The ecological furnishings of blaze in close Pacific island ecosystems accept accustomed little absorption in best Pacific island groups (Nunn, 1990). Despite the abeyant accent of wildfires for conservation, attainable health, and human-environment interactions, actual few studies of bonfire furnishings on Pacific island frondescence exist, and reliable, quantitative advice on absorption threats is bound (Keppel et al., 2014). Almost annihilation is accepted about how a bonfire affects bulb communities in the Pacific alfresco of Hawai’i (Hughes, Vitousek & Tuniston, 1991; D’Antonio & Vitousek, 1992; Hughes & Vitousek, 1993; Freifelder, Vitousek & D’Antonio, 1998; D’Antonio, Tunison & Loh, 2000; D’Antonio, Hughes & Vitousek, 2001; Ainsworth & Kauffman, 2009, 2010, 2013; Angelo & Daehler, 2013; Ellsworth et al., 2014), with a few studies in New Caledonia (McCoy et al., 1999), western Polynesia (Hjerpe, Hedenås & Elmqvist, 2001; Elmqvist et al., 2002; Franklin, 2007) and Guam (Athens & Ward, 2004). Furthermore, human-caused wildfires are added occurring on Pacific islands in the avant-garde era (Trauernicht et al., 2015), and islands are abnormally affected to anthropogenic disturbances (Keppel et al., 2014). In this paper, we use a atypical dataset to appraise the furnishings of wildfires on low-elevation and already heavily-invaded frondescence communities in the Society Islands, French Polynesia.
Few annal and no academic studies abide for French Polynesia of the ecological furnishings of bonfire in avant-garde times. Indeed, best Pacific island bulb communities, abnormally communities bedeviled by built-in bulb species, are not advised to abutment alive blaze regimes of the blazon apparent in some continental communities of agnate altitude due to differing agitation patterns, bulb structure, winds, and added factors (Cochrane, 2003; but see Hunter-Anderson, 2009). Although accustomed bonfire is anticipation to be acutely attenuate as a agitation in Pacific earthbound built-in bulb communities, botanists alive in the arena accept continued doubtable that anthropogenic blaze (alongside added animal land-use changes) has played an important role in assertive low- and mid-elevation earthbound frondescence communities. The botanical affirmation for a role of anthropogenic blaze are the all-encompassing low-elevation fernlands and grasslands which drew the absorption of aboriginal Western acreage botanists in the Pacific (including French Polynesia). These communities were usually declared as near-monocultures, bedeviled by either the built-in bracken Dicranopteris linearis (Gleicheniaceae) or several breed of grass. In some a cases, these fernlands and grasslands booty the anatomy of “savannas” with broadcast appearing copse in genera such as Metrosideros and Commersonia (Florence, 1997; Russell, Raich & Vitousek, 1998). For example, Dicranopteris fernlands are accepted in the Society, Cook, Austral, Hawaiian, and Wallis and Futuna islands (Florence, 1997; Sykes, 2016; Meyer, 2017). In a abounding assay of Society Islands frondescence arise in French, Papy (1954) arise an affiliation of Dicranopteris and grasses with fire, and appropriate that the aloft can resprout from rhizomes afterward wildfire. He additionally empiric that assertive coarse plants (Metrosideros collina, Melastoma denticulatum, and Dodonaea viscosa) are about associated with areas that accept burned. These observations are constant with added contempo ones from Hawai’i for Dodonaea viscosa and the affiliated Metrosideros polymorpha (following single, low-intensity fires; Ainsworth & Kauffman, 2009; D’Antonio, Tunison & Loh, 2000). Surveying the frondescence of the absolute close Pacific abounding decades later, Mueller-Dombois & Fosberg (1998) came to a agnate conclusion, arguing that Dicranopteris fernlands represent potentially anthropogenic post-disturbance communities because of their acutely low bulb diversity, and because no bulb breed added than Dicranopteris linearis are belted to these communities (i.e., these communities accommodate no abode specialists).
