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1 2009

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Influence of agricultural landscape structure on diversity of insect communities

Ryszkowski L., Karg J., Glura M.

Polish Journal of Ecology

2009

Vol. 57, nr 4

697-713

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.