Dynamics of bog-pine-dominated mires in the Jura Mountains, Switzerland: A tentative scheme based on synusial phytosociology

A description of the bog-pine (Pinus uncinata var. rotundata) dominated vegetation of uncut oligotrophic mires affected by drainage is given. Surveys were carried out at 17 sites along the Jura Mountains (Switzerland and France) in 1993, 1994, and 1995. Raised bogs of the Jura are generally of small size, and most vegetation changes in them have occurred as a result of the indirect impact of peat cutting. This activity led to the peat drying out and to colonization by trees, in particular by bog-pines. Integrated synusial phytosociology was used to describe the vegetation where bog-pine, spruce, and birch occur. Two spatio-temporal levels of organization were considered: the synusia and the phytocoenosis. At the phytocoenosis level, four vegetation types representing bog-pine stands of uncut and deep oligotrophic peats are described with their constitutive synusial composition. They represent: (1) phytocoenoses developing in the open, wet central parts of the bogs, where trees are scattered and of small size, (2) phytocoenoses with layered tree stands of medium size and with a higher density, and (3) phytocoenoses with tall trees, developing generally near the edge of the bogs or close to peat cuttings. A generalized qualitative dynamic model of the vegetation in relation to the development of bog-pine trees was developed. It shows the spatial and temporal organization of the constituent synusiae, as well as other underlying hypothetical functional relations. The different bog-pine-dominated vegetation types described in this study appear to have coexisted since the origin of the Jura bogs as a result of local polyclimaxes induced by differential waterlogged situations. They probably all belong to the same (primary) successional series, but have been affected by both autogenic and allogenic processes. During the development of the bogs the balance between the different communities changed. In particular, the vegetation types with dense and tall pine trees have undergone a drastic expansion since the Jura bogs were first affected by drainage

Stands structure, invasion, and growth dynamics of bog pine (Pinus uncinata var. rotundata) in relation to peat cutting and drainage in the Jura Mountains, Switzerland

A description of bog pine stands (Pinus uncinata Ramond var. rotundata (Link) Antoine) on uncut oligotrophic mires affected by drainage and nearby peat cuttings at three sites of the Jura Mountains (Switzerland) is given. In all sites, three situations were chosen: (i) central parts of the bogs, (ii) surfaces near cutting walls and bog margins, and (iii) intermediate situations. Population structures were characteristic for each situation. In the open and wet central parts of the bogs, trees were scattered, small, and uneven aged. In the intermediate situations, tree density was higher, and the stand was multilayered with taller and uneven-aged individuals. Near the edges of the bogs or close to the peat cutting walls, the trees were tall, even-aged, and younger with a high growth rate. The nonsynchronous colonization of the bog pine trees on the three sites indicates that local factors such as drainage and peat cuttings in the vicinity of the uncut surfaces were more influential than climate factors. Radial growth patterns, very similar between the sites and the various pinewood stands, and the numerous common pointer years reflect local and regional climate fluctuations. The pinewood development on uncut bogs in the Jura Mountains thus represents a recent dynamics, which is strongly linked to human activities

Spatio-temporal pattern of bog pine (Pinus uncinata var. rotundata) at the interface with the Norway spruce (Picea abies) belt on the edge of a raised bog in the Jura Mountains, Switzerland

In a bog site in way of paludification, a pine stand is declining, which presently is an infrequent phenomenon on the Swiss Jura scale. A transect was positioned in the bog, from the external and driest part (pine-spruce stand) towards the central and wettest part (pine stand). Water table, tree structure, tree age structure and pine radial growth were analysed with spatial and temporal references. The ground water level is very shallow and the hydrologic gradient is obvious during dry periods. Tree structure (height and diameter) is strongly linked to the hydrologic gradient. Two cohorts have invaded the bog with a 70-year-time period between them. The first one concerned the whole transect; it started around 1840 and could be related to a clear cutting on the fringe of the bog. After a quick initial radial growth, the pines reduced their radial growth abruptly (1870-1885), more quickly and strongly in the centre of the bog, where an important mortality was observed over the last 10 years. Bog pine can thus survive over decades with a very reduced growth and in very bogs probably constituted the bog pines' survival niche during paludification in the Jura bogs

Succession from bog pine (Pinus uncinata var. rotundata) to Norway spruce (Picea abies) stands in relation to anthropic factors in Les Saignolis bog, Jura Mountains, Switzerland

In Jura bogs, on deep and nutrient-poor peat, the ecotone between bog pine forest and Norway spruce forest is sharp and, in a few disturbed situations, no succession pine forest-spruce forest occurs. The bog Les Saignolis lies at the top of an anticline, on thin and oligotrophic peat. Several documents attest some anthropic disturbances (clear cut and drainage). Beside these historical data and with the aim of reconstructing vegetation dynamics and tree growth, we realised synusial phytosociological releves and, in a mixed pine-spruce stand, we studied tree radial growth. Following the clear cut, the bog pine, the pubescent birch, and the Norway spruce settled simultaneously. The birch disappeared rapidly. The present cohort of pine settled and grew rapidly, and then declined because of the competition by spruce. Spruce settled progressively and increased its growth regularly except when pine settled and grew. Interspecific competition between pines and spruces and intraspecific competition between dominant and sub-dominant spruces were put into evidence by radial growth analysis