# Using stone cover patches and grazing exclusion to restore ground-active beetle communities in a pseudo-steppe

Olivier Blight, Sylvain Fadda, Jérôme Orgeas, Philippe Ponel, Elise Buisson, Thierry Dutoit

► To cite this version:

Olivier Blight, Sylvain Fadda, Jérôme Orgeas, Philippe Ponel, Elise Buisson, et al.. Using stone cover patches and grazing exclusion to restore ground-active beetle communities in a pseudo-steppe. Journal of Insect Conservation, 2011, 15, pp.561-572. 10.1007/s10841-010-9358-3. hal-01329435

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# Using stone cover patches and grazing exclusion to restore ground-active beetle communities in a degraded pseudo-steppe

Olivier Blight · Sylvain Fadda · Jérôme Orgeas ·

Philippe Ponel · Elise Buisson · Thierry Dutoit

**Abstract** The dry grasslands of La Crau, a pseudo-steppe ecosystem located in Southern France, have experienced drastic reduction and degradation due to intensive agricultural activities for the past 50 years, leading to changes in their beetle assemblage. This valuable ecosystem is characterized by 50% stone cover, consisting of remnants from an old riverbed, and centuries-old sheep grazing. However, much of the stone cover has been removed for the purposes of cultivation. With the aim of restoring this ecosystem, we manipulated these two principal ecological factors: sheep grazing (grazing/exclusion) and stone cover (50% stone cover/no large stones). This study was conducted on a former cultivated field and on a pseudo-steppe area. On each of the two areas, 12 experimental units contained four different treatment patches: (1) stones × grazing, (2) no stones × grazing, (3) no stones × no grazing and (4) stones × no grazing, were randomly positioned. Data were obtained from 96 pitfall traps (one on each patch). After 4 years, restored stone cover combined with grazing exclusion significantly improved beetle abundance and increased beetle richness (38 species vs. 22 in the grazed-no-stones treatment), whereas no significant differences were recorded in the three other treatments. Our results therefore suggest that removing

grazing for a few years and restoring stone cover is a promising method to restore beetle assemblages in this type of ecosystem.

**Keywords** Mediterranean pseudo-steppe restoration · Sheep grazing · Beetle species richness

## Introduction

In Europe, natural ecosystems have been strongly modified by human activities since the Neolithic Age (Roberts 1989; Bell and Walker 1992; Guilaine 2006). Land management, through grazing and mowing, has contributed to the expansion of open landscapes, such as dry grasslands (Poschlod and WallisDeVries 2002; Dutoit et al. 2009). Although they may have been present before the Neolithic Age (Vera 1996), dry grasslands have mainly developed as a result of different types of traditional land use practices (i.e. pastoralism, hand mowing) and are semi-natural ecosystems (Poschlod and WallisDeVries 2002; Dutoit et al. 2009). More recently, agricultural intensification and the decline of traditional land management have been leading to the loss and fragmentation of dry grasslands and to considerable floristic and faunistic changes (Meyer and Turner 1994; WallisDeVries et al. 2002). Dry grasslands support a diverse and often specialized flora and fauna, including many rare and threatened species (Poschlod and WallisDeVries 2002; WallisDeVries et al. 2002). Conservation and restoration of these grasslands therefore constitute one of the major keys to the preservation of wider grassland biodiversity (Muller et al. 1998).

La Crau is a large plain of 60,000 ha in Southern France, located on the ancient delta of the Durance River, which was captured by the Rhône at the end of the Würmian

O. Blight (✉) · S. Fadda · J. Orgeas · P. Ponel
Institut Méditerranéen d'Ecologie et de Paléoécologie (IMEP, UMR CNRS IRD), Université Paul Cézanne, Europôle Méditerranéen de l'Arbois, BP 80, 13545 Aix-en-Provence Cedex 4, France
e-mail: olivierblight@aol.com

E. Buisson · T. Dutoit
Institut Méditerranéen d'Ecologie et de Paléoécologie (IMEP, UMR CNRS IRD), IUT de l'Université d'Avignon et des Pays de Vaucluse, Agroparc, BP 61207, 84911 Avignon Cedex 9, France
glaciation. This stony plain is shaped both by traditional human activities over the last 6,000 years (mainly sheep grazing) and by climatic and edaphic constraints (dryness, strong winds, stone cover reaching 50%) (Buisson and Dutoit 2006). These dry grasslands identified as a pseudo-steppe (Devaux et al. 1983) are good sites for testing restoration programs. Firstly, La Crau is a valuable site, both locally (Nature Reserve of "Coussouls de Crau") and internationally (E.U. Natura 2000 site) for species and habitat conservation; secondly, past and present human activities in La Crau grasslands are well documented (Henry et al. 2010); and thirdly, these dry grasslands are representative, being similar to many other semi-arid steppes in the Mediterranean region in terms of both their herbaceous plant community structures and their ecological processes, e.g. Dehesa in Spain (3 million ha), Montado in Portugal (700,000 ha) and other semi-arid steppes of North Africa and the Eastern Mediterranean (Buisson and Dutoit 2006). In the mid-twentieth century, the dry grasslands of La Crau underwent many intensive land-uses. The cultivation of melons and cereals, from 1965 to 1985, caused a large reduction in overall area of the semi-natural habitats. Plowing, soil fertilization and stone removal during cultivation modified the structure of large stretches of land. Disused for the past 20-30 years, these former cultivated fields are now characterized by low plant species richness. Grazing was reintroduced, but the vegetation did not recover (Römermann et al. 2005). Accordingly, a second parameter, stone cover, was investigated as a potential management tool to restore dominant perennial dry grassland plants (Buisson 2006). Stone cover had already been shown to structure the dry grassland plant community (Buisson and Dutoit 2004; Buisson et al. 2006). In dry habitats, stones create micro-habitats with better microclimatic conditions e.g. moisture and shade (Fowler 1988; Lahav and Steinberger 2001; Buisson 2006). They also favor perennial plants, which are dominant in La Crau (Blumler 1992), and protect plants from sheep grazing (Buisson 2006).

