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Environmental correlates of tree and seedlingsapling distributionsin a Mexican tropical dry forest

Yalma Luisa Vargas-Rodriguez 1,2, *, J. Antonio Va zquez-Garc a3 and G. Bruce Williamson 11 Department of Biological Sciences, 107 Life Sciences Building, Louisiana State University, Baton Rouge, LA70803, USA; 2 Current address: Carlos Fuero 543, Colonia Universitaria, Guadalajara, 44840, Jalisco,Me xico; 3 Centro Universitario de Ciencias Biolo gicas y Agropecuarias, Departamento de Bota nica y Zoo-log a, Universidad de Guadalajara, Km 15 carretera Guadalajara-Nogales, Las Agujas, Zapopan, 45110,Jalisco, Me xico; *Author for correspondence (e-mail: [email protected])

Received 28 June 2004; accepted in revised form 28 February 2005

Key words: Bray and Curtis ordination, Disturbance, Importance value, Regeneration, Specialization, Treediversity, Tropical deciduous forest

Abstract

Bray and Curtis ordination was used to explore which environmental variables explained importance valuesand the presenceabsence of tropical tree seedlings, saplings and adults in La Escondida-La Caban a, Sierrade Manantla n, Jalisco, Mexico. The diameters of trees 2.5 cm DBH and the presence and height of seedlings and saplings were measured in nine 0.1 ha sites. Four matrices including presenceabsence dataand importance value indices for trees and seedlings and saplings were analyzed through Bray and Curtisordination. The matrices were based on density, frequency, and dominance of adult trees as well asseedlings and saplings. The environmental matrix consisted of 18 variables, including elevation, slope,canopy gaps, disturbance, and soil variables. We recorded 63 tree species and 38 seedling and saplingspecies in the nine sites. The ordination explained 70.9% of the variation in importance value data for treesand 62.6% for seedlings and saplings. The variation explained in presenceabsence data for trees was 67.1and 77.4% for seedlings and saplings. The variance in the ordination axes of seedlings and sapling pres-enceabsence data was poorly explained by the number of gaps in the tree, shrub, or herb layer, suggestinglittle light specialization by seedlings and saplings. Habitat specialization for soil nutrients appears to beimportant in explaining the presenceabsence of seedlings and saplings. Seedling and sapling specializationalong different soil microsites could promote species coexistence in this forest, while heterogeneity in lightconditions may instead determine differences in growth and, thus, importance value of trees. Wehypothesize that in tropical dry forest in Jalisco, Mexico, a habitat specialization for soil resources is likely

more important at early stages in tree life histories than in later life history.

Introduction

In Mexico, 60% of the tropical vegetation istropical dry forest (TDF). Mexican TDF is widely

distributed across the Pacic lowlands on thewestern side of the country, covering most of Jalisco state and conned to small patches ineastern Mexico (Rzedowski 1978; Trejo and Dirzo

Plant Ecology (2005) 180:117134 Springer 2005DOI 10.1007/s11258-005-3026-9


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2000). The forest is characterized by marked sea-sonality in rain fall and its occurrence on moderatesteep slopes and rocky outcrops.

Tropical dry forests in western Mexico, includ-ing those in the studied area, are typically decid-uous, with short stature trees and high density of small size trees (Trejo 1998). Trees ca. 4 m tallconstitute 65%, those with heights between 4 and8 m are 31% and only 3% are 812 m height,some exceptional individuals reach 15 m. Treemean density is 3610 (800) individuals/ha and ba-sal area is ca. 56.8 m 2 /ha. Trees with diameter 10 cm represent only 20% of individuals and lessthan 5% are 30 cm, thus, the majority of treeshave diameters 2.5 cm (Rzedowski 1978; Trejo1998). Trees have extended crowns with bright and

peeling barks, as well as compound leaves. Most of the tree species (ca. 85%) are deciduous and few(ca. 15%) are evergreen, such as Ziziphus mexicanaRose and Prosopis laevigata (Willd.) M.C. Johnst.In addition, columnar and Opuntioideae cacti arecommon in this community (Rzedowski 1978;Trejo 1998).

TDF, throughout Mexico, is severely affected bylivestock, slash and burn agricultural practices,forest re, and selective logging. In 1990, only 27%of the original cover of tropical dry forest re-mained intact and 1.4% continues to be lostannually as a result of deforestation (Trejo andDirzo 2000). Forest res and livestock are alsocommon in Sierra de Manantla n Biosphere Re-serve (SMBR). Fire in the area has been mainlyassociated with agricultural burning, occurring inthe dry season (DecemberMay). Livestock activ-ity occurs during the rainy season (JuneOctober).However, forest protection is enforced in corezones through various mechanisms negotiatedwith agrarian communities (68% of reserves area)and private landowners (32% of reserves area). Inaddition, there are management goals in the bufferzone directed to implement sustainable practices inforestry, agriculture, livestock, and other naturalresource management activities (INE 2000).

TDF in Mexico is characterized by high a and bdiversity (Balvanera et al. 2002; Trejo and Dirzo2002). While species diversity has been shown tobe positively correlated with increasing precipita-tion across wet and dry forest in Puerto Rico(Murphy and Lugo 1986), a comprehensiveanalysis of Mexican TDF does not show such arelationship (Trejo and Dirzo 2002). Instead, it has

been suggested that Mexican TDF diversity ispositively related to potential evapotranspiration(Trejo and Dirzo 2002).

In addition, local site factors such as thepresence and size of canopy gaps, soil properties,anthropogenic disturbance, and total annualprecipitation may have important effects on TDFtree species richness, composition, abundance,and structure (Gonzalez and Zak 1996; Gentry1988; Oliveira-Filho et al. 1998; Gillespie et al.2000; Segura et al. 2003). For instance, variationin species diversity in the Neotropics could beexplained by total annual precipitation (Gentry1982, 1988). Associations of species with thosefactors and specialization to particular micro-habitats are hypothesized to contribute to species

diversity (Connell 1978; Gentry 1982; Denslow1987; Welden et al. 1991; Clark et al. 1993).Different tree species are best suited to differenthabitats, which may lead to habitat specializa-tion. Differential resource utilization might ex-press itself as microhabitat specializationbetween the species or as differences in geo-graphical distribution. On the other hand, theavailability of different resources may be sepa-rate in time and may become available duringdifferent seasons. For example, canopy gapsprovide different soil, light, and moisture condi-tions than the forest understory and could beexploited by species with specialized competitiveabilities (Denslow 1987; Oliveira-Filho et al.1998). Differences in species growth and survivalmay also occur in the absence of gaps alongsmaller light gradients, such as between 0.2 and6.5% available diffuse light (Lieberman et al.1989; Montgomery and Chazdon 2002). Inaddition, natural disturbances can cause spatialand temporal variability in the availability of resources leading to habitat differentiation.Consequently, variation in growth and survival of tree species under differing conditions of resourceavailability (for example micro-topography orlight) could result in habitat specialization (Kobe1999; Pearson et al. 2003).

