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...il detritivores, making up the largest biomass of grasslands invertebrates, have a particularly important ecosystem function in mineralising organic matter [3]. They transform litter into faecal pellets which decompose rapidly. For example, terrestrial isopods utilise more than 10% of the annual litter, increasing fourfold the surface available to micro-organisms [9,12,14]. It has been observed that the specific diversity and abundance of terrestrial isopods decrease in intensive agricultural systems, with particularly marked differences between organically managed and more conventional plots [17]. Herbicide application leads both to increased mortality and lowered fecundity [17]. These products reduce available food and can change soil pH, an important parameter for isopods [22]. Landscape modifications include enlargement of fields to make them amenable to mechanisation. Such increases in plot size may entail habitat fragmentation through disruption of continuous structures (verges, hedges, lanes) which permit species to survive. Hedgerows, for example, are important for biodiversity because a large number of species use them as refuges or conduits to more optimal habitats [16]. Incr...

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...plots [17]. Herbicide application leads both to increased mortality and lowered fecundity [17]. These products reduce available food and can change soil pH, an important parameter for isopods [22]. Landscape modifications include enlargement of fields to make them amenable to mechanisation. Such increases in plot size may entail habitat fragmentation through disruption of continuous structures (verges, hedges, lanes) which permit species to survive. Hedgerows, for example, are important for biodiversity because a large number of species use them as refuges or conduits to more optimal habitats [16]. Increased isopod mortality was observed in habitats where the structure had been simplified, without refuge zones [6]. Agricultural practices in these perennial habitats will affect these arthropods. Actions such as cutting or grazhttp://france.elsevier.com/direct/ejsobi European Journal of Soil Biology 41 (2005) 109–116 * Corresponding author. E-mail address: catherine.souty@univ-poitiers.fr (C. Souty-Grosset). 1164-5563/$ - see front matter © 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.ejsobi.2005.09.009 ing lead to reduction in vegetation height and biomass and a partial or tota...

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...o faecal pellets which decompose rapidly. For example, terrestrial isopods utilise more than 10% of the annual litter, increasing fourfold the surface available to micro-organisms [9,12,14]. It has been observed that the specific diversity and abundance of terrestrial isopods decrease in intensive agricultural systems, with particularly marked differences between organically managed and more conventional plots [17]. Herbicide application leads both to increased mortality and lowered fecundity [17]. These products reduce available food and can change soil pH, an important parameter for isopods [22]. Landscape modifications include enlargement of fields to make them amenable to mechanisation. Such increases in plot size may entail habitat fragmentation through disruption of continuous structures (verges, hedges, lanes) which permit species to survive. Hedgerows, for example, are important for biodiversity because a large number of species use them as refuges or conduits to more optimal habitats [16]. Increased isopod mortality was observed in habitats where the structure had been simplified, without refuge zones [6]. Agricultural practices in these perennial habitats will affect these ar...

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...assland type, with higher species diversity or number of individuals in temporary and permanent grasslands at Fors. Hedges were important in increasing isopod diversity within plots. Assemblages reflect grassland quality with high densities and diversity of woodlice in the permanent grasslands at Avon. © 2005 Elsevier SAS. All rights reserved. Keywords: Ecology; Bioindicators; Terrestrial isopods; Agriculture; Environment 1. Introduction Soil detritivores, making up the largest biomass of grasslands invertebrates, have a particularly important ecosystem function in mineralising organic matter [3]. They transform litter into faecal pellets which decompose rapidly. For example, terrestrial isopods utilise more than 10% of the annual litter, increasing fourfold the surface available to micro-organisms [9,12,14]. It has been observed that the specific diversity and abundance of terrestrial isopods decrease in intensive agricultural systems, with particularly marked differences between organically managed and more conventional plots [17]. Herbicide application leads both to increased mortality and lowered fecundity [17]. These products reduce available food and can change soil pH, an impor...