The success of restoration projects is mainly evaluated on the re-establishment of vegetation. However, ecological restoration needs to take into account the entirety of an ecosystem. The effects of ecological restoration on other groups, such as arthropods, are still largely unknown (Andersen and Sparling 1997; Davis et al. 2003; Longcore 2003; Waltz and Covington 2004; Woodcock et al. 2006). As they are widespread and numerically dominant, insects and more specifically beetles (Coleoptera) are important in monitoring studies: they occupy almost every type of available habitat and are present at all levels of trophic chains. Despite the typical beetle assemblage of La Crau (Bigot et al. 1983) and although habitat changes caused by agriculture can affect insect diversity (Huntly 1991), few

studies have focused on variations in beetle community structure in response to land restoration.

Fadda et al. (2007, 2008b) showed that 20 years after cultivation ceased, former cultivated fields still have very different beetle communities from the semi-natural ecosystem, despite the early restoration of a grazing regime. These differences in beetle communities may result from a loss of habitat quality, which is generally taken to explain the disproportionate decrease in insects in a cultivated landscape (Thomas et al. 2001). Habitat quality can be defined in La Crau as the presence of perennial dominant plants structuring the dry grassland plant community, providing beetles with food resources and protection, e.g. protection against high temperatures by creating shade and moisture, in the same way as stones do.

Thus, in order to provide recommendations for former cultivated field restoration, it appears essential to understand the effects of habitat restoration on other groups than plants. This study (1) aims to assess the role of grazing and stone cover on the ecological guild structure of beetle communities. Because it is impossible to restore full stone cover due to the vast area of former cultivated fields (more than 1,500 ha overall), this study also (2) aims to test the restoration of beetle communities by installing small randomized experimental areas of restored stone cover, herein called: "stone patches". As a first step toward dry grassland beetle recolonization on former cultivated fields, we hoped these small stone patches would act as refuges identified by an increase of total species-richness, total beetle density or of some specific beetle populations.

## Methods

### Study site

Situated, in the former delta of the Durance River, to the east of the Rhône valley and the Camargue, La Crau presents a landscape of semi-arid pastures (Fig. 1). This region is characterized by a Mediterranean climate with high inter-annual variability, low rainfall (400–500 mm per year) with maxima in spring and in autumn, long hot summers and mild winters (mean annual temperature: 14°C). On average, the sun shines 3,000 h per year and the very strong predominant wind ("mistral") blows from the North-West 334 days per year, thus increasing evaporation (Transpiration (Devaux et al. 1983). More than 50% of the soil surface is covered by stones transported by a river (the Durance) between 650,000 and 30,000 years ago. The substratum is an impermeable conglomerate bedrock, 40 cm deep, which makes ground water inaccessible to vegetation.
<figure><img src="image_2.png" /><figcaption>**Fig. 1** Map of France showing the geographical location of the study area. The dry grasslands of La Crau are inside the dotted triangle</figcaption></figure>

We selected two sites in the center of “Peau de Meau” sheepfold (43°33′E 4°50′N, elevation 10 m, 160 ha). The first (Control, C) is a remnant patch of semi-natural dry grassland (35 ha), representative of the remaining 11,500 ha of dry steppe vegetation with 50% stone cover and two dominant plants, *Brachypodium retusum* (Pers.) P.Beauv.L., Poaceae and *Thymus vulgaris* L., Lamiaceae (Buisson and Dutoit 2004; Römermann et al. 2005; Buisson 2006; Buisson et al. 2006). The second site (F) is a former cultivated melon field (5 ha), representative of the rest of the former cultivated fields in this area (1,500 ha). This site was planted with melons in 1971 and with cereal and alfalfa in 1972. Disturbances caused by melon and cereal cultivation were extensive, with plowing, soil fertilization and stone removal (Buisson and Dutoit 2004; Römermann et al. 2005; Buisson 2006). During the former

cultivation period, the largest stones were removed and filled along the field margins. These siliceous stones were barely distorted or broken by plowing as they are extremely solid.

These two sites were and still are grazed by itinerant sheep flocks in an extensive way: stocking rates are 1.5 animals/ha/year on the pseudo-steppe and 2.5 animals/ha/year on the former arable fields from March to June only, because of different land ownership (Dureau and Bonnefon 1998).

## Experimental design

In order to understand the relationships between ground-active beetles and both grazing and stone cover, 12 experimental units were installed randomly over approximately 5 ha on both sites in 2002. Each experimental unit was composed of two 3 × 1.5 m plots three meters away from each other to avoid edge effects (Buisson 2006; Dutoit et al. 2007): one fenced plot (ungrazed treatment) and one unfenced plot (grazed treatment) (Fig. 2). To test the effects of stones, each plot was split into two subplots or patches of 1.5 × 1.5 m. Large stones (>10 cm) were removed from one subplot of each plot in the dry grassland and added to the former cultivated field to create stone patches. The sampling period started in 2006 in order to allow 4 years of habitat modification by this stone cover and to avoid the negative effects of disturbance link to the implementation of stones.

## Beetle sampling

Beetle sampling was carried out with plastic pitfall traps (50 mm in diameter and 100 mm deep) which were partly

<figure><img src="image_3.png" /><figcaption>**Fig. 2** Experimental lay-out in La Crau area. In the dry grassland, which is considered as a control and the reference ecosystem, stones were removed, whereas in the former cultivated field they were placed on the soil as a restoration measure</figcaption></figure>
filled with a non-attractive mixture (ethylene-glycol) as a
catching, preservation fluid (Asteraki et al. 1995; Butter-
field et al. 1995; Dennis et al. 2002; Fadda et al. 2008a, b).
One pitfall trap was installed in the centre of each subplot,
providing 48 pitfall traps at each of the two sites. In each
pit, traps were changed twice over a continuous 3-month
sampling period from April to June 2006, spring being the
period of highest beetle abundance (Fadda et al. 2008a). A
total of 288 pitfall traps were thus analyzed. Beetles were
identified to the species level or the closest taxonomic
level.