Previous studies have shown that microhabitatspecialization with regard to topography and soilcharacteristics affect the distribution of severalplant groups, including tropical trees, melasto-mate shrubs, herbs, pteridophytes, and palms(Kahn and De Castro 1985; Liberman et al.1985; Poulsen and Baslev 1991; Basnet 1992;

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Toumisto and Roukolainen 1993; Clark et al.1998; Svenning 1999). For instance, distributionand abundance of some deciduous tree families(e.g., Leguminosae), are related to ecologicalgradients such as edaphic conditions and shadetolerance (Givnish 1999). Cation exchange levelaffects the distribution of 51 tree species inGhana (Swaine 1996). Soil organic matter, soilnutrients, texture, and moisture are stronglycorrelated with main axes of a PCA ordinationof tropical trees in a Bornean tropical rain forest(Webb and Peart 2000). In addition, adult treesand seedlings had different strengths of associa-tion with those variables (Webb and Peart 2000).Other species can be specialized along moisturegradients, reected by the greater numbers of

species that persist on protected side-slope areasdue to their higher dry season moisture levels(Hubbell 1995).

Even though previous studies used a quantita-tive multivariate approach to analyze how treespecies relate to environmental variables, only afew studies have considered the relationship be-tween the regeneration of tree species in seasonaltropical dry forest and environmental conditions(Lieberman and Li 1992; Oliveira-Filho et al.1998), and none have explored the possible con-tribution of environmental variables at differentstages in the life cycle of TDF trees.

Here we report the results of a study of treeforest composition and regeneration along a shortaltitudinal gradient in a tropical dry forest at LaEscondida-La Caban a, Sierra de Manantla n Bio-sphere Reserve, in the Ayuquila watershed, inwestern Mexico, to generate hypotheses abouttropical trees and regeneration patterns along soiland canopy gaps gradients. We addressed thefollowing question: What environmental variablescould explain major community gradients for bothtrees and seedlings and saplings? To answer thisquestion, we employed a multivariate gradientanalysis, Bray and Curtis ordination technique(also known as sociological ordination) (Curtisand McIntosh 1951; Beals 1984; McCune andGrace 2002), which produces pure communitygradients that can be correlated with measuredenvironmental variables. This approach has pro-vided many insights into the nature, organizationand dynamics of ecological communities (Whit-taker 1956, 1960; Terborgh 1973; Ludwig andReynolds 1988).

Methods

Study area

La Escondida-La Caban a gradient is located in thenorthern boundary of the SMBR, roughly 50 kmfrom the Pacic Ocean, in Jalisco state, WesternMexico. The study area lies between El Aguacate(municipio El Grullo) and Zenzontla ( municipioTuxcacuesco), northwest of ejido Zenzontla, alongthe Ayuquila-Armer a river, within the tributarywatershed La Pasio n-Cerro Blanco. The eleva-tional gradient extends from Arroyo La Escondidaat, 880 m to the top of Cerro la Caban a at, 1090 ma.s.l. (19 42 N, 104 07 W) (Figure 1).

La Escondida-La Caban a occupies the steep

foothills of the northern Sierra de Manantla n, inthe Sierra Madre del Sur, an area of roughtopography, within a hilly and dissected land-scape. Relief ranges from 10 to 66% slope incli-nation, along La Escondida and La Caban a hills.Microclimate at La Escondida-La Cabana ismoist, warm, and highly seasonal with a wet sea-son from June to October and a dry season fromDecember to May (Mart nez et al. 1991). Meanannual rainfall is 900 mm (range 6001000 mm)(Mart nez et al. 1991). Mean annual temperature is22 C (range 2228 C), free of frost. The tem-perature lapse rate is 4 C per 1000 m a.s.l.(Mart nez et al. 1991). TDF at La Escondida-LaCaban a corresponds to the Lower Montane Sub-humid Tropical Dry Forests of Holdridge (1967)and occupies 12,700 ha (9%) of the SMBR(Cuevas-G. et al. 1998).

Tertiary volcanic rocks are prevalent in thestudy area (Cruz 1989). Acidic intrusive rocks(granites) were found on sites 1, 2, 3, 4, 8 and 9,while intermediate extrusive rocks (rhyolites,andesites, and trachytes) prevailed on sites 5, 6,and 7. Land form is convex with boulders androcky outcrops.

Shallow, well-drained lime soils (Regosol eut-rico) were common in sites 5, 6 and 7. Some limesecondary soils such as Feozem ha plico and someLitosols occured. Litosols (with rocks greater than7.5 cm in diameter) were frequent at sites 1, 2, 3, 4,8 and 9. Fluvial sandy soils (Fluvisol eutrico) werefound on river banks and at the foothills of LaEscondida (CETENAL 1975, 1976).

Floristic checklists and descriptions of tropicaldry forest species in the SMBR (Va zquez-Garc a

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taken from random locations at each site. This soildepth is aimed to obtain the best nutrient (N)estimates (Castellanos et al. 2000). Soil pH wasmeasured with potentiometer. Nutrients (NO 3 ,NH 4 , P, Mn, Mg, K, Ca) were analyzed with theMorgan method. Percent organic matter wasmeasured by the WalkeyBlack method, and tex-ture was measured following the Bouyoucosmethod. Cation exchange capacity was obtainedusing ammonium acetate (Castellanos et al. 2000).At each site, observations were made on theoccurrence of different kinds of natural andhuman-related disturbance, following Va zquez-Garc a and Givnish (1998). These included thenumbers of fallen or damaged trees, tree stumps,browsed or grazed plants, and intensity of grazing

(evaluated by the amount of dung, cattle foot-prints, cattle droppings, and track livestock), aswell as the presence absence of signs of past res,erosion, and forest harvesting. The amount of disturbance was summarized, with a high valuesignifying high levels of disturbance and low valuesignifying low levels of disturbance (Va zquez-Garc a and Givnish 1998).

