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2 Polish Journal of Ecology

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Long-term effects of annual mowing on spatial structure of sedge meadows in vicinity of riparian forests

Kołos A., Próchnicki P.

Polish Journal of Ecology

2012

Vol. 60, nr 1

107-122

Mowing may lead to substantial modification of the spatial structure of phytocenoses and plant populations. An important factor contributing to such modification may be the vicinity of a forest. The aim of this work is to explain how the patterns of the spatial structure of sedge meadows patches change under the influence of annual mowing and how the proximity of a forest affects these changes. The research was conducted in the years 1985-2000 in the south-west part of the Białowieża National Park (NE Poland) Study fields were located in Caricetum acutiformis community, neighbouring ash-alder floodplain forest Fraxino-Alnetum. Three experimental plots and three respective control ones (5 x 5m) were established at the forest boundary (0 m), at a distance of 50 m and 100 m from the forest. Annual mowing conducted for 15 years caused an increase in meadow plants coverage in all mown plots. The spreading of two rush species was also observed - Calamagrostis canescens in patches lying inthe distance of 100 m from the forest edge, and Phragmites australis in the ecotonal zone. The most important changes in a spatial distribution of floristic richness were noticed in mown patches located at the greatest distance from the boundary of the forest. Mowing caused strengthening of the mosaic pattern naturally occurring within patches and changed their structure from "coarsegrained" to "fine-grained" one. Permanent management of sedge meadows caused an increase in a spatial diversity in the first 10 years in all patches, irrespective of their location. After 15 years of management a simplification of the spatial structure occurred. The spatial structure of the clonal species population (Lythrum salicaria, Lysimachia vulgaris) was characterized by relative stability only in the first 5 years of mowing and only in the quadrates located far from the forest. Response of plants of unitary type of growth to management was different - annual mowing caused substantial changes in the distribution of Cirsium palustre individuals in the plots located far from the forest while individuals of Cirsium rivulare in the ecotone remained constantly in their locations. It was found that it can be caused by the presence of clump sedges which may have a greater impact on population structure of that species than mowing.

Effect of distance from forest edge on the distribution and diversity of spider webs in adjacent maize field

Oleszczuk M., Ulikowska M., Kujawa K.

Polish Journal of Ecology

2010

Vol. 58, nr 4

759-768

The study was carried out on lowland agricultural lands in western Poland between July and August 2007. The influence of the proximity of forested areas on the occurrence of foliage-dwelling spiders was defined by measuring the abundance of spider webs on five transects situated at distances of 0, 20, 40, 60 and 80 metres from the forest edge. Generally, the greatest diversity and the highest total density were observed close to the forest edge, but an opposite relation was found for orb webs, built by spiders from the families Araneidae and Tetragnathidae, whose abundance was the lowest in close proximity to the forest. At a distance of 80 metres from the forest a slight increase in total abundance of webs was recorded, no doubt due to the presence of weeds, in which were recorded numerous occurrences of sheet and irregular webs. On all the transects studied, orb webs predominated on maize shoots, whereas only three-dimensional sheet and irregular webs occurred on weeds. Included in this discussion are some of the potential effects of the proximity of forest areas on foliage-dwelling spider populations in maize fields and on the possibilities for spiders limiting this crop's pests.