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... structure [4]. Invertebrates respond to different levels of nitrogen in plants. In general, an increase in nitrogen levels is correlated with a decrease in biodiversity [15]. Nevertheless, whether managed by intensive pasturing or by cutting, grasslands are less disturbed than by annual cultivation, and the annual cycle of numerous arthropod species can take place because of the rarity of ploughing, which is the biggest disturbance. The generally mild climate of Atlantic Europe permits the survival of a range of isopod species which include generalists, specialists and edge-of-range rarities [23,24]. As the climax vegetation in most Atlantic habitats is woodland, natural grasslands are relatively few. Most studies of detritivores have been conducted on woodland sites, where autumnal accumulation of leaf litter is pronounced. Agriculture is increasingly dominated by pastures, but their nature has changed markedly in recent years, with a tendency towards reseeding and intensification on the better soils, and reduction of grazing or abandonment in more marginal habitats. Intensive land-use practices reduce the available litter [1] and pollution will also reduce microbial activity, and thus ...

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...elective method of grassland management compared with grazing. Removal of forage will reduce available litter for soil decomposers [18]. Grazing brings other effects in addition to those common to both methods of exploitation. Depending on the herbivores present (cattle, sheep or horses), defoliation is generally selective, with different impacts on the invertebrate fauna. Trampling by herbivores causes not only disturbance of arthropods [15] but also a reduction in soil coverage by plants [3]. Isopods are sensitive to botanical composition, both for food [19] and through vegetation structure [4]. Invertebrates respond to different levels of nitrogen in plants. In general, an increase in nitrogen levels is correlated with a decrease in biodiversity [15]. Nevertheless, whether managed by intensive pasturing or by cutting, grasslands are less disturbed than by annual cultivation, and the annual cycle of numerous arthropod species can take place because of the rarity of ploughing, which is the biggest disturbance. The generally mild climate of Atlantic Europe permits the survival of a range of isopod species which include generalists, specialists and edge-of-range rarities [23,24]. As th...

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... structure [4]. Invertebrates respond to different levels of nitrogen in plants. In general, an increase in nitrogen levels is correlated with a decrease in biodiversity [15]. Nevertheless, whether managed by intensive pasturing or by cutting, grasslands are less disturbed than by annual cultivation, and the annual cycle of numerous arthropod species can take place because of the rarity of ploughing, which is the biggest disturbance. The generally mild climate of Atlantic Europe permits the survival of a range of isopod species which include generalists, specialists and edge-of-range rarities [23,24]. As the climax vegetation in most Atlantic habitats is woodland, natural grasslands are relatively few. Most studies of detritivores have been conducted on woodland sites, where autumnal accumulation of leaf litter is pronounced. Agriculture is increasingly dominated by pastures, but their nature has changed markedly in recent years, with a tendency towards reseeding and intensification on the better soils, and reduction of grazing or abandonment in more marginal habitats. Intensive land-use practices reduce the available litter [1] and pollution will also reduce microbial activity, and thus ...

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...nd quality with high densities and diversity of woodlice in the permanent grasslands at Avon. © 2005 Elsevier SAS. All rights reserved. Keywords: Ecology; Bioindicators; Terrestrial isopods; Agriculture; Environment 1. Introduction Soil detritivores, making up the largest biomass of grasslands invertebrates, have a particularly important ecosystem function in mineralising organic matter [3]. They transform litter into faecal pellets which decompose rapidly. For example, terrestrial isopods utilise more than 10% of the annual litter, increasing fourfold the surface available to micro-organisms [9,12,14]. It has been observed that the specific diversity and abundance of terrestrial isopods decrease in intensive agricultural systems, with particularly marked differences between organically managed and more conventional plots [17]. Herbicide application leads both to increased mortality and lowered fecundity [17]. These products reduce available food and can change soil pH, an important parameter for isopods [22]. Landscape modifications include enlargement of fields to make them amenable to mechanisation. Such increases in plot size may entail habitat fragmentation through disruption of contin...

