Fault Lines from North to South
The sharp gradients from drought-exposed hills, steep slopes with potential for more nutrient-rich seepage, to moist and wet depressions are characteristic of Østmarka. The fault lines mainly run from north to south. The greatest elevation differences and variations are in the northwest/west, ranging from deep valleys with over one hundred meters of height difference to more gently rolling areas. In the central and southeastern parts, the landscape is gentler and elevation differences are relatively smaller, although some deep and narrow ravines also exist here.
Bedrock and Surficial Deposits
Most of the bedrock consists of Precambrian gneisses, with limited availability of plant nutrients. The nutrient content varies significantly within this main group of bedrock types. There may also be nutrient-rich influence from seepage water.
Large parts of the Østmarka region have bare rock or thin surficial deposits, particularly on the hills. Moraine material is mainly found between Nøklevann and Elvåga, at the Børter lakes, in the Rausjøen-Mosjøen-Tonevannet valley, and scattered around the existing nature reserve.
The Geology Influences Which Plants Can Grow There
The underlying geology, surficial deposits, and topography affect the area’s productivity and vegetation. The most productive areas lie below the marine limit or on moraine, while hills with bare rock or thin surficial deposits have lower productivity. High-quality areas not only support faster tree growth but also generally higher primary production and often greater plant species diversity. Higher primary production also provides better opportunities for herbivores, from deer and small rodents to various invertebrate species.
Pine on the Hills and Spruce in the Valleys
The tree composition is dominated by pine on the hills and spruce in the valleys and lower-lying areas. Deciduous trees are generally scarce, but there are significant occurrences of aspen. Pine is particularly dominant in the west. In the southeastern parts, especially within the existing nature reserve, spruce is considerably more common. In smaller ravines and depressions, richer mire and swamp forests are found. In gentler landscapes, there are larger mires and lakes, as seen in the central part of the protected area.