Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

Abundance and physiognomic characteristics of woody natives

in a sub-urban talar forest remnant extensively

invaded by exotic vegetation

Leandro Alcalde1,2*; https://orcid.org/0000-0002-4365-243

Luisina Rodríguez-Allo3; https://orcid.org/0009-0004-8667-7182

1. Sección Herpetología, Instituto de Limnología Dr. R. A. Ringuelet, Boulevard 120 y 62, CP 1900, La Plata, Buenos

Aires, Argentina; alcalde@ilpla.edu.ar (*Correspondence).

2. Consejo Nacional de Investigaciones Científicas y Técnicas–Centro Científico y Tecnológico La Plata, 8 N° 1467,

Buenos Aires, Argentina.

3. Bioparque La Plata, Paseo del Bosque, Avenida Iraola y 52, CP 1900, La Plata, Buenos Aires, Argentina;

luisinaunlp@gmail.com

Received 21-XI-2024. Corrected 27-IX-2024. Accepted 26-XI-2024.

ABSTRACT

Introduction: The talares are small xerophytic forests dominated by the trees Celtis tala and Scutia buxifolia,

which are characteristic of the pampas in the Northeast of Buenos Aires Province, Argentina. Talares coexist

with areas facing significant urban and agricultural pressures, leading to their impoverishment, fragmentation,

and even local extinction.

Objective: To characterize a resilient talar patch within a suburban forest invaded by exotic vegetation to identify

the patterns and processes currently affecting native woody species.

Methods: The forest (55 ha) was divided into seven sampling sites. We assessed the abundance and physiognomic

variables of native woody species through random searches (approach 1). For exotic woody species, we used a

combination of transects and grids within the forest and on adjacent streets (approach 2). The analyses included

descriptive statistics, index calculations, and comparisons through confidence interval establishment and Chi-

square tests with Yates’ correction.

Results: Total sampling time per team member was 118.5 h for approach 1 and 48 h for approach 2. Two native

species dominate the studied talar patch: C. tala (88 %) and S. buxifolia (11 %), while other native woody spe-

cies were extremely rare (1 %). Exotic woody species were dominant structurally and numerically. We observed

variations of C. tala and S. buxifolia height between forest stands, most common under 3 m in height. The Mantle

Index indicated light competition due to shading caused by fast-growing, large exotic species. Damage due to fall-

ing eucalyptus branches was observed only in C. tala, although at a low percentage. S. buxifolia had 20 % and C.

tala 15 % of individuals with a shrub-like form with some cases being variable among forest stands. We propose

several manageent strategies aimed at favoring native species over exotics.

Conclusion: The studied forest is a hybrid ecosystem with neo-ecosystem traits, which implies a series of con-

servation problems for the remaining native woody species present. It is highly valuable for the conservation

of talares, particularly for one of its most emblematic species, S. buxifolia, which is virtually absent outside the

forest area.

Key words: adaptive management; forest resilience; hybrid ecosystems; suburban forests; habitat loss; woody

natives.

https://doi.org/10.15517/rev.biol.trop..v72i1.57706

CONSERVATION

2Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

INTRODUCTION

Grasslands represent the climax communi-

ty of the Pampa ecoregion, which spans Brazil,

Uruguay, and Argentina. They consist of vast

pastures occasionally interrupted by marsh-

es, meandering streams, shallow lagoons, and

small xeric forest patches that thrive in well-

drained soils. In the Southern Pampa, these

patches, locally referred to as talar forest patch-

es (TFPs), are found in three sub-ecoregions:

Rolling Pampa, Low-land Pampa, and Hill-land

Pampa (Cabrera, 1971; Matteucci, 2012; Parodi,

1940). TFPs are dominated by Celtis tala Gillies

ex Planch. and Scutia buxifolia Reissek, two

species with a relatively wide distribution in

Southern Bolivia, Paraguay, Northern Argen-

tina, Southern Brazil, and Uruguay. However,

dense populations of these species are primarily

restricted to the Southern range of Argentina,

particularly Buenos Aires province. Within

TFPs, C. tala and S. buxifolia often co-dominate

and are accompanied by less abundant species

(Cabrera, 1971). Due to the relatively recent

formation of Pampas soils after the last sig-

nificant sea level drop (late Holocene, approxi-

mately 3000 years ago: Cavalotto, 2002), TFPs

can be considered young forest communities. A

recent study found that TFP diversity is higher

in Northeastern patches due to their proximity

to Northern forest ecoregions and hygrophilous

forests, with diversity decreasing toward the

South and West (Torres-Robles, 2009).

Pre-Hispanic settlers utilized TFPs in vari-

ous ways (Paleo et al., 2002). However, during

the Hispanic period entire trees were used for

RESUMEN

Abundancia y características fisonómicas de leñosas nativas de un talar suburbano

remanente extensamente invadido por exóticas

Introducción: Los talares son pequeños bosques xerofíticos dominados por los árboles Celtis tala y Scutia buxi-

folia, característicos de las pampas en el noreste de la Provincia de Buenos Aires, Argentina. Los talares coexisten

con áreas que enfrentan presiones urbanas y agrícolas significativas, lo que ha llevado a su empobrecimiento,

fragmentación e incluso extinción local.

Objetivo: Caracterizar un talar resiliente ubicado en un bosque suburbano invadido por vegetación exótica, para

identificar los patrones y procesos que actualmente afectan a las especies leñosas nativas.

Métodos: El bosque (55 ha) se dividió en siete sitios de muestreo. Hemos evaluado la abundancia y las variables

de la fisiognomía de las especies leñosas nativas mediante búsquedas aleatorias (enfoque 1). Para las especies

leñosas exóticas, utilizamos una combinación de transectos y cuadrículas dentro del bosque y en calles aledañas

a él (enfoque 2). Los análisis incluyeron estadística descriptiva, cálculo de índices, y comparaciones mediante

establecimiento de límites de confianza y pruebas Chi-cuadrado con corrección de Yates.

Resultados: En total, el tiempo dedicado fue de 118.5 h por miembro del equipo para el enfoque 1 y 48 h por

miembro del equipo para el enfoque 2. Dos especies nativas dominan el parche talar estudiado: C. tala (88 %) y

S. buxifolia (11 %), mientras que otras especies leñosas nativas fueron extremadamente raras (1 %). Las especies

leñosas exóticas dominaron estructural y numéricamente. Observamos variación en la altura de C. tala y S. buxi-

folia entre los rodales forestales, siendo más comunes de menos de 3 m. El Índice de Manto indicó competencia

lumínica por la sombra causada por especies exóticas grandes y de rápido crecimiento. Hubo daño debido a la

caída de ramas de eucalipto solo en C. tala, aunque en un porcentaje bajo. En cuanto a la presencia de un hábito

arbustivo, S. buxifolia tuvo el 20 % y C. tala 15 % de individuos con forma arbustiva, siendo algunos casos variables

entre los rodales forestales. Proponemos varias estrategias de manejo tendientes a favorecer a las especies nativas

sobre las exóticas.

