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  • Author: Jaanus Paal x
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Abstract

The changes in tree layer saplings, shrub, field and moss layer in Järvselja Nature Reserve virgin forest compartment (JS226) were analysed on the ground of data collected in 1955, 1985, 1993 and 2012. Four forest stands (sub-compartments) were studied; in every stand one 4 × 4 m sample area was established: area A1 represented Hepatica nobilis and Anemone nemoralis dominanted spruce stand, area A3 – drained transitional mire pine forest, area A4 – Mercurialis perennis-rich spruce stand and area A5 – Hepatica nobilis and Anemone nemoralis dominanted aspen stand. The number of tree layer saplings and shrub layer stems, as well as their species content have changed largely in all sample areas, being a bit more stable only on area A1. In field layer the abundance of initial dominant species changed remarkably in all areas or were replaced by other species in the course of succession. Changes in moss layer were the most striking in drained transition mire forest (area A3), where Pleurozium schreberi, Sphagnum centrale and S. capillifolium dominating in 1955 were replaced by S. centrale in 1993. The experiment planning in the current study is regrettably insufficient: to study forest communities succession using only one 4 × 4 m sample area in every stand does not allow to gather representative data about the vegetation structure and its variation limits. Moreover, in that way it is not possible to separate the time-induced successional trend from the drainage impact that has an obviously prevailing importance in forest compartment JS226 being surrounded by ditches.

Abstract

The calcareous pine forests have one of the highest species diversity among the forest communities in northern Europe. We analysed their classification structure and the relationship with principal environmental variables on Gotland Island, South East Sweden. There were 14 species recorded in the tree layer, 60 species in the shrub layer, including 18 species of tree saplings, 273 species in the field layer and 80 species in the moss layer. The former classifications of the Gotland’s calcareous pine forests are conducted too coarsely or without statistical justification of established community types. In the current study the stands were classified into four community types, 1) Arctostaphylos uva-ursi-Tortella tortuosa type, 2) Brachypodium sylvaticum-Rhytidiadelphus triquetrus type, 3) Carex montana-Scleropodium purum type and, 4) Geranium sanguineum-Scleropodium purum type. All these community types have significantly different species content and they are mutually distinct also by numerous considered environmental variables. The species variation in the shrub, field and moss layers was related primarily with three rather strongly correlated variables: tree layer height, abundance of Picea abies (L.) H.Karst. and soil humus horizon depth. Soils were mainly the Sceletic Regosols or Calcaric Gleyic Regosols, but also Rendzic Leptosols.

Abstract

Fern-rich forest communities are presented in Estonia in mesic or moderately humid nutrient-rich habitats, in areas of drained mire forests, on floodplains and lower parts of talus slopes of the North-Estonian limestone escarpment (klint). In the recent official forest typology only one site type has been distinguished and labelled by the ferns: the Dryopteris site type in the scope of boreo-nemoral forests. The aims of the current study were (i) to clarify whether distinguishing between two fern-rich forest site types, one among the full-drained forests group and another in the boreo-nemoral forests group, is reasonable, and if so, then (ii) what the main characteristics of both considered forest site types are, (iii) what the main environmental factors determining the structure of these communities are, and (iv) what the mutual relationship between those forests and other fern-rich forest communities is. Our results asserted a distinct difference between the full-drained and undrained Dryopteris site type forests distinguished by the former scholars. The undrained boreo-nemoral fern-rich stands have developed in the same place in harmony with habitat conditions, while drained forests have significantly changed. It seems that despite some vagueness due to long-lasting post-drainage succession, it is nevertheless justified to recognise the fern-rich drained stands in Estonian forest typology as representing an autonomous forest site type in the group of full-drained forests. To avoid confusion in nomenclature, in the future, the undrained fern-rich boreo-nemoral forests site type could be named according to the most conspicuous indicator species as the Athyrium (filix-femina) site type and fern-rich stands on full-drained peat soils as the Dryopteris (expansa) site type.