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\begin{document}

\title{The effects of aridity and grazing on the relation between the dominant
shrub Artemisia kopetdaghensis and plants under its canopy}



\author[1]{Soroor Rahmanian}%
\author[1]{hamid ejtehadi}%
\author[1]{Mohammad Farzam}%
\author[2]{Martin Hejda}%
\author[1]{Farshid Memariani}%
\author[3]{Petr Pyšek}%
\affil[1]{Ferdowsi University of Mashhad}%
\affil[2]{Botany}%
\affil[3]{Institute of Botany Czech Academy of Sciences}%


\vspace{-1em}



  
  \date{May 22, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Aridity and intensive grazing have been confirmed to affect the
facilitative effects of dryland shrubs. However, their combined effects
on plant-plant interactions have rarely been tested. To test how these
two factors affect relations between plants, we analyzed 144 plots
(under shrub canopy vs. open areas) at 12 sampling areas established in
the conditions of two grazing regimes (high grazing vs. low grazing
intensity) and two different climatic regions (arid vs. semi-arid) in
northeastern Iran. A dominant shrub, Artemisia kopetdaghensis, was
selected as the model species. Further, we studied changes in plant life
strategies along the combined grazing and aridity stress gradients. We
used relative interaction indices to test the outcomes of plant-plant
interactions, calculated for species richness, Shannon diversity and
species abundances. Then we compared them using linear mixed-effect
models (LMM). The indicator species analysis was used to identify
species typical for the under-canopy of shrub and for the adjacent open
areas. The combination of stress factors affected the type and intensity
of plant-plant interactions and plant life strategies (CSR) of the
indicator species. Artemisia kopetdaghensis showed the highest
facilitation effect under the most intensive stress conditions (high
aridity/high grazing), which turned into competition under the low
stress conditions (low aridity/low grazing). In the arid region, the
canopy of shrub protected ruderal annual forbs and grasses with SR and
R-strategy, respectively, in both high (high aridity/high grazing) and
low grazing intensity (high aridity/low grazing). In the semi-arid
region and high grazing intensity (low aridity/high grazing), the shrubs
protected perennial forbs with C-strategy. Our FINDINGS highlight the
importance of context-dependent shrub management in the restoration of
vegetation damaged by intensive grazing.%
\end{abstract}%



\sloppy


\textbf{Introduction}

Species interactions are widely acknowledged as one of the most
important drivers of the plant community structure, biodiversity,
ecosystem function and dynamics (Callaway et al., 2005; Brooker et al.,
2008; Jankju, 2013). However, the outcome of plant-plant interactions
may vary, ranging from competition to facilitation, depending on
environmental severity (Grime, 1977; Brooker \& Callaghan, 1998) and on
the character of coexisting species (Armas et al., 2011; Pugnaire et
al., 2011). Interactions among plants may reduce the extreme abiotic and
biotic stresses such as aridity (L\selectlanguage{ngerman}ópez et al., 2016) and intensive
grazing (Smit et al., 2007 \& 2009; Holmgren \& Scheffer, 2010;
Soliveres et al., 2011) by creating suitable micro-habitats for drought-
or grazing-intolerant species (Bruno, Stachowicz \& Bertness, 2003;
Farzam \& Ejtehadi, 2017).

Grazing is essential biotic stress in dry rangelands due to its
extensive application and potential contribution to variation of
community structure, species composition, and degradation of ecosystem
services (Li et al., 2013, Díaz et al., 2007; Kéfi et al., 2007).
Research in the ecosystems driven by large herbivores shows that
unattractive, toxic or thorny plants may induce positive indirect (i.e.,
grazer mediated) effects on palatable herbs, shrubs or trees (Bakker et
al., 2004; Callaway et al., 2005; Smit et al., 2006). Grazing may affect
the outcome of plant-plant interactions as well, depending on the
ability of the nurse plant to moderate the effects of herbivores and on
the tolerance of the present species to herbivory (Baraza et al., 2006;
Vandenberghe et al., 2009). Further, nurse plants may protect the
neighbours against herbivory and enhance their recovery by increasing
resource levels (Rand, 2004; Acuña-Rodríguez et al., 2006).

The CRS strategy, distinguishing between the competitors, ruderals and
stress tolerators, provides a detailed view on the character of species
typical for different types of vegetation, i. e. with varying intensity
of environmental stress or grazing. The competitor, stress tolerator,
and ruderal (CSR) theory (Grime 1979), based on the quantitative
functional traits and life strategy, significantly improved the
possibilities for analyzing ecological processes (Grime, 1977; Hodgson,
Wilson, Hunt, Grime, \& Thompson, 1999).

Previous researches have explored the effects of livestock grazing and
climate on the relationships between plants (Metz \& Tielbörger, 2016;
Berdugo et al., 2018) but its effects on plant-plant interactions have
rarely been addressed (but see Soliveres and others~2011, Verwijmeren et
al., 2014; Filazzola et al., 2017). Moreover, the results of these
studies are not consistent. For instance, Soliveres et al. (2011) showed
that rabbit grazing caused positive interactions between the bunch grass
(\emph{Stipa tenacissima} ) and saplings of the shrub (\emph{Retama
sphaerocarpa} ) during winter and autumn. However, because of higher
grazing intensity in the summer, the interspecific interactions shifted
to neutral. Similarly, Holthuijzen and Veblen (2016) found that positive
interactions between \emph{Artemisia tridentata} ssp.\emph{wyomingensis}
and \emph{Poa secunda} decreased with increasing grazing intensity in
the arid region because grazing reduced productivity during the drought
periods more intensively. This may result in the absence of positive
interactions between plants due to different stressors (Smit and others
2009; Verwijmeren and others 2013; Michalet and others 2014). On the
contrary, Noumi et al. (2016) showedthat suppressive effects of shrubs
on \emph{Acacia tortilis}seedlings shifted to neutral with increasing
grazing stress. Therefore, an increase in facilitation due to the
combination of these two stressors can be expected. This research aimed
at investigating the intensity of herbivore effect on plant-plant
interactions when it is concurrent with drought. In addition, the CSR
plant life strategies were used to interpret the inconsistency in the
literature on changes in biotic plant interactions.

The selected dominant species, \emph{Artemisia kopetdaghensis} , is an
aromatic shrub that is widely distributed, ranging from warm and arid to
cold and semi-arid steppes of northeast Iran (180-400 mm) and parts of
Turkmenistan. We used \emph{A. kopetdaghensis} and its understory plants
as a model species to study the combined effects of grazing and climate
(arid region: high/low grazing, semi-arid region: high/low grazing),
aiming to answer the following questions: (i)What is the prevailing type
of interaction between the dominant shrub\emph{A. kopetdaghensis} and
the surrounding understorey herbs? (ii) Are the relations between
\emph{A. kopetdaghensis} and plants in its surroundings affected by
aridity and intensive grazing? 3) Do the effects of the shrub canopy
vary according to the different plant life strategies under the combined
effects of grazing and aridity?