Pacific archaeologists and paleoecologists accept concurred with the abstracts of botanists, invoking charcoal and added pollen annal as added affirmation that blaze is anthropogenic (Kahn et al., 2015; Stevenson et al., 2017), and that boundless “pyrophytic” acreage and fernland zones resulted from the use of blaze by the aboriginal colonizing bodies in French Polynesia and abroad in the Pacific (Dodson & Intoh, 1999; Kirch, 2000; Athens & Ward, 2004; Mann et al., 2008; but see Hunter-Anderson, 2009). It is important to accent that bounded adeptness that anthropogenic blaze promotes Dicranopteris savanna (e.g., references and informants cited in Meyer, 2017) is constant with these archeological and botanical interpretations, and may accept been the aboriginal catalyst which led Western board to doubtable a role for blaze in Pacific frondescence ecology. These absolute curve of affirmation point to anthropogenic blaze in aggregate with added animal impacts partially transforming the mid- and low-elevation frondescence of amphibian Pacific islands from backwoods to pyrophytic fernlands and grasslands, basic conceivably as anon as the aboriginal animal colonization of these islands (1000 C.E. for French Polynesia) (Mueller-Dombois & Fosberg, 1998; Kirch, 2000; Kahn et al., 2015; Stevenson et al., 2017).
The abstracts of botanists, archaeologists, and paleoecologists that blaze in the Remote Pacific is primarily of anthropogenic agent and has played an important role ecologically alone in transforming some low- and mid-elevation bulb communities into bracken and grass-dominated savannas are of accurate accent for absorption and animal affluence in French Polynesia, because anecdotal affirmation suggests that bonfire contest may be accepted during the 2000’s and 2010’s, and possibly accretion in affluence about to actual baselines. Although absolute annal are not publically available, arise account letters in bounded media (La Dépêche de Tahiti, arise circadian in Papeete, Tahiti and the “Polynésie 1ère” account website) announce wildfires contest on the islands of Tahiti in 2013 (two fires), 2015, and 2016, Mo’orea in 2008 and 2011, Huahine in 2016, Raiatea in 2016, and Bora Bora in 2013 (Society archipelago) and Nuku Hiva in 2012 and Ua Pou in 2013 (Marquesas archipelago). A non-peer-reviewed abstraction from a acreage advance accomplished by the University of California, Berkeley articular three wildfires on Moorea which occurred in 1991, 1995, and 1998 (Koehler, 1999), and fractional bonfire annal captivated by the Sapeurs-Pompiers de Moorea (the Moorea blaze department) account 5 wildfires occurring in the aboriginal bisected of 2011 (J.-M. Hokaupoko, 2013, claimed communication). Despite the abeyant accent of bonfire as a botheration for both absorption (J.-Y. Meyer, 2011, claimed communication) and animal affluence (Newman, 2014; J.-M. Hokaupoko, 2013, claimed communication) in French Polynesia, no arise abstraction has advised the ecological furnishings of bonfire in that country.
The absence of studies analytical ecological after-effects of bonfire in French Polynesia are apropos because akin studies from the Hawaiian Islands (which are ecologically agnate and allotment abounding built-in bulb genera) advance that wildfires may absolutely accept actual austere furnishings on avant-garde frondescence communities in means which appulse both biodiversity and the adeptness for approaching wildfires. Studies of bonfire on the island of Hawai’i (“the Big Island”) accept apparent that although a ample cardinal of built-in coarse and timberline bracken breed in wet and mesic forests appearance some adeptness to abide afterwards bonfire through resprouting or formation afterward lava-ignited bonfire (Ainsworth & Kauffman, 2009), and some built-in blooming breed arise to sprout alone afterward again wildfires that abort clutter (Ainsworth & Kauffman, 2013), best affirmation suggests that wildfires access affluence of alien blooming and grass species. Wildfires advance aggression of alien blooming breed in forests (Ainsworth & Kauffman, 2010), built-in timberline and timberline bracken afterlife (D’Antonio, Tunison & Loh, 2000; Ainsworth & Kauffman, 2013), and the backup of built-in communities with invasive grasslands (Hughes, Vitousek & Tuniston, 1991; Hughes & Vitousek, 1993; D’Antonio, Tunison & Loh, 2000; Ainsworth & Kauffman, 2013). These alien blooming and grass communities bind built-in bulb application (Ainsworth & Kauffman, 2010) and are alike added affected to approaching fires, assiduity a grass-fire aeon (D’Antonio & Vitousek, 1992; Freifelder, Vitousek & D’Antonio, 1998). It has been apparent that wildfires can arbitrate transitions amid ascendancy by altered invasive grasses (Hughes, Vitousek & Tuniston, 1991; D’Antonio, Hughes & Vitousek, 2001). Finally, fire-adapted grasses are affective upwards in acclivity (Angelo & Daehler, 2013). Taken together, these studies advance that wildfires in French Polynesia may abate abundances of some built-in bulb species, while accompanying accretion abundances of some alien species—particularly alien grasses—which may actualize fuels that access the anticipation of approaching wildfires.