Data analysis

Data were summarized using four communitymatrices and one environmental matrix. Twocommunity matrices consisted of tree importancevalues and tree presenceabsence data for 63 spe-cies. Two other community matrices includedimportance values and presenceabsence of seed-lings and saplings for 38 species. Matrices withimportance values were meant to relate commu-nities in terms of their composition, structure,distribution, and age of the nine forest stands,while presenceabsence matrices were meant torelate communities in terms of their compositionand distribution, regardless of forest structure andage. Thus, allowing relating environmental vari-ables to different community aspects.

Importance values for trees were calculatedfrom relative tree density, frequency, and domi-nance (basal area) (Curtis and McIntosh 1951;Cottam and Curtis 1956). We adapted importancevalues for seedlings and saplings by using height,instead of basal area, as a measure of dominance.

The environmental matrix included quantitativedata for elevation, slope, soil nutrients, soil pH,

soil organic matter, cation exchange capacity, treegaps, shrub gaps, herb gaps, and disturbance andcategorical data for exposure, topography, physi-ography, stones, and rocks.

Bray and Curtis variance-regression ordinationwas used in connection with the Srensen coeffi-cient of similarity distance. This type of ordinationgives a complete community structure regardlessof its relationship to environmental variables andproduces clear species patterns that reect theenvironmental space the way the biotic communityinterprets it (Beals 1984; McCune and Grace2002). Thus, Bray and Curtis, like most indirect(sociological) ordination techniques, has betterappeal than direct (environmental) ordinationtechniques.

Bray and Curtis can be applied to a matrixcontaining any distance measure, including non-Euclidean semi-metrics such as Srensen (Brayand Curtis) distance. This is important since semi-metrics, such as the Srensen and Jaccarddistances, are considered robust measures of eco-logical distance (Beals 1984; Faith et al. 1987). Incontrast, reciprocal averaging (RA) and principalcomponent analysis force a particular distance(Euclidean) measure on the analyst, which pro-duces inadequate results (Beals 1973, 1984) andRA is effective for, but limited to, single dimen-sional data.

Furthermore, papers that have compared Brayand Curtis with other methods provided evidencethat Bray and Curtis may perform better than theothers (Gauch et al. 1977; Robertson 1978; Gauchand Scrugs 1979; del Moral 1980; McCune 1994)and produces results identical to an ordinationbased on fuzzy set theory (Roberts 1986). Thus,Bray and Curtis is considered an effective ordina-tion technique and perhaps its only serious rival isMultidimensional Scaling (Beals 1984; Causton1988; Ludwig and Reynolds 1988; McCune andBeals 1993).

Endpoints for ordination were selected by vari-ance-regression, thereby reducing shortcomings of the original technique. The cutoff value used forthe ordination biplot was r 2=0.444, which resultsin a r-value that is signicantly correlated withordination axes. The relationship between tree,regeneration, and the environment was evaluatedusing Pearson correlations between the identiedaxes of the ordination and the environmentalvariables. P -values were not assigned because,

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strictly speaking, the ordination scores are notindependent of each other (McCune and Grace2002). The software used was PCORD v4.0 (mul-tivariate analyses for ecological data) (McCuneand Mefford 1999).

Results

A total of 63 tree species representing 51 generaand 27 families were recorded in 0.9 ha. Legumi-nosae had the largest number of species, with 14species. Acacia was the most speciose genus withve species. A total of 853 individual trees wererecorded in the studied area (0.9 ha), providing anestimate of 948 trees/ha. Importance values fortrees are shown in Appendix A. All nine sites wereconsidered separate in each analysis and were heresummarized in one single Appendix. A total of 38tree species in 30 genera and 18 families were re-corded as seedlings and saplings. The total numberof individual seedlings and saplings was 368, thusan estimated 409 individuals/ha. Importance val-ues for seedlings and saplings are shown inAppendix B. All nine sites were considered sepa-rate in each analysis and were here summarized inone single Appendix.

Bray and Curtis variance-regression ordination

axes accounted for a substantial cumulative per-centage of variance. For trees, the ordinationsexplained more of the variation in importancevalue data (70.9%) than presenceabsence data(67.1%). The opposite was true, for seedlings andsaplings, for which more variation in presence absence (77.4%) was explained than for impor-tance value (62.6%).

Importance values of trees

Sites 3 and 9 were selected as endpoints for axis 1,which extracted 32.3% of the original distancematrix (Figure 2). This axis was explained directlyby number of shrub gaps and P concentration andinversely by herb gaps (Table 2). Fifteen of 63species displayed a positive correlation with thisaxis and had greater importance values in areaswith greater P concentration and more shrub gaps(Table 3). Ceiba aesculifolia (H.B.K.) Britt. andBaker and Phenax hirtus (Sw.) Wedd. displayed anegative correlation with this axis (Table 3).

Sites 4 and 8 were selected as endpoints for axis2, which extracted 20.9% of the original distancematrix. This axis was explained inversely by ele-vation (Figure 2, Table 2). Ten species displayed apositive correlation with this axis and had agreater importance value with decreasing elevation(Table 3).

Sites 2 and 7 were selected as endpoints for axis3 (not shown), which extracted 17.7% of the ori-ginal distance matrix. None of the measuredenvironmental variables were correlated with thisaxis. Heliocarpus terebinthinaceus (DC.) Hochr.and Lysiloma microphyllum Benth. displayed apositive correlation with this axis and decreasedwith increasing importance value of Phenax hirtusand Thouinia serrata Radlk. (Table 3).

Presenceabsence of trees

Sites 8 and 3 were selected as endpoints for axis 1,which extracted 28.6% of the original distancematrix (Figure 3). This axis was explained directlyby slope and inversely by shrub gaps and distur-bance (Table 2). Species that were present in siteswith a greater slope and less shrub gaps anddisturbance were Acacia riparia H.B.K. ( r =0.841), Celtis iguanea (Jacq.) Sarg. ( r = 0.758),

Figure 2. Ordination diagram for axes 1 and 2 derived fromBray and Curtis ordination using sites ( m ), importance valuesof tree species, and environmental variables (vectors). Corre-lation values for each environmental variable with the two axesare reported in Table 2.