\textbf{Methods}

\textbf{Study area}

We selected two regions along the precipitation gradient in northeastern
Iran in the Khorassan-Kopet Dagh floristic province of the
Irano-Turanian region, located between 35°43'-36°44'N and 58°40'\selectlanguage{english}-60deg27'
E. Based on the meteorological data, Khaje has a dry climate and
Baharkish has a semi-arid climate, expressed by de Martonne aridity
index (see Table 1 for more details). The mean annual precipitation
(20-year mean) is 255 mm in Khaje and 385 in Baharkish. A steppe
vegetation with the dominant \emph{A. kopetdaghensis} Krasch.M.Pop. \&
Linecz ex Poljak prevails in both of these areas. This species is a
semi-shrub from the \emph{Asteraceae}family, native to northeastern Iran
and dominant throughout much of this region. \emph{Artemisia} species
have been documented to facilitate common annual and perennial forbs in
this region (Reisner et al., 2015) by creating favorable suitable
microsites, reducing evapotranspiration (e.g., Holthuijzen \& Veblen,
2015), mediating soil temperatures (Davies et al., 2007), raising soil
water content via hydraulic lift (e.g., Holthuijzen \& Veblen, 2015) and
accumulating soil nutrients (Cardon et al., 2013).

\textbf{Sampling design}

The two studied regions were 1600 ha and 1035 ha in size for the arid
and semi-arid regions, respectively. The HG and LG sites were of similar
size in both climatic regions. The distance between individual sampling
areas within each climatic region was less than one kilometer, which is
the least distance where we could identify plots with similar
characteristics. The HG and pairwise LG sites were relatively homogenous
in terms of topography, land use, and vegetation. The LG sites were
located within fences that have prevented grazing for around 35 years,
whereas HG sites were open and therefore have suffered long-term
overgrazing. Each plot was characterized by geographic coordinates and
altitude. In 2017, the number of individuals and percentage cover of all
vascular plant species was recorded between April and June, when the
growing season peaks in this region.

The decision about the grazing status of the sites (high grazing
intensity vs. occasional/low intensity grazing) was based on the median
number of dung droppings: 55.3 dung droppings per square meter in the HG
and 6.2 in the LG sites, and also on the width of the microterrace
livestock paths in a horizontal way (0.27+-0.09 m for the HG site and
0.04+-0.03 m for the LG site (see more information on the grazing history
in Table 1).

The sampling design was arranged in a hierarchical way: In each of the
two climatic regions (arid and semi-arid), we selected six sampling
areas, with a high grazed and a low grazed site in each sampling area,
arranged in a pairwise way (hereafter referred to as HG and LG sites).
Then, we sampled three plots under the \emph{A. kopetdaghensis} shrubs
and three adjacent plots outside the canopy of \emph{A. kopetdaghensis}
(hereafter referred to as under-canopy and open plots) in each HG as
well as LG site. Altogether, 144 plots were sampled: 2 climatic regions,
6 sampling areas in each climatic region, one pairwise HG and one LG
site in each sampling area and 6 plots (3 under-canopy and 3 open) in
each HG or LG sites (see Figure 1). We recorded the numbers of
individuals of all vascular plant species and their percentage covers
(as a proxy for biomass) and then calculated the Shannon index of
species diversity (H = -\selectlanguage{english}[?]si=1 pi ln pi) for each plot (Shannon, 1948);
pi is the proportion (n/N) of individuals of one particular species (n)
divided by the total number of individuals (N), and s is the number of
species.

To obtain comparable samples for assessing species richness in the
surrounding `open' plots (outside the canopy of \emph{A. kopetdaghensis}
), matching the size of each sampled \emph{A. kopetdaghensis} canopy, we
sampled at haphazardly selected paired points, located
\textasciitilde{}1 m away from the canopy edge of each sampled \emph{A.
kopetdaghensis} shrub. When the size of \emph{A. kopetdaghensis} was not
measured, a wire loop was shaped to match the size of the sampled
\emph{A. kopetdaghensis} canopy plot and then used to define the size of
the patch sampled in the `open' plot (Farzam \& Ejtehadi, 2017). Again,
all established plant abundance present on these open plots were
recorded and identified to the species level.

\textbf{Statistical analyses}

Relative interaction intensity (RII) was used to assess the effect of
shrubs on under-canopy vegetation (Armas et al., 2004) and was
calculated based on the cover, richness, and diversity (expressed as
Shannon index) of under-canopy vegetation: RII = (value under shrub --
value in the open)/(value under shrub + value open). Samples were paired
between each \emph{A. kopetdaghensis} shrub and its neighbouring open
plot. RII was used as an indicator of the facilitation by the target
shrub, based on the performance of under-canopy plants. The interaction
index has defined limits {[}-1,+1{]}, with positive values indicating
facilitation and negative values indicating competition.

The differences in RII indices for species richness, cover, and
diversity between the HG and LG sites and between the arid and semi-arid
regions were tested using the linear mixed-effect models, with
``sampling areas'' as a random effect, ``climatic region'' and
``grazing'' as fixed effects and RII based richness (RII-Richness),
cover (RII-Cover), and Shannon H (RII-Shannon diversity) as response
variables. All univariate analyses were performed in the R software,
using the NLME package. The script for the model testing the interaction
between ``climate'' and ``grazing'' were ``lme(Relative interaction
intensity\textasciitilde{}climatic region*grazing,
random=\textasciitilde{}1\textbar{}sampling area)''. The normality of
the input data was assessed based on Shapiro-Wilk tests, and the
normality of residuals was checked visually, by plotting the observed
values against the fitted values.

Further, we used the method of indicator species analysis to reveal the
preference of individual species for the HG versus LG sites in both the
arid and semi-arid climatic regions. With this approach, we could
determine the indicator species sensitive or resistant to high grazing
intensity in two different climatic regions. Indicator species analysis
has two main components: (i) recorded on either HG or LG sites only
(exclusivity); (ii) recorded on all samples of either the HG or LG group
(fidelity). The indicator value index was assigned to all species,
identifying species with the highest association values. The permutation
tests (999 permutations) were used to estimate the statistical
significance of individual species' indicator values (Dufrene \&
Legendre, 1997). The indicator species analyses were performed using the
``indicspecies'' package of the R software (R Development Core Team,
2013).

