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Basic and Applied Ecology 12 (2011) 733–742

ioneer effects on exotic and native tree colonizers: Insights for Araucariaorest restoration

islene Ganadea,c, Maria N. Miritib,∗, Guilherme G. Mazzochinia,c, Claudia P. Paza

Laboratório de Ecologia da Restauracão, Biologia, Universidade do Vale do Rio dos Sinos - UNISINOS, CP 275, CEP 93022-000, Sãoeopoldo, Rio Grande do Sul, BrazilDepartment of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USADepartamento de Botânica, Ecologia e Zoologia, Centro de Biociência, Universidade Federal do Rio Grande do Norte, CEP 59072970,atal, RN, Brazil

eceived 10 September 2010; accepted 29 September 2011

bstract

We integrate analyses of spatial association with empirical measures of juvenile performance to develop a strategy forraucaria forest restoration in Brazil. Because pioneer species can differentially facilitate or inhibit target species, we measureative Araucaria angustifolia and exotic Pinus taeda responses to two common pioneer species, Baccharis uncinella andernonia discolor in a clear-cut pine plantation. P. taeda establishment and growth was greater than that of A. angustifolia inll treatments, showing its potential for invasiveness. B. uncinella showed significant positive spatial associations with P. taedand negative spatial associations with A. angustifolia. V. discolor showed significant negative spatial associations with P. taedaut neutral spatial associations with A. angustifolia, it also supported a higher diversity of native species under its canopy than. uncinella. Experimental results show that these patterns are due to differential establishment restrictions imposed by bothioneers on target species. We conclude that B. uncinella promotes pine invasion while V. discolor restrains it. We suggesttrategies for Araucaria forest restoration and highlight the broad applicability of our approach to restoration programs.

usammenfassung

Wir kombinieren Analysen zur räumlichen Vergesellschaftung mit empirischen Messungen zum Erfolg der Juvenilen, um einetrategie für die Restauration von Araucaria-Wäldern in Brasilien zu entwickeln. Da Pionierarten Zielarten in unterschiedlichereise fördern oder hemmen können, maßen wir auf einer kahlgeschlagenen Kiefernplantage die Reaktion der einheimischen

raucaria angustifolia und der exotischen Pinus taeda auf zwei verbreitete Pionierarten: Baccharis uncinella und Vernoniaiscolor.

Pinus taeda fasste in allen Behandlungen schneller Fuß und wuchs schneller als A. angustifolia, wodurch ihr höheres Inva-

ionspotential zum Ausdruck kommt. Baccharis uncinella zeigte eine signifikant positive räumliche Assoziierung mit P. taeda,ber eine neutrale Beziehung zu A. angustifolia.

Vernonia discolor war mit P. taeda significant negativ und neutral mit A. angustifolia assoziiert, und sie beherbergte unter ihrerrone eine größere Vielfalt einheimischer Arten als B. uncinella. Experimente zeigten, dass diese Muster auf unterschiedlicheemmungen bei der Ansiedlung zurückzuführen sind.

∗Corresponding author. Tel.: +1 614 292 6997; fax: +1 614 292 2030.E-mail address: miriti.1@osu.edu (M.N. Miriti).

439-1791/$ – see front matter © 2011 Gesellschaft für Ökologie. Published by Elsevier GmbH. All rights reserved.oi:10.1016/j.baae.2011.09.011

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34 G. Ganade et al. / Basic and Applied Ecology 12 (2011) 733–742

Wir schließen, dass B. uncinella Kieferninvasionen begünstigt, während diese von V. discolor eingeschränkt werden. Wirchlagen Strategien für die Restauration von Araucaria-Wäldern vor und stellen die breite Anwendbarkeit unseres Unter-uchungsansatzes in Restaurationsprogrammen heraus.

