Aims and Methods in the Botanic Garden “De Wolf” of the State University Groningen (Netherlands)

A. Woodvegetations 1. Foliage trees, Conifers. Not mown. Herbs with great production of litter; hardly any mosses or fungi. 2. Foliage trees, Conifers, promiscuous forest. Mown once a year. Herbvegetation with less production of litter. In the last section rather more mosses and fungi than in the former two. 3. Foliage trees, Conifers, promiscuous forest. Mown twice a year. Herbs with little production of litter, mostly springflowering. In the promiscuous forest e.g. many Anemone nemorosa, Ranunculus ficaria and auricomus. Into the pinetum heath penetrates, especially in the lower parts and the open spaces. 4. Through the entire wooded area broad strips, also meant for paths, mown several times a year. Hardly any herbvegetation; abundant development of mosses and fungi. 5. In the entire wooded area spontaneous shoots of foliage trees. In certain sections no interference by man; here a “jungle” originates. In other places this development is checked by cutting. 6. In several places in the forest, where socalled trunk- and branch-manuring is practiced, abundant development ofwoodfungi, mosses and Myxomycetes, while gradually ferns settle on the decayed wood. B. Dams Partly unplanted, partly planted with foliage trees and with Conifers. Mown or not; in the former case mosses, lichens, fungi but little herbgrowth; in the latter rich development of herbs. C. Ruderal vegetations 1. Wide area in deciduous forest, where every year the wood — to be thinned out —- of small proportions is burned. Here also plants characteristic of such habitats, such as the moss Funaria hygrometrica and the fungus Flammula carbonaria. 2. Sections outside the forest, dug up in spring and autumn. “Weeds”. D. Meadowvegetations There are meadows within the forest and without. In the first case the vegetation is influenced by leaf- or needle-litter and by other “forestal conditions”. 1. Foliage-tree meadows and needletree meadows. Not mown. Herbvegetation with very great to great production of litter. No mosses or fungi. 2. Id. Mown once a year. Herbgrowth with less production of litter. Little development of mosses and fungi, in needletree meadows more than in foliage-tree meadows. 3. Id. Mown several times a year. Little herbvegetation. On the other hand many mosses and fungi. 4. Meadows outside the wood, so where the above mentioned influences of forestal conditions do not exist. a. Not mown. Herbvegetations with great litter production. Mosses nor fungi. b. Mown once a year. Herbvegetations with less production of litter. Mosses and fungi. c. Cut and weeded, so very intensive human influence. Herbs with very small production of litter. We also interfere in the mossvegetation; development of Sphagnum however is stimulated. After years the Sphagnum vegetation probably will become so dense that it starts to dominate; then interference will be necessary there too. One of these meadows might be described a little more in detail, viz. the orchid meadow. After the moment at which the most important plants have shed their seeds, the meadow is mown and the refuse is immediately removed. The impovering gradually progresses and the meadow, in which grasses dominated, begins to adopt the character of the socalled “bluegrass meadow”. Carices penetrate and a plant like Cirsium dissectum which is typical in such meadows, settles there quite spontaneously. Early in spring plants like Anemone nemorosa, Fritillaria meleagris, Primula elatior, flower here. Somewhat later there appear Lychnis flos-cuculi, Pedicularis palustris, Ajuga reptans, Rhinanthus glaber, Filipendula ulmaria, Molinea coerulea and orchids: Orchis majalis, Orchis maculata, Orchis morio, Orchis palustris, Listera ovata, Platanthera bifolia and Gymnadenia conopsea. But also mosses like Climacium dendroides and fungi like Sclerotinia tuberosa and species of Hygrophorus occur. Besides the above mentioned meadows there are at “de Wolf” also a number of meadowtypes in the making, where we will try to change only one factor at a time. 1. There are four meadows side by side under the same conditions of light and humidity, which also receive the same method of cultivation (mown a few times a year) on 4 greatly differing substrates, viz. a. on loamy sand, rich in humus; b. on calcareous seasand; c. on lime marl; d. on coalashes. The differences in overgrowth were extremely remarkable already in the first year; the further development can be studied. 