Edyta Regulska

Abstract The aim of this work was to estimate the potential of arable land to provide a regulating service – namely decomposition, following the CICES v5.1 theoretical framework and classification system. Arable land potential was estimated by characteristics of earthworms (Lumbricidae), notably the density and biomass of their populations. Arable lands accounts for about 60% of Poland, and such intensive land-use systems (and especially those involving large-scale monocultures) exert a significant impact on individual components of the environment, for example leading to a degradation of soil structure and an increase in its aeration, to mineralisation of humus, and to the release of carbon dioxide into the atmosphere. In this context, an important aspect is maintenance of resources of organic matter in soil, given that the latter not only plays a significant role in production, as a habitat and in regard to retention, but also mediates processes of carbon sequestration that have the potential to reduce the greenhouse effect. Since Charles Darwin conducted his classic studies of earthworms in the late 1800s, these species have been recognised as major actors in the processing of dead and decomposing organic matter. Earthworms improve soil bulk density, pore size, water infiltration rate, soil water content, and water-holding capacity. High earthworm densities are associated with well-drained, aerated, fertile soils. Characteristics of earthworm assemblages in terms of their biomass and density (also within ecological groups) can thus serve as valuable indicators of Ecosystem Services (ES) offered by agricultural ecosystems, given the key relationships pertaining between earthworms and critical soil processes for ES. The study areas are located in a young glacial landscape in Suwalskie Lake District in NE Poland (OM), as well as the Western Pomeranian Lake District in NW Poland (OP). The farmlands selected (of 90 and 100 ha respectively) are old structured landscapes under constant management for at least 100 years. The main site selection criterion was thus the existence of two spatially different configurations of arable land in each region – i.e. a heterogeneous one of small fields (PM) that belong to private owners; and a homogeneous one comprising large fields (PW) previously state-managed but now subject to a continuous method of cultivation. A total of 440 sampling points were analysed. Earthworms were collected under similar weather conditions in May (spring season) and in October (autumn season) over a two-year period (2007–2008). Pits 30 cm deep of cross-sectional area 0.25 m2 were dug out by hand, with specimens extracted in situ by a combination of sifting and hand-sorting and than fixed immediately in 70% ethanol. All the individuals were identified to species level, counted and weighted. Statistical calculations were made using SAS 9.2 software. To determine the significance of differences in quantitative characteristics of assemblages of earthworms, multifactorial analysis of variance (ANOVA) was conducted, with the significance level set at p = 0.05. The results of the analysis in supra-regional terms show that areas of more diversified spatial structure support a significantly higher density and biomass of earthworms than do structurally-poorer areas. This means that, in this aspect, the potential for providing decomposition services (ES) is higher in the mosaic of small fields than the homogeneous area. On a regional basis, the overall density and biomass of Lumbricidae points to significant differences between OM (“the masurian area”) and OP (“the pomeranian area”). It should be emphasised that differences between miscellaneous systems of agricultural areas are much more visible in the case of the OM area. The small fields of the OM area are much smaller than the corresponding fields in OP area, and are also crossed by numerous balks and mid-field roads.

Edyta Regulska

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