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Impact of apple orchard management strategies on earthworm (Allolobophora chlorotica) energy reserves
Soil Biology & Biochemistry 100 (2016) 252e254
Contents lists available at ScienceDirect
Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio
Short communication
Impact of apple orchard management strategies on earthworm (Allolobophora chlorotica) energy reserves verine Suchail b, Magali Rault b, Catherine Mouneyrac c, Nicolas Givaudan a, Se Yvan Capowiez d, * a
Agrolab Danmark A/S, Rojleskovej 18, DK-5500 Middelfart, Denmark ^le Agrosciences, 301 rue Baruch de Spinoza, BP 21239, Institut M editerran een de Biodiversit e et d’Ecologie marine et continentale, IMBE UAPV AMU IRD, Po 84916 Avignon, France c Universit e Catholique de l’Ouest, 3 Place Andr e Leroy, 49100 Angers, France d INRA Avignon, Site Agroparc, 84914 Avignon Cedex 09, France b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 April 2016 Received in revised form 23 June 2016 Accepted 27 June 2016 Available online 2 July 2016
To assess the effects of agricultural management strategies on earthworm energy reserves (glycogen and lipids), 16 apple orchards under different strategies (organic, Integrated Pest Management (IPM), conventional and abandoned) were selected. Soil samples and 10 adults of the most common earthworm species (Allolobophora chlorotica) were sampled in each orchard. The glycogen and lipid concentrations in the earthworms did not correlate with any soil characteristics and no significant differences in earthworm weight were observed between strategies. However, significantly lower glycogen and lipid concentrations were found in earthworms inhabiting conventional orchards, with a decrease of 45 and 63% compared to organic and abandoned orchards respectively. Earthworms from IPM orchards had intermediate values. This suggests that pesticide usage leads to the observed decrease of energy reserves in A. chlorotica. Thus the reduced insecticide use in IPM compared to conventional strategies, albeit significant, appears to be too small to result in pronounced effects on energy reserves in this earthworm species. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Lipids Glycogen Pesticides Organic IPM
Earthworms are important drivers of the physical, chemical and biological properties of the soil. Due to their burrowing activities, they are recognized as ‘soil ecosystem engineers’ (Jones et al., 1994). Often representing the largest biota biomass in soil, they are however exposed to agricultural practices which have a strong impact on their abundance and biodiversity (Pelosi et al., 2013). In agricultural fields, the application of pesticides is one of the most deleterious practices for earthworm communities (Paoletti et al., 1998) . Depending on ecological type and species, exposure to pesticides can negatively influence earthworm survival, biomass, physiology and behaviour (Pelosi et al., 2014). Furthermore, as earthworms have limited dispersal abilities (Christensen and Mather, 2004), they are exposed to a large number of applied substances and residues in the soil. To cope with these residues and limit their negative effects at the sub-individual level, earthworms may either modify their activities (avoidance) to decrease their
* Corresponding author. E-mail address: [email protected] (Y. Capowiez). http://dx.doi.org/10.1016/j.soilbio.2016.06.031 0038-0717/© 2016 Elsevier Ltd. All rights reserved.