2011 Gesellschaft für Ökologie. Published by Elsevier GmbH. All rights reserved.

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eywords: Facilitation; Invasion; Succession; Atlantic forest; SAD

ntroduction

Ecological restoration aims to determine predominantcological processes in degraded areas to develop new tech-ologies for site amendment. Succession theory provides aommon conceptual framework for restoration. The facil-tative or inhibitory (competitive or allelopathic) impactsf pioneer species influence future colonization (Jackson &illemsen 1976; Connell & Slatyer 1977; Myster 2004). Pio-

eer effects on seedling establishment can be species-specificMesquita, Ickes, Ganade, & Williamson 2001; Gomez-parício, Valladares, Zamora, & Quero 2005). Consequently,efining impacts of early colonizers can guide managementf species distribution or abundance to promote a target com-unity.Restoration can be challenging in poorly studied systems

hat lack data to establish target ecological functions. Theraucaria forest, located at the southern distribution of thetlantic Forest in southern Brazil, a global “hot-spot” of bio-

ogical diversity (Myers, Mittermeier, Mittermeier, Fonseca,Kent 2000), is such a system. Araucaria angustifolia

Araucariaceae), hereafter Araucaria, is the dominant speciesssociated with this forest. Despite the local and commer-ial value of Araucaria, fiscal initiatives beginning in theate 1960s stimulated replacement of Araucaria forests withlantations of Eucalyptus spp. and Pinus species. In south-rn Brazil, it is estimated that 87.4% of Araucaria forestsave been replaced with pasture, agriculture or monoculturesf exotic species (Ribeiro, Metzger, Martensen, Ponzoni, &irota 2009). The performance of Araucaria relative to these

xotics will influence restoration success.Extensive land conversion can hinder restoration due to

ovel feedbacks attributable to degradation and invasivepecies. Pine invasion is increasing in Araucaria remnantss in other parts of South America (Richardson, van Wilgen,

Nunez 2008; Zalba, Cuevas, & Boo 2008). Pinus spp.re exceptionally likely to be invasive because of their seedraits, short juvenile stage and long residence times (Higgins

Richardson 1998), which make it difficult to eradicate pinence established (Zalba et al. 2008). Even after plantations arelearcut and allocated for restoration, Pinus re-establishmentay jeopardize recolonization of local species (Ganade,anini, & Hübel 2008). Control of pine regeneration repre-ents a significant hurdle for restoration of Araucaria forests.

In this study, we quantify spatial patterns of colonization

nd growth of desirable and undesirable species in response toative pioneers. Our intent is to unveil potential mechanismsf colonization and species interactions that may structure

sdm

lant community development during restoration. Vernoniaiscolor and Baccharis uncinella, hereafter Vernonia andaccharis, are common, native woody pioneers in Araucariaystems. Measurement of species composition and seedlingate in patches defined by the presence or absence of theseioneers can inform management to promote Araucaria andeduce noxious species.

The present study aims: (1) to compare the spatial col-nization pattern of native Araucaria and exotic pine inclearcut Pinus taeda (hereafter Pinus) plantation; (2) to

uantify differences in the spatial associations between theocal species, Araucaria and Pinus, and the native pioneerpecies, Bacharis and Vernonia; (3) to compare establishmentnd growth of Araucaria and Pinus under the canopies ofacharis and Vernonia, and (4) to measure seedling establish-ent of non-target native woody species underneath Vernonia

nd Baccharis.We use a spatial approach because plant spatial asso-

iations can have long-term influences on population andommunity dynamics. Spatial patterns reflect biotic and abi-tic factors that influence germination, establishment, growthnd survival (Miriti, Howe, & Wright 2001; Maestre &ortina 2002). Because plant responses to neighbors cane size-specific (e.g. Miriti 2006), we divide focal speciesnto distinct size-classes. By linking spatial distributions withmpirical data, we identify factors that influence the estab-ishment and spread of Pinus and Araucaria and investigatef spatial association can be used as a cheap methodology foreveloping restoration tools.

aterials and methods

tudy area

The study was conducted in the São Francisco de Paulaational Forest (29◦23′–29◦27′S, 50◦23′–50◦25′W), whichccupies ca. 1607 ha and is situated on the plateau of Riorande do Sul, Brazil (930 m altitude). This site consistsf natural fragments of Araucaria forest surrounded by aatrix of pastures. Forty-four percent of the area is nativeraucaria forest, 17% is pine plantation, 1% is Eucalyptuslantation and 23% is Araucaria plantation. The Araucariaorest is a subtropical rain forest characterized by the canopyominance of A. angustifolia (Araucariaceae). The under-tory of this forest is most frequently represented by trees and

hrubs from 12 botanical families in which Rosaceae, Sapin-aceae, Euphorbiaceae, Meliaceae and Myrsinaceae are theost common (Fonseca et al. 2010).