Data analyses

Data obtained on the same subplot over the 3-month period
were pooled in order to perform the statistical analyses.

To assess the effects of grazing and stone cover on the
ground-active beetle community, we conducted ANOVA
for split-split-plot design on two separate models: one for
each site (F for Field and C for Control) (Tukey post-hoc
test) (R Statistical Computing version 2.3.0, pack-
age = "stats"). ANOVA were performed on beetle rich-
ness and abundance at each site. Split-split-plot ANOVA
were also performed on the abundance of four of the five
most common species, to relate their distribution to the
presence of grazing and stone treatments at each site.
Grazing and stone cover were treated as categorical
explanatory variables, P < 0.05 was considered significant.
Prior to statistical analysis, we examined all data distri-
butions using the Shapiro-Wilk W test for normality.
Because data were not normal, they were log-transformed,
normality and homogeneity of variances tested prior to
running split-plot ANOVAs.

A detrended correspondence analysis (DCA CANO-
CO—Ter Braak and Smilauer 1997) was conducted to
relate the distribution of the various assemblages of species
to study sites and treatments. The DCA was performed on

the [96 sampling units × 103 species (presence/absence)]
matrix. In the ordination, the down-weighting option of
rare species of CANOCO was applied.

Results

From April to June 2006, a total of 987 specimens
belonging to 103 species of Coleoptera were collected
("Appendix"). The datasets were dominated by *Asida
sericea* (Tenebrionidae) with 264 individuals, *Poecilus
sericeus* (Carabidae) with 134 individuals and *Longitarsus
succineus* (Chrysomelidae) with 81 individuals. These
three species accounted for 48% of the total abundance of
sampled beetles. We also caught 54 and 51 individuals of
*Endomia tenucollis* and *Microlestes luctuosus*, respec-
tively. For 41 species, only one individual was sampled.

We caught four species of conservation interest, *Bio-
planes meridionalis*, *Pleurodirus obesus*, *Pseudocleonus
cinereus* and *Amplimallon ruficorne*. These species were
exclusively caught on the dry grassland. *P. obesus* is an
endemic weevil from Southern France, where it is restric-
ted to the Lower Rhône Valley. *B. meridionalis* is a dar-
kling beetle common on dry grounds everywhere in
Provence, but shows a very limited distribution at a global
scale (Southern France and adjacent regions in Italy). The
remaining two species are present in other neighboring
countries but show a restricted distribution in Provence.

On the dry grassland, 661 individuals were captured
versus 326 individuals on the former cultivated field. The
dry grassland also had a significant greater species richness
than the former cultivated field with 76 species versus 61
species. This trend was confirmed on each subplot (Fig. 3).

Split-split-plot ANOVA showed that grazing with stones
had a significant effect on beetle abundances in the former
cultivated field: ungrazed subplots with stones had greater
beetle abundances than all other subplots in the former

<figure><img src="image_4.png" /><figcaption>**Fig. 3** a Mean abundance and b mean species richness of beetles per sampling unit for each subplot of former cultivated plot and control (pseudo-steppe), for ungrazed plot (thick line), s subplot with stones (pointed area). Arrows indicate unmodified state for each plot. a and b are the results of post-hoc tests of the split-split-plot ANOVA in Table 1 (n = 12)</figcaption></figure>
<table><caption>**Table 1** Split-split-plot ANOVA of treatment effects on beetle abundance and beetle richness of the former cultivated field and of the dry grassland</caption><thead><tr><th rowspan="3">Abundance</th><th colspan="5">Former cultivated field</th><th colspan="5">Dry grassland</th></tr><tr><th rowspan="2">F</th><th rowspan="2">P</th><th colspan="4">Mean value</th><th rowspan="2">F</th><th rowspan="2">P</th><th colspan="4">Mean value</th></tr><tr><th>S</th><th>nS</th><th>G</th><th>uG</th><th>S</th><th>nS</th><th>G</th><th>uG</th></tr></thead><tbody><tr><td>Grazing</td><td>7.13</td><td>*</td><td>-</td><td>-</td><td>5.71</td><td>7.91</td><td>0.78</td><td>ns</td><td>-</td><td>-</td><td>14.58</td><td>12.96</td></tr><tr><td>Stones</td><td>2.45</td><td>ns</td><td>7.46</td><td>6.17</td><td>-</td><td>-</td><td>2.81</td><td>ns</td><td>14.88</td><td>12.67</td><td>-</td><td>-</td></tr><tr><td>Grazing × Stones</td><td>6.13</td><td>*</td><td>Fig. 3</td><td>-</td><td>-</td><td>-</td><td>0.29</td><td>ns</td><td>-</td><td>-</td><td>-</td><td>-</td></tr><tr><td>Richness</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Grazing</td><td>11.97</td><td>**</td><td>-</td><td>-</td><td>4.04</td><td>5.58</td><td>8.41</td><td>*</td><td>-</td><td>-</td><td>5.91</td><td>7.86</td></tr><tr><td>Stones</td><td>0.58</td><td>ns</td><td>5.04</td><td>4.58</td><td>-</td><td>-</td><td>5.54</td><td>*</td><td>7.38</td><td>6.41</td><td>-</td><td>-</td></tr><tr><td>Grazing × Stones</td><td>1.39</td><td>ns</td><td>-</td><td>-</td><td>-</td><td>-</td><td>2.35</td><td>ns</td><td>-</td><td>-</td><td>-</td><td>-</td></tr></tbody></table>

S stones, nS no stones, G grazed, uG ungrazed

* P < 0.05; ** P < 0.01

cultivated field (Table 1; Fig. 3). No significant differences were observed on abundance in the dry grassland. Grazing had a significant effect on species richness at both sites: grazed plots had significantly lower species richness than ungrazed plots (Table 1). Stone cover had a significant effect on species richness in the dry grassland: subplots without stone cover had significantly lower species richness than subplots where the original stone cover represented 50% of the soil surface (Table 1).