Conclusión: El bosque estudiado es un ecosistema híbrido con rangos de neo-ecosistema que implica una serie

de problemas de conservación para los remanentes de leñosas nativas allí presentes. Es altamente valioso para la

conservación de los talares, particularmente para una de sus especies más emblemáticas, S. buxifolia, la cual está

prácticamente ausente fuera del área de bosque.

Palabras clave: manejo adaptativo; resiliencia de bosques; ecosistemas híbridos; bosques suburbanos; pérdida de

hábitat; leñosas nativas.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

firewood, construction, and fencing; fruits were

harvested for poultry feed; and cattle intrusion

facing an increasing overexploitation that led

to general impoverishment of the community

(Pochettino et al., 2014). The decline in TFP

species and the loss of many patches were noted

early by pioneer researchers (Bruch, 1937; Par-

odi, 1940). Today, few TFPs are effectively

protected, and most are either impoverished

or extinct due to various threats (Fundación de

Historia Natural Félix de Azara, 2006a; Guerre-

ro, 2019; Morello, 2006). Over the past 30 years,

conservationists have focused on the prob-

lems affecting TFPs, leading to new research

and proposals for effective protection measures

(Arturi, 1997; Arturi et al., 2006; Franco et al.,

2018). These conservation and research efforts

have highlighted two key issues: (i) invasion by

exotic plants and transformation of TFPs into

hybrid ecosystems, and (ii) generation of young

TFPs that established themselves (colonizer

TFPs) in areas where the soil has been disturbed

or where exotic trees were introduced as part of

the Pampas’ lignification process (Apodaca

& Guerrero, 2019; Morello, 2006). Globally,

implanted forests that support subsistence or

facilitate the creation of new native patches are

a widespread phenomenon (Lugo, 1997; Par-

rotta, 1992). Radical ecosystem transformations

have significantly altered native ecosystems

worldwide. Such transformations have sparked

theoretical debates and diverse conservation

practices in these increasingly degraded eco-

systems. The concept of a neo-ecosystem (or

transformed ecosystem: Aronson et al., 2014;

or emerging ecosystem: Clewell & Aronson,

2013), first proposed by Chapin & Starfield

(1997), refers to a system of biotic, abiotic, and

social factors that, due to human influence, dif-

fers from the historically dominant one. Neo-

ecosystems tend to self-organize and develop

new characteristics without intensive human

management (Hobbs et al., 2013). The chal-

lenge lies in determining where each system

falls on the gradient between an original state

and a neo-ecosystem. Miller & Bestelmeyer

(2016) stress the importance of identifying irre-

versibility thresholds in hybrid ecosystems to

guide ecological restoration efforts. They also

argue that, even if restoration is not feasible,

controlling exotic species-whether for eradi-

cation or not-should be a key consideration.

Managing exotic species, especially the most

harmful ones, can reduce pressure on natives

and potentially provide valuable functions if

kept within acceptable abundance levels (Bel-

nap et al., 2012; Davis et al., 2011; Simberloff,

2011). The aims of this study were: 1) to assess

the composition, abundance, and physiognomy

of a TFP within a suburban forest extensively

invaded by exotic plant species, and 2) to esti-

mate the abundance of these woody exotics in

the TFP and its surroundings. We believe that

identifying patterns in the physiognomy, abun-

dance, and local distribution of native woody

plants will help us understand the impact of

invasive species and guide effective remediation

and adaptive management strategies.

MATERIALS AND METHODS

Study Site: Las Banderitas Forest spans

55 hectares of forest and 6 hectares of shrubs

and grasses. Located Northwest of La Plata

city, near the headwaters of Carnaval stream

(34°54’58’’ S & 58°06’10’’ W), it is an ecosystem

where native and exotic woody plants coexist

(Fig. 1). The site lies in a suburban area with

three dispersed population centers covering

1 200 hectares of heavily modified Rolling

Pampa landscapes. The dominant land uses are

intensive, including 70 hectares of horticulture,

254 hectares of greenhouse floriculture, 35

hectares of soybean and corn fields, and smaller

areas for beekeeping, poultry farming, small

cattle and sheep farms, and pig breeding. The

remaining area consists of abandoned green-

houses and non-productive soil, which has

been colonized by native and exotic vegetation,

sometimes forming hybrid grasslands, shrub

lands, or small patches of exotic woody forest.

Urbanization is minimal, lower than 1 house /

hectare, and most pathways are unpaved. The

area is undergoing continuous change due to

city expansion, which is encroaching on rural

and natural spaces, creating stressful social and

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ecological sceneries (Frediani, 2013; Matteucci

& Morello, 2009).

Sampling design: We divided the 55 hect-

ares of forest into seven smaller stands (S1: 8

ha, S2: 10ha, S3: 4 ha, S4: 8.5 ha, S5: 6 ha, S6:

6.5 ha, S7: 12 ha), using existing paths and open

forest areas for demarcation (Fig. 1). Data col-

lection involved two approaches: (1) measuring

the abundance and physiognomic variables of

native trees through random searches inside

each stand, and (2) using transects and grids

to sample exotic and native woody plants for

assessing species abundance both inside and

outside the forest. In both cases the search

effort was measured in hours per person (we

always used two people), with each team mem-

ber given hours based on the search area (the

larger the stand area, the more hours were

dedicated proportionally). In total the complete

work related to each approach involved 118.5

hours / team member in approach 1and 48

hours /team member in approach 2. We exclud-

ed shrubs from the genera Pavonia and Bac-

charis from sampling and analysis due to their

extensive cover and abundant basal branching,

which made individual identification difficult

and required different methodologies. These

genera will be included in future studies where

understory vegetation will be addressed using

appropriate methodologies and analyses.

Approach 1: Involved three phases, each

covering the entire forest area. Phase 1 (initial

count) included 15 visits between 22 August

2020, and 5 November 2020. Phase 2 (first

re-count and new detections) comprised 56

visits from 13 November 2020 to 22 April 2022.