exposure or develop tolerance mechanisms, such as limiting uptake, biotransformation, or increased excretion (Givaudan et al., 2014). Theoretically, it could result in an energetic cost if, for example, avoidance decreases the foraging strategy and efficiency or if tolerance mechanisms require reallocation of reserves (Holloway et al., 1990; Durou et al., 2005). To test this assumption for earthworms, we chose apple orchards under different management strategies. Indeed apple orchards are among the most treated crops in the European Union (Eurostat, 2007) and we can assume earthworms living in these orchards will potentially face a large number and diversity of pesticides. Then our aim was to determine whether earthworm energy reserves (lipids and glycogen) were affected by pesticide usage or/ and by soil characteristics. Sixteen apple orchards were selected in a circular region of about 20 km diameter South of Avignon (South-East of France). Four of these orchards have been abandoned for at least 10 years and were chosen as controls. The 12 remaining orchards were all commercial but with different management strategies: four
N. Givaudan et al. / Soil Biology & Biochemistry 100 (2016) 252e254
followed the organic guidelines, four under Integrated Pest Management (IPM) and four under conventional protection. Synthetic pesticides are completely banned in organic orchards but ‘natural’ insecticides and mineral fungicides are authorized. In IPM orchards, pheromone dispensers, which cause sexual confusion, are used to target the apple main pest, Cydia pomonella and thus lower levels of insecticides are expected to be applied than in conventional ones. In all orchards, the most frequent earthworm species is Allolobophora chlorotica (Denoyelle et al., 2007), an endogeic species typically found in pastures and thus inhabiting orchards since they all have a grassy ground-cover. In April of 2008, 10 A. chlorotica adults were sampled in each orchard. For this, at least 10 random locations were chosen in each orchard to be the furthest possible from the borders and each location was separated from each other by at least 10 m. At each location, small pits (20 20 20 cm) were excavated and the soil was hand sorted to retrieve earthworms. Only one A. chlorotica adult was selected in each pit. Topsoil (0e20 cm) was also sampled in each pit and mixed for chemical characterisation (texture, pH, organic matter, N and P concentration). Treatment calendars for each orchard were collated and used to compute Treatment Frequency Indices (TFI, i.e. the number of pesticides applied at normal application rate over the year; Jørgensen, 1999) for the different classes of pesticides used. These included: mineral fungicides, ‘natural’ insecticides, synthetic fungicides and insecticides. These TFI for each management strategy were compared using Kruskal-Wallis tests. The collected earthworms were washed with water to eliminate soil, weighed and kept at 80 C until use. Glycogen and lipids were quantified in the whole soft tissues of individual earthworms. After homogenisation in liquid nitrogen, the powder obtained was homogenized further in 1.5 mL citrate buffer pH 5.0 for glycogen and lipid analysis. Total lipids were determined by a sulphophosphovanillin reaction according to the method of Frings et al. (1972). Glycogen was quantified using an enzymatic hydrolysis by amyloglucosidase according to Carr and Neff (1984) and the amount of glycogen was corrected for the glucose content in samples that were not incubated with amyloglucosidase. Olive oil and oyster glycogen (Sigma, Type III) were used as standards for each method, respectively. The values of glycogen and lipids concentrations (mg g1 of fresh earthworm weight) and earthworm weight were compared between management strategies using a mixed-effects linear model with orchard as a random factor (R package ‘nlme’; Pinheiro et al., 2016) followed by Tukey pairwise comparisons (R package ‘multcomp’; Horton et al., 2008). After log-transformation of the values, normality and homoscedasticity were reached (tested using Levene and Bartlett test respectively). The relationships between glycogen and lipids concentrations and the soil characteristics were studied using linear correlations. All computations were carried out in R version 2.14 (R Development Team, 2010). Despite a limited number of orchards in each management strategy, significant differences were observed regarding pesticide usage (Fig. 1). Pest control in organic orchards is based on a greater use of mineral fungicides (copper and sulphur) and natural insecticides (granulovirus, mineral oils and spinosad). In contrast, non-organic orchards mainly used synthetic pesticides. As expected, significantly lower levels of insecticides were applied in IPM than in conventional orchards (p ¼ 0.02). It is worth noting however that no significant differences were observed for the total TFI. The glycogen and lipid concentrations in earthworms showed significant differences with significantly higher values in abandoned and organic orchards compared to conventional orchards. Values for IPM orchards were intermediate and not significantly different from the other two management strategies (Fig. 2). No significant differences in soil characteristics were observed
253
Fig. 1. Mean Treatment Frequency Index values, for different kinds of pesticides, in the different management strategies applied in the apple orchards. Bars bearing different letters are different at the 5% level (Kruskal Wallis test). Each type of pesticides was tested separately (absence of letters means no significant difference).
