When we apply this information on the Vercors, this picture can be recognised to a certain extent. On the hand, Orchis spitzelii is never found in grasslands with Sesleria albicans, but it is present in open grassland communities. On the other hand, the species is only found in a nutrient poor situation in forests and at the fringes of the forests where vegetation is lacking. In all these cases coming up and growing is not a problem.
From the previous discussion, the conclusion can be drawn that Orchis spitzelii needs a dynamic situation, which prevents the occurrence of a closed plant community. In an open Pinus forest the species disappears immediately as soon as the vegetation becomes somewhat higher and richer in nutrients. Only on the places where nutrients are scarce and the vegetation is open, the species can be found. The richest location is 36, which is an open poorly developed Pinus sylvestris forest, which is trespassed by goats when they go to their grazing grounds higher up the mountain. On this moment, the influences of the goats are not clear. Do they eat the plants before they get flowers? Or do the goats create a more open and dynamic structure of the vegetation, which is the optimal biotope for Orchis spitzelii? Further research is necessary to answer these questions.
Natural factors can also create a certain dynamic situation. In the Pinus sylvestris forest on location 36 the trees are in a poor condition. Farmers in the neighbourhood told us that the branches of these poorly developed trees were often broken due to a heavy snowload in snowrich winters. The masses of broken branches on the ground make the forest less suitable for many plants. So, the vegetation on these places is badly developed. However, exactly on these places Orchis spitzelii was growing in abundance. Also Landwehr (1977) stresses the relevance of dynamic factors in the Orchis spitzelii biotope. Indeed, Landwehr mentions the relevance of a stable biotope. But in stable biotopes dynamic influences can be persistent and play a significant role. The dynamic factors are after all the same in every year, which implies that this is a very stable situation.
On the open steep slopes strong dynamics situations are effective due to falling humus particles, small stones and grit. We could check this during visits in late winter when the slopes higher up the mountain were no longer snow-covered, while the lower situated slopes were still in the shadows and consequently snow-covered. In that situation we could easily find out how much material falled down from the barren slopes to the snow in the shadows on the lower parts of the mountain. There proved to be a continuous �bombardment� of small particles which makes the slope inappropriate for most plants. In particular in these open stretches Orchis spitzelii is growing.
On a few places we studied the substrate on the slopes and on the steeper parts of the slopes just above the mountainpath. Orchis spitzelii grows here in particular in a loessial mixture rich in small stones and grit, which is pervious to water. There is not any stagnation if the flow of water, which is also caused by the inclination of the slopes. The soil contains however, due to the calcareous loess, sufficient water to provide the plants for water during the growing season. The richness of small stones and grit in the substrate makes the soil open for oxygen, which is important for an appropriate functioning of the mycorrhiza in the root system (see also Mrkvicka, 1992).
Mrkvicka (1992) states that this species is using the biotope in a very interesting way., namely by � Standortwechsel durch Biotopwechsel�. He has the opinion that Orchis spitzelii reaches its optimal situation when a total sum of environmental factors is met. One of these factors is the temperature in spring. He states that the locations of the open southerly inclined gritslopes high up the mountain profit so much from the sun in spring, that the �temperature-factor� is the same as on the lower locations in the forests.
Summarising, we can recognise the following types of locations:
The steep more or less vegetationless slopes
Most of these locations are high up in the mountains at an altitude of approximately 1700 meter (24, 31, 32 and 33). The soil is only partly covered by any form of vegetation. In some cases there are some low isolated trees of Pinus sylvestris. All these slopes are full on the south and they freely receive the influence of the sun. In nearly all cases Orchis spitzelii does not receive here any shadow. Though these slopes are high up in the mountains, southern species such as Linum salsoloides and Potentilla rupestris are in particular growing here due to the influence of the sun. We find here also Dactylorhiza sambucina, which is in the Vercors restricted to the higher altitudes. Arctostaphyllos uva-ursi, mentioned by Delforge (1994) is characteristic for these locations; they are lying as a carpet over the rocky outcrops. Two other characteristic species for these locations are Globularia nudicaullis and Polygala ssp. But the latter species is so common in many biotopes in the Vercors, that it can hardly be considered as a specific species for these slopes.
The locations on these slopes are mostly rich in the number of plants. We are of the opinion that till now we did only find a limited number of these locations. Taking the region in consideration, there are many other quite similar locations which we did not visit till now. These locations have much in common with the location in Switzerland, described by Hertel, 1988).
Approximately 500 meters lower, locations of Orchis spitzelii were found which have many characteristics in common with the higher locations. Mountain paths and roads have often steep parts above them, where the soil with its vegetation has been glided away. When these relatively steep edges have a southerly inclination, they receive the sun early in the season; in winter the snow is melted away here within a few days. Orchis spitzelii is growing here on the steep barren edges, just below the place where the vegetation is not shifted away. Often Gentiana angustifolia is accompanying Orchis spitzelii. Other plant species are scarce on these locations. Locations 3, 8, 11 and 18 are characteristic examples of this subtype.