Phase 3 (second re-count and new detections)

consisted of eight visits between 30 June 2022

Fig. 1. Study site. Note the seven stands (S1-S7) into which the 55 ha of forest were divided and the converging streets (154,

157, 160 and 178). White stars at the beginning and end of each street indicate the area in which woody plants were sampled

on the street shoulders out of the forest. Arrows indicate the course of the Carnaval stream. The area encircled represents the

influence area of the central wetland within the forest. The white lines represent the approximate position of transects within

stands. North is indicated by the red cone in the upper left corner of the figure.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

and 8 August 2022. We marked all sampled

native woody species with a paint dot on the

main trunk to prevent data duplication and

recorded them based on (a) growing habit

(arborescent or bushy), (b) height ( meters)

from ground level to the top edge of the crown,

eter (centimeters) at a point between 0.5 and

1 meter in height (measured on the dominant

trunk for bushy individuals), and (e) mode

of growth (erect or comb-shaped). We also

recorded standing dead individuals caused by

lightning, excess water, or unknown reasons.

We measured length variables using a semi-

rigid 10 m long tape. The sampling method

used in this approach was random. We ceased

random sampling when we accounted for near-

ly all C. tala and S. buxifolia individuals within

each stand. In other words, while the sampling

method was random, the outcome approached

a census. We used the ratio of recounted indi-

viduals to new detections to estimate the com-

pleteness of sampling within each stand.

Approach 2: Involved sampling using tran-

sects and grids. Within the forest, transects (20

x 4 meters; oriented Southeast-Northwest) and

grids (placed at the beginning, middle, and end

of each transect) were uniformly positioned

every 50 meters within each stand to ensure

consistent coverage across all stands, covering

25 % of each stand’s area. Outside the forest,

transects were placed on both sides of the four

roads leading into the forest, ensuring almost

complete coverage of the entire road area with

minimal gaps (Fig. 1). Transects measured the

abundance and height class frequency of woody

species > 1 m tall. We measured the abundance

of woody species < 1 m tall within 2 m2 circle

grids established at beginning, middle, and

end of each transect. Along the transects on

the streets out of the forest, we assessed plant

abundance but not the height class frequency

of all woody plants since shoulders constantly

suffer from pruning by municipality operators.

Data Analysis: We used data on native

woody species inside the forest to describe

the physiognomy and abundance of domi-

nant native trees. The dataset included three

variables: height, crown diameter, and trunk

perimeter. Heights were categorized into six

classes for analysis: 1 (< 1 m), 2 (1-2.99 m), 3

(3-4.99 m), 4 (5-6.99 m), 5 (7-8.99 m), and 6

(> 9 m). The height of C. tala and S. buxifolia

was statistically described using measures of

central tendency (arithmetic mean) and dis-

persion (standard deviation) and compared

between forest sites by establishing confidence

limits for the mean of each species per site. The

comparisons of the means were evaluated using

the confidence intervals of the means with an

alpha = 0.05 (the level used for the graphical

part) and also at an alpha = 0.01 (to have greater

confidence about the detected differences). We

calculated the Mantle Index (MI = Crown

Diameter / Height, Burger, 1939) to assess

how tree crowns relate to lighting, with val-

ues near zero indicating asymmetrical crowns.

To describe (using descriptive statistics and

graphs) and analyze (by calculating confidence

intervals for the mean) the index we followed

the same procedure in the dominant natives,

C. tala and S. buxifolia. For this purpose, we

excluded trees shorter than 3 meters tall. Trunk

diameter was derived from trunk perimeter and

used to estimate the basal area of trees in height

classes 2 to 6 using the formula Basal area = (π

/ 4) * trunk diameter². The basal area served as

a complementary measure of tree density.

Chi-square tests with Yates’ correction

were used to evaluate differences in the per-

centages and proportions of the most abundant

native woody plants, specifically in relation

with standing dead trees, trees growing hori-

zontally due to crushing by eucalyptus branch-

es, and specimens with a shrubby growth form.

The abundance of native and exotic woody

species inside the forest was addressed based

on the data obtained from transect sampling.

We assessed abundance by calculation of the

Relative Importance Index (RII: Pinkas et al.,

1971), an index of common usage in studies

of trophic ecology, here adapted to evaluate

the importance of each species. The index was

calculated for each species using the variables

6Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

% FO (Percentage Frequency of Occurrence),

% FH (Percentage Frequency of Height), and

% FN (Percentage Frequency of Numerosity).

The % FO variable represents the percentage

of transects into which a particular species was

found relative to the total number of transects

and grids conducted. The % FH variable is the

sum of the products between the mean of each

height class and the abundance of each spe-

cies within each height class, expressed glob-

ally as a percentage of the total height value for

each species. This was the only variable modi-

fied from the original RII, which uses volume

instead of height. Finally, the % FN variable is

the abundance of each species expressed as a

percentage of the total abundance of all species.

The RII values of each species were ranked as a

percentage relative to the highest RII value to

better visualize the importance of each species

and facilitate comparisons. Grid sampling was

employed to assess the abundance of saplings

within the forest.

We used Statistica 8.0 (StatSoft, 2007) and

SigmaPlot 10.0 (Systat Software, 2006) for data

analysis and graphing, with significance set at p

< 0.05. The entire dataset is available at Alcalde

(2024). Once you have accessed the page, you

should enter the full name of the first author

into the search bar. This will then display a set

of research data from which you can select the

desired one.

RESULTS

We detected a total of 4 029 native woody

trees and bushes across the seven forest stands:

3 553 C. tala, 454 S. buxifolia (present in all

stands), 30 Abutilon grandifolium (Will.) Sweet

(S5), 11 Sambucus australis Cham. & Schltdl.

(bushy and < 5 m tall, in S1-S3, S5, and S7), four

Senegalia bonariensis (Gillies ex Hook. & Arn.)

Seigler & Ebinger (S1, S2, and S4), three Ery-

thrina crista-galli L. (S2), and two Parkinsonia

aculeata L. (S5). Since C. tala and S. buxifolia

accounted for 99 % of the woody natives, we

focused our analysis on these dominant species.

C. tala had a higher density than S. buxi-

folia across all forest stands (Table 1). The late

species was so scarce at stands 3 to 7 that these

stands had to be grouped to obtain satisfactory

degrees of freedom for all comparisons and

analyses conducted. S. buxifolia exhibited high-

er density in S1 and S2, while C. tala was denser

in S3, followed by S5 and S1. The basal area of

C. tala for the entire forest was 860.27 m² (15.6

m²/ha), with the lowest value in S6 (10.61 m²,

1.6 m²/ha) and the highest in S3 (351.76 m²,

87.9 m²/ha) (Table 1).