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...e community [15,3]. Cutting is a non-selective method of grassland management compared with grazing. Removal of forage will reduce available litter for soil decomposers [18]. Grazing brings other effects in addition to those common to both methods of exploitation. Depending on the herbivores present (cattle, sheep or horses), defoliation is generally selective, with different impacts on the invertebrate fauna. Trampling by herbivores causes not only disturbance of arthropods [15] but also a reduction in soil coverage by plants [3]. Isopods are sensitive to botanical composition, both for food [19] and through vegetation structure [4]. Invertebrates respond to different levels of nitrogen in plants. In general, an increase in nitrogen levels is correlated with a decrease in biodiversity [15]. Nevertheless, whether managed by intensive pasturing or by cutting, grasslands are less disturbed than by annual cultivation, and the annual cycle of numerous arthropod species can take place because of the rarity of ploughing, which is the biggest disturbance. The generally mild climate of Atlantic Europe permits the survival of a range of isopod species which include generalists, specialists and ...

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...alfalfa, were sampled at Lusignan and Fors. The structure of the landscape and its capacity to provide connections between habitats have been found to be important for isopods. The proximity of a suitable habitat for a permanent community of isopods will favour colonisation of new habitats. In our study, this influence is shown by the relationship between connections and plots, irrespective of site. Thus, hedges are the source of woodlice for grasslands. Therefore, the major species present in a plot occur also in the connections. Isopods are very influenced by variations in habitat structure [5], while the presence of some woodlouse species is linked with the degree of openness of the land, although some shrubs may be present, whereas other species are most common in closed habitats [4]. In exploited plots, vegetation structure and composition are not sufficient to explain differences between Lusignan and Fors, both in number of individuals and in species richness. Another possible factor is the mode of exploitation of the grasslands. Specific diversity and abundance of terrestrial isopods declines in intensive agricultural systems, with marked differences between plots farmed organi...

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...e much used in rye-grass plots; in five plots of this type studied at Lusignan, no woodlice were found. In four of these plots, this may also be connected to the presence of cattle, which disturb woodlice by trampling and by elimination of litter [15]. Botanical composition, quality of plants and humidity are equally linked to soil type. However, soil data available at present for these sites are insufficient to evaluate such factors. Other, more general, factors also affect isopod communities. Climatic conditions (temperature, humidity) affect the number of individuals and their reproduction [13]. Also, the dominant species may change at different times of the year: populations of P. muscorum are highest in May, those of P. scaber in August, and A. vulgare in September. Despite these variations, while relative abundance may change, total isopod biomass remains constant [5]. Different species will react differently to environmental factors: competition pheromones are known to exist in isopods and affect the relationships between species. A large number of P. scaber in a habitat has a negative effect on growth of young A. vulgare, despite the fact that these species have well separated ...

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...ailable food and can change soil pH, an important parameter for isopods [22]. Landscape modifications include enlargement of fields to make them amenable to mechanisation. Such increases in plot size may entail habitat fragmentation through disruption of continuous structures (verges, hedges, lanes) which permit species to survive. Hedgerows, for example, are important for biodiversity because a large number of species use them as refuges or conduits to more optimal habitats [16]. Increased isopod mortality was observed in habitats where the structure had been simplified, without refuge zones [6]. Agricultural practices in these perennial habitats will affect these arthropods. Actions such as cutting or grazhttp://france.elsevier.com/direct/ejsobi European Journal of Soil Biology 41 (2005) 109–116 * Corresponding author. E-mail address: catherine.souty@univ-poitiers.fr (C. Souty-Grosset). 1164-5563/$ - see front matter © 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.ejsobi.2005.09.009 ing lead to reduction in vegetation height and biomass and a partial or total destruction of litter, affecting the entire community [15,3]. Cutting is a non-selective method of grassland manageme...

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...nd quality with high densities and diversity of woodlice in the permanent grasslands at Avon. © 2005 Elsevier SAS. All rights reserved. Keywords: Ecology; Bioindicators; Terrestrial isopods; Agriculture; Environment 1. Introduction Soil detritivores, making up the largest biomass of grasslands invertebrates, have a particularly important ecosystem function in mineralising organic matter [3]. They transform litter into faecal pellets which decompose rapidly. For example, terrestrial isopods utilise more than 10% of the annual litter, increasing fourfold the surface available to micro-organisms [9,12,14]. It has been observed that the specific diversity and abundance of terrestrial isopods decrease in intensive agricultural systems, with particularly marked differences between organically managed and more conventional plots [17]. Herbicide application leads both to increased mortality and lowered fecundity [17]. These products reduce available food and can change soil pH, an important parameter for isopods [22]. Landscape modifications include enlargement of fields to make them amenable to mechanisation. Such increases in plot size may entail habitat fragmentation through disruption of contin...

