Due to decrease in the area of extensively managed, semi-natural grasslands, that contribute to high biodiversity level preservation, the conversion of highly productive meadows to extensively managed, species-rich grasslands is now regarded as an important task for nature conservation. The aim of this long-term study was to assess the significance of restoration measures for diversity and trophic structure of above-ground insect community. That study challenges some weaknesses of previous studies as it was conducted with the use of suction trap enabling quantitative analyses of the changes in most insect taxa, and in a long time-span (1992–2005) in a set of permanent plots. The study area was located in a subalpine zone in Bavaria, near Laufen (Germany). The restoration process was initiated in 1996 by a cessation of fertilization and reduction of number of mowing to 1–2 per year. The changes in insect density and diversity (number of families) were monitored in ten restored and two reference plots with the aid of a suction trap. The changes in the insect community recorded during 14 years support findings from other studies that response of insect community to restoration process is usually slow on average. The short-term comparison in 2004–2005 between the restored and reference plots show that the first ones were characterized by more diverse (in term of family number) insect communities (as a whole as well as in guilds of predatory and parasitic species). From the other side, the long-term trend analysis shows that since 1998–2000 insect diversity and abundance was declining. Also trophic structure is fluctuating without clearly defined trend. These findings are in line with the results of the analyses of taxonomic composition similarity. They did not support the expectations neither that difference between initial and current taxonomical composition in a restored plot increases in time (mainly because of incoming new species), nor that spatial heterogeneity of insect assemblages should increase. However, spatio-temporal insect interactions between sample plots (located close to each other), linked to high movement ability of many insect taxa, could mask the changes in insect community caused by restoration.
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Environmental effects of the intensification of agricultural production have a profound impact on the ecological carrying capacity of agricultural landscapes for biodiversity. The recent view of the relationship between biodiversity and landscape structural characteristics showed the importance of the vegetation patch composition, heterogeneity and fragmentation of the habitats, their connectivity and scale dimension for biodiversity protection. There are two kinds of habitat/vegetation diversity in the agricultural landscape: crop fields which form a sort of matrix and the network of semi-natural or perennial patches of vegetation like shelterbelts, small patches of forests, meadows or wetlands. The studies were carried in mosaic and uniform agricultural landscape in west Poland. In the mosaic landscape, small areas of arable fields are presented as well as numerous semi-natural ecosystems being refuges for plants and animals (shelterbelts, small water bodies, strips of meadows, channels etc.). In the uniform landscape, large areas of arable fields and small number of refugial ecosystems are presented. The importance of these two kinds of landscape diversity for the family diversity of aboveground insect communities was studied in the agricultural landscape (Turew area) in Poznan region of Western Poland. The landscape is composed of the large (up to 100 ha area) fields (wheat and corn mostly) and a network of shelterbelts (black locust, oak) planted in the past (XIX century) as well as recently (with more than 10 species of trees). The studies were carried up from 1984 to 2005 in the different vegetation patches, wheat fields and shelterbelts, as well as at different distances from the shelterbelts. Quick-trap method, with a base area of 0.25 m2 was used to collect the above-ground insects. 10.20 samples were taken in each series. 133 families were recorded in the 1994.2005 period. The number of recorded families decreased with increasing distance from shelterbelt. This decrease is well described by negative exponential equation with fit measured by determination coefficient R[^2] = 0.97. The mean number of families found in wheat field at the 100 m distance shelterbelt was equal to 52.0 and was higher than their number recorded in wheat fields of the uniform landscape which amounted to 40.9. Groups of occasionally occurring and residential families were also studied. In the mosaic landscape the share of occasionally occurring families in total number of recorded families was equal to 0.29 (36 vs 124). In the uniform landscape, contribution of occasionally occurring families was 0.37 (43 vs 115). The landscape structure had negligible effects on occasionally appearing insects, which can be distributed by wind as well as by other factors, or are on a long-distance migration. The main factors counteracting the decline of biodiversity in agroecosystems are the mosaic structure of the landscape and dispersal properties of insects. Refuges occurring in mosaic landscape counterbalance the loss of insect diversity due to intensification of agriculture production. The influence of landscape structure on recurrence of insect families in consecutive years is so strong that combined changes of climate and crop pattern do not seem to have the significant effect.
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The autors dedicate this set of papers to the memory of Professor dr Lech Ryszkowski (1932-2007) Head of the Research Center for Agricultural and Forest Environment PAS who was devoted to the idea of linking agricultural management and ecology and who initiated our investigations an agricultural landscape.
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The studies on the role of recently established shelterbelts as refuges available for wintering insects were carried out in the years 1994-2002. Soil and litter samples were taken (the material being sorted manually) from five young (up to 7 years old) and two older midfield shelterbelts, from the ecotone zones and from the adjacent croplands. A high numbers (250-400) ind. m^-2) of insects, which biomass varied between 950 and 2300 mg dry wt. m^-2, were found to overwinter in young (4-7 years old) shelterbelts. The insects formed communities (dominated by Coleoptera) represented by over 50 families. Effects of the shelterbelt's age, the presence or absence of litter, specific composition of trees and the location of sampling plots within the shelterbelt on winteringinsects are discussed.
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The paper summarizes results of investigations done in 1999-2000 by several authors in Wielkopolska region, (western Poland) near Turew in young midfield shelterbelts and adjacent cereal fields. It was found that the soil organic matter content, as well as microbial and faunal biomass decrease gradually from the shelterbelt toward the field centre. The annual increase of carbon was assessed and possible sources of it (wind erosion, leaf fall, input of invertebrate faeces)considered. The results suggest, that excreta contribute significantly to total carbon input. The shelterbelts influence the biomass, density and composition of many soil and above-ground invertebrate taxa and individual size of animals occurring in bordering fields.
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A study of development of newly planted and its impact on some ecological processes (plant biomass decomposition, insects diversity enrichment, corridor effect for mammals) were conducted in Turew agricultural landscape (West Poland). The aim and general background of study was described. Study area was characterized.
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