Journal of Sustainable Agriculture, 34:38–56, 2010 Copyright © Taylor & Francis Group, LLC ISSN: 1044-0046 print/1540-7578 online DOI: 10.1080/10440040903396698
Soil Invertebrates as Bio-indicators in a Natural Area Converted from Agricultural Use: The Case Study of Vallevecchia-Lugugnana in North-Eastern Italy
1540-7578 1044-0046 WJSA Journal of Sustainable Agriculture, Agriculture Vol. 34, No. 1, Oct 2009: pp. 0–0
MAURIZIO G. PAOLETTI1, ALESSANDRA D’INCÀ1, EMANUELE TONIN1, STEFANO TONON1, CARLO MIGLIORINI2, GIANNANTONIO PETRUZZELLI3, BEATRICE PEZZAROSSA3, TIZIANO GOMIERO1, and DANIELE SOMMAGGIO4
TheG.Case M. Paoletti Studyetof al.Vallevecchia-Lugugnana in North-Eastern Italy
1
Department of Biology, Laboratory Agroecology and Ethnobiology, University of Padova, Padova, Italy 2 VenetoAgricoltura, Settore Ricerca e Sperimentazione, Legnaro (PD), Italy 3* CNR*, /Istituto per lo Studio degli Ecosistemi, Sede di Pisa, Italy 4 Dipartmtimento di Scienze e Tecnologie Agroambientali – Entomologia, Bologna University
This work aims to develop a sampling methodology, based on soil invertebrates, to provide a reliable and easy-to-perform measure of environmental quality. Hand-sorting and pitfall-trapping were the main sampling systems adopted because they are quick and easy to use and do not require particular skills or tools. Both agroecosystems (organic and conventional) and seminatural environments (planted woods, hedgerows, flooded areas) have been monitored in a coastal lagoon area reclaimed to farmland in North Eastern Italy. Taxa at high hierarchical levels proved to be useful in separating different type of habitat, but were unable to provide information about the type of rural management. Carabidae (Coleoptera) seem particularly useful in studying agroecosystems: 23 species have been collected, mainly in the organic farm and in the hedgerow. The earthworm population was mainly affected by type of soil. In agroecosystems, cultivated fields had fewer individuals with respect to hedgerow, probably due to disturbance caused by soil management practices.
Address correspondence to Maurizio G. Paoletti, Department of Biology, Laboratory Agroecology and Ethnobiology, University of Padova, Via U.Bassi 58/b, 35131 Padova, Italy. E-mail:
[email protected] 38
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KEYWORDS invertebrate macrofauna, bioindicators, sustainability assessment, sustainable farming, ground beetles, earthworms
INTRODUCTION Many groups of invertebrates are highly sensitive to environmental disturbance. For instance, they quickly respond to soil management practices (e.g. soil invertebrates) and are affected by landscape characteristics (e.g., refugia, reproduction sites, feeding habits). These characteristics made some invertebrates a valuable tool for monitoring landscape quality and the effects of change over time and space, and thus can be valuable as bio-indicators (McGeoch, 1998; Paoletti, 1999a; Mäder et al., 2002). The importance of terrestrial invertebrates in the assessment of environmental characteristics and changes in agroecosystems has been widely demonstrated across organic, integrated and conventional farming techniques (Paoletti et al., 1993; Kromp, 1989; Duelli and Obrits, 1998; Paoletti, 1999a; Mäder et al., 2002; Weibull et al., 2003; Büchs, 2003a). The anthropic impact and alteration of natural landscape have also been usefully assessed by these bio-indicators (Biber, 1988; Pimentel et al, 1992; Pfiffner and Niggli, 1996; Paoletti et al, 1998). The aim of this study was twofold: first, to apply an efficient, easyto-use and inexpensive sampling methodology that would reduce the number of samplings and samples to a minimum; and second, to test soil bio-indicators’ responses to changes in land use, and to compare different management options and different input farming, to assess whether invertebrates are useful bio-indicators of environmental conditions. Probably due to its widespread use, the term bio-indicators can have different meanings, and some authors have tried to clarify and standardize its use (e.g., McGeoch, 1998; Caro and O’Doherty, 1999; Niemi and McDonald, 2004). Following the nomenclature of McGeoch (1998), we considered bio-indicators as “taxa or taxonomic assemblages that are sensitive to environmental stress factors, and demonstrate the effect of these factors on biota and whose response is representative of the response of at least a subset of other taxa present in the habitat” (Niemelä, 2000). Bio-monitoring is also an important tool to assess loss of biodiversity (Niemelä, 2000). By providing a sampling methodology capable of assessing the effect of different land use practices over time, we hoped to improve biodiversity management and ecological engineering of agroecosystem and/ or anthropic environment. Such work could lead to guidelines to improve landscape quality (Gurr et al, 2004) and environmental health, by indicating, periodically, the adoption of management practices that have positive effect on biodiversity, such as reduced tillage, manuring and mulching, rotation,