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Conzattia multiora (B.L. Rob.) Standl. ( r = 0.735),Senna atomaria (L.) Irwin and Barneby ( r = 0.726)and Spondias purpurea L. ( r = 0.758). Species thatwere absent in sites with greater slope and less shrubgaps and disturbance were Casearia corymbosaH.B.K. ( r = 0.695), Nopalea auberi (r= 0.714),Senna mollisima (r= 0.695), and Stemmadeniadonnell-smithii (Rose) Woodson ( r= 0.701).

Sites 9 and 1 were selected as endpoints for axis2, which extracted 23.2% of the original distancematrix. This axis was explained directly by ionexchange and Mg concentration (Figure 3, Ta-ble 2). Acacia macilenta Rose ( r = 0.697), Acaly- pha cincta Muell. Arg. ( r = 0.697), Aeschynomeneamorphoides (S. Watson) Rose ex B.L. Rob.(r = 0.697), Hamelia jorullensis H.B.K.(r = 0.697), Hintonia latiora (Sesse and Moc. exDC.) Bullock ( r = 0.691), Nopalea karwinskiana(Salm-Dyck) Schumann ( r = 0.758), Pachycereus pecten-aboriginum (Engelm.) Britt. and Rose(r = 0.693), Pseudobombax ellipticum (S. Watson)

Dugand ( r = 0.697), and Triumfetta semitrilobaJacq. ( r = 0.697) were present in sites with higherion exchange and MgO; while Acacia cochliacan-tha Humb. and Bonpl. ex Willd. ( r = 0.733),Heliocarpus terebinthinaceus (r= 0.697), andIresine cassiniformis Schauer ( r= 0.669) wereabsent in sites with higher ion exchange and con-centration Mg.

Sites 9 and 7 were selected as endpoints for axis3, which extracted 15.3% of the original distance

Table 2. Pearson correlation ( r) of environmental variables and Bray and Curtis ordination axes using importance values and pres-enceabsence data of trees.

Variable Importance value data Presenceabsence-data

Axis 1 Axis 2 Axis 3 Axis 1 Axis 2 Axis 3

Elevation 0.082 0.684 0.551 0.523 0.657 0.488Tree gaps 0.436 0.168 0.491 0.043 0.484 0.568Shrub gaps 0.745 0.379 0.483 0.789 0.331 0.164Herb gaps 0.689 0.207 0.554 0.655 0.540 0.309Disturbance 0.418 0.575 0.469 0.753 0.033 0.310Slope 0.432 0.556 0.524 0.676 0.244 0.455Ion exchange capacity 0.485 0.095 0.380 0.213 0.845 0.276P 0.685 0.458 0.117 0.562 0.442 0.329NO 3 0.606 0.396 0.091 0.019 0.523 0.324Mg 0.132 0.452 0.044 0.575 0.669 0.294K 0.662 0.101 0.018 0.322 0.542 0.283% Organic matter 0.232 0.288 0.025 0.475 0.188 0.229pH 0.375 0.096 0.215 0.536 0.305 0.362

High correlations are in bold.

Table 3. Pearson correlation ( r) of tree importance values andBray and Curtis ordination axes.

Axis 1 Axis 2 Axis 3

Acacia cochliacantha 0.784Acacia macracantha 0.854Acacia pennatula 0.849Adelia barbinervis 0.874Albizia tomentosa 0.923

Casearia corymbosa 0.701Ceiba aesculifolia 0.781Enterolobium cyclocarpum 0.849Exostema mexicanum 0.882Ficus cotinifolia 0.882Ficus insipida 0.882Heliocarpus terebinthinaceus 0.725Jacaratia mexicana 0.817Lasiocarpus ferrugineus 0.801Lysiloma microphyllum 0.768Malpighia ovata 0.882Margaritaria nobilis 0.892Nopalea auberi 0.791Opuntia fuliginosa 0.913Phenax hirtus 0.709 0.666Pithecellobium acatlense 0.849Psidium guajava 0.849Senna mollisima 0.880Stemmadenia donnell-smithii 0.886Stemmadeniatomentosa var. palmeri

0.821

Tabebuia chrysantha 0.780Thouinia serrata 0.666Zanthoxylum fagara 0.849

Only correlations greater than an absolute value of 0.666 areshown.

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matrix. None of the measured variables explainedthis axis.

Importance value of seedlings and saplings

Sites 8 and 3 were selected as endpoints for axis1, which extracted 34.3% of the original distancematrix (Figure 4). This axis was explained in-versely by shrub gaps (Table 4). Two species(Ceiba aesculifolia and Lysiloma microphyllum )displayed a positive correlation with this axisand had greater importance values in areas withlower number of shrub gaps. Seven species dis-played a negative correlation with this axis(Table 5).

Sites 7 and 9 were selected as endpoints for axis2, which extracted 17.2% of the original distancematrix (Figure 4). This axis was explained directlyby tree gaps and inversely by Mg and K concen-tration (Table 4). Six species displayed a positivecorrelation with this axis and had greater impor-tance values in areas with greater number of treegaps and lower Mg and K concentration (Table 5).Spondias purpurea displayed a negative correlation

with this axis and its importance value was lowerwith lower values of Mg and K (Table 5).

Sites 5 and 4 were selected as endpoints foraxis 3, which extracted 11.1% of the originaldistance matrix (Figure 4). None of the measuredvariables explained this axis. Acacia riparia ,Bursera simaruba (L.) Sarg., Cordia inermis(Mill.) I.M. Johnst., and Croton fragilis H.B.K.were positively correlated with this axis and theirimportance values increased with decreasingimportance values of Bunchosia palmeri S. Wat-son, Comocladia engleriana Loes., Senna mollis-ima , and Tabebuia chrysantha (Jacq.) G. Nicolson(Table 5).

Presenceabsence of seedlings and saplings

Sites 8 and 4 were selected as endpoints for axis1, which extracted 36% of the original distancematrix. This axis was explained inversely by percentorganic matter (Figure 5). Casearia corymbosa(r= 0.772), Nopalea auberi (r= 0.772), Sennamollisima (r= 0.690), Spondias purpurea(r= 0.721), and Tabebuia chrysantha (r = 0.690)were present in sites with the most organic matter.

Figure 3. Ordination diagram for axes 1 and 2 derived fromBray and Curtis ordination using sites ( m ), presenceabsencedata of tree species, and environmental variables (vectors).Correlation values for each environmental variable with the twoaxes are reported in Table 2.

Figure 4. Ordination diagram for axes 1 and 2 derived fromBray and Curtis ordination using sites ( m ), importance valuesof seedlings and saplings species, and environmental variables(vectors). Correlation values for each environmental variablewith the two axes are reported in Table 4.