We also calculated the values for CSR plant strategies for all indicator
species as well as for \emph{A. kopetdaghensis} , following Pierce et
al. (2017), based on the following traits: specific leaf area (SLA),
leaf dry matter content (LDMC) and leaf area (LA). We collected the
leaves from robust and well-grown plants. Leaf material was collected
from 10 individuals of each species, packed in moist paper bags, sealed
in plastic bags, and stored in a thermal box until storage at 4 degC for
12--24 h. Depending on the size of leaves, 2--10 undamaged, fully
expanded young leaves (including the petiole) were measured per
individual. We determined the leaf area using a digital scanner and Leaf
Area Measurement v1.3 software (Andrew Askew, University of Sheffield,
UK). Turgid leaf fresh weight (LFW) was obtained from saturated leaves,
and leaf dry weight was determined after drying for 72 h in an oven at
70 degC. For CSR strategy analysis, values of LA, SLA, and LDMC were
inserted into the `StrateFy' spreadsheet 3 to calculate C, S, and R
percentages for each species (Pierce et al., 2017).

\textbf{Results}

\textbf{The effect of climate and grazing interaction on plant-plant
relations}

We found significant effects of both grazing and aridity on the outcome
of plant-plant interactions, expressed by the RII indices. In
particular, the RII indices for species richness, abundances, and
Shannon diversity were all positive in high aridity/high grazing
conditions. The RII values were neutral (i.e. not significantly
different from zero) for species richness and Shannon diversity in the
low aridity/low grazing conditions and also for Shannon diversity in the
low aridity/high grazing and even negative for RII-cover in low
aridity/low grazing regime (Table 2).

\textbf{Interaction intensity along the stress gradient}

For all three indices (cover, richness, and Shannon diversity), RII was
higher in the arid compared to the semi-arid climatic region (Figure 2).
The RII indices for species' cover, species' richness and Shannon
diversity were all positive on both the LG and HG sites in the arid
region, indicating a facilitative effect of the target
shrub,\emph{Artemisia kopetdaghensis} (Figure 2; Appendix A). However,
the response of RII to the grazing intensity varied with climatic
conditions. A significant facilitation (expressed by the positive RII
values) was recorded in the semi-arid region for species' cover and
richness, but only on the HG sites. The RII values for species' covers
were negative for the LG sites in the semi-arid region, indicating
competition rather than facilitation by the dominant shrub (Figure 2;
Appendix A). The RII values for Shannon diversity on the HG and LG sites
in the semi-arid region and the RII values for species' richness on the
LG sites in the semi-arid region did not significantly differ from zero,
indicating neutral interactions (Figure 2).

\textbf{Plant strategies and Indicator species}

The values of the C-S-R plant life strategies showed that \emph{A.
kopetdaghensis} was S-selected in all combinations of grazing and
aridity levels. Stress-tolerant species were dominant under the shrub's
canopy in both the high-stress sites (high aridity/high grazing) and the
low-stress sites (low aridity/low grazing), i.e. \emph{Poa bulbosa}
L.,\emph{Salsola dendroides} Pall., \emph{Achillea biebersteini} Afan.,
and\emph{Eremurus stenophyllus} (Boiss \& Buhse) Baker. However, the
stress-tolerant species (S) were replaced by ruderals (R-selected,
i.e.\emph{Alyssum desertorum} Stapf, \emph{Astragalus filicaulis} Kar.
\& Kir., \emph{Callipeltis cucullaria} (L.) Stev., \emph{Galium
tricornutum} Dandy) and competitors (C-selected, i.e. \emph{Cirsium
bornmuelleri} Sint. ex Bornm., \emph{Prunus pseudoprostrata} (Pojark.)
Rech.f, \emph{Thalictrum sultanabadense} Stapf - Table 3), respectively,
on the sites with intermediate stress levels: low intensity of livestock
grazing or aridity (high aridity/low grazing and low aridity/high
grazing).

Concerning the life cycle of indicator species, annuals prevailed on the
LG sites. Perennials were present on the HG sites of the arid region and
dominated in the semi-arid region, on both HG and LG sites (Table 3).

There were not many indicator species in the open plots, all of them
annual/perennial stress-tolerant species (e.g. \emph{Poa bulbosa} -HG
sites in the arid region; \emph{Aegilops triuncialis} and \emph{Achillea
biberesteinii} in LG sites of the semi-arid region- Table 3).

\textbf{Discussion}

\textbf{Shrub canopy mediated abiotic and biotic stresses}

Changes in relative interaction intensity (RII) indicate changes in
interaction type along a combined gradient of biotic and abiotic stress.
For all of the three RII indices (cover, richness, and Shannon
diversity), there was a decreasing trend from the highest towards the
lowest stress levels (Figure 2). The shrub (\emph{A. kopetdaghensis} )
showed facilitative effects, preserving species diversity and richness
as well as the total cover of species under its canopy. However, the
facilitative effect was significantly stronger in the drier climatic
region. Previous researchers (Bertness \& Callaway, 1994; Brooker \&
Callaghan, 1998; Butterfield, Bradford, Armas, Prieto \& Pugnaire, 2016)
have documented increases in the facilitation effect of the shrub by
moderating the aridity stress. In arid environments, facilitation
usually involves increasing the water and nutrient availability (Claus
Holzapfel \& Mahall, 1999). Besides that, the shade from the shrub
reduces extreme temperatures and decreases evaporation from the soil,
which may further facilitate the germination of seeds and growth of
seedlings. Therefore, this may explain why the shrub shows higher
facilitation in the arid than in the semi-arid regions (Smit et al.,
2007; Tirado et al., 2015; Farzam \& Ejtehadi, 2017).

The effect of \emph{A. kopetdaghensis} canopy was consistently
facilitative under intensive grazing. As \emph{A. kopetdaghensis} is
unpalatable, it is not usually grazed by livestock during the growing
season. Therefore, it provides mechanical refugee for palatable grasses
and forbs (reviewed by Milchunas \& Noy-Meir 2002; Baraza et al., 2006;
Graff et al., 2007; Holthuijzen \& Veblen, 2015). This result is
consistent with the ``repellent plant hypothesis'', suggesting that
grazing intolerant plants are protected by the surrounding grazing
tolerant plants (Milchunas and Noy-Meir 2002).

\textbf{Relative interaction index along the stress gradients}

Changes in type and/or intensity of plant-plant interaction along the
stress gradients have been one of the most discussed issues in plant
ecology in recent decades (Maestre, Callaway, Valladares, \& Lortie,
2009). There are contrasting reports on this in literature, as some
researchers conclude that the amelioration of abiotic stress was more
important than protection from grazing (Howard et al., 2012; Arroyo et
al., 2015). Other studies demonstrated that grazing was a more important
driver of the plant-plant interactions than abiotic stress in the
African savanna (Louthan et al., 2014; Filazzola et al., 2017).

