Het botanisch beheer van natuurreservaten op structuur-oecologische grondslag
Gorteria Dutch Botanical Archives , Volume 3 - Issue 2 p. 16- 28
The botanical control of nature reserves based on structure ecology In contrast with previous ideas the human control of nature reserves is nowadays seen as indispensable for the preservation of variety-in space and stability-in-time. Botanical control of nature reserves has for its object the conservation of their various plant communities against alterations coming from the inside and the outside. A second purpose is the enlarging of their internal spatial variety, for the more variety-in-space is present the more varietyin-time can be counteracted. In both cases the cybernetical term “regulation amplifying” is an adequate expression for our activities. The theoretically most difficult problem in modern control is due to its preponderant external character which type is inevitably leading to convergence and some loss of spatial structure. This loss will be the greater the more our methods and tools are going into the convergent direction. Some knowledge about this difficulty may however protect us from unjustified reproaches to the controller involved. Our ancestors did not meet these problems, firstly because they were missing the technical resources for increasing the environmental convergence to an excessive height and secondly because, as agrarians, they formed part of a whole, some relics of which we are trying to preserve now. The old-fashioned agricultural and mining systems automatically led to regulation amplifying in the landscape around their dwelling places by three factors: 1. Stability of the methods. 2. Isolation by distance (development of anthropogeneous ecoclines). 3. Action on a small scale. Provisionally estimated only 5—10 % has remained now of the former biological richness of the Netherlands (less than a century ago) which was mainly based on those three fundaments. All human operations in nature are bringing about change and disturbance. In fig. 1, expressing the second factor (ecocline of human influence) nearly all possible types of normal anthropogeneous disturbance are drawn as concentric circles around a village; the intensity of the influence is gradually decreasing from the inside to the outside: manuring, farming, hay-making, burning, pasturing, cutting of sods, digging out, coppice exploitation, extensive forestry, raking of sphagnum, removal of moss and litter and non-intervention. The two arrows directed to the centre not only indicate the effect of treading on ways but they are also marking the concentration of nutrients from the outside to the inside. In fig. 2 nearly the same types of disturbance are shown “en profil”, together with the principal effects on vegetation and soil and most of the synsystematical units belonging to the various categories of human influence. It is stressed that the removal of soil and organic materials are representing the two most important and at the same time most expensive measures for the botanical control of nature reserves in man-made landscapes. Two main types of control are discerned here, viz. an internal control (continuation of oldfashioned agricultural and mining methods within the reserve) and an external one (protection against the effects of modern agricultural and mining methods coming from the outside). With regard to both types three basic rules are given, for the greater part leaning on the three factors mentioned before: Basic rule I. The preservation of the botanical richness of a nature reserve is most assured if its treatment forms as good as possible a copy of and is directly connected with the methods applied formerly, and is later on subject to as little change as possible. Basic rule II. In case the character and size of a nature reserve are suitable, its internal regulation can be amplified by furthering the development of ecoclines based on the degree of human influence within the area. Basic rule III. Our controlling operations have to be done gradually and on a small scale. Basic rule IV. The external protection of nature reserves in landscapes with a coarse-grained pattern has to be based on their form and size. The more concentric the form and the larger the surface the more safe the areas will be against alterations threatening them from the outside. Basic rule V. If the extension of a nature reserve is sufficient the controller has to take advantage of the ecoclines which are developing along the outskirts by interaction of internal and external influences. In this connection it is a condition that oligotrophic circumstances are predominating over eutrophic ones. Basic rule VI. If alterations are induced from the outside the internal botanical control has to be directed on the delaying of the processes evoked by them.
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