C. tala consistently dominated numeri-

cally over S. buxifolia across all stands, with

particularly dominance in S3 to S7 where S.

buxifolia was extremely infrequent (Table 1).

Analysis of the height for S. buxifolia and C.

tala revealed that trees were less than 3 meters

height were predominant (Fig. 2, Table 1). The

overall height pattern of both species was simi-

lar, with both dominated by individuals shorter

than three meters in height. The forest stands

that replicated the global pattern of both spe-

cies, and partly explained it, were the stands at

the forest front (S1, S2 for both species, S3 for

C. tala), with a greater number of taller trees

observed at the stands on the opposite end of

the forest (Fig. 2, Table 1).

The mean height of S. buxifolia was not

different between S1 and S2, but both differed

from the mean of the groupings of the stands

at the opposite end of the forest (S3-7) using a

99 % confidence level (Fig. 3A).

When comparing the mean heights of C.

tala using stringent confidence intervals (99 %),

we also detected general height differences,

with lower means at the NE-NW front sites of

the forest (S1, S2, S3, and S5, being S2 the place

with the higher mean of them) compared to the

higher mean heights at the SE-SW sites on the

opposite end (Fig. 3B).

The comparison through the establishment

of 99 % confidence limits of the mean mantle

index did not detect differences between forest

stands for S. buxifolia equal to or greater than

three meters in height (the differences were not

detected even when using a more relaxed confi-

dence level of 95 %, Table 2 and Fig. 4A). How-

ever, it can be said that the mean mantle index

trends from higher values at the forest front in

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

Fig. 2. Number of S. buxifolia and C. tala trees (X-axis) of different height (Y-axis) for the entire forest and stand to stand (S.buxifolia for S3 to S7 were presented together, see text).

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Table 1

Global and stand to stand values of tree density (td), basal area (ba), and height of C. tala and S. buxifolia from the studied

forest.

stand ntd ba mean H (min-max) - 95 + 95 sd

S. Buxifolia

global 454 8.2 8.3 (0.15/ha) 1.6 (0.12-10) 1.5 1.8 1.5

S1 252 31.5 4.5 (0.56/ha) 1.6 (0.15-10) 1.4 1.8 1.4

S2 162 16.2 2.4 (0.24/ha) 1.5 (0.12-10) 1.2 1.7 1.4

S3-7 40 1 1.27 (0.03/ha) 2.7 (0.15-9) 2.08 3.3 2

C. Tala

global 3 553 64.1 860.2 (15.6/ha) 2.7 (0.1-13) 2.6 2.8 2.3

S1 839 104.5 141.4 (17.6/ha) 2.3 (0.1-9.2) 2.2 2.4 1.7

S2 311 31 116.4 (11.6/ha) 2.7 (0.1-11.6) 2.5 3.08 2.5

S3 1 322 330.5 351.7 (87.9/ha) 2.5 (0.1-11.8) 2.3 2.6 2.2

S4 183 20.8 36.6 (4.3/ha) 3.5 (0.1-10.2) 3.2 3.9 2.2

S5 667 112.3 111.4 (18.5/ha) 2.5 (0.1-12.4) 2.3 2.7 2.1

S6 37 5.53 10.61(1.6/ha) 4.5 (0.4-9.6) 3.9 5.1 1.8

S7 184 14.5 91.87 (7.6/ha) 5.5 (0.5-13) 5.1 5.9 2.8

td: trees/ha, ba: crude and referred to 1 ha, n: number of trees, min-max: minimum height – maximum height, - 95 % and +

95 %: confidence limits of mean, sd: standard deviation.

Table 2

Values and descriptive statistics of the mantle index for S. buxifolia and C. tala specimens equal to or greater than 3 meters

in height, presented for the entire forest and broken down by stand (S).

stand nmean (min-max) - 95 + 95 sd

Scutia buxifolia

global 71 0.76 (0.23-1.38) 0.7 0.82 0.24

S1 36 0.8 (0.23-1.38) 0.71 0.89 0.27

S2 17 0.67 (0.31-1.15) 0.55 0.79 0.23

S3-7 18 0.77 (0.46-1.05) 0.68 0.86 0.17

Celtis tala

global 1 285 0.66 (0.04-1.88) 0.62 0.67 0.23

S1 246 0.65 (0.2-1.47) 0.62 0.68 0.22

S2 67 0.69 (0.2-1.54) 0.62 0.75 0.26

S3 431 0.66 (0.2-1.78) 0.64 0.68 0.24

S4 100 0.71 (0.3-1.4) 0.66 0.76 0.24

S5 237 0.65 (0.04-1.8) 0.62 0.68 0.23

S6 30 0.71 (0.4-1.51) 0.63 0.8 0.23

S7 143 0.61 (0.29-1.19) 0.57 0.64 0.18

n: number of trees, (min-max): (minimum-maximum), -95 and + 95: confidence limits of the mean, sd: standard deviation.

Note that for the first species, neighboring stands S3 to S7 were grouped due to the low number of specimens in each one.

S1 and forest bottom in S7 (indicating crown

imbalance and higher competition for light)

toward higher values at the center of the forest

(and vice versa). The mean mantle index of C.

tala varied across forest stands, but significant

differences, as determined by 99 % stringent

confidence limits, were only noted between S4

and S7 (Table 2, Fig. 4B).

Of the two most abundant native woody

species, the phenomenon of standing dead trees

was observed only for C. tala at stands on the

NE-NW edge of the forest (S1, S2) and at the

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

stands on the opposite end (S5, S6, and S7), but

was not observed at the central forest stands.

The percentages of standing dead C. tala were

low across stands (S1: 0.4 %, S2: 1.9 %, S5: 5

%, S6: 2 %, S7: 3 %), and comparisons using

the Chi-square test with Yates’ correction did

not detect differences between them. Another

phenomenon we detected in C. tala but not in

S. buxifolia was the presence of trees growing

flattened with their main axis parallel or bent

relative to the ground due to the falling of large

branches, primarily from E. camaldulensis. The

Fig. 3. Box plots of the height. A. Of S. buxifolia. B. Of C. tala. Globally for the forest (G) and from each forest stand (S).

Black squares: mean, grey boxes: 95 % confidence limits of mean, extreme ends of vertical lines: minimum and maximum

height values.

Fig. 4. Box plots of the Mantle Index values. A. Of S. buxifolia. B. Of C. tala. Corresponding to tress equal or higher than

three meters in height. References as in Fig. 3.