In the arid region, strong facilitation was observed in both grazing
intensities, which suggests that the protection against aridity is more
important than protection from intensive grazing (Maestre et al., 2005;
Soliveres et al., 2011). Accordingly, a theory by Smit et al. (2009)
predicts relatively low importance of protection from grazing in
water-limited environments. In arid climates, herbivores are sparsely
distributed, and the availability of water or nutrients is more critical
for vegetation than protection from grazing (Ellis \& Swift, 1988). In
water-limited environments, the shrubs usually improve soil fertility
and microclimate under their canopies (Cortina \& Maestre, 2005, Maestre
et al., 2009). Also, shade from shrubs' and trees' canopy can retain
soil moisture at the soil surface and facilitate neighbours with
shallower roots (Maestre, Bautista \& Cortina, 2003). Therefore, the
dominant shrub may promote species richness and productivity by
providing safe microsites for species growing in harsh conditions (Bruno
et al., 2003).

On the other hand, in the semi-arid region, where plants presumably grow
in higher water availability, livestock grazing played a critical role
in determining the type and relative intensity of the shrub's
interaction with under-canopy species. The effect of the shrub's canopy
(RII) was positive on the HG sites, but turned into neutral or even
negative with lower livestock grazing intensity. A negative RII means
that herbs prefer to grow in the open areas rather than under the canopy
of shrubs, where they need to compete for light, nutrients and water
(Graff et al., 2007; Le Bagousse-Pinguet et al., 2012).

\textbf{Indicator species response to plant interactions in the
condition of stress}

This study shows that co-occurring plant species under the shrub canopy
may exhibit convergence in CSR plant life strategies in the conditions
of similar levels of stress, while different stress levels lead to
functional divergence. For instance, in the arid region, the dominant
strategy of indicator species under \emph{A. kopetdaghensis}converged to
S-R in the HG site. At the same time, species under the shrub's canopy
exhibited transition from S-R to R-selected in low grazing intensity.
This is likely because important drivers of vegetation structure, such
as disturbance (grazing) and stress (aridity), cause the loss of biomass
and redistribution of resources (Caccianiga, Luzzaro, Pierce, Ceriani \&
Cerabolini, 2006), S-selected species prevail under the canopy of
\emph{Artemisia} . However, on the LG sites in the arid region, the
canopy protects the surrounding plants from aridity only, so the stress
is less intensive than on the HG site. Therefore, most of the indicator
species under the shrub's canopy were annual forbs and grasses with R
strategy on the LG site. Plants with R\selectlanguage{english}-selected strategy absorb
nutrients more rapidly, grow faster, have shorter growth periods and
invest more into reproduction (Grime, 1977; Caccianiga et al., 2006;
Wang et al., 2018). Stress intolerant species were better candidates for
facilitation than stress-tolerant species (Graff \& Aguiar 2011). For
instance, in the arid conditions of Mediterranean shrublands, the stress
avoidant species, with high specific leaf area and rapid growth, coexist
with species featured by very low specific leaf area (Gross et al.,
2013).

In the semi-arid region, \emph{A. kopetdaghensis} canopy showed a
facilitative effect on the HG sites, supporting the establishment of
species with C-selected strategy, like \emph{Elymus~hispidus}
or\emph{Lactuca orientalis} , which have larger leaves and are generally
more palatable to livestock. This is mainly because \emph{A.
kopetdaghensis} is an unpalatable, stress-tolerant shrub, and its~canopy
creates microsites, protecting other species against grazing by large
herbivores. In contrast, \emph{A. kopetdaghensis} canopy has a
competitive or neutral effect on the perennial stress-tolerant species
on the LG sites in the semi-arid region. \emph{A. kopetdaghensis} shrubs
have a neutral effect or even compete with the under-storey species for
light and nutrients. Therefore, the dominant strategy of indicator
species under \emph{A. kopetdaghensis} in HG site shifted from C- to
S-selected in LG site.

On the contrary, we found only a few indicator species in the open plots
in both the arid and semi-arid regions. \emph{Poa bulbusa} was present
in the HG sites of the arid region, \emph{Aegilops triuncialis}
and\emph{Achillea biberesteinii} were on the LG sites of the semi-arid
region (Table 3). As suggested by Grime (1977), when the disturbance is
relatively low, species with S-strategy can maintain their dominance in
a community by occupying aboveground and belowground space rather than
by competing for resources.

\textbf{Conclusions}

Our results document that local-scale biotic processes, such as
facilitation by the shrubs, are important determinants of diversity
patterns. In general, shrubs are known to provide refugee for species in
harsh conditions, such as high aridity or overgrazing. Furthermore, we
argue that the discrepancy in the literature on changes in plant-plant
interactions may be partially explained by differences in plant life
strategies of species in the conditions of the combined effect of biotic
(grazing) and abiotic (aridity) stress. Therefore, in the arid region,
drought-escaping species like ephemerals and ruderals (R-selected) and
species tolerating stress (S-selected) but avoiding herbivory are highly
dependent on the facilitation under the canopy of shrubs. However, in
sites without severe aridity, canopy of the target shrub protected
competitive species (C-selected) in the conditions of high grazing
intensity (low aridity/high grazing). On the contrary, on sites without
intensive grazing and severe aridity (low aridity/low grazing),
facilitative effects of the shrub turned to neutral or even competitive.

\textbf{Acknowledgment}

This research is based on the results of a Ph.D. thesis by S. Rahmanian.
The financial support was provided by the Ferdowsi University of Mashhad
(FUM) {[}grant number 3/41568{]}. Special thanks go to Mohammad Reza
Joharchi and Zohre Atashgahi for their assistance in the identification
of the plants. MH and PP were supported by long-term research
development project RVO 67985939 (Czech Academy of Sciences).

\textbf{Conflict of interest}

None declared.

\textbf{Author contributions}

H.E, M.F and F.M designed the study. S.R collected the data, performed
the analysis and wrote the manuscript. M.H and M.F contributed to the
interpretation of the results and work on the manuscript. F.M and P.P
Commented on the manuscript. All authors contributed to different
versions of the manuscript and discussed the results and gave final
approval for its publication.

\textbf{Data accessibility}

Data will be made available in the Dryad Digital Repository

\textbf{References}

Acuna-Rodriguez, I.S., Cavieres, L.A., Gianoli, E. (2006). Nurse effect
in seedling establishment: Facilitation and tolerance to damage in the
Andes of central Chile. \emph{Revista chilena de historia natural}
,~\emph{79} (3), 329-336. doi:10.4067/S0716-078X2006000300005

Armas, C., Rodriguez\selectlanguage{english}-Echeverria, S., \& Pugnaire, F. I. (2011). A field
test of the stress\selectlanguage{english}-gradient hypothesis along an aridity
gradient.~\emph{Journal of Vegetation Science} ,~\emph{22} (5), 818-827.

