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Artificial Perches for Birds in Deforested Areas Favour a Seed Rain Similar to Woodland Remnants

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The lack of seeds represents one of the highest difficulties to overcome for the ecological restoration of areas that have been deforested. This study evaluates the effectiveness of artificial perches in increasing the abundance and species richness of bird-dispersed seeds and the similitude of seed rain composition (origin and habit of plant seeds), of deforested areas with and without artificial perches in relation to woodland remnants that serve as seeds source. The experiment took place in two sites of the Espinal ecoregion, Argentina. We found that in deforested areas, perches increased seed abundance and species richness in the seed rain in comparison with deforested areas without artificial perches. The species composition under artificial perches was similar to the seed rain dispersed in the woodland. However, a decrease in the richness of native species was significant in the deforested area, probably due to behavioral differences between opportunistic and obligate frugivorous. Seed of trees and shrubs species were well represented in the seed rain under artificial perches. Results from this study contribute to the understanding of nucleation and recovery mechanisms used by nature that reflect ecosystem resilience. We recommend using artificial perches in deforested areas with potential for recovery because it is an efficient technique to promote the entry of birds and increase seed rain, preserving features of the original environment. However, using artificial perches should be avoided in sites with potentially invasive non-native species.
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Articial Perches for Birds in Deforested Areas
Favour a Seed Rain Similar to Woodland Remnants
Brenda Yamile Guidetti ( guidettibrenda@gmail.com )
Consejo Nacional de Investigaciones Cienticas y Tecnicas https://orcid.org/0000-0002-9801-6048
Sebastian Dardanelli
INTA: Instituto Nacional de Tecnologia Agropecuaria
Fátima María Lourdes Miño
Universidad Autonoma de Entre Rios
Guillermo César Amico
Instituto de Investigaciones en Biodiversidad y Medioambiente
Research Article
Keywords: Deforestation, seed dispersal, birds, perches, non-native species, active restoration.
DOI: https://doi.org/10.21203/rs.3.rs-700313/v1
License: This work is licensed under a Creative Commons Attribution 4.0 International License. 
Read Full License
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Abstract
The lack of seeds represents one of the highest diculties to overcome for the ecological restoration of
areas that have been deforested. This study evaluates the effectiveness of articial perches in increasing
the abundance and species richness of bird-dispersed seeds and the similitude of seed rain composition
(origin and habit of plant seeds), of deforested areas with and without articial perches in relation to
woodland remnants that serve as seeds source. The experiment took place in two sites of the Espinal
ecoregion, Argentina. We found that in deforested areas, perches increased seed abundance and species
richness in the seed rain in comparison with deforested areas without articial perches. The species
composition under articial perches was similar to the seed rain dispersed in the woodland. However, a
decrease in the richness of native species was signicant in the deforested area, probably due to
behavioral differences between opportunistic and obligate frugivorous. Seed of trees and shrubs species
were well represented in the seed rain under articial perches. Results from this study contribute to the
understanding of nucleation and recovery mechanisms used by nature that reect ecosystem resilience.
We recommend using articial perches in deforested areas with potential for recovery because it is an
ecient technique to promote the entry of birds and increase seed rain, preserving features of the original
environment. However, using articial perches should be avoided in sites with potentially invasive non-
native species.
Introduction
The lack of seed supply is one of the main barriers to overcomefor ecological restoration in areas that
have been deforested(Shoo and Catterall 2013; Elgar et al. 2014). In this sense, the role of many
frugivorous birds species is essential in depositing seeds of the eshy fruits consumed and in this way
promote vegetation regeneration as they move towards the forest edges or degraded patches(Green and
Dennis 2007). This contribution can be very signicant in temperate regions where other groups of seed-
dispersing animals (i.e. reptiles and medium and large mammals) are not present or
showmarkeddecreases in their richness and abundances(Karubian et al. 2012). However, frugivorous
birds nd little incentive to move away or too far from the forest crossing open, deforested, or degraded
areas, where fruit abundance is low and the chances of being caught by their predators are
high(Mastrangelo 2014; Da Silveira et al. 2016). For this reason, deforested areas often receive negligible
seed rain, even if they are surrounded by natural vegetation.