between management strategies (Table 1), nor were there any significant linear relationships between glycogen or lipid concentrations and soil characteristics (all p-values > 0.1 for lipids and >0.3 for glycogen). Furthermore, despite high levels of variability for A. chlorotica fresh weight between orchards (ranging from 0.34 to 0.50 g), no significant difference was found between orchard management strategies (p ¼ 0.21). Energy budget is a balance between energy consumption (for maintenance and reproduction) and acquisition (through food). Available energy resources, estimated by measuring levels of the main storage compounds, can thus reflect energy demands, associated with life histories and environmental conditions that will promote or limit energy gain (Calow, 1991). We assumed that exposure to pesticides, depending on their toxicity (insecticides being the most relevant due to their higher toxicity) would have a negative influence. So far, this relationship was only observed for earthworms living in sites polluted with heavy metals (Holmstrup et al., 2011). However, in a laboratory experiment using 31 soils from various origins and with varying Cd content, Beaumelle et al. (2014) found that the Allolobophora caliginosa energy budget, especially lipid concentrations, was mostly significantly influenced by soil texture. In the present study we did not find significant relationships between soil characteristics and glycogen or lipid concentrations in A. chlorotica. This may be explained by the fact that this regional study was carried out on similar soil types (i.e. alluviosols from the Durance valley) and thus soil characteristics were not different between management strategies. Thus, in the studied apple orchards, the main factor governing energy budget in A. chlorotica was management strategy. For both glycogen and lipid concentrations a decreasing trend was observed from abandoned, to organic, IPM and conventional orchards. However, the only significant differences were observed between abandoned and organic versus conventional orchards. This suggests that insecticide use, quantitatively and qualitatively, decreases A. chlorotica energy reserves. Indeed, most of the insecticides applied in organic orchards are granulosis virus without known toxicity to non-target organisms (European Food Safety Authority, 2012) whereas those applied in non-organic orchards were, for the most part, neurotoxic (especially organophosphates). Although a significant reduction in synthetic insecticide use was observed between IPM and conventional orchards, this decrease was too small to result in significant differences in the energy budget of the earthworms inhabiting these
254
N. Givaudan et al. / Soil Biology & Biochemistry 100 (2016) 252e254
Fig. 2. Boxplots for lipids and glycogen concentrations in earthworms depending on the management strategies applied in the apple orchards (‘Conv.’ and ‘Aband.’ means conventional and abandoned respectively). Box-and-whisker-plots display median, minima, maxima, upper and lower quartiles. Boxplots bearing different letters are different at the 5% level (the statistical test was applied on log-transformed values).
Table 1 Means values (and SE) for the main soil physical and chemical characteristics for each management strategy.
Abandoned (n ¼ 4) Organic (n ¼ 4) IPM (n ¼ 4) Conventional (n ¼ 4)
Clay (%)
Silt (%)
Sand (%)
pH (Water)
OM (%)
N (g kg1)
P-Olsen (g kg1)
22.8 (0.8) 34.2 (1.4) 29.9 (2.5) 29.2 (3.0)
48.5 (2.4) 53.2 (2.1) 45.0 (4.0) 53.7 (1.5)
28.7 (2.5) 12.6 (1.7) 25.1 (7.7) 17.1 (2.2)
8.20 (0.08) 8.29 (0.09) 8.40 (0.11) 8.16 (0.06)
4.4 (0.52) 4.1 (1.88) 5.3 (0.93) 4.1 (1.43)
2.22 (0.27) 2.32 (0.95) 3.36 (0.69) 1.76 (0.27)
0.025 (0.008) 0.058 (0.021) 0.158 (0.025) 0.101 (0.038)