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... and P. cingendus [18]. The pattern for upland grasslands is not yet clear. Further investigations are needed to see if such guilds are found elsewhere, such as in Ireland, or in other natural grassland types, such as esker grassland or salt-marsh. The nature and structure of the soil are also very important factors. For example, inputs of fertilisers will change the pH to a degree dependent on the nature of the soil. Isopods have also been shown to react to variations in pH. A. vulgare is more sensitive than P. muscorum or P. scaber to acid pH and may be used as an indicator of acidification [20]. A. vulgare is very sensitive to pH, with a preference for 7.0 [22]. This species is equally influenced by levels of soil calcium [25], but is fairly tolerant to dessication [8]. P. muscorum is less influenced by alkaline pH (preferring a level of 6.1 [22]). Conversely, it is sensitive to variations in temperature [25] and, as it cannot burrow in the soil, to low humidity [11]. O. asellus tolerates lower pH, with a preference for 5.1 [22]. The abundance of isopods decreases 10 times faster than the level of pH [22]. These dips in pH can occur following the application of fertilisers, and part...

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... found elsewhere, such as in Ireland, or in other natural grassland types, such as esker grassland or salt-marsh. The nature and structure of the soil are also very important factors. For example, inputs of fertilisers will change the pH to a degree dependent on the nature of the soil. Isopods have also been shown to react to variations in pH. A. vulgare is more sensitive than P. muscorum or P. scaber to acid pH and may be used as an indicator of acidification [20]. A. vulgare is very sensitive to pH, with a preference for 7.0 [22]. This species is equally influenced by levels of soil calcium [25], but is fairly tolerant to dessication [8]. P. muscorum is less influenced by alkaline pH (preferring a level of 6.1 [22]). Conversely, it is sensitive to variations in temperature [25] and, as it cannot burrow in the soil, to low humidity [11]. O. asellus tolerates lower pH, with a preference for 5.1 [22]. The abundance of isopods decreases 10 times faster than the level of pH [22]. These dips in pH can occur following the application of fertilisers, and particularly nitrogen [16]. Fertilisers are much used in rye-grass plots; in five plots of this type studied at Lusignan, no woodlice were ...

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...lude generalists, specialists and edge-of-range rarities [23,24]. As the climax vegetation in most Atlantic habitats is woodland, natural grasslands are relatively few. Most studies of detritivores have been conducted on woodland sites, where autumnal accumulation of leaf litter is pronounced. Agriculture is increasingly dominated by pastures, but their nature has changed markedly in recent years, with a tendency towards reseeding and intensification on the better soils, and reduction of grazing or abandonment in more marginal habitats. Intensive land-use practices reduce the available litter [1] and pollution will also reduce microbial activity, and thus both processes may reduce the invertebrate detritivore biomass, leading to a loss in biodiversity. This foundation study, conducted at sites in Western France (Poitou-Charentes), sought to extend investigations of decomposition to semi-natural and managed grasslands, as an important vegetational/land-use category in these regions. It aimed to look at the abundance and diversity of isopods as a potential guide to ecosystem activity in natural and improved grasslands, and to relate this to their importance and conservation value. This ...

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...uence of landscape structural elements on isopod community structure in fields. 2. Materials and methods The study first set out to establish relative diversity and abundance of different woodlouse species in grassland fields and in the connecting elements of the landscape in spring. Observations were made at three sites in the Poitou-Charentes Region (Fig. 1): a Natura 2000 site at Avon (Deux Sèvres), the experimental base for INRA at Lusignan (Vienne) and the Fors sector (Deux Sèvres), which is also used by Inra and Cnrs at Chizé to study the impact of agricultural practices on biodiversity [2]. At Lusignan, the nature of the soils and history of crop rotations are known. At Fors, the fields have been mapped using GIS and have been the subject of major studies since 1994, involving crop rotations, and entomological and ornithological observations [2]. Preliminary results in 2003 indicate that the three selected sites are contrasting in both soil type and agricultural grasslands. Avon is semi-natural, Lusignan has experienced intensive practices over many years, whereas Fors is in a zone of mixed farming, with a more recent history of intensification. Different types of grasslands we...