10 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

percentage of flattened C. tala trees in each for-

est stand was low (S1: 2 %, S2: 6 %, S3: 1.5 %, S4:

2 %, S5: 4 %, S6: 5 %, S7: 2 %), and the compari-

son of these values using the Chi-square test

with Yates’ correction did not detect significant

differences between any pair.

Overall, S. buxifolia exhibited 20 % of

individuals with a shrub-like form, with similar

values across each forest stand (S1: 17 %, S2:

25 %, S3-7: 10 %). The comparison using the

Chi-square test with Yates’ correction detected

differences only between S2 and S3-7 (p <

0.05). Considering all sites, C. tala showed 15

% of individuals with a shrub-like habit. Com-

parisons between stands using the Chi-square

test with Yates’ correction detected differences

between stands at the SE-SW end of the forest

(except for S6 which had the lowest percentage)

and stands at the opposite end (NE-NW forest

edge) (Table 3).

The total number of woody species detect-

ed inside and outside the forest was similar (39

inside with seven native and 40 outside with

eight native), but the species composition dif-

fered (Table 4). Streets 154 and 160 each had

21 species, while Street 160 had the fewest

(19) and Street 178 had the most (29). Exotic

species were dominant, especially C. laevigata,

L. lucidum, C. australis, M. alba, L. sinense, G.

triacanthos, and P. a l ba . The former was the

most prevalent and, together with L. lucidum,

both dominated on the four streets. Gledit-

sia triacanthos was dominant only on Street

178 (limiting stands 5 to 7, Fig. 1). Fraxinus

pennsylvanica was dominant only on Street 157

(limiting stands 1 and 2, Fig. 1). Of the natives,

C. tala was present on all streets, but other

native species were mostly limited to Street 178,

with one species (V. cave n) only found on Street

160 (limiting stands 4 and 7, Fig. 1).

Both full RIIf and its simplified RIIs (with-

out using height frequency) version coincided

in provided the same global ranking of the

species inside the forest (Table 4). When com-

paring stand by stand, some of them showed

changes in the ranking of the top five species in

each case (Fig. 6). These differences occurred

at S1 to S4, where some large species (generally

E. camaldulensis) moved to less important posi-

tions and were replaced by species with greater

numerical abundance but not as tall (Table 4

and Fig. 5 for discordances between RIIf and

RIIs values).

The simplified % RIIs identified the follow-

ing five dominant species (listed in descending

order according to RIIs value): L. sinense, C. lae-

vigata, E. camaldulensis, M. alba, and L. lucidum

(inside forest), and C. laevigata, L. lucidum, M.

alba, L. sinense, and G. triacanthos (outside

forest). The exclusion of E. camaldulensis from

the top five species outside the forest and its

replacement by G. triacanthos, which turned

out to be particularly abundant in one of the

adjacent streets, explains the only differences

detected by the RIIs between inside and outside

the forest. Finally, grid sampling within the for-

est detected an almost absolute sapling abun-

dance of L. sinense (86 %), followed by L. nobilis

Table 3

Percentage of C. tala with shrub-like habit we found at each forest site (diagonal line) and its comparison between stands

using Chi-square test with Yates’ correction.

S1 S2 S3 S4 S5 S6 S7

S1 11 %

S2 NS 9 %

S3 NS NS 9 %

S4 NS * * 22 %

S5 * ** ** NS 26 %

S6 NS NS NS ** ** 5 %

S7 * ** ** NS NS ** 26 %

One asterisk represents significant differences (p < 0.05), two asterisks indicate highly significant differences (p < 0.01), and

NS represents no significance in the comparison.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

Table 4

Percentage values of frequency of occurrence (% FO), numerical frequency (% FN), height frequency (% FH), % RII full (%

RIIf) and RII simplified (% RIIs) of the woody species detected trough transect sampling.

Species % FO % FN % FH % RIIf% RIIs

Global forest

Oleaceae: Ligustrum sinense Lour. 78.6 42.4 20.5 100 100

Cannabaceae: Celtis laevigata Willd. 90.7 28.7 23.4 96 78.1

Myrtaceae: Eucalyptus camaldulensis Dehnh. 86.4 8.01 35.5 76 20.6

Moraceae: Morus alba L. 60.1 5.5 7.5 16 9.9

Oleaceae: Ligustrum lucidum W. T. Aiton 48.05 3.4 2.1 5 4.9

Cannabaceae: Celtis tala* 31.06 2.8 2.1 3 2.6

Cannabaceae: Celtis australis L. 29.1 1.2 1.3 2 1.07

Sapindaceae: Acer negundo L. 14.5 2.4 2.8 2 1.07

Lauraceae: Laurus nobilis L. 22.3 1.7 1.1 1 1.01

Fabaceae: Gleditsia triacanthos L. 13.1 0.6 0.7 < 1 < 1

Lauraceae: Cinnamomum glanduliferum (Wall.) Meisn. 12.1 0.2 0.4 < 1 < 1

Verbenaceae: Lantana camara L. 8.2 0.6 0.2 < 1 < 1

Rhamnaceae: Scutia buxifolia* 8.2 0.3 0.2 < 1 < 1

Rosaceae: Pyracantha coccinea M. Roem. 6.3 0.2 0.1 < 1 < 1

Fabaceae: Racosperma melanoxylon R. Br. 3.3 0.2 0.4 < 1 < 1

Salicaceae: Populus alba L. 1.45 0.45 0.36 < 1 < 1

Salicaceae: Salix babylonica L. 0.9 0.07 0.2 < 1 < 1

Pittosporaceae: Pittosporum tobira (Thunb.) W. T. Aiton 1.9 0.04 0.02 < 1 < 1

Arecaceae: Phoenix canariensis H. Wildpret 1.4 0.03 0.02 < 1 < 1

Arecaceae: Syagrus romanzoffiana (Cham.) Glassman 1.4 0.03 0.01 < 1 < 1

Fagaceae: Quercus robur L. 0.9 0.04 0.04 < 1 < 1

Adoxaceae: Sambucus australis* 1.4 0.04 0.01 < 1 < 1

Oleaceae: Fraxinus pennsylvanica Marshall 0.4 0.07 0.05 < 1 < 1

Rosaceae: Prunus serrulata Lindl. 0.9 0.02 0.02 < 1 < 1

Casuarinaceae: Casuarina cunninghamiana Miq. 0.4 0.05 0.02 < 1 < 1

Anacardiaceae: Schinus areira L. 0.9 0.02 0.01 < 1 < 1

Arecaceae: Livinstona australis (R. Br.) Mar. 0.9 0.02 0.09 < 1 < 1

Cupressaceae: Cupressus lusitanica Mill. 0.9 0.02 0.009 < 1 < 1

Arecaceae: Butia yatay (Mart.) Becc. 0.4 0.01 0.004 < 1 < 1

Fabaceae: Parkinsonia aculeata* L. 0.4 0.01 0.004 < 1 < 1

S1 (top five)