orchards. Our results could be useful for validating mechanistic models based on energy budgets aiming to simulate the effects of different agricultural practices on earthworm populations (Johnston et al., 2015). References Beaumelle, L., Lamy, I., Cheviron, N., Hedde, M., 2014. Is there a relationship between earthworm energy reserves and metal availability after exposure to field-contaminated soils? Environ. Pollut. 191, 182e189. Calow, P., 1991. Physiological costs of combating chemical toxicants: ecological implications. Comp. Biochem. Physiol. 100C, 3e6. Carr, R.S., Neff, J.M., 1984. Quantitative semi-automated enzymatic assay for tissue glycogen. Comp. Biochem. Physiol. 77B, 447e449. Christensen, O.M., Mather, J.G., 2004. Pesticide-induced surface migration by lumbricid earthworms in grassland: life-stage and species differences. Ecotoxicol. Environ. Saf. 57, 89e99. Denoyelle, R., Rault, M., Mazzia, C., Mascle, O., Capowiez, Y., 2007. Cholinesterase activity of Allolobophora chlorotica earthworms as a biomarker of exposure to pesticides in apple orchards under different management strategies. Environ. Toxicol. Chem. 26, 2644e2649. Durou, C., Mouneyrac, C., Amiard-Triquet, C., 2005. Tolerance to metals and assessment of energy reserves in the polychaete Nereis diversicolor in clean and
contaminated estuaries. Environ. Toxicol. 20, 23e31. European Food Safety Authority, 2012. Conclusion on the peer review of the pesticide risk assessment of the active substance Cydia pomonella granulovirus (CpGV). EFSA J. 10 (4), 2655. http://dx.doi.org/10.2903/j.efsa. 2012. 2655. Eurostat, European Commission, 2007. The Use of Plant Protection Products in the European Union: Data 1992-2003. Office for Official Publications of the European Communities, Luxembourg. Frings, C.S., Fendley, T.W., Dunn, R.T., Queen, C.A., 1972. Improved determination of total serum lipids by the sulpho-phospho-vanilin reaction. Clin. Chem. 18, 673e674. Givaudan, N., Wiegand, C., Le Bot, B., Renault, D., Pallois, F., Llopis, S., Binet, F., 2014. Acclimation of earthworms to chemicals in anthropogenic landscapes, physiological mechanisms and soil ecological implications. Soil Biol. Biochem. 73, 49e58. Holloway, G.J., Sibly, R.M., Povey, S.R., 1990. Evolution in toxin-stressed environments. Funct. Ecol. 4, 289e294. Holmstrup, M., Sorensen, J.G., Overgaard, J., Bayley, M., Bindesbol, A.-M., Slotsbo, S., Fisker, K.V., Maraldo, K., Wagner, D., Labouriau, R., Asmund, G., 2011. Body metal concentrations and glycogen reserves in earthworms (Dendrobaena octaedra) from contaminated and uncontaminated forest soils. Environ. Pollut. 159, 190e197. Horton, T., Bretz, F., Westfall, P., 2008. Simultaneous inference in general parametric models. Biom. J. 50, 346e363. Johnston, A.S.A., Sibly, R.M., Hodson, M.E., Alvarez, T., Thorbek, P., 2015. Effects of agricultural management practices on earthworm populations and crop yield: validation and application of a mechanistic modelling approach. J. Appl. Ecol. 52, 1334e1342. Jones, C.G., Lawton, J.H., Shachak, M., 1994. Organisms as ecosystem engineers. Oikos 69, 373e386. Jørgensen, L.N., 1999. Denmark’s action plans for pesticides: status and role of research. Nord. Jordbrugsforsk. 81, 201e202. Paoletti, M., Sommagio, D., Favretto, M., Petruzelli, G., Pezzarossa, B., Barbafieri, M., 1998. Earthworms as useful indicators of agroecosystem sustainability in orchards and vineyards with different inputs. Appl. Soil Ecol. 10, 137e150. Pelosi, C., Barot, S., Capowiez, Y., Hedde, M., Vandenbulcke, F., 2014. Pesticides and earthworms: a review. Agron. Sustain. Dev. 34, 199e228. Pelosi, C., Toutous, L., Chiron, F., Dubs, F., Hedde, M., Muratet, A., Ponge, J.-F., Salmon, S., Makowski, D., 2013. Reduction of pesticide use can increase earthworm populations in wheat crops in a European temperate region. Agric. Ecosyst. Environ. 181, 223e230. Pinheiro, J., Bates, D., DebRoy, S., Sarkar, D., R Core Team, 2016. Nlme: Linear and Nonlinear Mixed Effects Models. R Package Version 3.1-128. R Development Core Team, 2010. R: a Language and Environment for Statistical Computing. R Foundation for Statistical Computing.