Armas, C., Ordiales, R., \& Pugnaire, F. I. (2004). Measuring plant
interactions: a new comparative index.~\emph{Ecology} ,~\emph{85} (10),
2682-2686.

Arroyo, A. I., Pueyo, Y., Saiz, H., \& Alados, C. L. (2015).
Plant--plant interactions as a mechanism structuring plant diversity in
a Mediterranean semi\selectlanguage{english}-arid ecosystem.~\emph{Ecology and evolution}
,~\emph{5} (22), 5305-5317.

Bakker, E. S., Dobrescu, I., Straile, D., \& Holmgren, M. (2013).
Testing the stress gradient hypothesis in herbivore communities:
facilitation peaks at intermediate nutrient levels.~\emph{Ecology}
,~\emph{94} (8), 1776-1784.

Bakker, E. S., Olff, H., Vandenberghe, C., De Maeyer, K., Smit, R.,
Gleichman, J. M., \& Vera, F. W. (2004). Ecological anachronisms in the
recruitment of temperate light\selectlanguage{english}-demanding tree species in wooded
pastures.~\emph{Journal of Applied ecology} ,~\emph{41} (3), 571-582.

Baraza, E., Zamora, R., \& A. Hodar, J. (2006). Conditional outcomes in
plant--herbivore interactions: neighbours matter.~\emph{Oikos}
,~\emph{113} (1), 148-156.

Berdugo, M., Maestre, F. T., Kefi, S., Gross, N., Le Bagousse\selectlanguage{english}-Pinguet,
Y., \& Soliveres, S. (2019). Aridity preferences alter the relative
importance of abiotic and biotic drivers on plant species abundance in
global drylands.~\emph{Journal of Ecology} ,~\emph{107} (1), 190-202.

Bertness, M. D., \& Callaway, R. (1994). Positive interactions in
communities.~\emph{Trends in ecology \& evolution} ,~\emph{9} (5),
191-193.

Brooker, R. W., Maestre, F. T., Callaway, R. M., Lortie, C. L.,
Cavieres, L. A., Kunstler, G., \ldots{} \& Michalet, R. (2008).
Facilitation in plant communities: the past, the present, and the
future.~\emph{Journal of ecology} ,~\emph{96} (1), 18-34.

Brooker, R. W., \& Callaghan, T. V. (1998). The balance between positive
and negative plant interactions and its relationship to environmental
gradients: a model.~\emph{Oikos} , 196-207.

Bruno, J. F., Stachowitz, J. J., \& Bertness, M. D. 200.~\emph{Inclusion
of facilitation into ecological theory. Tree} ,~\emph{18} , 119-125.

Butterfield, B. J., Bradford, J. B., Armas, C., Prieto, I., \& Pugnaire,
F. I. (2016). Does the stress\selectlanguage{english}-gradient hypothesis hold water?
Disentangling spatial and temporal variation in plant effects on soil
moisture in dryland systems.~\emph{Functional Ecology} ,~\emph{30} (1),
10-19.

Caccianiga, M., Luzzaro, A., Pierce, S., Ceriani, R. M., \& Cerabolini,
B. (2006). The functional basis of a primary succession resolved by CSR
classification.~\emph{Oikos} ,~\emph{112} (1), 10-20.

Callaway, R. M. (2007). Positive interactions and community
organization. In~\emph{Positive interactions and interdependence in
plant communities} ~(pp. 295-333). Springer, Dordrecht.

Callaway, R. M., Ridenour, W. M., Laboski, T., Weir, T., \& Vivanco, J.
M. (2005). Natural selection for resistance to the allelopathic effects
of invasive plants.~\emph{Journal of ecology} ,~\emph{93} (3), 576-583.

Callaway, R. M., Brooker, R. W., Choler, P., Kikvidze, Z., Lortie, C.
J., Michalet, R., \ldots{} \& Cook, B. J. (2002). Positive interactions
among alpine plants increase with stress.~\emph{Nature} ,~\emph{417}
(6891), 844-848.

Grime JP (1979) Plant strategies and vegetation processes. John Wiley
and Sons, Chichester.

Jones, C. G., Lawton, J. H., \& Shachak, M. (1997). Positive and
negative effects of organisms as physical ecosystem
engineers.~\emph{Ecology} ,~\emph{78} (7), 1946-1957.

Cardon, Z. G., Stark, J. M., Herron, P. M., \& Rasmussen, J. A. (2013).
Sagebrush carrying out hydraulic lift enhances surface soil nitrogen
cycling and nitrogen uptake into inflorescences.~\emph{Proceedings of
the National Academy of Sciences} ,~\emph{110} (47), 18988-18993.

Bohlen, P. J., Groffman, P. M., Driscoll, C. T., Fahey, T. J., \&
Siccama, T. G. (2001). Plant--soil--microbial interactions in a northern
hardwood forest.~\emph{Ecology} ,~\emph{82} (4), 965-978.

Holzapfel, C., \& Mahall, B. E. (1999). Bidirectional facilitation and
interference between shrubs and annuals in the Mojave
Desert.~\emph{Ecology} ,~\emph{80} (5), 1747-1761.

Fleischer, C., \& Hommel, G. (2006). EMG-driven human model for orthosis
control. In~\emph{Human Interaction with Machines} ~(pp. 69-76).
Springer, Dordrecht.

Davies, K. W., Bates, J. D., \& Miller, R. F. (2007). The influence of
Artemsia tridentata ssp. wyomingensis on microsite and herbaceous
vegetation heterogeneity.~\emph{Journal of Arid Environments}
,~\emph{69} (3), 441-457.

Diaz, S., Lavorel, S., McIntyre, S. U. E., Falczuk, V., Casanoves, F.,
Milchunas, D. G., \ldots{} \& Campbell, B. D. (2007). Plant trait
responses to grazing--a global synthesis.~\emph{Global Change Biology}
,~\emph{13} (2), 313-341.

Dufrene, M., \& Legendre, P. (1997). Species assemblages and indicator
species: the need for a flexible asymmetrical approach.~\emph{Ecological
monographs} ,~\emph{67} (3), 345-366.

Farzam, M., \& Ejtehadi, H. (2017). Effects of drought and slope aspect
on canopy facilitation in a mountainous rangeland.~\emph{Journal of
Plant Ecology} ,~\emph{10} (4), 626-633.