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Sites 9 and 2 were selected as endpoints for axis2, which extracted 27.9% of the original distancematrix. This axis was explained directly by ionexchange and K concentration (Figure 5). Ceibaaesculifolia (r = 0.795) and Lysiloma microphyl-lum (r = 0.730) were present in sites with high ionexchange and K. Acacia cochliacantha (r = 0.795),Adelia barbinervis Schlecht.and Cham.( r = 0.730),

Croton ciliato-glandulifera Ort. ( r = 0.795), Lasio-carpus ferrugineus Gentry ( r = 0.795), Opuntia fuliginosa Griff. ( r = 0.730), Senna mollisima(r = 0.692), Stemmadenia tomentosa var. palmeri (Rose) Woodson ( r = 0.730), Tabebuia chrysantha(r = 0.692), and Zanthoxylum fagara (L.)C. Sargent ( r = 0.795) were present in sites withless ion exchange and K concentration.

Table 5. Pearson correlation ( r) of seedlings and saplings importance values and Bray and Curtis ordination axes.

Axis 1 Axis 2 Axis 3

Acacia cochliacantha 0.798Acacia riparia 0.750Adelia barbinervis 0.762 0.680Bunchosia palmeri 0.728Bursera simaruba 0.750Casearia corymbosa 0.699

Ceiba aesculifolia 0.679Comocladia engleriana 0.728Cordia inermis 0.750Croton fragilis 0.750Croton ciliato-glandulifera 0.798Lasiocarpus ferrugineus 0.798Lysiloma microphyllum 0.951Nopalea auberi 0.821Opuntia fuliginosa 0.732 0.726Senna mollisima 0.737 0.680Spondias purpurea 0.736Stemmadenia donnell-smithii 0.897Tabebuia chrysantha 0.673Zanthoxylum fagara 0.798

Only correlations greater than an absolute value of 0.666 are shown.

Table 4. Pearson correlation ( r) of environmental variables and Bray and Curtis ordination axes using importance values and pres-enceabsence data for seedlings and saplings.

Variable Importance value data Presenceabsence-data

Axis 1 Axis 2 Axis 3 Axis 1 Axis 2 Axis 3

Elevation 0.452 0.131 0.543 0.567 0.256 0.360Tree gaps 0.247 0.689 0.090 0.201 0.499 0.099Shrub gaps 0.718 0.110 0.251 0.593 0.474 0.294Herb gaps 0.587 0.248 0.275 0.393 0.642 0.427Disturbance 0.629 0.305 0.339 0.665 0.070 0.195Slope 0.644 0.169 0.210 0.597 0.271 0.077Ion exchange capacity 0.307 0.527 0.141 0.070 0.807 0.341P 0.502 0.527 0.024 0.257 0.627 0.318NO 3 0.237 0.633 0.058 0.123 0.574 0.016Mg 0.310 0.704 0.418 0.510 0.527 0.001K 0.288 0.689 0.238 0.064 0.712 0.515% Organic matter 0.590 0.330 0.192 0.703 0.122 0.549pH 0.377 0.006 0.098 0.316 0.065 0.115

High correlations are in bold.

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Sites 6 and 1 were selected as endpoints for axis3, which extracted 13.5% of the original distancematrix. None of the measured variables explainedthis axis.

Discussion

A total of 51 of the 65 species were associatedwith environmental variables using Bray andCurtis ordination and Pearson correlation. Ourdata support the hypothesis that the importancevalues of trees and seedlings and saplings arerelated to the interaction between soil resourcesand light gaps because soils in light gaps arefound to be nutrient rich, due to increased min-

eralization of organics under light conditions(Denslow et al. 1998). In addition, presence orabsence of trees ( i.e . adult stage) might bedetermined by disturbance and slope, whilepresence or absence of seedlings and saplings ( i.e .early life stage) might be strongly determined bysoil variables. Webb and Peart (2000), using anordination technique also found physiographicand light associations in 21 of 45 species of tropical seedlings and trees.

Importance values of trees

Availability of P, shrub gaps, and herb gaps ex-plained most of the variation in importance valuesof the overall tree community and, especially thedistribution of 17 tree species. Growth differencesin tropical trees are often found by increasingP-supply (Chapin 1980; Burslem et al. 1994). Thegreater importance value of legume, N-xing, treesat La Escondida-La Caban a (40% of total numberof trees) could result from high levels of P and lowlevels of N, which might enhance symbiosis, sur-vivorship, and growth (Vitousek and Howarth1991). Legumes trees, such as Acacia cochliacan-tha , Acacia macracantha , Acacia pennatula(Schlecht. and Cham.) Benth., and Enterolobium

cyclocarpum (Jacq.) Griseb., behave as light-demanding species with a strong response in bio-mass allocation and growth with increased Pavailability, as well as a higher phosphorous-useefficiency when P supply is low (Huante et al.1995). In contrast, late successional (shadetolerant) species, such as Recchia mexicana Moc.and Sesse , have relative low growth rates and showlittle or no response in growth to different P con-centrations and less dependency on nutrient sup-ply (Huante et al. 1995). The availability of P maynot be limiting the overall development of TDF asshown in Chamela (Campo et al. 2001). However,in La Escondida-La Caban a, where slash and burnagriculture and pasturing of livestock are commonland uses, P availability may be limiting tree spe-cies importance value since the effects of res andother disturbances could increase the rate at whichP is lost from the soil (Campo et al. 2001; Louetteet al. 2001). Only Ceiba aesculifolia and Phenaxhirtus importance values seem to be favored withdecreasing P. Disturbance, together with low P,may often limit st49mpo1-559.827598.44mbo96261t001; Louette


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importance values of 15 species in sites with moreshrub gaps and P might be also related to high soilresource availability that is often found in gap sites(Denslow 1980, 1998).