C. laevigata 100 37 36 100 100

E. camaldulensis 88 11 27 46 26.7

L. sinense 73 22 11 32 42.5

M. alba 81 11 10 23 24.5

L. lucidum 54 6 4 8 9.1

S2 (top five)

C. laevigata 97 25 22 100 80.03

L. sinense 72 41 18 95 100

E. camaldulensis 97 7 32 84 22.8

A. negundo 56 13 13 32 24.5

M. alba 75 6 9 25 14.8

12 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

Species % FO % FN % FH % RIIf% RIIs

S3 (top five)

C. laevigata 75 27 58 100 100

C. tala* 69 25 9 36 85.8

M. alba 88 13 8 29 58.9

E. camaldulensis 31 11 16 13 16.9

L. lucidum 50 7 2 7 17.6

S4 (top five)

L. sinense 91 72 40 100 100

E. camaldulensis 88 7 29 31 9.3

C. laevigata 68 11 15 17 11.1

M. alba 59 4 10 8 3.4

L. lucidum 50 2 2 2 1.6

S5 (top five)

C. laevigata 100 46 27 100 100

E. camaldulensis 79 11 45 61 23.2

L. sinense 63 17 8 22 19.7

C. tala* 50 7 5 8 7.2

M. alba 42 6 6 7 3.05

S6 (top five)

L. sinense 88 55 23 100 100

E. camaldulensis 92 14 55 91 26.03

C. laevigata 96 19 12 44 38.1

L. lucidum 50 3 2 4 3.2

M. alba 27 2 3 2 1.2

S7 (top five)

L. sinense 92 48 24 100 100

C. laevigata 96 33 26 87 72

E. camaldulensis 96 7 37 65 16.3

M. alba 58 3 5 7 3.2

L. lucidum 54 2 1 3 2.6

Street shoulders

C. laevigata 100 40.7 - - 100

L. lucidum 75 19.09 - - 35.1

M. alba 100 7.4 - - 18.8

L. sinense 100 1.1 - - 14.4

G. triacanthos 100 4.4 - - 11

C. tala* 100 2.9 - - 7.3

F. pennsylvanica 100 2.5 - - 6.3

C. australis 50 4.5 - - 5.5

P. a l b a 50 4.03 - - 4.9

L. nobilis 100 1.1 - - 2.7

R. pseudoacacia 75 1.01 - - 1.8

C. cunningamiana 75 1.005 - - 1.6

C. lussitanica 75 05 - - 1

S. bonareinsis* 25 1.5 - - < 1

E. camaldulensis 75 0.3 - - < 1

B. papyrifera 50 0.5 - - < 1

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

Species % FO % FN % FH % RIIf% RIIs

Salicaceae: Populus deltoides W. Bartram ex Marshall 100 0.2 - - < 1

Meliaceae: Melia azedarach L. 100 0.1 - - < 1

A. negundo 50 0.2 - - < 1

R. melanoxylon 50 0.1 - - < 1

S. areira 75 0.1 - - < 1

Q. robur 50 0.1 - - < 1

B. forficata 50 0.1 - - < 1

Cupressaceae: Cupressus sempervirens L. 25 0.1 - - < 1

S. babylonica 75 0.03 - - < 1

P. coccinea 50 0.04 - - < 1

S. australis* 25 0.07 - - < 1

E. japonica 50 0.03 - - < 1

P. aculeata* 25 0.04 - - < 1

V. cave n * 25 0.02 - - < 1

P. g ra n a t u m 25 0.02 - - < 1

L. camara 50 0.01 - - < 1

A. grandifolium 25 0.03 - - < 1

S. buxifolia* 25 0.01 - - < 1

C. glanduliferum 25 0.01 - - < 1

Phytolaccaceae: Phytolacca dioica* L. 25 0.01 - - < 1

Myrtaceae: Callistemon citrinus (Curtis) Skeels 25 0.01 - - < 1

Moraceae: Ficus cairica L. 25 0.01 - - < 1

Simaroubaceae: Ailanthus altissima (Mill.) Swingle 25 0.01 - - < 1

Species within forests but not detected trough transects

Scrophulariaceae: Myosporum laetum G. Forst. Present in S2

Rosaceae: Raphiolepis umbellata (Thunb.) Makino Present in S3

Grossulariaceae: Ribes rubrum L. Present in S1, S5, and S6

Fabaceae: Senegalia bonaeriensis* Present in S1-S4

Moraceae: Maclura pomifera (Raf.) C. K. Schneid.Present in S1, S2, and S3

Fabaceae: Robinia pseudoacacia L. Present in S6 and S7

Fabaceae: Erythrina crista-galli* Present in S2

Rutaceae: Citrus trifoliata L. Present in S5

Moraceae: Broussonetia papyrifera L. (Vent.) Present in S5

Malvaceae: Abutilon grandifolium* Present in S5

% FH: not calculated for transects out of the forests: see explanation in M&M section, % RIIf: using the three variables, %

RIIs: using % FO and % FN only. Note that the full % RIIf was not calculated for street´s species: see explanation in M&M

section. The ten species listed at the end of the table were not detected through transect samplings inside the forest due their

extremely low abundance. In addition, some trees were recently planted in few quantities (< 10) in the forest borders (thus

not listed in the table): Gynkgo biloba L. (Gynkgoaceae), Lagestroemia indica (L.) Pers. (Lythraceae), Cydonia oblonga Mill.

(Rosaceae), Eriobotrya japônica (Thunb.) Lindl (Rosaceae), Persea Americana Mill. (Lauraceae), Bauhinia forficata Link

(Fabaceae), Firmiana simplex (L.) W. Eight (Malvaceae), Schinus longifolius* Lindl. (Speg.) (Anacardiaceae), Ceiba speciosa

(A. St.Hill.) Ravenna (Malvaceae), Enterolobium contortisiliquum (Vell.) Morong (Fabaceae). Asterisks following species

names denote the species is native of the area.

14 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

(8 %), the pair C. tala-L. lucidum (2 % each),

and C. laevigata (1 %), while the remaining

percentage (1 %) corresponded to species with

very low representation of saplings (Fig. 5C).