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G. Ganade et al. / Basic and A

The climate has well-defined winter and summer sea-ons. Annual precipitation is approximately 2252 mm, withmedian annual temperature of 14.5 ◦C and with frost occur-

ing during the winter and the beginning of the spring (Backes999).

The study site is a former Pinus plantation that waslear-cut in 2001 and has since been colonized byarly-successional vegetation dominated by Vernonia andaccharis. The closest native forest is approximately 50 m

rom the study site. A few isolated Pinus adults are located athe edge of the study site. These trees are taller than 25 m ineight, and can produce and disperse seeds at short and longistances (Nathan et al. 2002). A small number of isolatedraucaria adults, which can spread seeds through secondaryispersal to at least 100 m from the source tree (Pereira &anade 2008), also occur near the edge of the study site.

ocal species

A. angustifolia is an emergent species whose classifications a pioneer or old growth species is controversial becauseeeds can germinate in a range of light conditions (Duartet al. 2002). However, low light significantly compromiseseedling growth (Souza et al. 2008). This native dioeciousymnosperm produces large, nutritious seeds (7–11 g) thatre widely consumed by birds and mammals during winterhen few other fruits are available (Reitz, Klein, & Reis 1983;aise & Vieira 2005). Seeds germinate rapidly and have highermination rates (Ferreira & Handro 1979).

P. taeda originates in North America and typically colo-izes high light environments. When light and nutrients arebundant, individuals mature within 5–10 years, and adultsan live for >200 years (Keeley & Zedler 1998).

V. discolor (Asteraceae) is a deciduous native pioneer thats common within clear-cut patches. Adults may reach 20 m ineight, but in the study area the maximum height recorded ism. Sesquiterpenes (lactones) have been frequently reported

or species of this genus (Catalán, Iglesias, Kavka, Sosa, &erz 1986) suggesting the potential for allelopathy.B. uncinella (Asteraceae) is a native pioneer shrub that

an reach up to 4 m in height within a few years. Flavonoidsnd the diterpenes are the most frequent secondary com-ounds found in this genus, which also suggests a potentialor allelopathy (Verdi, Brighente, & Pizzolatti 2005). Becauseaccharis establishment in grasslands is considered the firsttage in the expansion of Araucaria forest into old-field areasOliveira & Pillar 2004), the distribution of Baccharis maynhance Araucaria restoration.

apping and measurements

The study site was divided into 49, 10 m × 10 m plots.raucaria and Pinus up to 2 m height were mapped and

heir height and basal diameter were measured during Jan-ary through June 2006. Plants were re-measured after 23

us

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Ecology 12 (2011) 733–742 735

onths for growth. We also mapped individual Baccharis262 total) and Vernonia (254 total) with canopy area greaterhan 1.5 m2 and at least 1.5 m height. We found 207 and 1227ndividuals of Araucaria and Pinus, respectively, with Pinusaving over 3-fold the number of seedlings (<0.25 m) and20 times more subadults (SbA) than Araucaria.Pinus were initially divided into four size classes:

eedlings (Sd: ≤0.25 m), Juveniles I (J1: 0.25 ≤ 0.8 m), Juve-iles II (J2: >0.8 m ≤2 m), Subadults (SbA: >2 m). Theew flowering individuals encountered were later includeds adults. Similarly, Araucaria was grouped into four sizelasses, but with seedlings defined as individuals ≤0.30 mecause Araucaria’s large seeds cause rapid early growthompared to Pinus.

tatistical analyses

Spatial analyses were conducted using the programADIE, which quantifies spatial dispersion and assigns sig-ificance to non-random dispersion using randomizationethods (Perry 1998). We used three of the indices gener-

ted by SADIE: the aggregation index (Ia) the cluster index,v), and the association index (X). Local cluster indices aressigned to each 5 m × 5 m quadrat to describe local patterns either a patch or a gap. The association index X, describeshe spatial relationship between two populations. For eachuadrat, a local association index χk is positive when thewo populations have similar local cluster indices and is neg-tive with opposite local cluster indices at the kth quadratWinder et al. 2001). Details of SADIE analysis are presentedn Appendix A.