To overturn the resistance of birds entering deforested areas and dispersing seeds, some ecological
restoration projects have been drawn upon to the installation of articial perches for birds(Holl 1998;
Zanini and Ganade 2005; Guidetti et al. 2016). Articial perches increase structural complexity and
stimulate birds to use open areas and stay there for longer times(Donald and Evans 2006; Pejchar et al.
2008). In addition, since seed deposition by defecation and regurgitation occurs more often when birds
perch or immediately after they undertake ight(McDonnell and Stiles 1983), seeds tend to concentrate
under isolated trees, live fences, or other remaining vegetation that has survived disturbances and it is
used by birds as perch or rest points(Schlawin and Zahawi 2008; Pizo and dos Santos 2010; Cottee-
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Jones et al. 2015).In this way, articial perches constitute a nucleation technique that allows the
expression of recovery mechanisms used by nature(Schlawin and Zahawi 2008),reecting the resilience
of the ecosystem and prioritizing its bio-functionality(Sekercioglu 2007; Pejchar et al. 2008). The proper
seed rain promoted by perches facilitates the establishment of small patches of plant
regeneration(Guevara et al. 1992; Debussche and Isenniann 1994; Schleuning et al. 2011b). These
patches of secondary forest reduce the contrast between logged areas and forest, and by naturally drift
can occupy the empty spaces between them until integrating with the rest of the landscape(Reis et al.
2010).
Considering that landscape transformation due to agricultural activities affects more than 40% of the
planet's land area and is the main cause of biodiversity and ecosystem services decline(Foley et al.
2011), ecological restorations measures need to be thought as the rst alternative in those areas that
have possibilities for recovery.Deforested areas that are not actively intervened can remain in
intermediate successional states experiencing a very slow reversal towards the original ecosystem(Jones
and Schmitz 2009). Otherwise, these areas can end up taking the form of a different ecosystem with a
new species composition(Hobbs et al. 2006).The pioneer species dispersed by wind,mostly herbs and
grasses,are best represented in deforestedareas(Cubiña and Aide 2001; Zwiener et al. 2014). By
contrast, late succession species rarely reach open areas or take too long to do so(Corlett and Hau 2000;
Martínez-Garza and Howe 2003). Moreover, seeds of tree or shrub species are rapidly predated, tend to
immediately germinate or die after a certain latency time(Hardwick et al. 2004).Consequently, after long
periods of disturbance, it is unlikely that the pre-existing soil seed bank will contribute signicantly to the
regeneration of vegetation(Nepstad et al. 1996; Sione et al. 2016).On the other hand,active restoration
actions such as direct seed planting in bare soil or reforestation plans, often fail in proper species
selection(Griscom and Ashton 2011; Corbin and Holl 2012)or are performed with only one or a few
species given the high costs involved(WWF International 2005; Corbin and Holl 2012).Instead,
deforested areas with articial perches for birds can recover the species of the original environment,
through an ecological ow in which nearby forest remnants act as seeds source(Reis et al. 2010; Corbin
and Holl 2012; Rocha-Santos et al. 2017).
Unfortunately, the barriers that get in the way of restoration processes are multiple and diverse. Areas
recovering from disturbance may be more susceptible than mature ecosystems to invasion bynon-
nativespecies present in the landscape(Huebner and Tobin 2006; McCay et al. 2009). It can be
considered as onedisadvantageof the perches. Given that woodynon-nativeplants with eshy fruits
dispersed by avian frugivorous are usually more successful in increasing their distribution range than
othernon-nativeand native plants, their dispersal under articial perches is a point that must be
considered(Ponce et al. 2012).
This study evaluates the effectiveness of articial perches for birds in deforested areas of the center of
the Province of Entre Ríos (Espinal ecoregion), Argentina, where the native woodland has potential for
recovery. The questions to be answered are: 1- do articial perches increase the abundance and species
richness of the seed rain dispersed by birds?, 2- does the origin (native or non-native) of the seed
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composition differ between the woodland remnants and under the articial perches in deforested areas?,
and 3- do articial perches facilitate the arrival of woody species that then can act as natural perches in
degraded environments?
Materials And Methods
Study area
The experiment was conducted in the subtropical woodland of the Espinal ecoregion. We selected two
sites in the Paraná Department, in the center of Entre Ríos Province, Argentina (Fig 1), to perform the
experiments. The two sites were more than 15 kilometers apart. The rst site (PSM) was located in the
“Parque General San Martín” (31°43'30" S, 60°20'00" W), a natural protected area with a size of 400 ha.