Split-split-plot ANOVA showed significant negative effects of grazing for *P. sericeus*, *M. luctuosus* and marginally significant for *E. tenuicollis* on the former cultivated field (Table 2). For *M. luctuosus* and *E. tenuicollis* significant negative effects were also observed on the dry grassland (Table 2). Grazing had significant positive effects on *A. sericea* in the dry grassland (Table 2) while in the former cultivated field, grazing × the treatment without stones had significant positive effects (Table 2; Fig. 4). Split-split-plot ANOVA showed significant positive effects of stones on *P. sericeus* abundances in the dry grassland (Table 2). Unlike the former species, the fourth most abundant species, *L. succineus*, is not at the adult stage a ground-active beetle, so we did not include it in the analyses.

Axis 1 of the Detrended Correspondences Analysis (8.2%; Fig. 5) ordination clearly discriminated the dry grassland samples associated with species such as *A. sericea*, *B. meridionalis* and *P. cinereus*, from the former cultivated field samples associated with species, such as *E. tenuicollis* and *M. luctuosus*. Some species such as *P. sericeus* and *L. succineus*, were found at both sites. *A. sericea* is typically found in open dry and sandy habitats, under stones. It is a saprophagous and occasionally omnivorous species like most Tenebrionidae (Thé rond 1976). *B. meridionalis* is also found under stones, in open dry habitats (Soldati 2007). *P. cinereus* is a xero-

thermophilous species which lives in steppes or dunes (Koch 1992). Both *E. tenuicollis* and *M. luctuosus* are detritophagous, living in dry and warm habitats. *P. sericeus* is a thermophilous predatory ground-beetle found in grasslands. *L. succineus* is a phytophagous and polyphagous flea-beetle that lives in varied dry biotopes. It is widely distributed in Europe (Doguet 1994). Moreover, dry grassland samples were more homogenous than samples of the former cultivated field.

## Discussion

The beetle community of the degraded habitat was more influenced by treatments than the dry grassland beetle community. This may be the result of years of intensive exploitation, highlighting the necessity of restoring the more stable and valuable dry grassland beetle community. Despite the discrimination between communities from the two study sites which still existed 4 years after the restoration of stone cover and grazing exclusion, our results show that stone patches and grazing managements are starting to act as refuges on the former cultivated field.

### Sheep grazing

Greater beetle richness on ungrazed plots and a change in beetle structure were found 4 years after grazing exclusion began. These results confirm a general trend observed in the literature, i.e. that grazing can modify the structure and the composition of beetle communities (Butterfield et al. 1995; Cole et al. 2002; Dennis et al. 2002; Kruess and Tscharntke 2002; Dennis 2003; Grandchamp et al. 2005; Woodcock et al. 2005). In the former cultivated field, grazing exclusion enhances beetle richness: 52 species were sampled in ungrazed plots versus 32 in grazed plots.
<table><caption>**Table 2** Split-Split-plot ANOVA of treatment effects on abundance of the four most abundant beetle species (*Poecilus sericeus*, *Asida sericea*, *Endomia tenuicollis* and *Microlestes luctuosus*) on the two sites</caption><thead><tr><th rowspan="3"></th><th colspan="5">Former cultivated field</th><th colspan="5">Dry grassland</th></tr><tr><th rowspan="2">F</th><th rowspan="2">P</th><th colspan="4">Mean abundance</th><th rowspan="2">F</th><th rowspan="2">P</th><th colspan="4">Mean abundance</th></tr><tr><th>S</th><th>nS</th><th>G</th><th>uG</th><th>S</th><th>nS</th><th>G</th><th>uG</th></tr></thead><tbody><tr><td><em>Poecilus sericeus</em></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Grazing</td><td>4.821</td><td>*</td><td>-</td><td>-</td><td>0.41</td><td>1.08</td><td>1.821</td><td>ns</td><td>-</td><td>-</td><td>1.58</td><td>2.51</td></tr><tr><td>Stones</td><td>0.052</td><td>ns</td><td>0.79</td><td>0.7</td><td>-</td><td>-</td><td>4.162</td><td>*</td><td>1.46</td><td>2.62</td><td>-</td><td>-</td></tr><tr><td>Grazing × Stones</td><td>1.316</td><td>ns</td><td></td><td></td><td></td><td></td><td>0.085</td><td>ns</td><td></td><td></td><td></td><td></td></tr><tr><td><em>Asida sericea</em></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Grazing</td><td>14.184</td><td>***</td><td>-</td><td>-</td><td>1.38</td><td>0.21</td><td>24.873</td><td>***</td><td>-</td><td>-</td><td>7.29</td><td>2.12</td></tr><tr><td>Stones</td><td>7.529</td><td>**</td><td>0.46</td><td>1.13</td><td>-</td><td>-</td><td>0.034</td><td>ns</td><td>4.63</td><td>5.61</td><td>-</td><td>-</td></tr><tr><td>Grazing × Stones</td><td>7.765</td><td>*</td><td>Fig. 5</td><td></td><td></td><td></td><td>0.009</td><td>ns</td><td></td><td></td><td></td><td></td></tr><tr><td><em>Endomia tenuicollis</em></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Grazing</td><td>3.667</td><td>ns</td><td>-</td><td>-</td><td>0.62</td><td>1.25</td><td>4.661</td><td>*</td><td>-</td><td>-</td><td>0.08</td><td>0.29</td></tr><tr><td>Stones</td><td>0.021</td><td>ns</td><td>0.97</td><td>0.92</td><td>-</td><td>-</td><td>1.103</td><td>ns</td><td>0.2</td><td>0.16</td><td>-</td><td>-</td></tr><tr><td>Grazing × Stones</td><td>1.047</td><td>ns</td><td></td><td></td><td></td><td></td><td>1.103</td><td>ns</td><td></td><td></td><td></td><td></td></tr><tr><td><em>Microlestes luctuosus</em></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Grazing</td><td>5.771</td><td>*</td><td>-</td><td>-</td><td>0.67</td><td>1.33</td><td>0.314</td><td>ns</td><td>-</td><td>-</td><td>0.04</td><td>0.08</td></tr><tr><td>Stones</td><td>2.475</td><td>ns</td><td>1.25</td><td>0.75</td><td>-</td><td>-</td><td>0.314</td><td>ns</td><td>0.08</td><td>0.04</td><td>-</td><td>-</td></tr><tr><td>Grazing × Stones</td><td>0.275</td><td>ns</td><td></td><td></td><td></td><td></td><td>0.314</td><td>ns</td><td></td><td></td><td></td><td></td></tr></tbody></table>