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...ent times of the year: populations of P. muscorum are highest in May, those of P. scaber in August, and A. vulgare in September. Despite these variations, while relative abundance may change, total isopod biomass remains constant [5]. Different species will react differently to environmental factors: competition pheromones are known to exist in isopods and affect the relationships between species. A large number of P. scaber in a habitat has a negative effect on growth of young A. vulgare, despite the fact that these species have well separated dates of hatching, so as to minimise competition [7]. Floristic composition is very important for arthropods, and particularly for terrestrial isopods. The Lusignan plots lacking isopods were temporary or permanent grasslands planted with rye-grass or cocksfoot grass, while woodlice were encountered in grasslands with a mixture of grasses and leguminous herbs. A. vulgare feeds preferentially on dicotyledonous plants such as legumes, rather than monocotyledonous (e.g. grasses) [19]. The age and quality of plants are also important in habitat choice [15]. In our study plots isopods were more numerous in grasslands at least 3 years old than in you...

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...other natural grassland types, such as esker grassland or salt-marsh. The nature and structure of the soil are also very important factors. For example, inputs of fertilisers will change the pH to a degree dependent on the nature of the soil. Isopods have also been shown to react to variations in pH. A. vulgare is more sensitive than P. muscorum or P. scaber to acid pH and may be used as an indicator of acidification [20]. A. vulgare is very sensitive to pH, with a preference for 7.0 [22]. This species is equally influenced by levels of soil calcium [25], but is fairly tolerant to dessication [8]. P. muscorum is less influenced by alkaline pH (preferring a level of 6.1 [22]). Conversely, it is sensitive to variations in temperature [25] and, as it cannot burrow in the soil, to low humidity [11]. O. asellus tolerates lower pH, with a preference for 5.1 [22]. The abundance of isopods decreases 10 times faster than the level of pH [22]. These dips in pH can occur following the application of fertilisers, and particularly nitrogen [16]. Fertilisers are much used in rye-grass plots; in five plots of this type studied at Lusignan, no woodlice were found. In four of these plots, this may als...

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...hed each plot and its borders and connections, and woodlouse were hand collected over a total cumulated period of about 1 hour. At the three sites hand collecting was made in April. Except in Avon, collecting was carried out separately in connections, borders and plots. During collecting, the type of soil (sandy, clayey), the quantity of stones, the degree of cloudiness and the plant species present were noted. The proportion of bare soil and height of vegetation were also recorded for each sub-plot, as were any human activities (cutting, silage, fertilisation etc.). As in Hornung and Warburg [10], the Shannon–Wiener forC. Souty-Grosset et al. / European Journal of Soil Biology 41 (2005) 109–116110 mula was used for species diversity H ′ − ∑ Si1 niN × Ln niN ; ni meaning the number of individuals of the species i in the sample of N individuals. 3. Results Seven woodlouse species belonging to four families were encountered in the grasslands examined. Clear differences were seen between study sites both for species diversity and abundance (Tables 2 and 3), and for the different types of grasslands (Fig. 2). The species were differentially represented at the three sites. Oniscus as...

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...bject of major studies since 1994, involving crop rotations, and entomological and ornithological observations [2]. Preliminary results in 2003 indicate that the three selected sites are contrasting in both soil type and agricultural grasslands. Avon is semi-natural, Lusignan has experienced intensive practices over many years, whereas Fors is in a zone of mixed farming, with a more recent history of intensification. Different types of grasslands were studied (Table 1); artificial, temporary and permanent as defined in agricultural statistics by the Ministry of Agriculture, Fisheries and Food [11]. ‘Artificial grasslands’ are those established for less than 5 years and sown exclusively with leguminous fodder crops (alfalfa, clover). Temporary grasslands are similarly less than 5 years old sown with fodder grasses, pure or mixed with leguminous plants. Permanent grasslands are composed of hardy herbaceous fodder plants; they comprise both fields sown for a long time (6–10 years) and natural grasslands, not reseeded. At both farmland sites plots were chosen using a map of crop types for 2003 in conjunction with their morphological characteristics and accessibility. Each plot was subdivid...