The purpose of this cardboard is to accommodate a baseline for human-caused bonfire furnishings on breed richness, abundance, and affiliation affinity in low-elevation, heavily-invaded bulb communities in French Polynesia in the modern, post-European acquaintance era through assay of commutual acreage sites. In this study, we appraise frondescence changes associated with wildfires at low elevations (<380 m) on the island of Mo’orea in the Society archipelago of French Polynesia (Fig. 1). We investigate how low-elevation bulb communities alter amid austere areas and adjoining allegory areas that accept no accepted contempo bake history, and apprehend bonfire to accept abounding furnishings on the agreement and about abundances of bulb breed in our abstraction sites. Allegory areas in this abstraction do not represent accustomed frondescence communities, but instead are accessory forests bedeviled by alien breed that accept regrown in areas austere or able by bodies afterward animal colonization ∼1000 year BP (Mueller-Dombois & Fosberg, 1998; Kirch, 2000). Built-in forests in French Polynesia, which anchorage best actual ancient bulb and bearcat diversity, are primarily belted to college elevations (Meyer, 2010), and do not artlessly acquaintance ample wildfires.
Given what is accepted from antecedent observations from added islands, we accept that austere areas will accept a decidedly altered frondescence affiliation from not afresh austere or adapted allegory areas. We apprehend that grasses and ferns, abnormally Dicranopteris linearis, will be present at college accommodation in austere areas than in allegory areas. We additionally apprehend that austere areas will accommodate added alien breed and college abundances of alien breed than are present in allegory areas, but that built-in (especially herbaceous) frondescence will abide or recolonize austere sites (Ainsworth & Kauffman, 2009, 2013). We investigate whether armpit or austere cachet (burned or comparison) is added cogent in answer breed assortment and empiric affluence in abstraction areas. We appraise which bulb breed are present through colonization, regrowth, or persistence, in austere areas. One aim of this abstraction is to analyze which of the breed absolute in an already awful adapted bulb affiliation are adequate to become added abounding or invasive afterwards wildfire, with appropriate absorption to avant-garde invasives and plants that are accepted to access blaze hazard. These after-effects may accept implications for absorption efforts in southeastern Polynesia and abroad in Oceania.
We conducted assay on the island of Mo’orea, French Polynesia (17°32′S, 149°50′W) during the austral-spring dry division of October and November 2013 (Fig. 1). The wetter summer division lasts from December–April, and the drier winter division lasts from May–November. Ample condensate contest can action in the mostly dry winter months, and there can be abounding interannual aberration in accumulative rainfall. Weather base abstracts provided by the Moorea Coral Reef Ecosystem LTER for August 2006–October 2010 address account boilerplate temperatures alignment from 24.5 to −27.2° C, and account accumulative condensate amid 0.8 mm and 716.8 mm (Washburn, Brooks & Moorea Coral Reef LTER, 2013). Apprehension are about abiding and bedeviled by southeasterly barter winds, although able wind events, including cyclones, action somewhat consistently (http://mcrlter.msi.ucsb.edu/data/variable/).
We formed at three sites, anniversary absolute two abstraction areas: a post-wildfire (“burned”) breadth that was commutual with a nearby, “comparison” breadth (within 0.2–0.5 km) that had no contempo history of blaze or agronomical modification. Post-wildfire sites represented a array of times back blaze disturbance, absolute austere area, aboriginal frondescence communities, elevations, slopes, aspects, and microclimates. We chose to assignment in sites ahead advised by Koehler (1999), breadth austere and allegory areas at a audible armpit had the aforementioned or actual agnate slopes, aspects, boilerplate rainfalls, and clay types (Bonvallot et al., 1993), and an added armpit with agnate description. The seasonality and severity of the burns were not controlled for in analyses, and the post-wildfire acute altitude are not known, anniversary of which can access breed affluence and affluence in post-wildfire communities. We analyze that this accumulating of sites in not meant to represent bulb affiliation assumption for different-aged sites, because we did not admeasurement or ascendancy for site-to-site aberration in temperature, precipitation, and added factors important in alignment bulb communities.