Contents lists available at ScienceDirect
Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio
Short communication
Impact of apple orchard management strategies on earthworm (Allolobophora chlorotica) energy reserves verine Suchail b, Magali Rault b, Catherine Mouneyrac c, Nicolas Givaudan a, Se Yvan Capowiez d, * a
Agrolab Danmark A/S, Rojleskovej 18, DK-5500 Middelfart, Denmark ^le Agrosciences, 301 rue Baruch de Spinoza, BP 21239, Institut M editerran een de Biodiversit e et d’Ecologie marine et continentale, IMBE UAPV AMU IRD, Po 84916 Avignon, France c Universit e Catholique de l’Ouest, 3 Place Andr e Leroy, 49100 Angers, France d INRA Avignon, Site Agroparc, 84914 Avignon Cedex 09, France b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 April 2016 Received in revised form 23 June 2016 Accepted 27 June 2016 Available online 2 July 2016
To assess the effects of agricultural management strategies on earthworm energy reserves (glycogen and lipids), 16 apple orchards under different strategies (organic, Integrated Pest Management (IPM), conventional and abandoned) were selected. Soil samples and 10 adults of the most common earthworm species (Allolobophora chlorotica) were sampled in each orchard. The glycogen and lipid concentrations in the earthworms did not correlate with any soil characteristics and no significant differences in earthworm weight were observed between strategies. However, significantly lower glycogen and lipid concentrations were found in earthworms inhabiting conventional orchards, with a decrease of 45 and 63% compared to organic and abandoned orchards respectively. Earthworms from IPM orchards had intermediate values. This suggests that pesticide usage leads to the observed decrease of energy reserves in A. chlorotica. Thus the reduced insecticide use in IPM compared to conventional strategies, albeit significant, appears to be too small to result in pronounced effects on energy reserves in this earthworm species. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Lipids Glycogen Pesticides Organic IPM
Earthworms are important drivers of the physical, chemical and biological properties of the soil. Due to their burrowing activities, they are recognized as ‘soil ecosystem engineers’ (Jones et al., 1994). Often representing the largest biota biomass in soil, they are however exposed to agricultural practices which have a strong impact on their abundance and biodiversity (Pelosi et al., 2013). In agricultural fields, the application of pesticides is one of the most deleterious practices for earthworm communities (Paoletti et al., 1998) . Depending on ecological type and species, exposure to pesticides can negatively influence earthworm survival, biomass, physiology and behaviour (Pelosi et al., 2014). Furthermore, as earthworms have limited dispersal abilities (Christensen and Mather, 2004), they are exposed to a large number of applied substances and residues in the soil. To cope with these residues and limit their negative effects at the sub-individual level, earthworms may either modify their activities (avoidance) to decrease their
* Corresponding author. E-mail address: [email protected] (Y. Capowiez). http://dx.doi.org/10.1016/j.soilbio.2016.06.031 0038-0717/© 2016 Elsevier Ltd. All rights reserved.
exposure or develop tolerance mechanisms, such as limiting uptake, biotransformation, or increased excretion (Givaudan et al., 2014). Theoretically, it could result in an energetic cost if, for example, avoidance decreases the foraging strategy and efficiency or if tolerance mechanisms require reallocation of reserves (Holloway et al., 1990; Durou et al., 2005). To test this assumption for earthworms, we chose apple orchards under different management strategies. Indeed apple orchards are among the most treated crops in the European Union (Eurostat, 2007) and we can assume earthworms living in these orchards will potentially face a large number and diversity of pesticides. Then our aim was to determine whether earthworm energy reserves (lipids and glycogen) were affected by pesticide usage or/ and by soil characteristics. Sixteen apple orchards were selected in a circular region of about 20 km diameter South of Avignon (South-East of France). Four of these orchards have been abandoned for at least 10 years and were chosen as controls. The 12 remaining orchards were all commercial but with different management strategies: four
N. Givaudan et al. / Soil Biology & Biochemistry 100 (2016) 252e254