olonizer performance in response to pioneers

To determine differences in establishment between Arau-aria and Pinus seedlings in response to pioneers, wentroduced seeds of both species in 10 blocks of three treat-

ents: below Baccharis, below Vernonia and in open areas.o establish these blocks, we first located an open area and

hen randomly chose Vernonia and Baccharis individualsithin five meters. A group of 16 seeds, spaced 5 cm from

ach other and marked with popsicle sticks, was placed underach pioneer treatment. Seeds were protected with cageso avoid predation. Nevertheless, seed predators penetratedraucaria cages. Unaffected seeds were subsequently rear-

anged in 8 blocks with 8 seeds each in new cages. Forinus, the number of germinated seeds, established seedlingsnd dead seedlings were registered monthly for 6 months.or Araucaria, only seed germination after 1 month waseasured due to high mortality. Probability of germination,

stablishment and survival was compared between treatments

sing proportion data applied to a GLM with binomial errortructure and logit link function using the program R.

To determine differences in growth of juvenile Araucariar Pinus in response to neighboring pioneers, the habitat of

7 pplied Ecology 12 (2011) 733–742

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Table 1. SADIE analysis (n = 49 quadrats) showed significant spa-tial structuring for all species. Ia = index of aggregation, vi = meanindex of clustering for gaps, and vj = mean index of clustering forpatches. P-values were derived from randomization statistical tests(5967 randomizations).

Ia vi vj

Araucaria angustifoliaAll individuals 1.449* 1.20NS −1.445*

Seedling 1.893** 1.713** −1.868**

Juvenile 1 1.469* 1.425* −1.479*

Juvenile 2 1.31NS 1.28NS −1.31NS

Pinus taedaAll individuals 2.565*** 2.492*** −2.376***

Seedling 3.130*** 3.129*** −3.163***

Juvenile 1 2.729*** 2.753*** −2.596***

Juvenile 2 1.591* 1.614** −1.559*

Vernonia discolor 2.027*** 1.717** −2.103***

Baccharis uncinella 1.829** 1.928** −1.809**

NS, non-significant.*P < 0.025.

**P < 0.01.***

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36 G. Ganade et al. / Basic and A

ach individual was categorized according to their positionelative to neighbor status (Baccharis, Vernonia, Pinus, Noanopy). The “No Canopy” habitat was defined as a placehere the target juvenile was at least 0.25 m from any canopy.or Araucaria, all individuals sampled in the 2006 surveyere included in the 2008 survey. For Pinus, however, due to

he large quantity of individuals under Baccharis and Pinus,e sub-sampled large clusters during the second survey with

he exception of individuals located under Vernonia or witho canopy cover, which were scarce. After sampling, thetudy area was divided into 4 m2 sub-plots for growth anal-ses. These data were obtained by taking the mean heightnd mean basal diameter of all individuals present within aub-plot.

Differences in growth were assessed using analysis ofovariance (ANCOVA). Final height (H2) was modeled as aependent variable, with habitat as the main factor and initialeight (H1) as a covariate. The ratio D/H was calculated as thelongation response. D represents the absolute gain in basaliameter (D2 − D1) and H the gain in height (H2 − H1). Toetermine significant differences in elongation, the incrementn diameter was modeled as the dependent variable, habitats the main factor and height increment as a covariate. A sig-ificant interaction between habitat and a covariate indicatedifferences in growth and elongation among individuals inesponse to neighboring canopy identity.

abitat light characterization

Differences in light interception between habitats wereeasured using hemispherical photographs taken at 0.25 m

eight. Canopy openness was estimated with Gap Light Ana-yzer 2.0 software (Frazer, Canham, & Lertzman 1999).

easurements were made in the Vernonia, Baccharis ando canopy habitats defined in the seed experiment. Theinus habitat was characterized by taking hemispherical pho-

ographs at random points below ten sub-adult canopies.he data was analysed with ANOVA (Systat 2001), utiliz-

ng percent canopy openness (arcsine transformed) as theependent variable and habitat as the main factor. Differ-nces among habitats were compared with Tukey’s post-hocest.

ffect of the pioneer species on the regenerationf non-target natives

We investigated the effect of Vernonia and Baccharis onhe regeneration of non-target native tree species by sam-ling the seedling community within 10 randomly locatedlocks. Each block contained one individual of both pio-eer species located 5 m apart. Below these canopies, we