Study sites assorted in location, time back burn, and added characteristics, but were all amid on the wetter ancillary of the island (Table 1). Armpit 1 was amid at the Col des Trois Cocotiers (accessible via the “Three Coconuts trail”) on the saddle amid Mount Tohi’e’a and Mount Mou’aroa. This bonfire originated from a baby bivouac at the top of the backbone (J.-Y. Meyer, claimed communication) in 2004 (nine years afore this assay was conducted), afire <1 ha. The armpit receives an boilerplate anniversary condensate of 4,500–5,000 mm, was characterized in 1993 as accepting an boilerplate anniversary temperature of 20–22.7 °C (Bonvallot et al., 1993), and is in absolute sunlight throughout the day. The abruptness at this armpit varies with a best of 30%. The adjoining allegory breadth was agnate to the austere breadth but receives hardly added shade, and was amid to the west of the austere area.
Summary of characteristics for austere and allegory sites, which accept no contempo history of disturbance.
Site 2 is additionally amid on the southwest ancillary of the island, arctic of the boondocks of Ha’apiti. According to Koehler (1999), the blaze occurred in 1995 (18 years afore survey), starting in a noni (Morinda citrifolia, or “nono” in Tahitian) bake-apple acreage and traveling up the abruptness of a west-facing backbone for about 1 km. The amplitude of the austere breadth was ∼300 m, with a absolute breadth of ∼4 ha. The abruptness of this armpit averaged about 25% slope, and the backbone can accept absolute ablaze for the absolute day. The boilerplate anniversary precipitation is 1,720–2,000 mm, with an boilerplate anniversary temperature of >22.7 °C (Bonvallot et al., 1993). The adjoining allegory breadth was amid to the northeast of the austere area.
Site 3 was amid on the southwest ancillary of the island, southeast of Ha’apiti. According to Koehler (1999), the bonfire occurred in 1991 (22 years afore this assay was conducted), and started as a accumulation of afire decay in a cemetery on the outskirts of Ha’apiti. The blaze catholic forth a west-facing backbone for about 1.5 km. The absolute austere breadth was ∼5 ha, boilerplate beyond 250 m in width. The abruptness is ∼25% forth the absolute breadth of the austere armpit (Koehler, 1999). The backbone receives absolute sunlight for the majority of the day, the boilerplate anniversary precipitation at the armpit is 2,000–2,350 mm, and the boilerplate anniversary temperature is >22.7 °C (Bonvallot et al., 1993). The adjoining allegory breadth was amid to the southeast of the burn. Center credibility of all austere and allegory areas, and absolute breadth austere were estimated application Google Earth (Google, 2013).
Each of the commutual abstraction areas at three sites (Sites 1, 2, and 3) comprises a post-wildfire austere breadth and an adjacent, unburned allegory area, for six absolute abstraction areas. Bristles transect curve were placed in anniversary abstraction area, for a absolute of 30 transects. Transect curve were placed about 4 m afar in allegory areas and in bake sites breadth the appearance of the post-fire breadth allowed. For continued burn-scar sites, transects were placed hardly afterpiece to one addition or end-to-end. Frondescence was sampled at 4 m intervals forth the breadth of anniversary transect (starting at the aught point, for a absolute of 13 samples per transect and n = 390 absolute abstracts points) at all sites forth credibility on a 50 m transect tape, application a adjustment adapted from the Line Interception Adjustment (or “line-intercept method,” Canfield, 1941).
For anniversary austere and allegory area, all individuals of vascular bulb breed affecting and anon aloft a vertical barometer column placed at 4 m intervals were recorded. Lichens and mosses were not included in this study. Alone plants were counted on transect credibility (as “observed abundance”) and articular to the breed akin in the acreage if possible, and photographs were taken for afterwards verification. For plants that could not be field-identified, samples were calm for assay at the University of California, Berkeley Gump Base application online and printed bulb identification keys (Moorea Digital Flora Project, Murdock, 1999; Whistler, 1996). Samples and photographs were absolute through able assessment (of J.-Y. Meyer, R. Taputuarai, and J. Nitta). Voucher specimens calm from anniversary armpit accept been deposited in the University Herbarium (UC) at the University of California, Berkeley. Acreage surveys were conducted beneath the allotment of a University of California Berkeley admittance associated with an undergraduate educational advance (ESPM C107) from the Government of French Polynesia.
Plant breed were categorized by agent as built-in or introduced, and aural the class of alien species, a acumen was fabricated amid “Polynesian introduction” (prior to European contact) and “modern introduction” (post European contact) for assay (Table 2). Actual attendance was adjourned by accord and able opinions including the following: Austin (1991), Butaud, Gérard & Guibal (2008), Butaud (2010), Florence (1997, 2004), Florence et al. (2007), McCormack (2007), Meyer (2004), J.-Y. Meyer (2013, claimed communication), J. Nitta (2013, claimed communication), Prebble (2008), Wagner & Lorence (2002) and Whistler (1996, 2009).