The second site (REA) was located in the “Reserva de Uso Múltiple Escuela J.B. Alberdi” (31°50'12" S,
60°31'25" W), with a size of 20 ha. The woodlands of the region are low and xerophytic and vary from
dense to open. There can be distinguished two tree stratum (a low and continuous one, 6 to 10 m high,
and another discontinuous with isolated individuals exceptionally exceeding 12 m in height), a relatively
poor shrub stratum, and a relatively well developed herbaceous stratum(Matteucci 2012). Historically
these woodlands have undergone different alterations, being subjected to logging, selective extraction of
dominant species for poles, wood, rewood, and charcoal, as well as overgrazing by livestock and the
replacement of native trees with fast-growing exotic species plantations(Johnson and Zuleta 2013).
Moreover, in recent decades, intensive agriculture has advanced on the remaining woodland, producing
woodland loss and fragmentation(Arturi 2006; Matteucci 2012). The climate is warm and humid, with an
average annual temperature of 20°C and annual rainfall exceeding 1200 mm. The precipitation is
concentrated from the austral spring through summer to early fall (from October to April); however, there
is usually a water decit in the soil (due to high temperatures) during this period of the year(Matteucci
2012).
Experimental design
We set up twenty-four sampling blocks: 14 blocks set on the PSM between December 2014 and May
2016, and another 10 blocks set in the REA between May 2015 and May 2016. Each block consisted of a
native woodland area and an adjacent deforested area. We set seed traps consisting of 0.5 x 0.5 m
"mosquito net" plastic fabric (mesh size of 1.5 mm), raised from the ground 0.25 m with galvanized wire
structures to prevent predation of the seeds by rodents(García et al. 2010). In each sampling block, two
traps were placed within the native woodland area (“woodland” treatment) separated from each other by
two meters, and two traps in the deforested area. Within the deforested area, one of the traps was placed
under an articial perch built with a 2-meter high bamboo pole and two wooden rods one meter long and
5 mm in diameter, crossed together and tied to the top end of the pole (“perch” treatment). The other trap
was placed in the open area (“open treatment), two meters away from the axis of the pole of the articial
perch. Articial perches were located at a distance between 10 and 40 meters from the edge of the native
woodland area and separated by at least 25 meters away from the articial perches of the contiguous
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sampling blocks (Online resource 1- Fig 1). The deforested area of the blocks has undergone diverse uses
(extraction of dominant species, extensive cattle ranching, small-scale agriculture, and rewalls).
However, in both sites the soil was well conserved, covered by grass and herbaceous species (not bare,
compacted, under limited drainage, or invaded by exotic grass species).
We collected seeds in the traps every 21 days. Whole fruits were discarded, and only seeds that had been
dispersed by birds were analyzed.Since there are no frugivorous bats conrmed in the study
area(Barquez and Díaz 2020),the possibility of confusing bird feces with bat feces was ruled out.The
samples were dried on a stove for 60 minutes at 80° C to remove moisture and stored in paper envelopes.
Seeds found in the traps were identied at the species level under a stereomicroscope (Nikon SMZ645,
with magnication up to 50 X).For this purpose, a reference collection was made with seeds of eshy
fruits species collected within the study area. We additionally reviewed specimens of the Instituto de
Botánica Darwinion herbarium and consulted bibliographic material(Alzugaray and Carnevale 2009;
Abraham de Noir and Bravo 2014). For each species of seed, we recorded the origin (native and non-
native) and habit (tree, shrub, vine, or herb). Further, two types of habit were considered: type 1 included
trees and shrubs with erect stems (woody species that can act as natural perches), while type 2 included
vines and herbs. Seeds that could not be identied were considered as morphospecies only if seemed to
come from fruits dispersed by birds (showing no signs of adaptation to anemochory or epizoochory).
Data analysis
To assess the effect of articial perches on the abundance and species richnessof seed rain reaching
deforested areas, generalized linear mixed models were used. The abundance model included negative
binomial distribution and log link function, while anormal distribution was used in the case of the
species richness model(Crawley 2007; Zuur et al. 2009; Logan 2010). Treatment (woodland, perch, and
open) was included as a xed factor. Seed traps (n=2), sampling blocks (n=10 and 14) nested within the
sites (PSM and REA) were included in the model as random factors.
