L. Lőkös szerk.: Studia Botanica Hungarica 27-28. 1996-97 (Budapest, 1978)

Nagy, János; Figeczky, Gábor: Decay of peat moss cushions on the Lake Bence-tó in the northern part of the Great Hungarian Plain

Studia bot. hung. 27-28, pp. 163-167, 1996-97(1998) DECAY OF PEAT MOSS CUSHIONS ON THE LAKE BENCE-TÓ IN THE NORTHERN PART OF THE GREAT HUNGARIAN PLAIN J. NAGY and G. FIGECZKY Dept. of Botany and Plant Physiology, University of Agricultural Sciences H-2103 Gödöllő, Páter K. u. 1, Hungary Decay of peat moss cushions has been observed in the Scdici cinereae-Sphagnetum recurvi association of the lake Bence-tó (northern part of the Great Hungarian Plain) since 8 September, 1994. During these two years 36% of the investigated cushions died. The two Sphagnum species composing the cushions decay at the same ratio. The critical cushion size on this lake is 31 cm x 29 cm. Smaller cushions than this have hardly any chance to survive. According to our experiences the main reason of this decay is the insufficient water supply. Due to this the contiguous cushions become more and more divided each year and finally dry out completely. The closed shrub layer contributes to the decrease of vaporization of the peat moss layer and the soil surface. If the foliage of Salix cinerea, which forms the shrub layer, is opened, peat moss cushions tend to lose more water, thus have less chance to survive. Key words: peat moss cushions, Sphagnum fimbriatum, Sphagnum squarrosum INTRODUCTION Peat mosses occur only in wet habitats, which are poor in nutrients and avoid lime. They require a lot of water, therefore usually found in bogs, or in sites where precipitation and moisture content of the air provide sufficient amount of water and create highly acidic soil for them (ORBÁN and VAJDA 1983). Peat moss cushions of the willow peat bog of the lake Bence-tó (northern part of the Great Hungarian Plain) (Fig. 1) are formed on the "feet" (base of the trunk) of Salix cinerea shrubs, and are composed either only of Sphagnum fimbriatum, only of S. squarrosum or of both species. Changes of the size and the species composition of the cushions were investigated between 8 September, 1994 and 1 September, 1996. By the middle or the end of summer, after the lake had dried out completely, peat moss cushions tended to dry out entirely, too. As peat moss cushions dried out more and more each year, once large cushions were divided into smaller and smaller ones. Finally the smallest cushions did not regenerate during next year's wet period.