2. Three meadows develop on loamy sand, rich in humus, and under the same conditions of light and cultivation (mown a few times a year) but under different conditions of humidity; a. moist; b. drier; c. dry. For six meadows, on loamy soil, rich in humus and under similar conditions of light and moisture, the identical cultivation is practiced (mown once a year) viz. respectively on the 1st day of the months June to November inclusive. E. Heaths The grass- and herbvegetation is either mown here, or cut or weeded. If necessary the development of mosses too is checked, that of Ericaceae and Sphagnum on the contrary is stimulated. It is not the intention ever to interfere with the growth of Sphagnum in heaths. 1. Myricaand Vaccinium heath. In a shallow dell, where water stagnates in a few places in winter only. As yet no Sphagnum development. 2. Callunaand Erica heath. There are two large and a series of small dells in it. A great part of this heath is submersed all winter long. This heath, where Empeirum nigrum has been introduced, harbours plants we might expect on such soil in nature just as well; Pedicularis sylvatica, Gentiana pneumonanthe, Arnica montana, Orchis maculata, Sphagnum cushions; in deeper pits Narthecium ossifragum, Eriophorum angustifolium, or on a peaty soil Andromeda polifolia and Oxycoccus quadripetalus; in more bare places (sodded patches, mostly on paths) Drosera rotundifolia, Pinguicula vulgaris and Lycopodium inundatum. 3. Pinus montanaand Rhododendron heath. Principally alpine species. F. Walls and stony meadows Here human interference is very great on account of repeated weeding. Only herbs with a very slight production of litter, such as alpine herbs and rosetteplants are tolerated. On the stones many mosses and lichens. G. Pools As has been made clear in the part treating the water-provision, there are brooks and pools with eutrophic subsoil water and others with oligotrophic rainwater. The former type of water on the one side feeds a few small pools in the promiscuous forest and flows past mown pastures, where it makes it possible for Sphagnum to develop, while on the other side it flows through foliage tree-forest and part of the meadows where it provides water for a pool which is choking up, and for a few other pools of various depths. In, and bordering, these pools an abundant growth of water-, swamp- and shoreplants. The oligotrophic rainwater is caught in the pinetum and on the heaths (vide eo loco) in more or less deep valleys without drainage. They have all been excavated in the boulderclay-soil so that no water is lost by percolation. Where the water stagnates very much, ~ Spaghnum cushions develop, which have been evidently growing these last few years. In the pinetum we sometimes tolerate leaftree-shoots in the dells, so that a swampforest may originate; in other places it is destroyed by cutting. In the Pinas rnontana-Rhododendron-vzWey the rainwater stagnates m a small runnel. Along the sides development of Spaghnum. Further there are four pits on the southborder of the grounds of various size and depth, excavated in the clay and bordered by claydams. The first, shallow, is without water for some time in dry summers; tree- and herbshoots are then taken away. This oligotrophic pool has a.o. already many remarkable micro-organisms. On the dams of the second, deeper, pit, which never quite falls dry, a strong development of Polytrichum commune originated on the bare clay. Of late we see it die down, while new growths do not appear. Along the shores of the pool much Marchantia polymorpha, Pellia epiphylla; in the pool algae, a.o. Chara vulgaris. The 3rd and 4th pits are not bordered by dams; they are part of a valley which is submersed in winter. Here a.o. magnificent growth of Hypericum humifusum. The valleys and pits in this area are bordered by rows of Conifers and of leaftrees resp. Further there are still a few other dells, lying in the leaftreeforest and in the meadows. Some have stagnating water in winter, others have not. There is, however, in all those valleys sufficient water to enable the growth of resp. a hygromorphous forest- and a hygromorphous meadow-vegetation. Of course it is impossible, in this short survey, to describe everything that happens in the botanic garden “de Wolf”, to discuss all the plants that occur there. A more explicit description of only a few sections was chosen, while the photo’s reproduced here also give an impression of the grounds. There is continuous vegetation in nearly all sections of the garden and most plants have no fixed place, chosen by the gardeners, but they themselves “choose” there spot for development. The chance that they find habitats congenial to their growth is great because there are so many different conditions in “de Wolf”. We have tried to give an impression of the exceptional character of “de Wolf” in this paper and also of the great variety of vegetationtypes which have developed there in the course of about 25 years.