We compared seed composition in the different treatments (woodland, perch, and open) analyzing the
relative abundance of each species per sample. We conducted an ordination with Euclidean dissimilarity
values calculated by a non-metric multidimensional scaling (NMDS) and a permutational multivariate
analysis of variance, using the metaMDS and adonis functions of the
“vegan”
package in R(Oksanen et
al. 2017).
We analyzed the effect of articial perches on the seeds abundance and species richness according to
the origin of plants (native or non-native) using generalized linear mixed models inated in zeros with
normal distribution for both variables (in this case morphospecies were removed from the data set). The
model included treatment (woodland, perch, and open), the origin of species (native or non-native), and
their interaction as xed factors. Finally, we analyzed the possible effect of articial perches on the
colonization of woody species that can act as natural perches. The relative seed abundance and the
species richness for both types of habit (trees and shrubs or vines and herbs) were calculated for each
sample and generalized linear mixed models inated in zeros with normal distribution were used for both
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variables, with treatment, type of habit and their interaction as xed factors. All models were evaluated
according to the AIC(Burnham and Anderson 2002). Statistical analyses were carried out using the
“glmmTMB”
package in R (Fournier et al. 2012; Skaug et al. 2013; Magnusson et al. 2016; R Development
Core Team 2018).
Results
Abundance and species richness in seed rain
The abundance of seeds that reached articial perches in the deforested area was higher compared to
woodland treatment, while in the open area without perches the seed abundances decreased signicantly
(Fig 2. a). The model that best explained the variation in seed abundance included treatment (woodland,
perch, and open) as the explanatory variable (Table 1), as opposed to the null model (Online Resource 1-
Table 1).
Species richness in the seed rain was similar in theperchesand woodland treatment, while in the open
area treatment was lowest (Fig. 2. b). The model that best explained the variation in species richness in
seed rain included treatment (woodland, perch, and open) as the explanatory variable (Table 1), as
opposed to the null model (Online Resource 1- Table 1). 
Species composition of seed rain
Seed rain in the woodland and the articial perches were similar in terms of their composition, as it is
shown in the ordering of NMDS points (Online resource 1- Fig 2).A very small percentage of variation in
the composition in seed rain was explained by the different treatments (R2= 0.03, Online Resource 1-
Table 2).
Within the woodland, the abundance of native species was 30.51% of the total identied seeds, under
articial perches 24.67% and in open area traps 10%. Results of the GLMM indicate that this trend in the
seed dispersal is general and does not appear to be linked to one of the treatments (Table 2 and Online
Resource 1- Table 3).In the case of articial perchesparticularly, non-native seeds increase their
abundance along the year with a maximum peak from October to December, while native seeds have their
maximum peak from January to June and decrease their abundance along the year (Fig. 3). Despite non-
native seed abundance was higher than native seed abundance in all treatments, non-native species
richness was lower than native species richness. In the woodland, there were 23 native species of seeds
while only ve were non-native species. In the deforested area under articial perches, there were 13
native species and six non-natives species. In the open area treatment seeds from only two species were
identied, one was native and the other non-native. Results of the GLMM for species richness concerning
the origin indicate that in both treatments, articial perches and open area traps, there was a signicant
decrease of native species richness (Table 2 and Online Resource 1- Table 3).
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Results of GLMM for the type of habit indicate that type 1 species (trees and shrubs with erect stems)
signicantly increase the abundance in seed rain; however, in the treatment without perches, the
abundance of seeds from this type decreases signicantly (Table 3 and Online Resource 1- Table 4). For
species richness, the model indicates that type 1 species increase the richness in seed rain signicantly,
nevertheless in the treatment without perches, the richness of this type of habit decreases signicantly
(Table 3 and Online Resource 1- Table 4).