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margin wild vegetation hedges, shelterbelts, etc. (El Titi, 1989; Paoletti et al. 1998; Paoletti, 1999a). In our study, we decided to focus on soil invertebrate macrofauna, as it is easy to isolate and includes several groups, such as carabids and earthworms, which are widely distributed (Lövei and Sunderland, 1996; Kromp, 1999) and sensitive to environmental change, in particular to human disturbance (Dufrêne and Legendre, 1997; Paoletti, 1999a). Carabids are important soil predators, easy to trap due to their mobility on the soil surface. As well as being widely distributed, they are considered sensitive indicators of environmental conditions (Kromp, 1999; Mäder et al, 2002; Shah et al, 2003). Earthworms are important detritivores (Edwards and Fletcher, 1988; Paoletti et al. 1998; Paoletti, 1999b); they are essential in the composting and recycling of soil nutrients and contribute to maintaining an open soil structure, facilitating the processes of aeration and drainage. Together with other soil biota, they represent a consistent source of food for poliphagous predators that can be active against some crop pests.
MATHERIAL AND METHODS Site Description Our study was carried out in Vallevecchia, an estate of 700 hectares of coastal area in Northeastern Italy owned by the local regional authority (Figure 1). In the early 1960s, the natural marsh that covered the area was converted to agricultural use, and a pine-wood shelterbelt was planted along the coast
FIGURE 1 The study site and its geographic location.
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to reduce coastal erosion and dune maintenance and to preserve interior crops from the salty wind. The formerly wild area was then turned into an intensive farming estate: this caused the alteration of the microclimate, including soil and vegetation patterns, and simplified the environment (Veneto Agricoltura, 2009). Since the 1990s, resettlements have been carried out in order to thin out the pine-wood shelterbelt along the sea and by planting hedgerows between the fields and returning part of the fields to their original condition, through the establishment of small, brackish water and freshwater shallow lakes (AA.VV., 2006). In addition, some fields were devoted to organic farming to lower environmental impact. In other terms, this regional public estate was reshaped, and is still in this process, in order to preserve the local environment and to promote tourism. To study the effect of these interventions on local biodiversity and in particular on soil fauna, a monitoring program has focused on soil taxa, in order also to supply suggestion for improving environmental management. Seven sampling sites were chosen in the area: the pine-wood belt along the cost, the holm-oak paths inside the pine wood, two areas flooded by seawater and freshwater to form small shallow lakes, a field cultivated with conventional high input techniques, a field under organic cultivation, and a hedgerow along the organically cultivated field. • The pine-wood shelterbelt was planted between the 1950s and 60s to consolidate the coastal dunes and protect the inner cropland from salty winds and costal erosion, and includes two different species of pine: Pinus pinea (L.), and Pinus pinaster (Ait.). • The holm-oak paths, planted at the beginning of the 1990s, include Quercus ilex (L.), Quercus pubescens (Willd.) and Robus fruticosus (L.). • The two flooded areas are considered an important migration site for many aquatic bird species: the area flooded with freshwater, boarded by a canal and its bank on the northern side and an artificial freshwater fish-pond for shrimps on the east side, includes arbustive and herbaceous plants such as Thypa latifolia (L.), Phragmites australis (Cav.), Schoenoplectus lacustris (L.), Miriophyllum spicatum (L.), Bellis perennis (L.) and Rumex sp. The area flooded with seawater hosts species such as Salicornia veneta (Pignatti and Lausi), Tamarix gallica (L.), Halimione portulacoides (L.) and Aster tripholium (L.). • Both cultivated fields considered lay in an agricultural area reclaimed from a lagoon territory at the beginning of the 1970s; the conventional field is cultivated with rotation of corn, sugar beet and wheat, using herbicides, chemical fertilizers and insecticides when needed. The other field has been organically cultivated since 1998, and a rotation of wheat, soybeans and barley has been established. The field is fertilised with bovine manure (25 tons/ha/yr−1). The hedgerow, introduced at the beginning of
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the 1990s, includes Ulmus minor (Miller), Quercus robur (L.), Alnus glutinosa (L.) and Salix alba (L.).