Filazzola, A., Westphal, M., Powers, M., Liczner, A. R., Woollett, D. A.
S., Johnson, B., \& Lortie, C. J. (2017). Non-trophic interactions in
deserts: Facilitation, interference, and an endangered lizard
species.~\emph{Basic and Applied Ecology} ,~\emph{20} , 51-61.

Fugere, V., Andino, P., Espinosa, R., Anthelme, F., Jacobsen, D., \&
Dangles, O. (2012). Testing the stress\selectlanguage{english}-gradient hypothesis with aquatic
detritivorous invertebrates: insights for biodiversity\selectlanguage{english}-ecosystem
functioning research.~\emph{Journal of Animal Ecology} ,~\emph{81} (6),
1259-1267.Gomez-Aparicio, L., Zamora, R., Gomez\selectlanguage{english}-Aparicio, L., Zamora,
R., Castro, J., \& Hodar, J. A. (2008). Facilitation of tree saplings by
nurse plants: Microhabitat amelioration or protection against
herbivores?.~\emph{Journal of Vegetation Science} ,~\emph{19} (2),
161-172.

Graff, P., \& Aguiar, M. R. (2011). Testing the role of biotic stress in
the stress gradient hypothesis. Processes and patterns in arid
rangelands.~\emph{Oikos} ,~\emph{120} (7), 1023-1030.

Graff, P., Aguiar, M. R., \& Chaneton, E. J. (2007). Shifts in positive
and negative plant interactions along a grazing intensity
gradient.~\emph{Ecology} ,~\emph{88} (1), 188-199.

Grime, J. P. (1977). Evidence for the existence of three primary
strategies in plants and its relevance to ecological and evolutionary
theory.~\emph{The american naturalist} ,~\emph{111} (982), 1169-1194.

Gross, N., Borger, L., Soriano\selectlanguage{english}-Morales, S. I., Le Bagousse\selectlanguage{english}-Pinguet, Y.,
Quero, J. L., Garcia\selectlanguage{english}-Gomez, M., \ldots{} \& Maestre, F. T. (2013).
Uncovering multiscale effects of aridity and biotic interactions on the
functional structure of Mediterranean shrublands.~\emph{Journal of
Ecology} ,~\emph{101} (3), 637-649.

He, Q., \& Bertness, M. D. (2014). Extreme stresses, niches, and
positive species interactions along stress gradients.~\emph{Ecology}
,~\emph{95} (6), 1437-1443.

Holmgren, M., \& Scheffer, M. (2010). Strong facilitation in mild
environments: the stress gradient hypothesis revisited.~\emph{Journal of
Ecology} ,~\emph{98} (6), 1269-1275.

Holthuijzen, M. F., \& Veblen, K. E. (2015). Grass-shrub associations
over a precipitation gradient and their implications for restoration in
the Great Basin, USA.~\emph{PloS one} ,~\emph{10} (12), e0143170.

Howard, K. S., Eldridge, D. J., \& Soliveres, S. (2012). Positive
effects of shrubs on plant species diversity do not change along a
gradient in grazing pressure in an arid shrubland.~\emph{Basic and
Applied Ecology} ,~\emph{13} (2), 159-168.

Jankju, M. (2016). Potential and constraints on dryland restoration:
Case studies from Iran.~\emph{Ecological restoration: Global challenges,
social aspects and environmental benefits} , 177-192.

Jankju, M. (2013). Role of nurse shrubs in restoration of an arid
rangeland: effects of microclimate on grass establishment.~\emph{Journal
of Arid Environments} ,~\emph{89} , 103-109.

Jankju, M. (2008). Individual performances and the interaction between
arid land plants affected by the growth season water pulses.~\emph{Arid
Land Research and Management} ,~\emph{22} (2), 123-133.

Kefi, S., Rietkerk, M., Van Baalen, M., \& Loreau, M. (2007). Local
facilitation, bistability and transitions in arid
ecosystems.~\emph{Theoretical population biology} ,~\emph{71} (3),
367-379.

Le Bagousse\selectlanguage{english}-Pinguet, Y., Gross, E. M., \& Straile, D. (2012). Release
from competition and protection determine the outcome of plant
interactions along a grazing gradient.~\emph{Oikos} ,~\emph{121} (1),
95-101.

Lopez, R. P., Squeo, F. A., Armas, C., Kelt, D. A., \& Gutierrez, J. R.
(2016). Enhanced facilitation at the extreme end of the aridity gradient
in the Atacama Desert: a community\selectlanguage{english}-level approach.~\emph{Ecology}
,~\emph{97} (6), 1593-1604.

Louthan, A. M., Doak, D. F., Goheen, J. R., Palmer, T. M., \& Pringle,
R. M. (2014). Mechanisms of plant--plant interactions: concealment from
herbivores is more important than abiotic-stress mediation in an African
savannah.~\emph{Proceedings of the Royal Society B: Biological Sciences}
,~\emph{281} (1780), 20132647.

Maestre, F. T., Callaway, R. M., Valladares, F., \& Lortie, C. J.
(2009). Refining the stress\selectlanguage{english}-gradient hypothesis for competition and
facilitation in plant communities.~\emph{Journal of Ecology} ,~\emph{97}
(2), 199-205.

Maestre, F. T., Valladares, F., \& Reynolds, J. F. (2005). Is the change
of plant--plant interactions with abiotic stress predictable? A
meta\selectlanguage{english}-analysis of field results in arid environments.~\emph{Journal of
Ecology} ,~\emph{93} (4), 748-757.

Maestre, F. T., Bautista, S., \& Cortina, J. (2003). Positive, negative,
and net effects in grass--shrub interactions in Mediterranean semiarid
grasslands.~\emph{Ecology} ,~\emph{84} (12), 3186-3197.

Maestre, F. T., Bautista, S., Cortina, J., \& Bellot, J. (2001).
Potential for using facilitation by grasses to establish shrubs on a
semiarid degraded steppe.~\emph{Ecological Applications} ,~\emph{11}
(6), 1641-1655.

Memariani, F., Zarrinpour, V., \& Akhani, H. (2016). A review of plant
diversity, vegetation, and phytogeography of the Khorassan-Kopet Dagh
floristic province in the Irano-Turanian region (northeastern
Iran--southern Turkmenistan).~\emph{Phytotaxa} ,~\emph{249} (1), 8-30.

Metz, J., \& Tielborger, K. (2016). Spatial and temporal aridity
gradients provide poor proxies for plant--plant interactions under
climate change: a large\selectlanguage{english}-scale experiment.~\emph{Functional Ecology}
,~\emph{30} (1), 20-29.

Milchunas, D. G., \& Noy\selectlanguage{english}-Meir, I. (2002). Grazing refuges, external
avoidance of herbivory and plant diversity.~\emph{Oikos} ,~\emph{99}
(1), 113-130.