The fact that elevation explained secondary axisof importance values of the overall tree commu-nity suggests that the effect of short elevationgradients may not be an overriding factor on theorganization of community at small scales, whereother factors, such as nutrient supply and naturalenemies become more important (Lieberman et al.1985; Vargas-Rodriguez 1998; Va zquez-Garc aand Givnish 2000). Only rarely has elevation beenthe major variable explaining community organi-zation along short elevational gradients (Lott et al.1987). In addition, elevation showed no relation-

ship to species richness along a larger elevationalgradient at the El Tecolote ravine, western Sierrade Manantla n (Cuevas-G. 2002). However, theinuence of anthropogenic disturbance to thisarea, may confound the effects of elevation on thespecies composition of this community (Louetteet al. 2001). In our study, evergreen species such asFicus cotinifolia H.B.K. Ficus insipida Willd.Albizia tomentosa (Micheli) Standl. Exostemamexicanum A. Gray, and Margaritaria nobilisL. increased in importance value as elevationdecreased. This may be attributed more to anincrease in soil moisture in wetter sites, close tostream of lower areas. Changes in tree basal area,height, and stem diameter, factors that contributeto our estimation of importance value, were alsofound to be dependent on (Segura et al. 2003).

Presenceabsence of trees

Shrub gaps, slope and degree of disturbance werethe primary environmental variables that ex-plained the variation in the presenceabsence of trees. Competition for light between subcanopyand canopy trees in different successional stagesmay be occurring, and contribute to speciesdiversity. For example, canopy tree Lysilomamicrophyllum formed a dense shade at one site,preventing the establishment of pioneer species.Consequently, gap dynamics and the interactionof canopy and subcanopy gaps, create heteroge-neity in light distribution throughout TDF andcan therefore inuence species composition(Montgomey and Chazdon 2001; Quigley and

Platt 2003). Anthropogenic activity also plays amajor role in the composition of La Escondida-La Caban a TDF forest, in which the presences of 14 tree species are related to disturbance. Theinuence of disturbance on forest compositionand structure also has been found in Central andSouth American TDF forest (Gonzalez and Zak1996; Gillespie et al. 2000). Species correlationswith gaps and disturbance are often found(Denslow 1987; Oliveira-Filho et al. 1998), but incontrast with the present data, soil variables alsoproduced correlations, and explained importantvariation for axis 2.

Patchy availability of nutrients in tropical dryforest confers special patterns in microbiologicalsoil activity (Roy and Singh 1994). Higher

amounts of organic C, N, and P are available atne microsites scales and attract ne roots fromsurrounding areas to support tree growth (Royand Singh 1994). Acacia spp. create islands of fertility with larger soil microbial biomass, Cand N mineralization, and organic and total N(Reyes-Reyes et al. 2002). Therefore, the patchyavailability of ion exchange and Mg may bedetermining the presence of 12 tree species in LaEscondida-La Caban a forest, which are probablyspecialized to microhabitats with these soil char-acteristics (Burslem et al. 1995; Swaine 1996).

In this study, species such as Celtis iguanea,Conzzatia multiora , and Senna atomaria wereassociated with slopes. Studies of habitat associa-tions in mesic to wet tropical forests also havefound slope-specialists (Clark et al. 1998; Harmset al. 2000; Webb and Peart 2000). The spatialdistribution of soil resources may result from dis-turbance history or differences in slope character-istics, since gaps tend be more abundant on steepslopes (Poorter et al. 1994). In addition, speciesassociated to slopes might be responding to a gra-dient of soil characteristics such as water avail-ability (Becker et al. 1988), nutrients (Botschek etal. 1996; Gonzalez and Zak 1996), or soil texture(Chauvel et al. 1987).

Importance value of seedlings and saplings

Gaps in the shrub and tree layers create hetero-geneity of light in the understory. Not surprisingly,importance values of seedlings and saplings werestrongly related to the presence of gaps. In high

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light conditions, tree seedlings achieved higherrelative growth rates and net assimilation rates(Rincon and Huante 1993). Pioneer species, inparticular, are light demanding and are morenegatively affected by low light environments thanshade-tolerant species (Rincon and Huante 1993).The pioneers Lysiloma microphyllum and Ceibaaesculifolia had lower importance values in areaswith few gaps. These results suggest that theimportance values of seedlings and saplings de-pend on light availability. Light limitation mayreduce growth in the sapling stage, but does notcontribute to increased mortality because suscep-tible seedlings will have already died. Seasonalopenings due to tree canopy deciduousness pro-vide temporal sites of high light, allowing different

growth rates depending on the season (Rincon andHuante 1993). Therefore, seedlings and saplings of TDF species might be able to persist under a rangeof light environments, with little selection for lightresource. In this sense, the classical theory of nichespecialization does not apply in seedlings andsapling TDF populations (Welden et al. 1991;Brokaw and Busing 2000).

Ordination axes for seedlings and saplings wereexplained by K and Mg concentrations, nutrientsthat play important roles in plant physiology. Mgis a key element in chlorophyll structure and Kfunctions mainly as an osmoregulator and canaffect cell size. Both elements are especially criticalin the TDF community where they help preventmortality resulting from drought stress. For in-stance, TDF seedlings respond to drought stresswith an increase in chlorophyll concentration(Khurana and Singh 2001). In addition, K and Mgconcentrations appear to be correlated with treespecies richness in the tropics and are consideredas limiting resources in Amazonian forests (Gentry1988; Burslem et al. 1995; Marschner 1995). Aresponse in growth with increasing Mg has beenfound in tropical trees (Burslem et al. 1995;Gunatilleke et al. 1997). Seasonal rainfall and itseffects on the reduction of microbial activity dur-ing the dry season affect the availability of theseelements (Campo et al. 1998), and consequently,the distribution and importance value of seedlingsand saplings. Pioneer species were positively cor-related with this axis which is consistent with thenotion that pioneers are more dependent onnutrient availability than shade-tolerant species(Rincon and Huante 1994).

Presenceabsence of seedlings and saplings

The presence and distribution of tropical decidu-ous seedlings and saplings may be more inuencedby habitat specialization for soil resources thanlight. The variance in axes from ordinations of ourpresence and absence data of seedlings and sap-lings was explained by soil variables and not bygaps. Soil organic matter affects acidity, soilmoisture and nitrogen availability resulting indifferent gradients of those factors, and therebydetermining species distributions. In addition, soilorganic matter contributes to cation exchangecapacity, which then controls K retention. Lowdensities of seedlings between 130 cm tall occur inthe tropical dry forest of Western Mexico (Vargas-

Rodriguez 1998), suggesting that mortality is highin early life stages. This is also consistent with ahigher mortality of seedlings in suboptimalhabitats found in a Bornean rain forest (Webb andPeart 2000). Poor nutrient conditions (low levels of cation exchange capacity), or the inability of seedlings to form symbioses with mycorrhizascould explain limits to establishment rather thandifferences in light regime resulting from canopygaps (Givnish 1999; Hubbell et al. 1999; Swaine1996). Diversity in Mexican TDF may be main-tained more by symmetric competition for soilresources and specialization along soil micrositegradients than by predators and pathogens relatedmortality (Harms et al. 2000).