The stand by stand discrimination of the spe-

cies that presented saplings is as follows: (S1)

C. glanduliferum, L. sinense (dominant), and S.

buxifolia; (S2) A. negundo, C. glanduliferum, L.

sinense (dominant), M. alba, palm indet., and S.

buxifolia; (S3) C. laevigata, C. tala (dominant),

E. camaldulensis, L. camara, L. lucidum, and

L. sinense (dominant); (S4) E. camaldulensis,

L. sinense (dominant), and P. coccínea; (S5) G.

triacanthos, L. camara, L. sinense (dominant),

and P. a l b a ; (S6) E. camaldulensis, L. camara,

and L. sinense (dominant); and (S7) L. sinense.

DISCUSSION

This study inventories and establishes a

baseline for the species’ composition and abun-

dance of woody plants in a suburban forest

under urban pressure and suggests manage-

ment strategies to enhance native species. We

characterized the forest as a neo-ecosystem

based on Clewell & Aronson (2013) and Aron-

son et al. (2014) ecosystem concepts. These

ecosystems, described by Chapin & Starfield

(1997), arise from the interplay of biotic, abi-

otic, and social factors, creating a new eco-

system distinct from the historical one due to

human influence. They tend to self-organize

and sustain themselves with minimal human

intervention (Hobbs et al., 2013).The studied

forest exhibited the following characteristics:

(1) C. tala was the dominant native woody

species both inside and outside the forest, fol-

lowed by S. buxifolia (which was nearly absent

outside the forest), being other native species

more abundant in the surroundings than in

the forest; (2) there were 33 woody exotic spe-

cies (Table 4), five of them being structurally

and numerically dominant over native species;

(3) most S. buxifolia and C. tala individuals

were < 3m in height; and (4) the mantle index,

which indicates imbalanced growth due to

light competition, revealed intense competition

for light in both species, particularly notice-

able in young individuals. Characteristics 2-4,

combined with the apparent greater success of

exotic species in being dispersed by frugivorous

birds (see disclaimers views in Traveset 2015;

Fig. 5. Percentage values (Y-axis) of occurrence frequency

(fo), numerical frequency (fn), height frequency (fh),

relative importance index in its full version (If), and its

simplified version (excluding height frequency, Is). A. For

the five species identified as most important by this index in

the transects within the forest. B. outside the forest. C. The

pie chart shows the percentage of saplings detected through

grid sampling within the forest. References: CL: C. laevigata,

CT: C. tala, EC: E. camaldulensis, GT: G. triacanthos, LL: L.

lucidum, LN: L. nobilis, LS: L. sinense, MA: M. alba, O: other

species (A. negundo, C. glanduliferum, E. camaldulensis,

G. triacanthos, L. camara, M. alba, palm indet., P. a l b a , P.

coccinea, and S. buxifolia.

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

Fig. 6. Profile of the forest strata and their composition considering the woody species detected in the sampling by transects

according to their numerical frequency and height. The pie charts at the base of the figure correspond to the lower shrub

layer and the regeneration of trees from the lower strata (< 5m). The pie charts in the center of the figure represent the

percentage composition of abundance of the middle layer, dominated by specimens of species whose height does not exceed

15m, but also with the presence of growing specimens from the next layer. Finally, the pie charts in the upper portion of

the figure illustrate the composition of the upper layer with trees over 15m tall. References: AN: A. negundo, CA: Celtis

australis, CG: Cinnamomum glanduliferum, CL: Celtis laevigata, CT: Celtis tala, EC: Eucalyptus camaldulensis, GT: Gleditsia

triacanthos, LC: Lantana camara, LL: Ligustrum lucidum, LN: Laurus nobilis, LS: Ligustrum sinense, MA: Morus alba, O:

species with less than 10 individuals (see discrimination above), PA: Populus alba, SB: Scutia buxifolia. Composition of less

abundant species (OTHER) by stratum and stand: S1 < 5 m (CA-CG-EC-Pittosporum tobira-Sambucus australis-Schinus

areira) / S1 / 5-15 m (AN-CA-CG-LL-LN-LS-S. areira-SB) / S2 < 5 m (Butia yatay-CA-CG-CT Cupressus lusitanica-EC-GT-

LN-LS-P. tobira-Pyracantha coccinea) / S2 / 5-15 m (CA-CG-CT-GT-LL-LN-Salix babylonica-SB) / S3 < 5 m (GT-LN-PA-P.

coccinea-Racosperma melanoxylon-S. australis) / S3 / 5-15 m (AN-CA-LL-PA-R. melanoxylon) / S4 < 5 m (AN-Casuarina

cunninghamiana-CA-CT-CG-Fraxinus pennsylvanica-GT-LN-Phoenix canariensis-P. tobira-P. coccinea-Quercus robur-R.

melanoxylon-SB) / S4 / 5-15 m (AN-CG-LL-PA-Q. robur-SB) / S5 < 5 m (CG-C. lusitanica-EC-GT-P. aculeata-P. canariensis-

Syagrus romanzoffiana) / S5 / 5-15 m (CA-GT-LS-LL-S. babylonica) / S6 < 5m (CA-CT-CG-GT-Livinstona australis-LC-

Prunus serrulata-S. romanzoffiana) / S6 / 5-15 m (CA-CG-GT-LL-LN-LS) / S7 < 5 m (CT-CG-EC-LC-S. romanzoffiana) / S7

/ 5-15 m (CG-CT-LL-LN-SB).

16 Revista de Biología Tropical, ISSN: 2215-2075 Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

Vergara-Tabares, et al. 2022) suggest that the

studied forest have reached the threshold of

irreversibility required to be considered as a

neo-ecosystem, as proposed by Miller & Bestel-

meyer (2016).

There were published many works evi-

dencing dispersion of the plants by bird present

in the study site (De la Peña, 2002; Guidetti,

2020; Murriello et al., 1993; Weyland et al.,

2014). We observed this phenomenon dur-

ing fieldwork Native birds (Mimus saturni-

nus, Pitangus sulphuratus, Turdus rufiventris,

T. amaurochalinus) have fed upon over exotic

plants but also displayed a high consumption

over both dominant natives, particularly over

S. buxifolia during the coldest months. We

observed two fructification periods in the late

species (fall-winter and late spring) contrary to

C. tala (late spring-summer).

We believe that the central wetland of

the studied forest and the higher soils in the

wetland surroundings may contribute to the

heterogeneity within stands S1, S2, S4, and S7,

surely favoring the survival of TFPs in these

stands. Similarly, the elevated areas near the

Carnaval stream’s floodplain might explain the

survival of TFPs in stands 3 and 5. The great-

est abundance of S. buxifolia and the tallest

trees of this species were found around the

central wetland. Flooding in the wetland likely

protected the ancient trees from logging and

provided suitable conditions for the species.