Discussion
Articial perches produced a signicant increase in the abundance in the seed rain that reach deforested
areas surrounding the Espinal woodland remnants. The abundance of seeds found under articial
perches indicates that these structures act as a focus of attraction for birds and promote their arrival,
facilitating the entry of plant propagules and giving rise to seed nucleation points in areas that have lost
woody cover(Zwiener et al. 2014). These results agree with those obtained by most restoration programs
that have used articial perches around the world(Guidetti et al. 2016). In the few studies that did not
nd a signicant increase in seeds under articial perches, the duration of sampling may have been
insucient, considering that birds require a certain period of adaptation to start using these
structures(Shiels and Walker 2003). Predation of dispersed seeds by other animals was also considered
another possible cause(Holl 1998). Increasing abundance in seed rain in deforested areas is crucial,
especially given that having a nearby source of propagules does not always imply a bigger seed rain and,
in addition to that, a large proportion of the seeds arriving in the area do not survive until
germination(Graham and Page 2012; Reid and Holl 2013). Therefore, the use of articial perches then
results in higher plant densities than projects based on passive restorations(Tres and Reis 2009; Schorn
et al. 2010).
The installation of articial perches also produced a signicant increase in species richness compared to
seed rain in deforested areas without perches. Perches give temporal and spatial continuity to the diverse
interactions between frugivorous birds and plants in the forest,enabling, for example, the dispersal of
rare species seeds by anti-apostatic selection, an important mechanism that structures the diversity of
forests in recovery(Karubian et al. 2012; Carlo and Morales 2016).Thus, the seed rain under perches
reects in part the reproductive potential of endozochoric plants(Guimarães et al. 2008). Nevertheless,
the process of seed dispersal from the woodland to the open area involves not only fruit consumption but
also the movement of the birds. In this sense, there are someforest visitors or habitat generalists species
more adapted tothe conditions indeforested areas, butforest specialist species may refuse to cross the
edge of the woodland, dispersing seeds mostly in the forest interior or ying straight ahead directly to
another forest remnant(Bennun et al. 1996; García et al. 2010; Pizo and dos Santos 2010; Carlo et al.
2013).Generally, frugivorous bird species with non-specialized diets (species that consume fruits based
on their availability in the environment) are the ones that arehabitat generalists, making the most
important seed dispersal among different environments(Puricação et al. 2014).This characteristic of
thefrugivorous bird assemblagecan be the reason for the diminution of the seed species richness
observed in the articial perches in comparison to the woodland treatment. It is expected that as the
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development of secondary forest patches progresses in the deforested areas, more forest specialists and
obligate frugivorous species will begin to move within the forest, increasing much more the species
richness in the seed rain also there(Schleuning et al. 2011a; García and Martínez 2012; Bomm et al.
2018).
Seed composition under articial perches was similar to that of the woodland. Since seed ow is
established from the neighboring woodland remnants, perches can promote vegetation similar to the
original ecosystem(Schorn et al. 2010). Considering that the identity of the seed rain species has
decisive effects on the natural succession of the sites, the control in the seeds’ dispersal of non-native
species could be one of the factors that seriously condition the use of articial perches. It is quite
common for invasive species toproduce large amounts of fruits(Gleditsch and Carlo 2011). Here, the
dispersal of non-native species was high in all treatments, even within the woodland.The noticeable
difference between native and non-native species abundance was strongly inuenced by the quantity of
Morus alba
(Common Mulberry; Moraceae) dispersed seeds. This species has a large number of seeds
per fruit (56.8 ± 15.7) and a large number of fruits per adult tree (1000-10000, SD, pers. obs.), ripen at the
studied area from October to early December(SD, pers. obs.). But, while the abundance of native seeds
did not decrease signicantly outside the woodland, the richness of native species did. Again,the reason
for the difference observed between the species richness in the articial perches and the woodland
treatmentcould be the movement of occasional or opportunistic frugivorous being attracted to the
woodland when the amount of exotic fruits increases abruptly or tracking the presence of others across
the foraging landscape(Carlo et al. 2007; Puricação et al. 2014). Instead, obligate frugivorous species
get involved in much more interactions to sustain their basic metabolic requirements and have more
selective foraging behaviors(Schleuning et al. 2011a; Sebastian-Gonzalez 2017; Bomm et al. 2018), but
do not leave the forest as frequently(Puricação et al. 2014), increasing the seed rain species richness of
native plants inside the woodland. However, thinking about the possibilities of ecological restoration is
interesting to state that several non-native species differ on the fruitingseason with native(Gosper 2004;
White and Vivian-Smith 2011). In the study area, the fruiting peak for non-native eshy fruit species was
detected from October to December, while for the native species the peak is between January and
February and another occurs between May and June(Scarpa 2013). So, installation of articial perches
could be carried out if species with eshy fruits in nearby woodland remnants are well
recognized,avoiding sites where non-native species are present or placing them only at the time of the
year when the invasive species have fewer fruits(Prather et al. 2017).