Pierce, S., Negreiros, D., Cerabolini, B. E., Kattge, J., Diaz, S.,
Kleyer, M., \ldots{} \& Tampucci, D. (2017). A global method for
calculating plant CSR ecological strategies applied across biomes
world\selectlanguage{english}-wide.~\emph{Functional ecology} ,~\emph{31} (2), 444-457.

Pugnaire, F. I., Armas, C., \& Maestre, F. T. (2011). Positive plant
interactions in the Iberian Southeast: mechanisms, environmental
gradients, and ecosystem function.~\emph{Journal of arid environments}
,~\emph{75} (12), 1310-1320.

Team, R. C. (2013). RA lang environ stat comput.~\emph{Development Core
Team} .

Rahmanian, S., Hejda, M., Ejtehadi, H., Farzam, M., Py\selectlanguage{polish}š\selectlanguage{english}ek, P., \&
Memariani, F. (2020). Effects of livestock grazing on plant species
diversity vary along a climatic gradient in northeastern
Iran.~\emph{Applied Vegetation Science} ,~\emph{23} (4), 551-561.

Rahmanian, S., Hejda, M., Ejtehadi, H., Farzam, M., Memariani, F., \&
Py\selectlanguage{polish}š\selectlanguage{english}ek, P. (2019). Effects of livestock grazing on soil, plant functional
diversity, and ecological traits vary between regions with different
climates in northeastern Iran.~\emph{Ecology and evolution} ,~\emph{9}
(14), 8225-8237.

Rand, T. A. (2004). Competition, facilitation, and compensation for
insect herbivory in an annual salt marsh forb.~\emph{Ecology}
,~\emph{85} (7), 2046-2052.

Reisner, M. D., Doescher, P. S., \& Pyke, D. A. (2015). Stress-gradient
hypothesis explains susceptibility to Bromus tectorum invasion and
community stability in North America's semi-arid Artemisia tridentata
wyomingensis ecosystems.~\emph{Journal of Vegetation Science}
,~\emph{26} (6), 1212-1224.

Shannon, C. E. (1948). A mathematical theory of communication.~\emph{The
Bell system technical journal} ,~\emph{27} (3), 379-423.

Smit, C., Rietkerk, M., \& Wassen, M. J. (2009). Inclusion of biotic
stress (consumer pressure) alters predictions from the stress gradient
hypothesis.~\emph{Journal of Ecology} ,~\emph{97} (6), 1215-1219.

Smit, C., Vandenberghe, C., Den Ouden, J., \& M\selectlanguage{ngerman}üller-Schärer, H. (2007).
Nurse plants, tree saplings and grazing pressure: changes in
facilitation along a biotic environmental gradient.~\emph{Oecologia}
,~\emph{152} (2), 265-273.

Smit, C., Den Ouden, J. A. N., \& Müller\selectlanguage{english}-Scharer, H. E. I. N. Z. (2006).
Unpalatable plants facilitate tree sapling survival in wooded
pastures.~\emph{Journal of Applied ecology} ,~\emph{43} (2), 305-312.

Soliveres, S., Garcia\selectlanguage{english}-Palacios, P., Castillo\selectlanguage{english}-Monroy, A. P., Maestre, F.
T., Escudero, A., \& Valladares, F. (2011). Temporal dynamics of
herbivory and water availability interactively modulate the outcome of a
grass--shrub interaction in a semi\selectlanguage{english}-arid ecosystem.~\emph{Oikos}
,~\emph{120} (5), 710-719.

Tirado, R., Brathen, K. A., \& Pugnaire, F. I. (2015). Mutual positive
effects between shrubs in an arid ecosystem.~\emph{Scientific Reports}
,~\emph{5} (1), 1-8.

Vandenberghe, C., Smit, C., Pohl, M., Buttler, A., \& Frelechoux, F.
(2009). Does the strength of facilitation by nurse shrubs depend on
grazing resistance of tree saplings?.~\emph{Basic and Applied Ecology}
,~\emph{10} (5), 427-436.

Verwijmeren, M., Rietkerk, M., Bautista, S., Mayor, A. G., Wassen, M.
J., \& Smit, C. (2014). Drought and grazing combined: contrasting shifts
in plant interactions at species pair and community level.~\emph{Journal
of Arid Environments} ,~\emph{111} , 53-60.

\textbf{TABLE 1} Basic characteristics and grazing history of the arid
and semi-arid regions in northeastern Iran.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
\begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
Region\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
Khawjeh Kalat 35\selectlanguage{ngerman}° 43'- 35° 50' N, 60° 27' - 60° 34' E\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
Khawjeh Kalat 35\selectlanguage{ngerman}° 43'- 35° 50' N, 60° 27' - 60° 34' E\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
Baharkish 36\selectlanguage{ngerman}° 44' - 36° 42' N, 58° 40' - 58° 36' E\strut
\end{minipage} & \begin{minipage}[b]{0.19\columnwidth}\raggedright\strut
Baharkish 36\selectlanguage{ngerman}° 44' - 36° 42' N, 58° 40' - 58° 36' E\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Climate classification (De Martonne)\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Arid\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Arid\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Semi-arid\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Semi-arid\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Mean annual precipitation (mm)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
255\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
255\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
385\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
385\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Mean annual temperature\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
17.9\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
17.9\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
13\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
13\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
De Martonne Index\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
9\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
9\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
15.5\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
15.5\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Elevation (m)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
630-810\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
630-810\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1580-2390\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
1580-2390\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Management\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textbf{Grazing area}\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textbf{Area protected from grazing}\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textbf{Grazing area}\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
\textbf{Area protected from grazing}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Grazing history\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Seasonal- free ranging\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
protected in the last 35 years, occasional light grazing in some
years\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Seasonal- free ranging\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Protected in the last 35 years, occasional light grazing in some
years\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Grazing type\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Seasonal, 20 March - 10 May\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Seasonal, 20 March - 10 May\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Seasonal, 20 May - 23 July\strut
\end{minipage} & \begin{minipage}[t]{0.19\columnwidth}\raggedright\strut
Seasonal, 20 May - 23 July\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Grazers type\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Sheep (90\%), goat (10\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Sheep (90\%), goat (10\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Sheep (90\%), Goat (10\%)\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Sheep (90\%), goat (10\%)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
Grazers density\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
3 AUM/ha\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0-0.5 AUM/ha\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
2 AUM/ha\strut
\end{minipage} & \begin{minipage}[t]{0.17\columnwidth}\raggedright\strut
0-0.5 AUM/ha\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