S stones, nS no stones, G grazed, uG ungrazed

* P < 0.05; ** P < 0.01; *** P < 0.001

<figure><img src="image_5.png" /><figcaption>**Fig. 4** Mean abundances of *Asida sericea* on formerly-cultivated field subplots, ungrazed (thick line) and with stones (dash area). a and b are the results of post-hoc tests of the split-split-plot ANOVA shown in Table 2 (n = 12). S stones</figcaption></figure>

This is consistent with a study by Kruess and Tscharntke (2002) who observed a higher diversity on sites where grazing was excluded for 5 years and a slightly higher diversity on sites where grazing was excluded for 2 years.

When we focus on the response of the more abundant beetle species in the dataset, this general trend with respect to grazing is not always confirmed. While abundances of *P. sericeus* and *M. luctuosus* increase significantly without grazing, abundances of *A. sericea* are drastically reduced.

Similar variations in response of these different populations were also observed at a large scale in exclosures of 0.2–3.7 ha (Fadda et al. 2008a). This confirms that ecological processes controlling beetle communities occur within a few square meters and can thus be studied at a small scale (Kruess and Tscharntke 2002).

These differences in species response to the type of treatment shows how complex it is to elaborate a restoration plan, each species having its own ecological needs. Some ecological parameters, such as vegetation complexity, can explain the general trend of higher beetle richness in ungrazed plots. These plots offer greater resources: plant height, plant biomass and plant cover are higher than on grazed plots. The greater production of seeds in ungrazed plots can also explain this general trend, seeds being an attractive food source for many insects (Fadda et al. 2008a). These parameters contribute to a habitat complexity which usually offers a wider range of resources for different beetle species (Morris 2000). The high beetle richness in ungrazed plots can also be explained by the high grazing pressure in La Crau: 1.5 sheep/ha/year versus the advised 0.5 sheep/ha/year (Dureau and Bonnefon 1998). This disturbance regime appears to be greater than the Intermediate Disturbance (Connell 1978) which could be expected to improve species richness and diversity for the area (Fadda et al. 2008a). Thus, 4 years of grazing exclusion contributed to the creation of a habitat composed
<figure><img src="image_6.png" /><figcaption>**Fig. 5** Detrended correspondence analysis ordination [96 sampling units × 103 species (presence/absence)] of a beetle species: only species contributing more than 1% (i.e. 26 species) are visualized and b samples. See "Appendix" for species abbreviations</figcaption></figure>

of a mosaic of structurally heterogeneous vegetation patches, a type of habitat, which has been shown to support higher species richness (Dennis 2003).

## Stone cover

Stone removal in the dry grassland leads to significantly lower species richness. Stone removal modifies the habitat, and dry grassland species have fewer affinities with this new habitat, like in the case of *P. sericeus* whose abundances were lower where stones were removed. On the former cultivated field, beetle richness and abundances are only slightly greater on plots with stones. The reasons why stones have a significant effect on the dry grassland and a weaker effect on the former cultivated field may be that: (1) in the dry grassland, stones have been on the soil surface for at least 30,000 years (Colomb and Roux 1978), versus 4 years in the former cultivated field (time since stone cover restoration at the beginning of the experiment, following a 30 year period without stones which had been removed to allow cultivation) and this 4 year period is probably not sufficient to recreate the conditions necessary to the establishment of the dry grassland beetle assemblage; (2) the “stone patches” in the former cultivated field were placed too far (several dozen meters) from the dry grassland to act as refuges favoring their rapid colonization by beetles and the restoration of the beetle community. Fadda et al. (2008b) have already found an edge effect from a remnant patch of pseudo-steppe in former cultivated fields for beetle species. These preliminary results, however, suggest that the restoration of stone cover can be expected to reduce the difference between the two sites. After 4 years, the distributions of some typical dry

grassland species, such as *P. sericeus*, change according to treatment: this species tends to increase on ungrazed plots with stones. Thus, there is evidence that this combination of treatments is in the process of recreating habitat for typical dry grassland beetle species.

Like vegetation, stone cover restoration contributes to improve the quality of habitat essential to dry grassland functioning. Habitat heterogeneity is currently acknowledged as making an important contribution to the quality of a habitat by providing a greater number of ecological niches which directly favor beetle diversity (Brose 2003). The high quality of this habitat results from two principal characteristics of stones: (1) in dry ecosystems, stones create, at the soil surface, a micro-habitat with better conditions of moisture and temperature, considered to be important ecological parameters in beetle activities (Nève 1994; Tauber et al. 1998) since they offer beetles protection against climatic variations (Nève 1994). The findings of Fokuhl (2007) are similar on the positive effect of stones on ant communities; (2) stones favor perennial plants, which are dominant in the dry grassland, by allowing them to grow more roots (Blumler 1992), and also protect plants from sheep grazing (Bourrelly et al. 1983). Dry grassland plant restoration will favor colonization and persistence of beetles dependant on particular dry grassland vegetation, such as *Longitarsus obliteratoides* (Chrysomelidae) whose larvae grows on *Thymus vulgaris* roots (Doguet 1994).