A large proportion of the seeds that reached the site favored by the articial perches in the experimental
area were woody plant species, as it has also been found by Prather
et al
. (2017) in Houston, USA. In this
sense, articial perches act in a similar way to isolated trees and remnant shrubs that persist
todisturbance,accelerating the colonization of woody species below and around their canopy(Slocum
2001; Schlawin and Zahawi 2008).Afterdeveloping,these trees or erect shrubs could act as natural
perches for birds and successively improve conditions in the deforested area (providing shade, food, and
nesting sites).Regeneration in deforested areas appears to be irregular and dependent on the formation
of vegetation groups or nuclei that facilitate the recruitment of seeds from the forest, the establishment
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of new seedlings, and the expansion of woody plant cover(Carlo and Morales 2016).The inuence of
these nuclei continues even in later successional stages, showing a higherdensity of trees, basal area,
and species richness in their vicinity(Slocum 2001; Schlawin and Zahawi 2008).
The experience states that articial perches for birds are easy to implement, require little labor for
manufacture and installation, and have substantially low costs, taking into account that they can be
manufactured from materials recycled or found in the site(Holl 1998; Reis et al. 2010; Graham and Page
2012). In the future, it would be interesting to analyze what happens with more complex perches, or with
a grouped arrangement of perches, since large nuclei are proven to be more attractive to birds(Holl 1998;
Toh et al. 1999; Corbin and Holl 2012)and here only the simplest model has been studied. Perches seem
to be a possible alternative when there are remnants of woodland in the proximity of the open area. It
would also be interesting to study the optimal distances relative to the edge of the remnant for which
perches are most effective in the Espinal(Pizo and dos Santos 2010). Nevertheless, while a big challenge
of restoration in deforested areas is to attract birds to deposit seeds, there can be other barriers to plant
regeneration(Holl et al. 2000; Reid and Holl 2013). For that reason, we considered that articial perches
may be much more successful in ecosystems that are suciently resilient and just need minimal
intervention.Subtropical and temperate environments with disturbance matrices similar to the ones
considered here have shown a signicant increase in seedlings established under articial
perches(Guidetti et al. 2016).The soil andenvironmental conditions (low elevation, warm temperatures,
and abundant rainfall) during and immediately after the period of highest native seeds dispersal at the
experimental sites are expected to favor germination and seedling growth(Holl 2013).Further, both sites
were located in protected areas, making thecommitment of stopped disturbances and ensuring that care
can be prolonged in time.In other contexts, additional measures and multiple approaches (such as soil
transposition or livestock exclusion) may be required(Bevilacqua Marcuzzo et al. 2013).
In conclusion, articial perches function as a nucleation technique to increase seeds dispersal by birds in
deforested areas around Espinal woodland remnants. Articial perches increased the abundance and
species richness in the seed rain, with a species composition similar to that of the woodland. Using
articial perches should be avoided in sites with potentially invasive non-native species. However, in
places where native and non-native species show different fructication peaks, articial perches could be
used in certain periods of the year, avoiding the dispersal of undesirable seeds of invasive species. In
addition, articial perches principally facilitate the arrival of woody species that then also serve as natural
perches; this can progressively improve the conditions in the deforested area, having a positive impact
even in later successional stages.
Declarations
Funding
For this work Brenda Guidetti received nancial support provided by the Consejo Nacional de
Investigaciones Cientícas y Técnicas (CONICET), Argentina; the Instituto Nacional Tecnología
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Agropecuaria (INTA), Argentina and Idea Wild Foundation. The funders had no role in study design, data
collection and analysis, decision to publish, or preparation of the manuscript.
Conicts of interest/Competing interests
We declare and conrm that the present manuscript has been approved by all co-authors as well as by
the responsible authorities. We also declare no conicts of interests.
Availability of data and material
All the data is available in appendix of supplementary information
Code availability
Not applicable
Authors' contributions
Brenda Guidetti, Sebastián Dardanelli and Guillermo Amico contributed in manuscript conceptualization
and experiment methodology, Brenda Guidetti and Fátima Miño did the eld work and data curation,
Brenda Guidetti performed the formal analysis, validation, data visualization, writing and original draft
preparation, Sebastián Dardanelli and Guillermo Amico worked on the project administration, the
supervision, review and editing. All authors read and approved the nal manuscript.