AUM: Animal Unit Month

\textbf{Table 2} Results of linear mixed-effect models, testing the
effects of climate, grazing, and their interactions on RII.Shannon,
RII.Richness and RII.Cover.\selectlanguage{english}
\begin{longtable}[]{@{}llllllllll@{}}
\toprule
& Climate & Climate & Climate & Grazing & Grazing & Grazing & Climate \selectlanguage{ngerman}×
grazing & Climate \selectlanguage{ngerman}× grazing & Climate \selectlanguage{ngerman}× grazing\tabularnewline
\midrule
\endhead
& df & F & p & df & F & p & df & F & p\tabularnewline
RII-Cover & 1 & 17.46 & \textless{}.001*** & 1 & 13 & 0.0006*** & 2 &
15.6 & \textless{}.0001***\tabularnewline
RII-Richness & 1 & 9.56 & 0.01** & 1 & 5.07 & 0.02* & 2 & 4.88 &
0.01**\tabularnewline
RII-Shannon & 1 & 7 & 0.02* & 1 & 3.62 & 0.06 & 2 & 3.87 &
0.02*\tabularnewline
\bottomrule
\end{longtable}

***\emph{p} \textless{} .001, **\emph{p} \textless{} .01,
*\emph{p}\textless{} .05, no asterisk (\emph{p} \textless{} .1)

\par\null

\textbf{TABLE 3} List of indicator species found under \emph{A.
kopetdaghensis} canopy and on open plots of the HG and LG sites in the
arid and semi-arid regions, showing the exclusivity and fidelity of
indicator species. Significances refer to indicator values (exclusivity
\selectlanguage{ngerman}× fidelity) (*p \textless{} 0.05, **p \textless{} 0.01, ***p \textless{}
0.001, permutations = 999).\selectlanguage{english}
\begin{longtable}[]{@{}lllllll@{}}
\toprule
Species of the under-canopy plots & Semi-arid LG & Semi-arid HG &
Arid-LG & Arid-HG & Life cycle & CSR\tabularnewline
\midrule
\endhead
\emph{Achillea biebersteini} Afan. & 0.045* & & & & A & S\tabularnewline
\emph{Alyssum desertorum} Stapf & & & 0.002** & & A &
R/SR\tabularnewline
\emph{Astragalus} (\emph{Caprini}) \emph{citrinus} Bunge & & 0.01* & & &
P & S\tabularnewline
\emph{Astragalus filicaulis} Kar. \& Kir. & & & 0.002** & & A &
R/CSR\tabularnewline
\emph{Astragalus oxyglottis} M.Bieb. & & 0.01* & & & A &
S/SR\tabularnewline
\emph{Bromus danthoniae} Trin. & & & 0.03* & & A & S\tabularnewline
\emph{Bromus tectorum} L. & 0.005** & & & & A & S/SR\tabularnewline
\emph{Callipeltis cucullaria} (L.) Stev. & & & 0.04* & & A &
R\tabularnewline
\emph{Cirsium bornmuelleri} Sint. ex Bornm. & & 0.01* & & & P &
CS\tabularnewline
\emph{Elymus~hispidus~}(Opiz) Melderi & & 0.001*** & & & P &
CSR\tabularnewline
\emph{Eremurus stenophyllus} (Boiss \& Buhse) Baker & 0.005** & & & & P
& S\tabularnewline
\emph{Galium tricornutum} Dandy & & & 0.001*** & & A & R\tabularnewline
\emph{Lactuca orientalis} Boiss. & 0.046* & & & & P & CR\tabularnewline
\emph{Poa} \emph{bulbosa} L. & & & & 0.006** & P & SR\tabularnewline
\emph{Prunus pseudoprostrata} (Pojark.) Rech.f & & 0.01* & & & P &
S\tabularnewline
\emph{Salsola dendroides} Pall. & & & & 0.01* & P & SR\tabularnewline
\emph{Thalictrum sultanabadense} Stapf & & 0.005** & & & P &
CSR\tabularnewline
Species of the open plots & \textbf{Semi-arid LG} & \textbf{Semi-arid
HG} & \textbf{Arid LG} & \textbf{Arid HG} & \textbf{Life cycle} &
\textbf{CSR}\tabularnewline
\emph{Achillea biebersteini} Afan. & 0.04* & & & & A & S\tabularnewline
\emph{Aegilops triuncialis} L. & 0.004** & & & & A & SR\tabularnewline
\emph{Poa} \emph{bulbosa} L. & & & & 0.01* & P & SR\tabularnewline
\bottomrule
\end{longtable}

Abbreviations of the C-S-R plant life strategies: C: competitive, S:
stress tolerating, R: ruderal. Abbreviations of the life cycle: A:
annual, P: prennial

\textbf{Figure legends}

\textbf{Figure 1.} a) Map of the study area in NE Iran, showing the
Khajeh Kalat as an arid region, with \textasciitilde{}255 mm of annual
precipitation and Baharkish rangeland as a semi-arid region, with
\textasciitilde{}385 mm of annual precipitation, b) Natural habitat
with\emph{Artemisia kopetdaghensis} as a dominant species, c) Plant
communities around Artemisia kopetdaghensis, the arrows point to other
species under the canopy of \emph{A. kopetdaghensis}

\textbf{Figure 2.} Comparisons of relative interaction indices
(RII-Richness, RII-cover, and RII- Shannon diversity) of \emph{A.
kopetdaghensis} between the HG and LG sites in the arid and semi-arid
regions.

\textbf{Appendices}

\textbf{Appendix A.} Mean values of the relative interaction intensity
(RII), corresponding to the relative effect of the canopy
of\emph{Artemisia kopetdaghensis} on the under-canopy communities.\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
\textbf{Climatic region} & \textbf{Grazing} & \textbf{RII-Richness} &
\textbf{RII-Cover} & \textbf{RII-Shannon diversity}\tabularnewline
\midrule
\endhead
Arid & HG & 0.2 & 0.33 & 0.16\tabularnewline
& LG & 0.19 & 0.26 & 0.18\tabularnewline
Semi-arid & HG & 0.18 & 0.3 & 0.01\tabularnewline
& LG & -0.14 & -0.38 & -0.11\tabularnewline
\bottomrule
\end{longtable}

\textbf{Hosted file}

\verb`Figure 1.docx`  available at \url{https://authorea.com/users/425793/articles/530516-the-effects-of-aridity-and-grazing-on-the-relation-between-the-dominant-shrub-artemisia-kopetdaghensis-and-plants-under-its-canopy}

\textbf{Hosted file}

\verb`Figure 2.docx`  available at \url{https://authorea.com/users/425793/articles/530516-the-effects-of-aridity-and-grazing-on-the-relation-between-the-dominant-shrub-artemisia-kopetdaghensis-and-plants-under-its-canopy}

\selectlanguage{english}
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\end{document}

