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1 2006

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Dispersal of harpalus rufipes (Degeer) (Carabidae) between shelterbelt and cereal field

Kujawa Krzysztof, Sobczyk Dariusz, Kajak Anna

Polish Journal of Ecology

2006

Vol. 54, nr 2

243-252

Former studies usually show a positive effect of landscape heterogeneity on different groups of animals occurring in crop fields but some controversies have been discovered. The aim of this study was to answer the question whether the introduction of mid-field tree belts can help to increase numbers of predatory carabids in crop fields. Distance and the direction of movements of individually marked carabids caught in traps in the shelterbelts and in the adjacent crop fields were measured during one week of July (in 2003 and 2004). Pitfall traps (N=360) were placed 2 meters apart in 30 parallel rows which formed a rectangle of 58 x 22 m divided into 5 strips (5 rows in each one). Strip A was located in the shelterbelt, the others (B-E) were placed in the field. Beetles (exclusively - Harpalus rufipes (Degeer, 1774) which predominated in both habitats) after being marked with fast drying paint (non-dissolving in water, not harmful, and using dot code) were released at the same spots where they were caught. Accordingly 1099 and 1683 individuals in both years were marked and the number of recaptured individuals was equal to 259 (24%) and 307 (18%). Proportion of recapture rate for individuals marked in particular strips ranged between 18 and 28%. Mobility of the beetles was similar in both years (15.9 m and 16.5 m; t = 0.59, df=579, P> 0.5). Individuals marked within the shelterbelt (strip A) were in both years caught much further away (25 and 27 m) than the individuals marked in opposite strip E, located in crop field (15 and 17.5 m). Differences between the distance covered daily by insects marked in the field and in the shelterbelt were statistically significant whereas differences between distances covered within the field by insects marked in particular strips - were not significant. Only 8-9% of insects marked in the shelterbelt (strip A) was recaptured in the same strip while recapture rate for individuals marked in other strips was higher -16 to 32%. The proportion of insects marked in the field (strip B, C, D, E) and recaptured in the shelterbelt was very low (2-11%). The comparison of recapture rates between strips A and B also shows that insects move mostly from the shelterbelt to the field. As much as 30-34% of the insects marked in the shelterbelt were caught in the bordering field. Among the insects marked in the next strip B, adjacent to the shelterbelt, only 10-11% individuals were caught in the shelter-belt. Presented results indicate that dominating direction of the dispersal in the mosaic landscape is from the shelterbelt to the field.