Concluding remarks

Different light conditions created by light gaps andseasonal canopy openings inuence species differ-entiation among canopy and subcanopy trees, anddifferentiation in growth and importance value of tree populations. In contrast, seedlings and sap-lings appear mostly to be light generalists and areable to tolerate a wide range of light conditions(Brokaw and Busing 2000; Wright 2002).However, we hypothesize that habitat specializa-tion for soil resources is likely more important indetermining species success at early stages in lifethan in later stages in TDF at Jalisco, Mexico.Also, the pattern of niche differentiation of adulttropical trees observed along soil gradients (Clarket al. 1999; Svenning 1999, 2001; Webb and Peart2000) appears to occur at the seedling stage.

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Acknowledgements

This project was nanced by CONACYT (96-06-002Project), IDEAWILD and CUCBA-University of Guadalajara. First author thanks E. Fabia nVera Torres, Pablo Carrillo, Margarita Ayo n,Eduardo Herna ndez, Celso Corte s, EtelbertoOrtiz, and Ana Paula Reyes for their help witheld work. Francisco Santana Michel, Luis

Guzma n and herbaria IBUG staff helped withspecies identications. Saara Dewalt, JenniferCramer, Heather Passmore, Blanca FigueroaRangel, and La zaro Sa nchez Vela zquez madeimportant suggestions to this manuscript. Specialthanks Saara DeWalt for reviewing drafts of thispaper. BIOL 7093 course at Louisiana StateUniversity provided important ideas to thisresearch.

Appendix A . Density, frequency, basal area, and importance value for tree species within the 0.9 ha study area in La Escondida-LaCaban a, Jalisco, Mexico.

BA (dm 2) % Freq. Density Tree/ha BA dm 2 /ha Sites found in I.V.

Leguminosae Acacia cochliacantha 6.14 2.22 5.56 6.82 4,9 0.45Leguminosae Acacia macilenta 3.07 1.11 2.22 3.42 1 0.20Leguminosae Acacia macracantha 3.97 4.44 7.78 4.41 8,9 0.64Leguminosae Acacia pennatula 0.41 1.11 1.11 0.46 9 0.12Leguminosae Acacia riparia 5.31 6.67 7.78 5.90 3,4 0.81Euphorbiaceae Acalypha cincta 0.13 1.11 1.11 0.15 1 0.11Euphorbiaceae Adelia barbinervis 2.64 2.22 2.22 2.93 8,9 0.27Leguminosae Aeschynomene amorphoides 0.06 1.11 1.11 0.07 1 0.11Leguminosae Albizia tomentosa 30.06 15.56 23.33 33.40 1,5,6,8 2.37Malpighiaceae Bunchosia palmeri 13.44 5.56 7.78 14.93 2,5 0.87Burseraceae Bursera fagaroides 6.48 5.56 5.56 7.20 3,4,5,6,9 0.67Burseraceae Bursera grandifolia 32.94 14.44 17.78 36.61 1,2,5,7 2.15Burseraceae Bursera kerberi 2.32 1.11 1.11 2.58 5 0.15Burseraceae Bursera simaruba 19.29 4.44 5.56 21.44 4 0.82Flacourtiaceae Casearia corymbosa 3.92 7.78 17.78 4.35 5,7,8,9 1.21Bombacaceae Ceiba aesculifolia 197.69 40.00 51.11 219.66 1,2,3,4,5,6,7,8,9 7.88Ulmaceae Celtis iguanaza 1.79 6.67 6.67 1.99 2,3,4 0.71Cactaceae Cephalocereus alensis 4.42 2.22 2.22 4.91 3,5 0.30Cochlospermaceae Cochlospermum vitifolium 0.14 2.22 2.22 0.16 1,2,9 0.23Rhamnaceae Colubrina triora 1.27 3.33 3.33 1.41 4,5,8 0.36Anacardiaceae Comocladia engleriana 4.95 3.33 3.33 5.50 5 0.42Leguminosae Conzattia multiora 1.54 3.33 3.33 1.71 1,3,4 0.36Leguminosae Coursetia glandulosa 6.95 3.33 3.33 7.72 1,3 0.46Capparaceae Crateva palmeri 0.08 1.11 1.11 0.09 5 0.11Euphorbiaceae Croton fragilis 0.06 1.11 1.11 0.07 4 0.11Leguminosae Enterolobium cyclocarpum 10.43 1.11 1.11 11.59 9 0.29Rubiaceae Exostema mexicanum 11.89 2.22 2.22 13.22 8 0.43Moraceae Ficus cotinifolia 8.66 2.22 3.33 9.63 8 0.41Moraceae Ficus insipida 22.80 2.22 2.22 25.33 8 0.62Sterculiaceae Guazuma ulmifolia 11.38 4.44 5.56 12.64 4,5,7 0.69Rubiaceae Hamelia xorullensis 0.54 1.11 1.11 0.60 1 0.12Tiliaceae Heliocarpus terebinthinaceus 40.80 23.33 31.11 45.33 2,3,4,5,6,7,8,9 3.34Rubiaceae Hintonia latiora 3.04 2.22 2.22 3.38 1,2,6 0.28Amaranthaceae Iresine cassiniiformis 0.52 4.44 4.44 0.57 3,4,9 0.46Caricaceae Jacaratia mexicana 46.08 16.67 17.78 51.20 1,2,4,5,7,8,9 2.53Malpighiaceae Lasiocarpus ferrugineus 43.87 13.33 27.78 48.75 2,4,9 2.62Leguminosae Lysiloma microphyllum 538.22 74.44 341.11 598.02 1,2,3,4,5,6,7,8,9 26.27Malpighiaceae Malpighia ovata 0.09 1.11 2.22 0.10 8 0.15Euphorbiaceae Margaritaria nobilis 130.38 3.33 6.67 144.87 5,8 2.72Cactaceae Nopalea Aubert 3.61 10.00 10.00 4.02 5,6,7,8,9 1.07Cactaceae Nopalea karwinskiana 0.05 1.11 1.11 0.06 1,2 0.11Cactaceae Opuntia fuliginosa 0.38 1.11 1.11 0.43 8,9 0.12Cactaceae Pachycereus pecten-aboriginum 124.47 28.89 43.33 138.30 1,2,3,5,6,8 5.60Urticaceae Phenax hirtus 144.94 5 5.56 101.11 161.04 1,2,3,4,5,6,7,8 9.74

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Appendix A. Continued.