followed the organic guidelines, four under Integrated Pest Management (IPM) and four under conventional protection. Synthetic pesticides are completely banned in organic orchards but ‘natural’ insecticides and mineral fungicides are authorized. In IPM orchards, pheromone dispensers, which cause sexual confusion, are used to target the apple main pest, Cydia pomonella and thus lower levels of insecticides are expected to be applied than in conventional ones. In all orchards, the most frequent earthworm species is Allolobophora chlorotica (Denoyelle et al., 2007), an endogeic species typically found in pastures and thus inhabiting orchards since they all have a grassy ground-cover. In April of 2008, 10 A. chlorotica adults were sampled in each orchard. For this, at least 10 random locations were chosen in each orchard to be the furthest possible from the borders and each location was separated from each other by at least 10 m. At each location, small pits (20 20 20 cm) were excavated and the soil was hand sorted to retrieve earthworms. Only one A. chlorotica adult was selected in each pit. Topsoil (0e20 cm) was also sampled in each pit and mixed for chemical characterisation (texture, pH, organic matter, N and P concentration). Treatment calendars for each orchard were collated and used to compute Treatment Frequency Indices (TFI, i.e. the number of pesticides applied at normal application rate over the year; Jørgensen, 1999) for the different classes of pesticides used. These included: mineral fungicides, ‘natural’ insecticides, synthetic fungicides and insecticides. These TFI for each management strategy were compared using Kruskal-Wallis tests. The collected earthworms were washed with water to eliminate soil, weighed and kept at 80 C until use. Glycogen and lipids were quantified in the whole soft tissues of individual earthworms. After homogenisation in liquid nitrogen, the powder obtained was homogenized further in 1.5 mL citrate buffer pH 5.0 for glycogen and lipid analysis. Total lipids were determined by a sulphophosphovanillin reaction according to the method of Frings et al. (1972). Glycogen was quantified using an enzymatic hydrolysis by amyloglucosidase according to Carr and Neff (1984) and the amount of glycogen was corrected for the glucose content in samples that were not incubated with amyloglucosidase. Olive oil and oyster glycogen (Sigma, Type III) were used as standards for each method, respectively. The values of glycogen and lipids concentrations (mg g1 of fresh earthworm weight) and earthworm weight were compared between management strategies using a mixed-effects linear model with orchard as a random factor (R package ‘nlme’; Pinheiro et al., 2016) followed by Tukey pairwise comparisons (R package ‘multcomp’; Horton et al., 2008). After log-transformation of the values, normality and homoscedasticity were reached (tested using Levene and Bartlett test respectively). The relationships between glycogen and lipids concentrations and the soil characteristics were studied using linear correlations. All computations were carried out in R version 2.14 (R Development Team, 2010). Despite a limited number of orchards in each management strategy, significant differences were observed regarding pesticide usage (Fig. 1). Pest control in organic orchards is based on a greater use of mineral fungicides (copper and sulphur) and natural insecticides (granulovirus, mineral oils and spinosad). In contrast, non-organic orchards mainly used synthetic pesticides. As expected, significantly lower levels of insecticides were applied in IPM than in conventional orchards (p ¼ 0.02). It is worth noting however that no significant differences were observed for the total TFI. The glycogen and lipid concentrations in earthworms showed significant differences with significantly higher values in abandoned and organic orchards compared to conventional orchards. Values for IPM orchards were intermediate and not significantly different from the other two management strategies (Fig. 2). No significant differences in soil characteristics were observed
253
Fig. 1. Mean Treatment Frequency Index values, for different kinds of pesticides, in the different management strategies applied in the apple orchards. Bars bearing different letters are different at the 5% level (Kruskal Wallis test). Each type of pesticides was tested separately (absence of letters means no significant difference).