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...nd quality with high densities and diversity of woodlice in the permanent grasslands at Avon. © 2005 Elsevier SAS. All rights reserved. Keywords: Ecology; Bioindicators; Terrestrial isopods; Agriculture; Environment 1. Introduction Soil detritivores, making up the largest biomass of grasslands invertebrates, have a particularly important ecosystem function in mineralising organic matter [3]. They transform litter into faecal pellets which decompose rapidly. For example, terrestrial isopods utilise more than 10% of the annual litter, increasing fourfold the surface available to micro-organisms [9,12,14]. It has been observed that the specific diversity and abundance of terrestrial isopods decrease in intensive agricultural systems, with particularly marked differences between organically managed and more conventional plots [17]. Herbicide application leads both to increased mortality and lowered fecundity [17]. These products reduce available food and can change soil pH, an important parameter for isopods [22]. Landscape modifications include enlargement of fields to make them amenable to mechanisation. Such increases in plot size may entail habitat fragmentation through disruption of contin...

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...ere the structure had been simplified, without refuge zones [6]. Agricultural practices in these perennial habitats will affect these arthropods. Actions such as cutting or grazhttp://france.elsevier.com/direct/ejsobi European Journal of Soil Biology 41 (2005) 109–116 * Corresponding author. E-mail address: catherine.souty@univ-poitiers.fr (C. Souty-Grosset). 1164-5563/$ - see front matter © 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.ejsobi.2005.09.009 ing lead to reduction in vegetation height and biomass and a partial or total destruction of litter, affecting the entire community [15,3]. Cutting is a non-selective method of grassland management compared with grazing. Removal of forage will reduce available litter for soil decomposers [18]. Grazing brings other effects in addition to those common to both methods of exploitation. Depending on the herbivores present (cattle, sheep or horses), defoliation is generally selective, with different impacts on the invertebrate fauna. Trampling by herbivores causes not only disturbance of arthropods [15] but also a reduction in soil coverage by plants [3]. Isopods are sensitive to botanical composition, both for food [19] and through v...

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...h as cutting or grazhttp://france.elsevier.com/direct/ejsobi European Journal of Soil Biology 41 (2005) 109–116 * Corresponding author. E-mail address: catherine.souty@univ-poitiers.fr (C. Souty-Grosset). 1164-5563/$ - see front matter © 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.ejsobi.2005.09.009 ing lead to reduction in vegetation height and biomass and a partial or total destruction of litter, affecting the entire community [15,3]. Cutting is a non-selective method of grassland management compared with grazing. Removal of forage will reduce available litter for soil decomposers [18]. Grazing brings other effects in addition to those common to both methods of exploitation. Depending on the herbivores present (cattle, sheep or horses), defoliation is generally selective, with different impacts on the invertebrate fauna. Trampling by herbivores causes not only disturbance of arthropods [15] but also a reduction in soil coverage by plants [3]. Isopods are sensitive to botanical composition, both for food [19] and through vegetation structure [4]. Invertebrates respond to different levels of nitrogen in plants. In general, an increase in nitrogen levels is correlated with a d...

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...ods than a 1- C. Souty-Grosset et al. / European Journal of Soil Biology 41 (2005) 109–116 115 year plot. Any cultivation that took place in the preceding year is also important for isopod populations. These may be in a colonisation phase, a phenomenon that will require a longer study to confirm. Further, isopods, being crustaceans, need a relatively damp environment and leguminous plants maintain soil humidity better than do grasses. Isopod diversity depends both on plant assemblages and on habitat humidity. Soil coverage will also help to retain moisture and to maintain a favourable habitat [21]. The alfalfa plots at Fors and cocksfoot at Lusignan had more than 10% bare soil. Exposed rocks would heat up in the sun, a factor that would tend to exclude woodlice. However, in Israel, as in other arid countries, terrestrial isopods were preferentially encountered under stones [10]. In conclusion, our results, from this preliminary study, suggest that certain woodlice species may be characteristic of various Atlantic grasslands, possibly due to their different habitat preferences (pH, humidity etc.). These species may be useful as easily identified bioindicators of undisturbed, semi-natura...