BA (dm 2) % Freq. Density Tree/ha BA dm 2 /ha Sites found in I.V.

Nyctaginaceae Pisonia aculeata var. aculeata 2.33 5.56 5.56 2.59 4,5 0.60

Leguminosae Pithecellobium acatlense 1.06 1.11 1.11 1.18 9 0.13Bombacaceae Pseudobombax ellipticum 12.83 1.11 1.11 14.26 1 0.34Myrtaceae Psidium guajava 0.06 1.11 1.11 0.06 9 0.11Simaroubaceae Recchia mexicana 0.56 1.11 1.11 0.62 5 0.12Leguminosae Senna atomaria 1.54 1.11 1.11 1.71 3 0.14Leguminosae Senna mollisima 0.04 1.11 1.11 0.04 5,6,8,9 0.11Sapotaceae Sideroxylon capiri subsp. tempisque 60.30 3.33 3.33 67.00 2,5 1.39Anacardiaceae Spondias purpurea 165.23 43.33 66.67 183.59 1,2,3,4,5,6,7,8,9 8.08Apocynaceae Stemmadenia donnell-smithii 4.89 13.33 20.00 5.44 1,5,6,8,9 1.67Apocynaceae Stemmadenia tomentosa var. Palmeri 8.53 7.78 13.33 9.47 8,9 1.13Cactaceae Stenocereus queretaroensis 4.65 3.33 3.33 5.16 2,4,8 0.42Bignoniaceae Tabebuia chrysantha 10.34 11.11 11.11 11.49 1,2,4,5,6,8,9 1.30Burseraceae Terebinthus acuminata 126.25 3.33 4.44 140.27 5 2.57Sapindaceae Thouinia serrata 16.59 4.44 5.56 18.43 1,2,5,8 0.78Sapindaceae Thouinidium decandrum 5.62 4.44 5.56 6.24 2,5,6,8 0.59Tiliaceae Triumfetta semitriloba 0.38 1.11 1.11 0.43 1 0.12Rutaceae Zanthoxylum caribaeum 2.41 6.67 8.89 2.68 4,5,6,7 0.79Rutaceae Zanthoxylum fagara 0.12 1.11 1.11 0.14 9 0.11

Totals 1914.98 947.78 2127.76

All nine sites were considered separate in each analysis and were here summarized in one single Appendix.

Appendix B . Density, frequency, mean height and importance value for seedlings and saplings species within the 0.9 ha in La Es-condida-La Caban a, Jalisco, Mexico.

% Freq. Density Trees/ha Mean height Sites found in I.V.

Leguminosae Acacia cochliacantha 3.33 13.33 0.53 9 2.24Leguminosae Acacia macracantha 1.11 1.11 3.00 8 4.28Leguminosae Acacia riparia 1.11 1.11 1.66 4 2.47Euphorbiaceae Adelia barbinervis 8.89 12.22 0.44 8,9 2.76Leguminosae Aeschynomene amorphoides 1.11 5.56 0.10 1 0.73Leguminosae Albizia tomentosa 2.22 2.22 0.85 1,5 1.62Malpighiaceae Bunchosia palmeri 2.22 2.22 1.29 5 2.21Burseraceae Bursera fagaroides 4.44 4.44 0.45 4,6,9 1.55Burseraceae Bursera grandifolia 17.78 33.33 0.09 1,2,7,8 5.18Burseraceae Bursera simaruba 1.11 1.11 0.34 4 0.70Flacourtiaceae Casearia corymbosa 21.11 41.11 0.22 5,7,8,9 6.42Bombacaceae Ceiba aesculifolia 27.78 37.78 0.14 1,2,3,4,5,6,7,8 6.92Cactaceae Cephalocereus alensis 4.44 5.56 0.15 3,5 1.24Cochlospermaceae Cochlospermum vitifolium 2.22 2.22 0.42 1,2 1.04Anacardiaceae Comocladia engleriana 1.11 1.11 0.62 5 1.07

Boraginaceae Cordia inermes 2.22 2.22 1.24 4 2.15Leguminosae Coursetia glandulosa 2.22 5.56 0.30 3 1.15Euphorbiaceae Croton fragilis 1.11 4.44 0.96 4 1.80Euphorbiaceae Croton ciliato-glandulifera 6.67 11.11 0.38 9 2.29Tiliaceae Heliocarpus terebinthinaceus 6.67 6.67 0.54 2,6,9 2.15Rubiaceae Hintonia latiora 1.11 1.11 1.54 1 2.31Caricaceae Jacaratia mexicana 4.44 4.44 0.66 1,4,9 1.83Malpighiaceae Lasiocarpus ferrugineus 6.67 8.89 0.51 9 2.28Leguminosae Lysiloma microphyllum 28.89 53.33 0.09 1,2,3,4,5,6,7 8.27Euphorbiaceae Margaritaria nobilis 1.11 1.11 2.50 8 3.61Cactaceae Nopalea Aubert 11.11 28.89 0.19 5,7,8,9 4.08Cactaceae Nopalea karwinskiana 2.22 2.22 0.59 1,2 1.27

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% Freq. Density Trees/ha Mean height Sites found in I.V.

Cactaceae Opuntia fuliginosa 3.33 3.33 0.43 8,9 1.29

Cactaceae Pachycereus pecten-aboriginum 3.33 3.33 0.33 2,5,8 1.15Urticaceae Phenax hirtus 5.56 6.67 0.51 1,7,8 1.96Leguminosae Senna mollisima 7.78 10 0.36 5,8,9 2.32Anacardiaceae Spondias purpurea 15.56 23.33 0.24 1,2,3,4,5,7,8 4.47Apocynaceae Stemmadenia donnell-smithii 25.56 45.56 0.18 1,5,8 7.32Apocynaceae Stemmadenia tomentosa var. Palmeri 2.22 2.22 0.90 8,9 1.68Bignoniaceae Tabebuia chrysantha 3.33 3.33 0.55 5,8,9 1.45Sapindaceae Thouinidium decandrum 2.22 3.33 0.49 2,8 1.22Rutaceae Zanthoxylum caribaeum 7.78 10 0.20 5,6,7 2.11Rutaceae Zanthoxylum fagara 2.22 3.33 0.63 9 1.41

Totals 408.89

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