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Nematode communities along the transect shelterbelt - ecotone - crop field

Dmowska E.

Polish Journal of Ecology

2007

Vol. 55, nr 4

665-680

The study was carried out in western Poland (Turew region) in two shelterbelts of different age (the younger - 6 years old and the older - 11 years old) planted cross croplands, in adjacent field and in the field located in deforested area (control field). Soil samples were taken twice: in the autumn and spring from the centre of each shelterbelt, from the ecotone, and in the field at a distance of 15 and 50 m from the edge of the shelterbelts. The density of nematode communities fluctuated unpredictably, in autumn it was very low and ranged from 276 to 641 x 10[^3] in spring it ranged from 388 to 1931 x 10[^3] individuals per 1 m[^2]. Most numerous trophic groups were: bacterivores, fungivores and obligate plant feeders, while facultative plant feeders, omnivores and predators achieved low level. The abundance of predators in older shelterbelt was significantly (P [less-than or equal to] 0.05) higher than that in the younger one and decreased with increasing distance from the shelterbelt towards the field. The communities in shelterbelt and its ecotone were more diverse, which was reflected by the higher number of genera (19-31) and higher values of Shannon-Wiener diversity index H'(3.3 - 4.0), than those in the fields where the number of genera ranged from 15 to 25 and Shannon-Wiener diversity index H' ranged from 2.5 to 3.5. In the younger shelterbelt and in the control field the soil food-web assessed with indices derived from analysis of nematode communities was considered as composed mainly of basal components, i.e. cosmopolitan species feeding on bacteria and fungi occurring everywhere even in degraded environments. While the web in older shelterbelt was consisted mainly of enrichment components, i.e. bacteria feeding species of very short life cycle, with high food requirements which occur in the environment rich in bacteria. The values of Channel Index which informs about the predominant pathway of decomposition (through bacteria or fungi) showed that in majority of sites bacterial processes predominated. Only in the older shelterbelt the participation of fungal decomposition channel was higher (>50%) and increased with increasing distance from the shelterbelt towards the centre of the field. The results of Correspondence Analysis showed that first two axis explained 40.3% of the variance. The generic composition of nematode communities in the 11 years old shelterbelt differed from that in the 6-years old shelterbelt. Nematode communities inhabiting the ecotone of younger shelterbelt were very similar to the communities in the shelterbelt, while the communities in ecotone of older shelterbelt differed from those in the shelterbelts. Nematode communities inhabiting the control field were similar to those inhabiting the field adjacent to younger shelterbelt.