2

laced four 0.5 m quadrats positioned 0.3 cm from the trunkn each cardinal direction. We counted and identified alloody plants below 0.8 m in height within these quadrats.lants that could not be identified to the species level were

bhV

P < 0.001.

dentified to genus, family, or separated as morphotypes onhe basis of their phylotaxy, leaf vessel characteristics, leafdge pattern, and the shape and color of cotyledons andeaves. In most cases, these characteristics can distinguishpecies, even when dealing with different developmen-al stages. The density and richness of these establishedeedlings under each species were compared using ANCOVASystat 2001). Species abundance and richness were mod-led as dependent variables, habitat (Vernonia or Baccharis)as included as the main factor and the canopy area of theioneers was a covariate.

esults

patial distributions

Although each species occurred throughout the study site,ll species showed significant clusters of high and low den-ity. SADIE analyses revealed that all classes of Pinus wereignificantly aggregated in discrete patches (Table 1). Despiteignificant aggregation of J2, these individuals were moreparsely distributed with lower density clusters comparedo other classes (Table 1). In general, Araucaria patcheshowed lower density than Pinus (Table 1). Seedlings and1 were aggregated and occurred in discrete patches. Themall number of J2 Araucaria presented a random distri-ution (Table 1). Both pioneer species occurred in distinct,

igh density patches; Baccharis showed higher density thanernonia (Table 1).

G. Ganade et al. / Basic and Applied

Table 2. Values of the association index (X) for the analysis ofspatial association show distinct associations between the pioneerneighbors Vernonia discolor and Baccharis uncinella and the colo-nizing species Araucaria angustifolia and Pinus taeda. Associationsfor each size class within species also show distinct responses. Anal-yses are presented for all size classes combined and for each sizeclass separately.

B. uncinella V. discolor

Araucaria angustifoliaAll individuals −0.2045** −0.104NS

Seedling −0.009NS −0.086NS

Juvenile 1 −0.2327** −0.058NS

Juvenile 2 −0.2427*** −0.022NS

Pinus taedaAll individuals −0.068NS −0.3336***

Seedling 0.1740** −0.115NS

Juvenile 1 0.1398** −0.2643***

Juvenile 2 −0.1982** −0.2104***

NS, non-significant.**

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P < 0.01.***P < 0.001.

patial associations

Araucaria and Pinus were distinctly associated with Bac-haris and Vernonia (Table 2). Araucaria juveniles wereissociated from Baccharis, but seedling associations wereot significant. Araucaria juveniles were not significantlyssociated with Vernonia for any class (Table 2). In contrast,inus seedlings and juveniles were positively associated withaccharis but juveniles were consistently dissociated fromernonia (Table 2).

olonizer performance

Pioneers had distinct influences on target species. Pinusermination (F = 3.97, df = 2.18, P = 0.037) and estab-ishment (F = 7.01, df = 2.18, P = 0.0056) increased underaccharis, were intermediate in open areas and decreasednder Vernonia (Fig. 1A and C). Pinus mortality decreasednder Baccharis, was intermediate in open areas andncreased under Vernonia (F = 5.36, df = 2.18, P = 0.0149,ig. 1D). Araucaria germination decreased under Baccha-is and increased under Vernonia, but this tendency was notignificant (F = 1.7, df = 2.14, P = 0.21, Fig. 1B).

In general, juveniles of Pinus grew faster than AraucariaFig. 2). ANCOVA showed significant interaction terms,ndicating contrasting height and elongation rates of Pinusuveniles in response to treatments (Table 3; Fig. 2A–C).inus juveniles in the No-Canopy treatment showed thereatest height increase and those under conspecific crowns

he least. However, juveniles located below Baccharis andernonia showed similar height increases (Fig. 2A). Juvenilesn the No-Canopy and Vernonia treatments showed slower

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Ecology 12 (2011) 733–742 737

longation compared to those growing below Baccharis anddult Pinus (Table 3; Fig. 2C). Together, these results sug-est that the environment created by these pioneer speciesan influence the allocation patterns of juvenile Pinus.

