Changes taking place in the natural tropical forests are intricate, and the ecological processes which they entail are only gradually becoming understood. Human interference in these processes frequently leads to unforeseen consequences, silvicultural treatments being apt to be applied long before much is known about the characteristics of the constituent species and the particular successional phases on which treatments have been imposed.

Perturbations create gaps of varying sizes. Both regeneration in the gaps and the latter's restoration to a state of equilibrium, depend on their size and the intensity of the disturbance. Deflected successions may occur in sensitive ecosystems whereby progress towards vegetational climax is permanently interrupted. In Africa, the human impact on the natural vegetation has been more severe and for a much longer period than in either the Amazon or in large areas of the Indo-Malaysian rain-forest.

Apart from the limitations of existing silvicultural techniques for inducing regeneration and promoting growth, vital management decisions are commonly based on the results of regeneration sampling. But this traditional sampling technique does not make sufficient use of the indications provided by Iiocourt's ‘living space’ theory. However, modified procedures which can easily be undertaken and which assign more appropriate areas of occupation to individual seedlings, saplings, poles, and trees in the stand, provide more realistic estimates of the overall stocking. Though much damage is done to saplings and poles by the felling of large trees, the severity of damage is related more to the number of trees felled than to the basal area or volume removed. However, research into effects of alternative logging regimes (monocyclic versus poly cyclic) is required to resolve, for particular forest types, the issue of appropriate management/silvicultural prescriptions.

On the basis of silvicultural research in Nigeria, tentative conclusions have been reached that the growth of a residual stand after exploitation can be accelerated by shelterwood treatments. In particular, climber cutting and opening of the canopy by poisoning are effective treatments in promoting recruitment of saplings and poles from seedlings, and their subsequent growth and survival. Controlled logging can be as effective as a poisoning operation to remove shade-casting, uneconomic emergents, and if substituted for such shelterwood poisoning could reduce the expense of implementing forest treatment.

In forest management, account must be taken of differing capacities for growth between different species—especially in response to different silvicultural treatments. Thus in the experiments discussed, heavy poisoning promoted greater increments than selective poisoning, though the difference was not statistically significant.

At the beginning of the twentieth century, the Galilee Mountains were still practically a ‘closed system’, as a result of which the balance of land-use was more or less preserved. Rural settlements had then hardly developed, and stagnation of the few remaining mountain towns was observed. In general, the roads were unpaved routes, the economy served for subsistence only (based mainly on agricultural terraces), while most of the area was of forest or rocky ground serving as pasture.

During the British Mandatory period, the Galilee Mountains area opened up slowly, and this process has increased ever since the establishment of the State of Israel. The Mountains are facing a tremendous increase in population as a result of natural local increase (mostly Arabs) and migration (mostly Jews). This excessive mountain population in Israel is an unusual phenomenon in comparison with other mountain regions in the western world, which have generally decreased in population though there, too, the equilibrium of land-use has been shaken—for instance in the Swiss Alps (Bugmann, 1980; Gallusser, 1980; Messerli et al., 1980), and in the Rocky Mountains of the United States (Kelly, 1980).