An Introduction to QBS (Soil quality index based on the evaluation of soil arthropods) and its application - An Italian Experience
Mesofauna as bio-indicators Their number is outstanding Their role in soil formation and transformation is well-recognized The area covered during their life cycle is strictly representative of the site under examination Their life time and natural history allow to obtain interesting considerations on soil ecological conditions, and finally Several species belonging to this group have already been recognized as useful biological indicators of soil quality.
Soil Biota Knowledge
The QBS Index In general, soil invertebrate-based indices consider the consistency and richness of populations Most recently, the QBS Index Qualita Biologica del Suolo or Biological Quality of Soil was proposed. QBS index is based on the concept that the higher is soil quality, the higher will be the number of microarthropod groups well adapted to soil habitat
Taxonomic requirements of QBS Index Reduction or loss of pigmentation and visual apparatus Streamlined body form Reduced and more compact appendages (hair, antenna, legs) Reduction or loss of flying Jumping or running adaptations Reduced water-retention capacity
Main Phases of QBS Application Sampling Micro-arthropods extraction Setting the collected specimens Determination of biological forms Calculation of QBS Index
Sampling Samples for QBS calculation has to be collected when soil is wet and not after heavy rain. A 10*10 cm area is dug up to 10 cm depth.
Extraction of microarthropods Samples have to be carried in a thermal shock Soil fauna has to be extracted within 48 hours of sampling A simple and best Berlese-Tullgren funnel (25 cm dia, 2 mm mesh, 60 W lamp at 25 cm distance) can be used. Extraction duration (never less than 5 days) will be proportionate to water content in the sample. It will be slightly shorter for litter. Preservation should be done with 2 parts ethanol 75% and 1 part glycerol.
Specimens Setting Extracted specimens are observed under a stereomicroscope at low magnification (range 5-100x; usually 20-40x are sufficient) by pouring the animals with the liquid. Collembolans are separately treated.
Separation
Separation of Collembolas
Case Study 1: Permanent grasslands and arable lands - Balugola (BA): this is the oldest permanent grassland, established around 1736 and irrigated by traditional flood irrigation method until some years ago. - Botti (BO): flood irrigated permanent (> 100 years) grassland. - Galli (GA): permanent (> 100 years) grasslands, but not irrigated in the previous 20 years. - Medica (ME): former vineyard (30 years ago). At the time of sampling it had been cultivated with alfalfa for 2 years. - Troni (TR): former permanent grassland (> 100 years), ploughed for the first time 20 years ago. At the time of sampling it was cultivated with sugarbeet.
Application of QBS The biological soil quality was evaluated by using the QBS Collembola (QBS-c) and QBS Arthropods (QBS-ar). The QBS-c values were particularly high in the irrigated permanent grassland (Botti), owing to the high occurrence of species well adapted to edaphic life and submersion (Folsomides parvulus)
Result
Result
Conclusions The soils of Botti and Medica are very similar in species richness, but quite different as far as QBS-c is concerned. According to the increasing values of QBS-ar and QBS-c, the soils of the study sites can be ordered along the following sequence Troni < Medica < Balugola < Galli.
Case Study 2: Land use comparison at Rubiano site The objective of the research was to evaluate the biodiversity and the soil quality associated to different land uses. For this purpose, ten study sites were chosen.
Case Study 2: Land use comparison at Rubiano site Main characteristics of the selected sites were:
Soil microarthropods taxa, EMI and QBS for the Rubbiano sites
Regression between SDI (Soil Disturbance Intensity) and QBS for the Rubbiano study area The intensity of human disturbance on soil (SDI Soil Disturbance Intensity) was expressed as the inverse of the number of the years since the last tillage operation; for shrubland and wood, conventional values of 0.03 and 0.01 respectively were adopted. In Fig. 1, the regression of QBS on SDI is shown; the analysis of these data produced a significant fitting: r2 = 0.83 (P <0.01).
Case Study 3: Sewage sludge impact on soil microarthropods and earthworms The objective of this experiment was the evaluation of the effects of sewage sludge application on microarthropods communities and the possible heavy metals accumulation in earthworm. The study area is represented by Cremona province, in Po valley (Northern Italy). Inside the study area three experimental sites, corresponding to the more diffuse soil types, were chosen; for each site one field treated with sewage sludge (during a period ranging between 1 and 3 years) and a second one, with the same crop and management, but without sewage sludge application were sampled.
Results The results showed that the application of sewage sludge to the investigated soils not reduced the biodiversity of soil microarthropods.
Case Study 4: Land use and crop types in the Taro River Regional Park (Peretti, 2000) The present research was aimed to characterise microarthropod communities in relation to land use and crop type within the Taro River Regional Park (Parma). The study sites were located in the areas used by the bird Burhinus oedicnemus during the feeding activity, as a part of the LIFE Project 98NAT/IT/5138 Restoration of river habitat for bird communities. Fifteen areas were sampled, with three replicates for each area. The sampling campaign was carried out between May and October 2000.
QBS values for different crops/land use
Case Study 5: Organic and Conventional Farming The aim of this study was the comparison of the impacts on soil microarthropods, caused by different agricultural systems (organic and conventional) on different crops. For this purpose two study areas, both within Parma province, were chosen: Fraore and Bazzano. Fraore is located in the upper part of Po valley, near Parma; the elevation is 55 m a.s.l., the landscape is dominated by agricultural land uses with few trees or hedges and high inputs of fertilisers and pesticides. Bazzano is located on the Apennine, the elevation is 470 m a.s.l..; the land use is characterised by extensive agricultural areas and wooded areas. For each study area soil samples for microarthropods extraction were collected from fields cultivated with different crops and with different systems (organic and conventional); from the microarthropds extracted the QBS and the Collembola/Acari ratios were calculated.
QBS and Collembola/Acari ratio (C/A) for organic and conventional crops at Fraore (Parma) and Bazzano (Parma) sites
Conclusions The analysis of the overall data showed significant differences in QBS values determined by land use type. Three main land use types were found among the case studies: forest, permanent grasslands + poliennial crops, arable lands (annual crops); the QBS average values increase according to the anthropic pressure reduction. The analysis of single eu-edaphic taxa as a function of land use showed that some groups, such as Acari or Collembola are not or weakly affected by land use type, while Protura, Diplopoda, Chilopoda and Pseudoscorpionida are strongly affected. Also the agricultural system (i.e. conventional, organic) generally determines significant differences in QBS values; however these differences are larger for the most intensive crops, such as corn or tomato, and smaller (in some case not significant) for the low input crops, such as wheat and barley.