Plant breed recorded at the three abstraction sites, categorized by ample taxonomic groups.
Line-intercept transect abstracts were acclimated to account about frequencies of species’ abundances for austere and allegory areas at anniversary of the three abstraction sites. Empiric abundances were affected as absolute cardinal of individuals in anniversary breed affiliated beyond all bristles transects in one abstraction area. Absolute breed affluence was affected as cardinal of breed encountered on all transects in anniversary area. Plants were organized for assay by attendance in austere areas, allegory areas, or both, and graphed by class for added examination. Differences amid breed affluence by class of agent was adjourned with Pearson’s Chi-squared tests for proportions, with the absent antecedent that the austere areas accept the aforementioned accommodation of breed affluence by class of agent as the allegory areas. Agnate calculations were fabricated for empiric abundances of plants by class of origin.
To assay the about accent of armpit (SITE) and austere or allegory cachet (STATUS) in free the bulb affiliation in an area, we complete abstracted sets of Poisson-distributed ambiguous beeline models (GLMs) for breed richness, and for empiric abundances at anniversary transect point (Poisson and Gaussian models were run in anniversary case and compared to anniversary added with AIC and log likelihood values). We included an alternation aftereffect of SITE:STATUS in anniversary model. Akaike’s Advice Criterion adapted for baby sample sizes (AICc) was activated to anniversary archetypal set for archetypal selection.
For bulb abstracts in anniversary assay area, we performed a two-dimensional non-metric multi-dimensional ascent (NMDS) application a Bray-Curtis adverse cast to appraise community-level differences amid sites and amid austere and allegory areas, application alone transects as abstracts points. Bray––Curtis NMDS analyses appraise affiliation agreement and structure. We active Wisconsin bifold acclimation (using R amalgamation “vegan” “metaMDS” analysis, Oksanen et al., 2018). After-effects of the NMDS were evaluated application a permutational multivariate assay of about-face (“adonis” in R software amalgamation “vegan”) clay the NMDS adjoin austere or allegory cachet of abstraction areas. A statistically cogent amount of the “adonis” F-test would announce that the austere areas are altered from the allegory areas in agreement of affiliation composition, abstinent in boxlike aberration from the centroid of anniversary accumulation in allotment space.
All analyses were conducted in “R” adaptation 3.1.3 (R Core Team, 2015), with added bales “vegan” adaptation 2.5-2 (Oksanen et al., 2018), “MASS” adaptation 7.3-34 (Venables & Ripley, 2002), and “AICcmodavg” adaptation 2.1-1 (Mazerolle, 2017).
Wildfire at all surveyed sites had ample furnishings on the breed agreement of the constant communities, in adverse to allegory areas. Breed that were alone present in allegory areas (23 species), outnumbered those that were alone present in austere areas (11 species), but showed commensurable affluence to breed that were present in both austere and allegory areas (23 species) (Fig. 2). Some of the best accepted breed present alone in allegory areas included the built-in bracken Angiopteris evecta, the Polynesian-introduced amber Zingiber zerumbet, the avant-garde addition Miconia calvescens, and the attic Cocos nucifera. In austere areas, some of the best accepted breed were the built-in bracken Dicranopteris linearis and the built-in timberline Metrosideros collina. Breed begin in all sites included the built-in timberline Hibiscus tiliaceus and the avant-garde addition Paraserianthes falcataria.
Burned and allegory sites independent a absolute of 57 vascular bulb breed (one club moss, 13 ferns, 14 monocots, and 29 eudicots; Table 2). Of the vascular plants, 54 were articular to the breed level, and three alien breed were accustomed altered identifiers for analysis. At allegory sites, 46 breed were begin in total, with 34.8% built-in species, 17.4% Polynesian alien species, and 41.3% avant-garde alien breed (with three anonymous breed of alien origin). By comparison, 34 breed were begin in austere sites, 38.2% of which were natives, 5.9% Polynesian, and 50.0% avant-garde introductions (Figs. 3 and 4; raw abstracts visualized in Supplementary Material). Empiric abundances assorted on a site-to-site basis, with bonfire accretion empiric abundances at two of three sites, and acutely abbreviating empiric abundances at Armpit 2.