Sampling Tecniques Each pitfall trap consisted of an outer plastic pot (130 mm length, 105 mm internal diameter) sunk into the soil, containing another smaller plastic pot (80 mm length, 100 mm internal diameter) 1/3 filled with a saturated solution of water, sugar and cusine salt as preservative solution, and a drop of liquid soap. A small sheet of polystyrene protected 1 cm over the traps from rainfall flooding. During each sampling period, traps were left in each site for 7 days, and trapped materials were then collected. Hand sorting soil samples, five per site (30 cm x 30 cm, 20 cm depth) were collected with a spade and sorted on a white sheet and visible invertebrates were collected by hand and soft forceps, and put in an 80% ethanol solution. Details about this technique and its importance in the study of soil fauna can be found in the work of Anderson and Ingram (1993). In the laboratory all samples were washed, sorted and classified using a stereomicroscope and the appropriate literature. In minor cases specialists were consulted for their taxonomical expertise. Three soil samples per site were also analyzed (following procedures of G.U. 248/99 and method EPA 3050+6010 C-00) for composition and main nutrients in order to measure differences in the distribution of invertebrates to differences in soil composition. The presence of heavy metals in soil samples (Cu, Zn, Pb, Cd) was also analyzed (following procedures of G.U. 185/99, Method XI.1).
Statistics Data were analized using Statistica ver. 7.1 (StatSoft Italia srl, 2005). Normality of data was verified using the Kolmogorov-Smirnoff test. To compare different sites, analysis of variance (ANOVA) has been used if the distribution was normal, and the Kruskal-Wallis test otherwise. Multivariate analysis was applied to data and in particular cluster analysis using Ward method and Euclidean distance and correspondence analysis to ordinate the sites on the basis of invertebrate population.
Sampling Dates Sampling was carried out in spring and fall: from March 2003 until May 2005. Spring samples were collected in March 2003, April 2004, and May 2005; fall samples were collected in October 2003 and October 2004. Fall sampling of 2005 was not considered as only a few individuals were collected due to exceptionally dry conditions. Sampling dates were chosen to correspond to periods of suitable soil humidity.
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RESULTS Soil Analysis The seven sites show clear differences between chemicals analysed as shown in Table 1. The correspondence analysis applied to chemicals and sites clearly separate three group of soils: woods, flooded area, and agroecosystems (Figure 2). The soil in pine and holm-oak woods is characterized by a high quantity of sand (98 %), and calcium and magnesium were higher than in other sites. The soil in flooded areas is rich in lime and clay, sodium, and sulphur. Finally, the soils in agroecosystems are characterized by an high percentage of organic matter, nitrogen and phoshorus (only total). Considering soil analisys in wooded areas soils no differences between has been found between the pine and holm-oak soil, indicating an high similarity between these two sites. Also the two flooded soils are very similar despite the difference in the type of water; the only significant difference has been found for total Mg, which is higher in freshwater than in seawater. Some differences have been found in agroecosystem soils. In particular, the organic farm soil seems to be richer in some nutrients, especially
0,4
Autovalue: 0,01787 (15,45%)
0,3 0,2
Correspondence Analysis: Sites × Chemicals
Sand
Agroecosystems Ptot
Ntot
Organic CF
0,1
Hedgerow
Kexc
0,0 –0,1 –0,2
OrgMat
Ca Mg Pin–Hol
Conv. CF
Woods Pass S
Ktot Clay Lime Fresh WA Brack WA
Na
Flooded areas –0,3 –0,6 –0,4 –0,2
0,0 0,2 0,4 0,6 0,8 Autovalue: 0,08618 (74,50%)
1,0
1,2
1,4
Chemicals Sites
FIGURE 2 Correspondence analisys applied to chemicals and sites. Legend: Pin-Hol: woods areas; Fresh WA: freshwater flooded area; Brack WA: brackish flooded area; Organic CF: organic field; Conv CF: conventional field. The percentage of inertia explained by the axes appears in parentheses.
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p >0.05 p