Ribichich (1996) reported that TFPs near the

Rio de La Plata shoreline showed dominance

of S. buxifolia over C. tala, while further from

the coast, both species co-dominated, with

C. tala becoming more dominant. This study

demonstrated S. buxifolia’s tolerance to some

flooding, suggesting that flooding limits C. tala.

Indeed, TFPs closer to the river shoreline are

nearer to the surface water table compared to

more inland ones (Arturi, 1997). This pattern

was also observed in S. buxifolia from Martin

Garcia Island and Punta Lara Natural Reserve,

where the species adapted to varying soil mois-

ture levels, including some flooding (Arturi &

Juarez, 1997).

The TFPs within the studied forest were

significantly impacted by taller and faster-

growing exotic species due to shading. We

observed a significantly higher proportion of

standing dead C. tala compared to none for S.

buxifolia. This could be explained by two fac-

tors (which may even combine additively): (1)

most exotic trees that provide significant shade

are deciduous (like C. tala), allowing S. buxifo-

lia (an evergreen species) to photosynthesize

during the autumn and winter, and (2) C. tala’s

intolerance to waterlogging versus S. buxifolia’s

higher resistance to it (as mentioned in previ-

ous paragraphs), particularly in areas close to

the central wetland. Highly invasive species

often exhibit similar competitive behavior in

their introduced environments across world-

wide. Several exotic species we found in the

studied forest were reported for various Argen-

tine ecosystems (Fundación de Historia Natural

Félix de Azara, 2006b; Zagel, 2006). Ligustrum

lucidum was recorded invading the Punta Lara

Natural Reserve’ hygrophilous forests 79 years

ago (Cabrera & Dawson, 1944), and by later

years, the site was dominated by pure stands of

L. lucidum (Dascanio & Ricci, 1988). This spe-

cies has significantly impacted native woody

species in coastal TFPs. Thirty years after inva-

sion patches showed 80 % of individuals stand-

ing dead compared to the 20 % reported earlier

(Franco et al., 2018; Goya et al., 1992). Ribich-

ich & Protomastro (1998) suggested that the

invasion of L. lucidum might have been acceler-

ated by the exclusion of cattle in the 1980s, as

cows previously grazed on this species.

We think that the abundance of each

woody exotic in the studied forest is primarily

influenced by their presence in areas outside

the forest (a facilitating factor) and secondarily

by subtle soil characteristics within the forest

(a limiting factor). In that sense, the eradica-

tion of certain invasive woody exotics would be

extremely difficult, considering the multiplic-

ity of life history strategies (re-growth from

stumps, root sprouting, abundant palatable

fruits with highly germinal seeds, fast growth).

Although there are no entirely successful

examples of controlling invasive exotics once

Revista de Biología Tropical, ISSN: 2215-2075, Vol. 72: e57706, enero-diciembre 2024 (Publicado Dic. 02, 2024)

they are established (Aragón & Groom, 2003),

some acceptable success has been achieved with

significant operational and economic efforts.

Examples include control of blackberries (Maz-

zolarri et al., 2011), privets and green ashes

(Fontes, 2015), honey locusts (Sosa et al., 2015),

and white mulberries (Torresin et al., 2013).

The cost-benefit ratio of these efforts often

makes them unfeasible in the long term, as even

a slight relaxation can lead to re-colonization.

The Rolling Pampa ecosystems, espe-

cially around the densely populated Buenos

Aires Metropolitan Area (Instituto Nacional de

Estadística y Censos, 2012a; Instituto Nacio-

nal de Estadística y Censos, 2012b; Instituto

Nacional de Estadística y Censos, 2016), have

been heavily exploited and degraded over cen-

turies, losing their original condition (Manuel-

Navarrete et al., 2009; Matteucci & Morello,

2009; Morello & Mateucci, 2000). The region

now consists of hybrid and neo-ecosystems

with complex, not fully understood dynamics,

yet they still support many valuable native spe-

cies of high conservation value.

Miller & Bestelmeyer (2016) emphasized

the importance of neo-ecosystems in successful

conservation strategies. Effective management

should focus on supporting desirable species

rather than solely eradicating undesirable ones

(Belnap et al., 2012; Davis et al., 2011; Seastedt

et al., 2008; Simberloff, 2011). Given the chal-

lenges of restoring historical conditions, efforts

should prioritize mitigating and containing

invasive species while promoting local econom-

ic benefits through methods like pruning and

native planting (Arturi et al., 2006; Doumecq

& Arenas, 2018; Plaza-Behr et al., 2016; Vargas-

Monter, 2012; Wilcox, 2000). Different pruning

methods (selective, mixed, low) have been rec-

ommended to positively affect growth of native

renewals, especially when applied to rotating

small parcels and combined with native plant-

ing for environmental restoration (Adminis-

tración de Parques Nacionales, 2007; Arturi et

al., 2006; Franco et al., 2018; Plaza-Behr et al.,

2016). Such practices would likely benefit the

native species in the studied forest. Our study

identifies viable populations of two declining

species: the tree S. buxifolia and the Argentine

flag butterfly Morpho epistrophus argentinus

Fruhstorfer (Nymphalidae) recently reported

there (Alcalde & Rodríguez-Allo, 2023), which

depends on S. buxifolia as its host. The site also

supports a ground orchid Chloraea membrana-

cea Lindl. (Orchidaceae) and other threatened

native herbs (Delucchi, 2006) like Senecio selloi

(Spreng,) DC. (Asteraceae) and Cypella herber-

tii (Lindl.) Herb. (Iridaceae), providing hope

for their conservation.

Ethical statement: the authors declare that

they all agree with this publication and made

significant contributions; that there is no con-

flict of interest of any kind; and that we fol-

lowed all pertinent ethical and legal procedures

and requirements. All financial sources are fully

and clearly stated in the acknowledgments sec-

tion. A signed document has been filed in the

journal archives.

ACKNOWLEDGMENTS

The authors are grateful to the “Asociación

Vecinal para la Protección del Bosque Las

Banderitas” and all the neighbors who, in one

way or another, have shown interest in protect-

ing this forest and its resident species. This

work is ILPLA Scientific Contribution N° 1248.

Although this research did not receive any

specific grant, resources from ANPCYT and

CONICET allocated to LA for other studies

conducted in the same study area were partially

utilized. A. Di Maggio has kindly improved the

English, especially during the first round of

revision; we extend our gratitude to her.

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