After 4 years, our results show that “stone patches” are starting to act as refuges. As for their role as a source of beetles for the rest of the former cultivated field, we can only hypothesize that “stone patches” will act in the same way as other nuclei used in restoration projects, like tree trunks or wooden discs in forests. Wooden discs have been
recommended in restoration programs as refuges for fauna in forests presenting a scarcity or an absence of fallen logs (Bowie and Frampton 2004; Woldendorp and Keenan 2005) because they provide a habitat with higher moisture and ecological niches (Bowie and Frampton 2004).

The use of pitfall traps as a sampling method in this study may be controversial, in view of the size of our patches (i.e. 1.5 × 1.5 m). It is commonly felt that the home range of invertebrates may overlap the location of more than one pitfall trap if these are placed in close proximity (Digweed et al. 1995). However, Baker and Barmuta (2006) tested the effect of spatial autocorrelation and depletion on beetle communities using 75 mm diameter pitfall traps located at variant inter-pitfall trap distances (1, 5, 10, 25, 50 and 100 m). They found no evidence of spatial correlation and thus no evidence of more similar community composition when traps are in closer proximities. Our results appear to be consistent with this later study. Indeed, the significant effects of grazing and stones recorded at the scale of our patches show that we probably have no autocorrelation among pitfall traps. Moreover, even if there had been an autocorrelation between pitfall traps, it would merely have decreased the effects of grazing and stones, certainly not created them. The action range of non-attractive pitfall traps is dependent on various factors: (1) trap diameter, (2) the habitat to be sampled and (3) species-specific characteristics (body size, mobility, activity). Here we used somewhat smaller pitfall traps than in previous studies on beetle communities, studying beetle communities composed mainly of small individuals with relative low mobility and activity.

We conclude that restoration of stone cover using “stone patches” with reduction or exclusion of sheep grazing during the first years of restoration management may be the

ideal combination of treatments to successfully enhance beetle species richness and abundances on former cultivated fields, although this may be a long process considering the discrimination between the two beetle communities. Similar results have previously been observed on vegetation. Buisson (2006) also recommended stone cover restoration with grazing exclusion during the first year of restoration, as this provides good habitat quality for dry grassland plant species in former cultivated fields.

## Conclusion

In this study we show that even small stone patches dispersed randomly are efficient to increase beetle richness and abundance on former cultivated fields. Using several “stone patches” dispersed over a wide area maximizes edge effects between the ecosystem to be restored and the restored habitat patches which could be considered as nuclei in accordance with Reis et al. (2003). These nuclei may initially act as refuges, thus serving as a population source and subsequently leading to faster restoration of beetle communities. Various sizes and spatial distributions of patches should now be tested to identify the most efficient design.

**Acknowledgments** We thank the Conservatoire-Etudes des Ecosystèmes de Provence and the Eco-Musée de Crau for allowing us access to the Nature Reserve of Peau de Meau.

## Appendix

See Table 3.