A Poisson archetypal of breed affluence ∼ SITE STATUS had the best allegorical ability (evidence arrangement compared to aing best archetypal = 16.42) (Table 3A). We begin that allegory areas had greater breed affluence than austere areas (P < 0.001); Armpit 1 had the greatest breed affluence (Table 4). GLM assay of empiric abundances (Table 3B) produced one archetypal with allegorical ability (abundance = SITE STATUS SITE:STATUS). Fixed aftereffect constant estimates (Table 5) appearance that “comparison” cachet had college affluence about than austere areas (P = 0.079), admitting the aftereffect admeasurement was almost baby (0.152). As was the case for the breed affluence GLM, the aerial point appraisal and statistical acceptation of the ambush in anniversary case indicates that added nuanced models with college allegorical ability could be developed.
Model alternative for breed affluence and for empiric abundance.
Fixed aftereffect constant estimates from GLM assay of absolute breed richness, from the top AIC c-selected model.
Fixed aftereffect constant estimates from GLM assay of empiric abundance, from the top AIC c-selected model.
Species affluence was compared amid abstraction areas by class of agent (Fig. 3). Pearson’s Chi-squared tests for accommodation appearance no differences amid accommodation of breed in the native, Polynesian introduction, and avant-garde addition categories for austere and allegory areas at anniversary armpit (χ2 = 1.43, df = 2, P = 0.434 at Armpit 1; χ2 = 3.65, df = 2, P = 0.161 at Armpit 2; and χ2 = 3.58, df = 2, P = 0.167 at Armpit 3). Back avant-garde and Polynesian introductions are aggregate into one “introduced species” category, this aftereffect does not change, that is, there are no statistically cogent differences amid accommodation of built-in and alien breed by built-in against alien categories (P-values on χ2 tests are all >0.2).
Proportional abundances of all individuals were additionally compared beyond austere and allegory areas in three sites by class of agent (Fig. 3). Pearson’s Chi-squared tests appearance statistically cogent differences amid accommodation of abundances of individuals in the native, Polynesian introduction, and avant-garde addition categories for austere and allegory areas at anniversary armpit (χ2 = 7.523, df = 2, P = 0.023 for Armpit 1; χ2 = 10.697, df = 2, P = 0.005 for Armpit 2; and χ2 = 76.705, df = 2, P < 10–5 for Armpit 3). Back avant-garde and Polynesian introductions are aggregate into one “introduced species” category, after-effects are still statistically cogent (P = 0.09 for Armpit 1; P = 0.005 for Armpit 2; and P = 0.01 for Armpit 3). Bonfire decidedly added the proportional affluence of individuals in the “introduced species” class at Sites 1 and 3, but decreased the proportional affluence of alien breed at Armpit 2.
Plant breed agreement and abundances by transect were analyzed application two-dimensional NMDS, which converged in 20 iterations, for a affected accent = 0.160 (considered an adequate fit), Procrustes basis beggarly boxlike absurdity = 1.64e-05, and best residuals = 2.98e-05. NMDS after-effects were advised with alone credibility apery breed affluence and empiric abundances of a audible transect (Fig. 5). There was no overlap in the credibility amid the austere and allegory areas, visually advertence ample differences amid austere and allegory communities in allotment space. Credibility for anniversary of the allegory areas were awful amassed and did not overlap with credibility from added sites, advertence abounding differences in communities amid altered (not afresh burned) allegory areas. In contrast, credibility for the austere areas are awful alloyed and about ambiguous from anniversary other, and within-site advance of credibility in NMDS-ordination amplitude is beyond for the austere areas than for the allegory areas. The “adonis” permutational multivariate assay of about-face agitated out on the NMDS produced assay accomplishment ethics of F1,28 = 14.734 and R2 = 0.345, with P < 0.001, acceptation that compositional differences amid groups (in this case austere and allegory areas) are awful statistically significant.
Even in an already heavily impacted bulb community, bonfire in low-elevation Pacific island frondescence creates communities that are actual agnate amid sites, admitting allegory sites with no contempo history of agitation abide almost audible from one another. Bonfire does not arise to change the admeasurement of breed in a affiliation by their class of agent (i.e., native, Polynesian introduction, or avant-garde introduction). Counter to our aboriginal hypothesis, we did not acquisition added alien breed in austere areas than allegory areas. Empiric abundances were about college in allegory areas than austere areas, but the aftereffect of bonfire was awful capricious amid sites, and bonfire abundantly bargain empiric affluence at one of three sites (Site 2), possibly due to post-wildfire altitude for about-face or added abysmal variables. Our NMDS after-effects (followed by multivariate about-face analysis) additionally appearance cogent differences in breed agreement of austere and allegory areas.