between management strategies (Table 1), nor were there any significant linear relationships between glycogen or lipid concentrations and soil characteristics (all p-values > 0.1 for lipids and >0.3 for glycogen). Furthermore, despite high levels of variability for A. chlorotica fresh weight between orchards (ranging from 0.34 to 0.50 g), no significant difference was found between orchard management strategies (p ¼ 0.21). Energy budget is a balance between energy consumption (for maintenance and reproduction) and acquisition (through food). Available energy resources, estimated by measuring levels of the main storage compounds, can thus reflect energy demands, associated with life histories and environmental conditions that will promote or limit energy gain (Calow, 1991). We assumed that exposure to pesticides, depending on their toxicity (insecticides being the most relevant due to their higher toxicity) would have a negative influence. So far, this relationship was only observed for earthworms living in sites polluted with heavy metals (Holmstrup et al., 2011). However, in a laboratory experiment using 31 soils from various origins and with varying Cd content, Beaumelle et al. (2014) found that the Allolobophora caliginosa energy budget, especially lipid concentrations, was mostly significantly influenced by soil texture. In the present study we did not find significant relationships between soil characteristics and glycogen or lipid concentrations in A. chlorotica. This may be explained by the fact that this regional study was carried out on similar soil types (i.e. alluviosols from the Durance valley) and thus soil characteristics were not different between management strategies. Thus, in the studied apple orchards, the main factor governing energy budget in A. chlorotica was management strategy. For both glycogen and lipid concentrations a decreasing trend was observed from abandoned, to organic, IPM and conventional orchards. However, the only significant differences were observed between abandoned and organic versus conventional orchards. This suggests that insecticide use, quantitatively and qualitatively, decreases A. chlorotica energy reserves. Indeed, most of the insecticides applied in organic orchards are granulosis virus without known toxicity to non-target organisms (European Food Safety Authority, 2012) whereas those applied in non-organic orchards were, for the most part, neurotoxic (especially organophosphates). Although a significant reduction in synthetic insecticide use was observed between IPM and conventional orchards, this decrease was too small to result in significant differences in the energy budget of the earthworms inhabiting these
254
N. Givaudan et al. / Soil Biology & Biochemistry 100 (2016) 252e254
Fig. 2. Boxplots for lipids and glycogen concentrations in earthworms depending on the management strategies applied in the apple orchards (‘Conv.’ and ‘Aband.’ means conventional and abandoned respectively). Box-and-whisker-plots display median, minima, maxima, upper and lower quartiles. Boxplots bearing different letters are different at the 5% level (the statistical test was applied on log-transformed values).
Table 1 Means values (and SE) for the main soil physical and chemical characteristics for each management strategy.
Abandoned (n ¼ 4) Organic (n ¼ 4) IPM (n ¼ 4) Conventional (n ¼ 4)
Clay (%)
Silt (%)
Sand (%)
pH (Water)
OM (%)
N (g kg1)
P-Olsen (g kg1)
22.8 (0.8) 34.2 (1.4) 29.9 (2.5) 29.2 (3.0)
48.5 (2.4) 53.2 (2.1) 45.0 (4.0) 53.7 (1.5)
28.7 (2.5) 12.6 (1.7) 25.1 (7.7) 17.1 (2.2)
8.20 (0.08) 8.29 (0.09) 8.40 (0.11) 8.16 (0.06)
4.4 (0.52) 4.1 (1.88) 5.3 (0.93) 4.1 (1.43)
2.22 (0.27) 2.32 (0.95) 3.36 (0.69) 1.76 (0.27)
0.025 (0.008) 0.058 (0.021) 0.158 (0.025) 0.101 (0.038)
orchards. Our results could be useful for validating mechanistic models based on energy budgets aiming to simulate the effects of different agricultural practices on earthworm populations (Johnston et al., 2015). References Beaumelle, L., Lamy, I., Cheviron, N., Hedde, M., 2014. Is there a relationship between earthworm energy reserves and metal availability after exposure to field-contaminated soils? Environ. Pollut. 191, 182e189. Calow, P., 1991. Physiological costs of combating chemical toxicants: ecological implications. Comp. Biochem. Physiol. 100C, 3e6. Carr, R.S., Neff, J.M., 1984. Quantitative semi-automated enzymatic assay for tissue glycogen. Comp. Biochem. Physiol. 77B, 447e449. Christensen, O.M., Mather, J.G., 2004. Pesticide-induced surface migration by lumbricid earthworms in grassland: life-stage and species differences. Ecotoxicol. Environ. Saf. 57, 89e99. Denoyelle, R., Rault, M., Mazzia, C., Mascle, O., Capowiez, Y., 2007. Cholinesterase activity of Allolobophora chlorotica earthworms as a biomarker of exposure to pesticides in apple orchards under different management strategies. Environ. Toxicol. Chem. 26, 2644e2649. Durou, C., Mouneyrac, C., Amiard-Triquet, C., 2005. Tolerance to metals and assessment of energy reserves in the polychaete Nereis diversicolor in clean and
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