<table><caption>**Table 3** List of beetle species and their abundances caught in the former cultivated field (F) and in the dry grassland (C)</caption><thead><tr><th>Families</th><th>Species name</th><th>Abbreviation</th><th>F</th><th>C</th><th>Total</th></tr></thead><tbody><tr><td rowspan="2">Anobidae</td><td><i>Dignomus</i> sp.</td><td>Disp.</td><td>0</td><td>2</td><td>2</td></tr><tr><td><i>Xyletinus</i> sp.</td><td>Xysp.</td><td>0</td><td>2</td><td>2</td></tr><tr><td rowspan="4">Anthicidae</td><td><i>Anthicus tristis</i> (W. L. E. Schmidt 1842)</td><td>Antr</td><td>2</td><td>0</td><td>2</td></tr><tr><td><i>Endomia tenuicollis</i> (Rossi 1792)</td><td>Ente</td><td>45</td><td>9</td><td>54</td></tr><tr><td><i>Hirticomus hispidus</i> (Rossi 1792)</td><td>Hihi</td><td>1</td><td>1</td><td>2</td></tr><tr><td><i>Microhoria terminata</i> (W. L. E. Schmidt 1842)</td><td>Mite</td><td>2</td><td>0</td><td>2</td></tr><tr><td>Aphodiidae</td><td><i>Pleurophorus caesus</i> (Creutzer 1796)</td><td>Plca</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Apionidae</td><td><i>Thymapion</i> sp.</td><td>Thsp.</td><td>0</td><td>1</td><td>1</td></tr><tr><td rowspan="2">Brachyceridae</td><td><i>Brachycerus muricatus</i> (Olivier 1790)</td><td>Brmu</td><td>0</td><td>2</td><td>2</td></tr><tr><td><i>Brachycerus undatus</i> (Fabricius 1798)</td><td>Brun</td><td>0</td><td>1</td><td>1</td></tr><tr><td rowspan="3">Buprestidae</td><td><i>Trachys scrobiculatus</i> (Kiesenwetter 1857)</td><td>Trsc</td><td>8</td><td>0</td><td>8</td></tr><tr><td><i>Capnodis tenebricosa</i> (Olivier 1790)</td><td>Cate</td><td>7</td><td>1</td><td>8</td></tr><tr><td><i>Sphenoptera gemmata</i> (Olivier 1790)</td><td>Spge</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Byrrhidae</td><td><i>Curimopsis maritima</i> (Marsham 1802)</td><td>Cuma</td><td>0</td><td>1</td><td>1</td></tr></tbody></table>
<table><caption>**Table 3 continued**</caption><thead><tr><th>Families</th><th>Species name</th><th>Abbreviation</th><th>F</th><th>C</th><th>Total</th></tr></thead><tbody><tr><td>Cantharidae</td><td>Rhagonycha fulva (Scopoli 1763)</td><td>Rhfu</td><td>0</td><td>1</td><td>1</td></tr><tr><td rowspan="10">Carabidae</td><td>Acinopus picipes (Olivier 1795)</td><td>Acpi</td><td>3</td><td>5</td><td>8</td></tr><tr><td>Dinodes decipens (L. Dufour 1820)</td><td>Dide</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Licinus silphoides (P. Rossi 1790)</td><td>Lisi</td><td>2</td><td>0</td><td>2</td></tr><tr><td>Poecilus sericeus (Fischer von Waldheim 1824)</td><td>Pose</td><td>36</td><td>98</td><td>134</td></tr><tr><td>Harpalus sulphuripes (Germar 1824)</td><td>Hasu</td><td>0</td><td>4</td><td>4</td></tr><tr><td>Microlestes luctuosus (Holdhaus in Apfelbeck 1904)</td><td>Milu</td><td>48</td><td>3</td><td>51</td></tr><tr><td>Harpalus distinguendus (Duftschmid 1812)</td><td>Hadi</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Cicindela maroccana Fabricius 1801</td><td>Cima</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Paradromius linearis (Olivier 1795)</td><td>Pali</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Agonum permoestum (Puel 1938)</td><td>Agpe</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Cerambycidae</td><td>Oberea erythrocephala (Schrank 1776)</td><td>Ober</td><td>2</td><td>0</td><td>2</td></tr><tr><td>Cetoniidae</td><td>Protaetia oblonga (Gory & Percheron 1833)</td><td>Prob</td><td>1</td><td>2</td><td>3</td></tr><tr><td rowspan="13">Chrysomelidae</td><td>Longitarsus succineus (Foudras 1860)</td><td>Losu</td><td>18</td><td>63</td><td>81</td></tr><tr><td>Dibolia cryptocephala (Koch 1803)</td><td>Dicr</td><td>0</td><td>2</td><td>2</td></tr><tr><td>Hispa atra (Linnaeus 1767)</td><td>Hiat</td><td>1</td><td>4</td><td>5</td></tr><tr><td>Bruchidius bimaculatus (Olivier 1795)</td><td>Brbi</td><td>6</td><td>19</td><td>25</td></tr><tr><td>Aphthona euphorbiae (Schrank 1781)</td><td>Apeu</td><td>2</td><td>25</td><td>27</td></tr><tr><td>Sphaeroderma rubidium (Graells 1858)</td><td>Spru</td><td>0</td><td>2</td><td>2</td></tr><tr><td>Psylliodes chrysocephala (Linnaeus 1758)</td><td>Psch</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Cryptocephalus fulvus (Goeze 1777)</td><td>Crfu</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Phyllotreta foudrasi (Brisout 1873)</td><td>Phfo</td><td>2</td><td>0</td><td>2</td></tr><tr><td>Chaetocnema cf. hortensis (Geoffrog 1785)</td><td>Chho</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Hypocassida subferruginea (Schrank 1776)</td><td>Hysu</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Labidostomis taxicornis (Fabricius 1792)</td><td>Lata</td><td>2</td><td>1</td><td>3</td></tr><tr><td rowspan="6">Coccinellidae</td><td>Scymnus frontalis (Fabricius 1787)</td><td>Scfr</td><td>1</td><td>1</td><td>2</td></tr><tr><td>Coccinella septempunctata (Linnaeus 1758)</td><td>Cose</td><td>2</td><td>1</td><td>3</td></tr><tr><td>Scymnus mediterraneus (Iablokoff-Khnzorian 1972)</td><td>Scme</td><td>0</td><td>5</td><td>5</td></tr><tr><td>Scymnus sp.</td><td>Scsp.</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Atomaria sp.</td><td>Atosp.</td><td>1</td><td>1</td><td>2</td></tr><tr><td>Cucujidae</td><td>Oryzaephilus surinamensis (Linnaeus 1758)</td><td>Orsu</td><td>3</td><td>1</td><td>4</td></tr><tr><td rowspan="15">Curculionidae</td><td>Pseudocleonus cinereus (Schrank 1781)</td><td>Psci</td><td>0</td><td>10</td><td>10</td></tr><tr><td>Limobius borealis (Paykull 1792)</td><td>Libo</td><td>5</td><td>1</td><td>6</td></tr><tr><td>Tychius tibialis (Boheman 1843)</td><td>Tyti</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Coniocleonus nigrosuturatus (Goeze 1777)</td><td>Coni</td><td>0</td><td>5</td><td>5</td></tr><tr><td>Otiorrhynchus vitellus (Gyllenhal 1834)</td><td>Otvi</td><td>0</td><td>2</td><td>2</td></tr><tr><td>Cycloderes guinardi (Jacquelin du Val 1852)</td><td>Cygu</td><td>1</td><td>1</td><td>2</td></tr><tr><td>Sitona discoideus (Gyllenhal 1834)</td><td>Sidi</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Trachyphloeus monspeliensis (Hustache 1932)</td><td>Trmo</td><td>0</td><td>3</td><td>3</td></tr><tr><td>Pleurodirus obesus (Abeille 1904)</td><td>Plao</td><td>0</td><td>2</td><td>2</td></tr><tr><td>Trichosirocalus horridus (Panzer 1801)</td><td>Trho</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Conorhynchus mendicus (Gyllenhal 1834)</td><td>Come</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Larinus sturnus (Schaller 1873)</td><td>Last</td><td>1</td><td>1</td><td>2</td></tr><tr><td>Polydrususformosus (Mayer 1779)</td><td>Pofo</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Cybocephalidae</td><td>Cybocephalus sp.