These after-effects taken calm accommodate affirmation that bonfire impacts on the built-in affiliation of plants alter from armpit to site, and may be accompanying to microclimate or added anatomy drivers affecting the aboriginal frondescence affiliation (Thaxton & Platt, 2006; Hoffmann et al., 2012), or backdrop of the blaze contest themselves (such as temperatures, intensity, calefaction flux, abode time; Frost & Robertson, 1985; Thaxton & Platt, 2006), and post-fire acute altitude (Frost & Robertson, 1985) that were not abstinent in this study.
Our after-effects advance that there is a cogent basic of the low-elevation bulb affiliation that is anon benefitting from bonfire action and are present alone in austere areas. We found, as antecedent studies have, that the built-in bracken Dicranopteris linearis (Gleicheniaceae) colonized austere areas, constant with observations of the pyrophytic Dicranopteris savanna acclaimed by added board (Papy, 1954; Mueller-Dombois & Fosberg, 1998; Meyer, 2017). We did not acquisition college attendance of grasses in general, as has been acclaimed in Hawai’i (Hughes, Vitousek & Tuniston, 1991; Hughes & Vitousek, 1993; D’Antonio, Tunison & Loh, 2000; Ainsworth & Kauffman, 2013), although we begin that the non-native invasive grass Melinis repens (natalgrass, Poaceae) was present alone in the austere sites. This breed is advised invasive in both French Polynesia and Hawai’i, and the aforementioned pattern—presence in austere areas only— was arise by D’Antonio, Hughes & Tunison (2011). It should be acclaimed that all our abstraction sites were amid on the wet ancillary of the island, and that non-native grasses are present in affluence alone on the dry ancillary of Mo’orea. A abstraction advised to sample the dry ancillary of Mo’orea ability ascertain added invasives that may be overextension through alternation with wildfire.
Among added breed begin alone in austere areas are the built-in copse Metrosideros collina (Myrtaceae) and Commersonia bartramia (Malvaceae). This is constant with observations of Metrosideros collina in affiliation with either blaze or Dicranopteris savanna (Papy, 1954) and of C. bartramia in Dicranopteris savanna (Florence, 2004; Meyer, 2017). One ascertainment of the built-in timberline Phyllanthus manono (syn. Glochidion manono, Phyllanthaceae) in a austere breadth is absorbing to the accustomed history of this breed accustomed that this brand has about been arise from abashed contexts in Remote Oceania (Hembry, 2017), but it was not acclaimed at the time of the assay if this was an alone that had resprouted or developed from seed. Of added breed begin in affiliation with fire, pineapple (Ananas comosus, Bromeliaceae) is a bake-apple crop that may accept been buried afterward the fires, and accordingly adequate does not represent a “naturalized” breed benefitting from fire. Papaya (Carica papaya, Caricaceae), on the added hand, does assume to account from blaze in western Polynesia (Franklin, 2007) although we are not acquainted of affirmation that it is aborigine in southeastern Polynesia breadth this abstraction took abode (Sykes, 2016).
Of the breed present in both austere and allegory areas, the built-in timberline Hibiscus tiliaceus (Malvaceae) is the best abundant, followed by a ambiguous avant-garde invasive, Paraserianthes falcataria (Fabaceae). This breed (syn. Falcataria molluccana, Albizia falcataria), back compared to added invasives, has been articular as accepting asymmetric furnishings on breed accident in close systems it invades (Pyšek et al., 2012). Several built-in and alien overstory copse are present in both austere and allegory sites, but are added accepted in the latter. These accommodate the built-in Neonauclea forsteri (Rubiaceae), the Polynesian-introduced Inocarpus fagifer (Fabaceae), and the avant-garde introductions Spathodea campanulata (Bignoniaceae) and Mangifera indica (mango; Anacardiaceae). We advance that these accept alone persisted through low-intensity blaze in baby numbers. Alternation of overstory copse in or at the margins of low-intensity burns may be added common, and such observations should be acclaimed in approaching studies on this topic.
Of the comparison-area alone plants, notable are attic (Cocos nucifera, Arecaceae), which may accept been planted, a host of built-in breed which may be awful fire-intolerant, including Ixora mooreensis (Rubiaceae) and Xylosma suaveolens (Flacourtiaceae), a ample cardinal of built-in bracken species, and an invasive breed of appropriate affair in French Polynesia, Miconia calvescens (Melastomataceae), which densely invades contrarily undisturbed areas (Meyer & Florence, 1996).
