau (10.1.2), Mojave Basin and Range (10.2.1), Northern Basin and Range (10.1.3), Snake River Plain (10.1.8)

Imperata cylindrica south eastern U.S. Southern Coastal Plain (8.5.3), Southern 2,761 Florida Coastal Plain (15.4.1) Microstegium eastern temperate forest Blue Ridge (8.4.4), Central Appalachians 1,856 vimineum (8.4.2), Interior Plateau (8.3.3), Interior River Valleys and Hills (8.3.2), Northern Piedmont (8.3.1), Piedmont (8.3.4), Ridge and Valley (8.4.1), Southwestern Appalachians (8.4.9), Western Allegheny Plateau (8.4.3) Miscanthus south eastern U.S. Blue Ridge (8.4.4), Central Appalachians 86 sinensis (8.4.2), Northern Piedmont (8.3.1), Piedmont (8.3.4), Ridge and Valley (8.4.1), Southeastern Plains (8.3.5), Western Allegheny Plateau (8.4.3) Neyraudia south Florida Southern Florida Coastal Plain (15.4.1) 295 reynaudiana Pennisetum ciliare Sonoran Desert, Arizona Sonoran Basin and Range (10.2.2), 2,402 Sonoran Desert (10.2.2) Phragmites upper Midwest wetlands, Huron/Erie Lake Plains (8.2.2), North 3,539 australis Atlantic coast Central Hardwood Forests (8.1.4), Northern Lakes and Forests (5.2.1), Southern Michigan/Northern Indiana Drift Plains (8.1.6) Schismus arabicus California, Mojave Desert Sonoran Basin and Range (10.2.2), 229 Sonoran Desert (10.2.2) Schismus barbatus arid shrublands Sonoran Basin and Range (10.2.2), 236 California, Mojave Desert Sonoran Desert (10.2.2) Taeniatherum Great Basin, western US Central Basin and Range (10.1.5), 393 caput-medusae Northern Basin and Range (10.1.3), Sierra Nevada (6.2.12), Wasatch and Uinta Mountains (6.2.13)

Supplemental Table S3: Percent deviance explained and ΔAIC for all covariates in each model. Percent deviance explained refers to the top-ranked model and the percent explained by each of the model covariates. ΔAIC is calculated as the change in AIC from the top ranked model if each covariate is dropped.

Grass Species (Model) Variable ΔAIC % Deviance Explained B. tectorum (Occurrence) Top-ranked model n/a 7.1 Road 14 0.1 BPS 49 0.4 Ecoregion 1093 6.2 Development 20 0.1 Invaded 20 0.6 B. tectorum (Frequency) Top-ranked model n/a 9.3 Road 1 0 BPS 42 0 Ecoregion 1162 0.4 Development 23 8.3 Invaded 81 0.6 I. cylindrica (Occurrence) Top-ranked model n/a 5.9 Road 45 1 BPS 5.3 0.4 Ecoregion 203 4.1 Invaded 8.1 0.2 I. cylindrica (Frequency) Top-ranked model n/a 7 Road 55 1.4 BPS 7.4 0.5 Ecoregion 186 4.6 Invaded 1.3 0.1

M. sinensis (Occurrence) Top-ranked model n/a 10 Road 8.3 7.4 Invaded 2.3 3

M. vimineum (Occurrence) Top-ranked model n/a 2.3 Road 6.8 0.4 Ecoregion 21.2 1.6 Invaded 2.5 0.2 M. vimineum (Frequency) Top-ranked model n/a 3.9 Road 12.6 0.7 Ecoregion 37.8 2.6 Invaded 2.6 0.3 N. reynaudiana (Occurrence) Top-ranked model n/a 13.8 Development 37.7 5 Invaded 44.91 6 11

N. reynaudiana (Frequency) Top-ranked model n/a 11.3 Development 14.9 3.5 Invaded 40.8 6 P. ciliare (Occurrence) Top-ranked model n/a 7.4 Road 53.7 2.3 BPS 4.1 0.6 Ecoregion 8.4 0.4 Development 5.5 0.3 Invaded 60.9 2.6 P. ciliare (Frequency) Top-ranked model n/a 10.8 Road 68.7 4.8 Ecoregion 10.9 0.9 Development 2.3 0.2 Invaded 30 2.2 S. barbatus (Occurrence) Top-ranked model n/a 11 Road 5 2.2 BPS 1.4 3.5 Invaded 4.6 2 T. caput-medusae (Occurrence) Top-ranked model n/a 10.1 Ecoregion 61.6 8.1 Development 0.5 0.3 Invaded 20.3 2.7 T. caput-medusae (Frequency) Top-ranked model n/a 14.8 Ecoregion 68.7 11.3 Development 1.1 0.5 Invaded 20.7 3.4

Key: Road- distance to road BPS- biophysical setting Ecoregion- Level III ecoregion Devevelopment- percent development Invaded- grass invaded pixel % Dev. Explain- Percent Deviance Explained

Supplemental Table S4: Ecological and anthropogenic covariates included in the fire occurrence, size, and frequency models.

Category Model Covariate Data Source Reference Ecological Ecoregion EPA Level III Ecoregions (3) Ecological Potential Vegetation LANDFIRE Biophysical Setting (BPS140, Veg) (4, 5) Anthropogenic Percent Development LANDFIRE Existing Vegetation Type (EVT140, PHYS) (5, 6) Anthropogenic Distance to Road Tiger Lines (Roads) (7)

Supplemental Figure S1: Histograms of A) counts of fires and B) proportion of fires for grass species that significantly increased fire frequency. Invaded pixels (dark purple) were more likely to burn multiple times during the study period than uninvaded pixels (light purple).

References

1. Invasive Plant Atlas of the United States (2018) Invasive plant atlas of the United States - database of plants invading natural areas. URL: http://www.invasiveplantatlas.org/. (Accessed June, 2018). Available at: https://www.invasiveplantatlas.org/index.html.

2. U.S. Department of Agriculture (2018) FEIS. Forest Service, Rocky Mountain Research Station, Missoula Fire Sciences Laboratory (Producer). Fire Effects Information System, [Online]. Accessed 20 June 2018. Available: www.feis-crs.org/feis/#.

3. U.S. Environmental Protection Agency (2013) Level III Ecoregions of the Conterminous United States. U.S. EPA Office of Research & Development (ORD) - National Health and Environmental Effects Research Laboratory (NHEERL). Accessed 15 October 2018. https://www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states

4. LANDFIRE (2014) Biophysical Setting, LANDFIRE 1.4.0, U.S. Department of the Interior, Geological Survey. Accessed 30 April 2018 at https://www.landfire.gov/version_comparison.php?mosaic=Y. doi:10.1590/s1809- 98232013000400007.

5. Rollins MG (2009) LANDFIRE: a nationally consistent vegetation, wildland fire, and fuel assessment. Int J Wildl Fire 18:235–249.

6. LANDFIRE (2014) Existing Vegetation Type Layer, LANDFIRE 1.4.0, U.S. Department of the Interior, Geological Survey. Accessed 30 March 2018 at https://www.landfire.gov/version_comparison.php?mosaic=Y. doi:10.1590/s1809- 98232013000400007.

7. TIGER/Line Shapefiles (2016) (machine readable data files) / prepared by the U.S. Census Bureau.