Acknowledgments
The permit for eld research was granted by Dirección General de Recursos Naturales Entre Ríos (DGRN),
in Authorization N°. 003/15 (File N°. 1.733.195). We thank director Alfredo Berduc from Parque General
San Martín, and Valeria Tiropolis, Viviana Fussi and Alba Flores from Reserva de Uso Múltiple Escuela
J.B. Alberdi. Special thanks to Rubén G. who assisted us for perches construction and during eld work.
We also thank Claudia Alzugaray, Cesar Massi, Geraldina Richard and Berenice Schneider for helping in
some seed species identication. We thank Romina Vidal-Russell for English revision of the manuscript.
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Tables
Table 1Abundance and richness of the seed rain in the different treatments (woodland, perch and open).
Estimated parameters, standard error,
z
value and
p
value of variables for GLMMs selected according to
the AIC criterion.
Estimate Std. Error
z
value Pr (>|
z
|)
Abundance  
       (intercept) 1.75 0.59 2.91 0.003 **
       perch 0.13 0.22 0.61 0.543
       open -4.53 0.32 -13.90 < 0.001***
Richness  
       (intercept) 0.69 0.16 4.20 < 0.001***
       perch -0.13 0.05 -2.34 0.019*
       open -0.96 0.05 -12.51 < 0.001***
Signicance code (0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘’).
Table 2 Seed rain abundance and species richness according to plant origin (native and non-native).
Estimated parameters, standard error,
z
value, and
p
value of explanatory variables for GLMMs selected
according to the AIC criterion.
Page 17/21
Estimate Std. Error
z
value Pr (>|
z
|)
Abundance  
 (intercept) 24.82 3.62 6.86 < 0.001 ***
 open -20.52 14.98 -1.37 0.171
 perch -2.61 4.43 -0.59 0.556
 native -16.99 3.49 -4.86 < 0.001 ***
 open : native 17.61 24.31 0.72 0.469
 perch : native 10.59 6.94 1.52 0.127
Richness  
 (intercept) 0.67 0.14 4.69 < 0.001 ***
 open -0.56 0.08 -6.63 < 0.001 ***
 perch -0.02 0.07 -0.26 0.797
 native 0.48 0.06 7.78 < 0.001 ***
 open : native -0.51 0.11 -4.58 < 0.001 ***
 perch : native -0.49 0.11 -4.20 < 0.001 ***
Signicance code (0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘’).
Table 3 Seed rain abundance and species richness according to types of habit (type 1 including trees and
shrubs and type 2 including vines and herbs). Estimated parameters, standard error,
z
value, and
p
value
of the explanatory variables for GLMMs selected according to the AIC criterion.
Page 18/21
Estimate Std. Error
z
value Pr (>|
z
|)
Abundance  
          (intercept) 0.10 0.05 1.92 0.054 .
          open -0.10 0.02 -4.86 < 0.001 ***
          perch -0.04 0.02 -1.81 0.069 .
          type 1 0.23 0.02 14.81 < 0.001 ***
          open: type 1 -0.21 0.03 -7.23 < 0.001 ***
          perch: type 1 -0.02 0.03 -0.66 0.506
Richness  
          (intercept) 0.10 0.05 2.09 0.036 *
          open -0.11 0.02 -5.35 < 0.001 ***
          perch -0.04 0.02 -1.95 0.051 .
          type 1 0.22 0.01 14.06 < 0.001 ***
          open: type 1 -0.19 0.03 -6.82 < 0.001 ***
          perch: type 1 -0.02 0.03 -0.71 0.476
Signicance code (0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘’).
Figures
Page 19/21
Figure 1
Map of Argentina showing the Espinal Ecoregion (shaded area) and both experimental sites (PSM and
REA) located in the center of the Province of Entre Ríos.
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Figure 2
(a) Average abundance of seed rain per trap recorded every 21 days inside the woodland (n=5947), under
the articial perches (n=2901) and in open area (n=27). (b) Average species richness of seed rain per trap
recorded every 21 days inside the woodland (n=38), under the articial perches (n=29) and in open area
(n=6).
Figure 3
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Temporal variation through the year in average seed abundance (log transformed) of native (green dots)
and non-native (orange) species under articial perches.
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