Our after-effects highlight four alien and/or invasive breed which may be facilitated by blaze and which are of affair to acreage administration in French Polynesia and the Pacific region. Natalgrass (Melinis repens), a avant-garde addition begin alone in austere sites in this study, is discussed above. Miscanthus floridulus (Poaceae) is abounding added abounding in austere than allegory sites in our study, as are Paraserianthes falcataria and Lantana camara. Miscanthus floridulus is a Polynesian-introduced grass which is advised a baneful edger in Hawai’i, although not in French Polynesia, and is advised built-in on Guam and the arctic Mariana Islands, breadth it is a ascendant basic of fire-prone anthropogenic savannas (Minton, 2006). Although ranked alone sixth in affluence in austere sites, L. camara is a avant-garde addition that is apparently of college affair than some of the added abounding species. Fire-Lantana interactions, including the achievability of a “fire cycle” or absolute acknowledgment amid the two, are of appropriate affair and accept been arise from continental close areas (Fensham, Fairfax & Cannell, 1994; Duggin & Gentle, 1998; Hiremath & Sundaram, 2005; Berry, Wevill & Curran, 2011). The flammability and added blaze adaptations of this breed compared to added frondescence in this arrangement are not known. L. camara is bird-dispersed in French Polynesia (Spotswood, Meyer & Bartolome, 2012), and so has the abeyant to access its ambit rapidly through berry dispersal. L. camara is appointed by the French Polynesian government as one of the best austere invasive plants in the country (Meyer & Butaud, 2007).
The allegory sites, like best low-elevation bulb communities on Mo’orea and abroad in French Polynesia, are accessory backwoods or brier communities heavily invaded by, and in abounding cases bedeviled by, non-native breed of angiosperms. These heavily invaded bulb communities accept developed over a acreage use history that includes animal allowance of acreage for agronomics and timber, the agronomics of agroforests by Polynesians afore European contact, the afterlife of built-in birds as berry dispersers, the aishment of seabird colonies and their comestible inputs, and the addition of ungulates (especially pigs; Sus scrofa) (Kirch, 2000; Meyer, 2004; Steadman, 2006; Dotte-Sarout & Kahn, 2017). There is no affirmation to advance that these heavily adapted frondescence communities at low elevations on Mo’orea accept a accustomed blaze administration of the array which occurs in continental regions. Blaze in this ambience should be anticipation of as an anthropogenic agitation that has abstruse furnishings on these primarily non-native frondescence communities. We begin that in this context, blaze facilitates a subset of the built-in flora (such as Dicranopteris linearis and Metrosideros collina) but additionally facilitates several of the best annihilative invasive plants in French Polynesia (Paraserianthes falcataria, and L. camara), and two alien grasses advised invasive in Hawai’i (Melinis repens, Miscanthus floridulus), one of which is listed as a baneful edger by the accompaniment of Hawai’i (Miscanthus floridulus).
Our after-effects authenticate that bonfire on Mo’orea causes cogent changes in bulb communities, accretion affinity of communities amid sites, accretion abundances of alien breed in austere areas, and alteration affiliation agreement by facilitating colonization by Dicranopteris linearis as able-bodied as non-native breed that accept accepted absolute blaze acknowledgment interactions. These changes are present in all post-wildfire sites (including the oldest armpit of 22 years). Long-term changes to the frondescence affiliation that advance non-native and fire-prone breed could be abnormally adverse on baby close islands because they are added affected to invasion, and the bulb assortment is already almost low (Elton, 1958; Vitousek et al., 1996).
Pacific islands invasives are analogously understudied (Pyšek et al., 2008, 2012), and agitation anatomy has not been advised in abounding Pacific island groups. Our after-effects may be generalizable to added islands both aural the Society Islands alternation and abroad in French Polynesia and southeastern Polynesia, breadth the aboriginal frondescence communities are agnate to those on Mo’orea, and the invasive breed attainable to arrive post-wildfire sites appear from the aforementioned basin of attainable species. These after-effects are important in ablaze of accepted contempo letters of bonfire contest in bounded account media from assorted islands in French Polynesia, and because both bonfire affluence and absolute austere breadth per year may access in approaching years with altitude change, attendance of invasive species, accretion populations that await on blaze for agronomical and decay management, and added changes in animal acreage use.
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