For Araucaria, ANCOVA showed a significant interac-ion between pioneer and covariate treatments, indicatinghat rates of height increment were significantly different forach pioneer treatment (Table 3; Fig. 2B). Araucaria heightncrement was greatest in the No-Canopy treatment, interme-iate below Baccharis or Pinus, and lowest below VernoniaFig. 2B). No differences in elongation (D/H) of Araucariaere detected among pioneer treatments because diameter

ncrement (D) per unit of height increment (H) did not differignificantly among treatments (Table 3; Fig. 2D).

abitat light characterization

Canopy openness was highest in the No Canopy treatmentmean = 35.8%, ±0.024SE), intermediate under Vernoniamean = 23.7%, ±0.016SE), and Baccharis (mean = 20%,0.012SE), and lowest under Pinus sub-adult canopies

mean = 16.7%, 0.011SE; F = 25.24; df = 3.36; P < 0.001).airwise comparisons have shown that No Canopy was sig-ificantly different from all other treatments (P < 0.001 forll comparisons) for other significant comparisons only Ver-onia was different from Pinus (P = 0.012).

egeneration of non-target species

Vernonia supported 2.5 times greater richness of nativeree seedlings than Baccharis (F = 25.25, df = 1.8, P < 0.001).rom these 136 recruits representing 16 species, 12 wereertebrate-dispersed. Ten species were completely identifiedo species level, 2 were identified to genus level, 1 to familyevel and the remaining 3 were morphotyped. We found noifference in the density of native tree seedlings below theanopy of either species (F = 4.3, df = 1.8, P = 0.072).

iscussion

The dynamics between native pioneers and exotic speciesncountered in this study have general consequences thatan occur and be tested in other ecological systems. Ouresults suggest that the exotic P. taeda presents a significantarrier to Araucaria forest restoration. Spatial analyses inte-rated with establishment and growth measurements showhat the pioneer B. uncinella improves Pinus colonizationhile jeopardizing native colonization. In contrast, the pio-eer V. discolor decreases Pinus colonization with positiveffects on native species colonization. Without intervention,

nvasion and slow Araucaria restoration.Although aggressive colonization after disturbance and

ong dispersal distances can contribute to extensive pine

738 G. Ganade et al. / Basic and Applied Ecology 12 (2011) 733–742

Pinus establishment

Baccharis Open Vernonia

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Fig. 1. Results from a seeding experiment performed at the study site where groups of seeds from Pinus taeda and Araucaria angustifoliawere introduced on 10 and 8 replicates, respectively, of three different treatments: below Baccharis unccinela, below Vernonia discolor andin Open areas. Subfigures are as follows: (A) probability of pine germination after 6 months, (B) probability of Araucaria germination after 1m and (Di s showg

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onth, (C) probability of pine establishment after 6 month intervalsnterval measured through maximum likelihood methods. Treatmentermination).

nvasion, Pinus colonization shows significant patchiness in

ur site. The distinct responses of Pinus to local pioneers sug-est that Pinus colonization is driven by Baccharis facilitationnd Vernonia inhibition.

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able 3. The focal species Araucaria angustifolia and Pinus taeda shows evaluated by ANCOVA. F values and degrees of freedom (df) are showD) and elongation (E) (growth in diameter per unit of growth in height) ofour different neighbor treatments: No-canopy, and under Baccharis uncin

df Araucaria angustifolia

H D E

eighbor (N) 3 1.9NS 2.83* 0.70N

ovariate (C) 1 178.5*** 325.3*** 35.34*

× C 3 16.01*** 11.5*** 0.9NS

rror 138

S, non-significant.*P < 0.025.

***P < 0.001.

) probability of pine mortality. Error bars represent 95% confidenceed significant differences in all cases except for panel B (Araucaria

Facilitation of pine is common in early succession.

xperiments in the Araucaria forest show reduced Pinusstablishment with neighbor vegetation removal (Ganadet al. 2008). In Mediterranean environments, Pinus sylvestris

ed significant growth differences in response to canopy treatmentn for the ANCOVA results for height growth (H); diameter growthAraucaria angustifolia and Pinus taeda individuals established inella, Vernonia discolor and Pinus taeda crowns.