</td><td>Cysp.</td><td>0</td><td>1</td><td>1</td></tr><tr><td rowspan="3">Dasytidae</td><td>Enicopus pilosus (Scopoli 1763)</td><td>Enpi</td><td>0</td><td>25</td><td>25</td></tr><tr><td>Dolichosoma simile (Brulle 1832)</td><td>Dosi</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Dasytes tristiculus (Mulsant & Rey 1868)</td><td>Datr</td><td>0</td><td>4</td><td>4</td></tr></tbody></table>
<table><caption>**Table 3** continued</caption><thead><tr><th>Families</th><th>Species name</th><th>Abbreviation</th><th>F</th><th>C</th><th>Total</th></tr></thead><tbody><tr><td>Dermestidae</td><td>Dermestes pardalis (Billberg 1808)</td><td>Depa</td><td>2</td><td>6</td><td>8</td></tr><tr><td>Dynastidae</td><td>Pentodon bidens (Pallas 1771)</td><td>Pebi</td><td>6</td><td>1</td><td>7</td></tr><tr><td rowspan="2">Elateridae</td><td>Agriotes sordidus (Illiger 1807)</td><td>Agso</td><td>2</td><td>0</td><td>2</td></tr><tr><td>Drasterius bimaculatus (Rossi 1790)</td><td>Drbi</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Endomychidae</td><td>Merophysia formicaria (Lucas 1852)</td><td>Mefo</td><td>14</td><td>11</td><td>25</td></tr><tr><td>Histeridae</td><td>Hister grandicollis (Illiger 1807)</td><td>Higr</td><td>1</td><td>0</td><td>1</td></tr><tr><td rowspan="2">Lathridiidae</td><td>Cholovocera formicaria (Motschulsky 1838)</td><td>Chfo</td><td>6</td><td>10</td><td>16</td></tr><tr><td>Melanophthalma fuscipennis (Mannerheim 1844)</td><td>Mefu</td><td>2</td><td>1</td><td>3</td></tr><tr><td>Leiodidae</td><td>Ptomaphagus sericatus (Chaudoir 1845)</td><td>Ptse</td><td>4</td><td>1</td><td>5</td></tr><tr><td rowspan="3">Meloidae</td><td>Mylabris variabilis (Pallas 1781)</td><td>Myva</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Hycleus duodecimpunctatus (Olivier 1811)</td><td>Hydu</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Meloe tuccius (Rossi 1792)</td><td>Metu</td><td>0</td><td>2</td><td>2</td></tr><tr><td rowspan="2">Melolonthidae</td><td>Amphimallon ruficorne (Fabricius 1775)</td><td>Amru</td><td>0</td><td>10</td><td>10</td></tr><tr><td>Rhizotrogus cicatricosus (Mulsant 1842)</td><td>Rhci</td><td>0</td><td>2</td><td>2</td></tr><tr><td>Mordellidae</td><td>Mordellidae (G. sp.)</td><td>Mosp.</td><td>0</td><td>4</td><td>4</td></tr><tr><td>Oedemeridae</td><td>Oedemera crassipes Ganglbauer 1881</td><td>Oecr</td><td>4</td><td>0</td><td>4</td></tr><tr><td>Orthoperidae</td><td>Arthrolips picea (Comolli 1837)</td><td>Arpi</td><td>7</td><td>2</td><td>9</td></tr><tr><td>Phalacridae</td><td>Phalacrus corruscus (Panzer 1797)</td><td>Phco</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Pselaphidae</td><td>Pselaphidae (G.sp.)</td><td>Pssp.</td><td>1</td><td>0</td><td>1</td></tr><tr><td rowspan="2">Scarabaeidae</td><td>Onthophagus emarginatus (Mulsant & Godart 1842)</td><td>Onem</td><td>1</td><td>2</td><td>3</td></tr><tr><td>Onthophagus furcatus (Fabricius 1781)</td><td>Onfu</td><td>0</td><td>2</td><td>2</td></tr><tr><td>Scydmaenidae</td><td>Stenichnus cf. helferi (Schaum 1841)</td><td>Sthe</td><td>1</td><td>0</td><td>1</td></tr><tr><td rowspan="15">Staphylinidae</td><td>Sepedophilus immaculatus (Stephens 1832)</td><td>Seim</td><td>4</td><td>26</td><td>30</td></tr><tr><td>Tasgius pedator (Gravenhorst 1802)</td><td>Tape</td><td>3</td><td>1</td><td>4</td></tr><tr><td>Atheta sp.1</td><td>Atsp.</td><td>1</td><td>3</td><td>4</td></tr><tr><td>Xantholinus elegans (Olivier 1795)</td><td>Xael</td><td>1</td><td>3</td><td>4</td></tr><tr><td>Ocypus obscuroaeneus schatzmayri (J. Muller 1923)</td><td>Ocob</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Ocypus ophthalmicus (Scopoli 1763)</td><td>Ocop</td><td>0</td><td>7</td><td>7</td></tr><tr><td>Quedius crassus Fairmaire 1860</td><td>Qucr</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Astenus anguinus (Baudi 1848)</td><td>Asan</td><td>2</td><td>0</td><td>2</td></tr><tr><td>Atheta sp.2</td><td>At sp</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Anotylus inustus (Gravenhorst 1806)</td><td>Anin</td><td>3</td><td>0</td><td>3</td></tr><tr><td>Tachyporus nitidulus (Fabricius 1781)</td><td>Tani</td><td>5</td><td>2</td><td>7</td></tr><tr><td>Oligota pumilio (Kiesenwetter 1858)</td><td>Olpu</td><td>3</td><td>0</td><td>3</td></tr><tr><td>Quedius semiobscurus (Marsham 1802)</td><td>Guse</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Athenini (G.sp.)</td><td>Athsp.</td><td>0</td><td>1</td><td>1</td></tr><tr><td rowspan="6">Tenebrionidae</td><td>Asida sericea (Olivier 1795)</td><td>Asse</td><td>38</td><td>226</td><td>264</td></tr><tr><td>Omophlus lepturoides (Fabricius 1787)</td><td>Omle</td><td>0</td><td>1</td><td>1</td></tr><tr><td>Bioplanes meridionalis (Mulsant 1854)</td><td>Bime</td><td>0</td><td>8</td><td>8</td></tr><tr><td>Scaurus atratus (Fabricius 1775)</td><td>Scat</td><td>0</td><td>2</td><td>2</td></tr><tr><td>Gonocephalum granulatum pusillum (Fabricius 1791)</td><td>Gogr</td><td>1</td><td>0</td><td>1</td></tr><tr><td>Total</td><td></td><td>326</td><td>661</td><td>987</td></tr></tbody></table>

The nomenclature follows the internet site "Fauna Europaea"

<figure><img src="image_7.png" /></figure>
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