df Pinus taeda

H D E

S 3 0.2NS 0.5NS 7.06***

** 1 238.9*** 212.3*** 214.9***

3 23.6*** 22.34*** 11.99***

124

G. Ganade et al. / Basic and Applied Ecology 12 (2011) 733–742 739

Fig. 2. Juvenile Pinus taeda showed greater height growth and elongation (A and C respectively) than juvenile A. araucaria (B and Drespectively) in response to canopy treatments. Canopy treatments are Baccharis uncinella, Vernonia discolor, Pinus taeda and No Canopy,arranged from lowest to greatest openness. ANCOVA revealed that both species grew fastest in the No Canopy treatment (P < 0.001). Ani ed for t

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nteraction between initial height and canopy treatment was observ

egeneration is largely restricted to shrub canopies (Gomez-parício et al., 2005; Castro, Zamora, Hódar, & Gómez 2004)ue to decreased evapotranspiration, which increases survivalespite slower growth of pine in shaded areas. Preliminaryxperiments in the Araucaria system show that introducedeeds of Pinus have significantly higher seedling establish-ent under Baccharis crowns due to lower leaf-cutter ant

ttack than under Vernonia crowns (unpublished data). Theseesults support Baccharis facilitation of Pinus colonization.

In contrast, inhibition best explains the relationshipetween Pinus and Vernonia. Vernonia’s seasonal leaf litteray hinder Pinus seedlings to obtain sufficient light. Once

erminated, reduced seedling elongation through this litterayer may increase mortality due to the low energy reservesf their small seeds (Ganade & Westoby 1999). Pinus per-ormance under Vernonia is also diminished by high seedlingortality and invertebrate seed predation, especially by ants

f the genus Acromirmex. Finally, sesquiterpenes, character-stic of the Vernonia genus (Bazon et al. 1997), may inhibit

inus germination and seedling growth (Kelsey & Locken987; Fischer, Weidenhamer, & Bradow 1989). Sesquiter-enes can produce fungicidal effects (Krishna Kumari,

cnn

he elongation response of P. taeda but not for A. angustifolia.

asilamani, Ganesh, Aravind, & Sridhar 2003) that mayrevent inoculation of ectomycorrhizae (Javaid 2007) in theoots of pine.

Factors that promote germination and establishment, how-ver, do not necessarily enhance growth (Miriti 2006). Pinusrowth was higher in habitats with no plant neighbors and wasimilar under neighboring Bacharis or Vernonia even thoughaccharis promoted higher survival of Pinus seedlings thanernonia. Pinus can, however, invest in height growth underow light conditions, which may permit it to overtop short-tatured Baccharis more easily than Vernonia, which caneach 20 m.

Our results suggest that dispersal limits Araucaria col-nization. Araucaria showed weak habitat preference withbroad distribution and no significant patchiness. Arau-

aria only showed well-defined clusters at the seedling stageith dense clumps located primarily near the few adult treesresent near the site. Hooper, Legendre and Condit (2005)ound that limited dispersal was the largest barrier for the

olonization of large-seeded pioneers. Indeed, the amount ofeighboring native forest is a key factor for improving colo-ization of Araucaria and other native trees in managed areas

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f the Araucaria forest region (Fonseca et al., 2009). Man-gement of Araucaria restoration should therefore includetrategies for seed introduction.

As with Pinus, Araucaria spatial associations with Bac-haris and Vernonia show stage dependence. The lack ofignificant associations between Araucaria seedlings andaccharis or Vernonia suggests that this life history stage

s insensitive to neighbor species. Araucaria’s large seedsontain vast energy reserves that permit seedlings to grown low light environments without having to compete foresources (cf. Leishman & Westoby 1994). In contrast, theignificant negative spatial associations between Baccharisnd Araucaria at larger juvenile stages suggest strong com-etition. Eining, Mertz, and Hampp (1999) noted that 70 daysfter germination, there was a decrease in the growth rate ofraucaria shoots, suggesting depletion of seed reserves withize. Indeed, experimental results demonstrate that Araucariauveniles decrease in growth due to nutrient competition withurrounding vegetation (Zanini et al. 2006). Depletion ofeed reserves is a critical transition determining Araucariaensitivity to local resources.

Despite no differences in seedling density below Vernoniand Baccharis, we identified higher native species richnesselow Vernonia, suggesting that this species may increaselant diversity either by improving establishment conditionsr by providing suitable perches to attract dispersers.

mplications for restoration

Spatial associations can reveal important non-random pat-erns of community development that are of general interesto restorations. We have shown that when combined withmpirical data, spatial information can be used to identifyritical interactions that can hinder restoration. We suggesthat the present approach should be used as a first step in anyestoration program lacking baseline research.

As our data show, unmanaged restoration initially presentsapid germination and establishment of Pinus. We havebserved pine maturing at this site after only five yearsrom establishment. If this site is left to natural succession,ocal reproductive individuals and neighboring plantationsre likely to sustain persistent Pinus propagule pressurend promote Pinus invasion (Zalba et al. 2008). In con-rast, although Araucaria juveniles can colonize under Pinus,rowth is poor. In a study of Araucaria regeneration in pinelantations in the Atlantic Forest, Pereira and Ganade (2008)eport that Araucaria juveniles did not overtop Pinus after0 years. These findings suggest that without interventionraucaria restoration would require centuries.Direct removal of reproductive Pinus can control invasion

Zalba et al. 2008; Cuevas & Zalba 2010). Experimen-

al studies of seed and seedling introduction confirm thatinus does not establish or grow successfully under adultraucaria (Emer & Fonseca 2011). Thus, removal of adultnd juvenile Pinus should allow Araucaria to become well

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Ecology 12 (2011) 733–742

stablished and preclude future Pinus invasion. To reduce fur-her invasion after Pinus removal, Baccharis densities shoulde reduced while simultaneously encouraging establishmentf Vernonia. This procedure may have long-lasting favorableffects on site restoration.

Araucaria establishment and growth can be promoted byowing seeds at high densities to reduce propagule limitationnd counter potential effects of seed predation (Pereira &anade 2008). Transplantation of large Araucaria juveniles

n open gaps with fertilization could accelerate Araucariaestoration.

In conclusion, the application of spatial associations pro-ides a novel and inexpensive use of established methodsnd reveals important mechanisms that impact restoration.nteractions between pioneers, target and exotic species mayrove to be an important focus for management in a varietyf degraded systems.

cknowledgements

GG received a CNPq – PQ grant. MNM received financialupport from The Ohio State University. GM and CP wereupported by CNPq Undergraduate Training Grant.

ppendix A.

SADIE analyses use spatially referenced counts to iden-ify clusters of locally high density (patches) or low densitygaps). Quadrat counts generate the null hypothesis thatlants are randomly distributed in the study arena. The param-ter D is the minimum distance required to reorganize thebserved counts within the study arena to obtain a uniformistribution. A mean value of D, Dm, is obtained by averagingfrom multiple iterations in which observed counts are ran-

omly distributed within the sample area. The ratio betweenand Dm is used to calculate an index of aggregation, Ia,

hich when greater than or equal to unity, identifies signif-cant clusters of patches or gaps throughout the study areaPerry, Winder, Holland, & Alston 1999).

Local cluster indices, vi representing patches and vj rep-esenting gaps are assigned to each 5 m × 5 m quadrat toescribe local pattern; vi and vj are determined using databtained during the redistribution of points described above.etails for calculating vi and vj can be found in Perry et al.

1999). The expectation of vi is 1 and the expectation ofj is −1. From values of vi > 1.5 and vj < −1.5 indicate aignificant patch or gap, respectively.

We also analysed spatial associations between Araucariand Pinus, and the pioneer species. These associationsescribe the spatial relationship between two populations and

re denoted by the local association index �k. This index isetermined by comparing the value of local cluster indicesf two populations at the kth quadrat (Winder, Alexander,olland, Wooley, & Perry 2001). Specifically, zk1 refers to

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he value of the cluster index for population 1 at the kthuadrat, and zk2 refers to the cluster index value of the kthuadrat for population 2. Allowing q to refer to the mean ofluster indices for a given population, then for n quadrats,k = n(zk1 − q1)(zk2 − q2)/[�k (zk1 − q1)2�k(zk2 − q2)2]0.5.By referencing population-specific cluster indices, bias

elated to differences in overall population density is avoided.ositive associations (χk > 0) occur when local cluster

ndices, vi or vj, have the same sign; negative associationsχk < 0) occur when they have different signs. Overall asso-iation between two populations, X, is the mean of the localk. Significance of X is determined by random reassign-ent of the local cluster indices for each population andith allowance for small-scale auto-correlation of vi and vj

or each population (Dutilleul 1993). As with local clusterndices, local association indices can be contoured to explic-tly map regions of significant association.

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