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This research involved three years of field work in Glen Tanar, NNR, in northeast of Scotland. The role and seedbed preparation on regeneration of native pinewood and birchwood has been studied. The ground disturbance effects on soil seed bank, soil nutrient dynamics and ground vegetation recovery have been investigated in detail. Effect of light and burning of soil or fertiliser on Scots pine and silver birch seedling survival and growth were monitored in the laboratory to provide some information for the field observations. Germination of pine and birch seeds began about 3 weeks after experimental sowing at the end of July, 1988. However, the number of germinants in 1989 and 1990 was much lower than in 1988. 90% of Scots pine viable seeds died or failed to germinate and more than 95% of birch viable seeds failed to germinate. The germination of pine and birch seedlings was greatly increased when the moss and litter layers were completely removed by the `Burning' and `Pull' treatments. With treatments in which no humus was removed, the treatments `Control' and `Cut', little or no germination of pine and birch seeds occurred. Mortality of both pine and birch seedlings established in 1988 is significantly less on all sub-plots of ground treatments than seedlings established in 1989. Seedlings which were established after light burning are suffering the highest mortality in most cases, possibly because of competition from unburnt <i>Calluna</i> shoots and the rapid recovery of the ground flora in this treatment. Birch seedlings established in 1989 are suffering higher mortalities than pine seedlings established in 1989 on most of the ground treatments. Scots pine and birch seedlings were significantly depressed in relation to increasing shade in terms of height growth, biomass production and relative growth rates, which might suggest that birch and pine are both shade-avoider and light-demanding species. Scots pine seedlings demonstrate a much lower compensation point (3% RLI, relative light intensity) than birch (12% RLI) seedlings. Scots pine would thus have better survival than birch under shaded conditions of 10% RLI or less. The laboratory experiment showed that birch and pine seedling height growth was enhanced by burning or PK fertiliser treatments. Burning plus PK fertiliser is better than burning alone. Growth of Scots pine and silver birch seedlings in the absence of PK fertiliser additions was enhanced by burning but not by ash additions. Seedling height, relative growth rate, biomass and nutrient assimilation were greater on burned soil. Birch seedling demonstrates higher growth rate, higher height growth and more sensitive response to burning or fertiliser addition than pine seedling. However, the field study showed that height growth of pine and birch was not significantly increased by burning. The field enumeration surveys at Glen Tanar showed that some forms of soil disturbance (mechanical or burning) might be necessary and beneficial to Scots pine and birch regeneration. However, in the longer term, fencing (or some forms of protection from browsing) is very important to secure tree regeneration since the significant effect of initial soil disturbance was eliminated 12 years after the disturbance.

Deforestation problem at a global level in general and in developing countries in particular have been an issue of prime concern among researchers and both government and non government organisations all over the world. Its causes have been identified as the daily demand of people for fuelwood, fodder and small timber in rural areas of developing countries in general and India in particular. This led to the emergence of a new concept of social forestry with agroforestry or farm-level tree growing as its integral part in the late 1970's. The programmes and projects on both social forestry and agroforestry in India have been dealt with in a 'top-down' approach to planning. Perhaps that it why they have not achieved the desired success. The reverse approach or 'bottom-up' approach because of its time and resource consuming nature, has not been adopted by the Government. Therefore, 'microplanning' a compromise approach, has been suggested in the present study. As individual households are at the lowest level of the microplanning system, household level linear programming models have been developed in this study. The models have been developed and tested on a field survey of three villages in the Haryana state in India. The study has demonstrated that tree planting on farms can increase farm income and can play a significant role in rural development in India. The models developed in this study can be used to estimate farm incomes following the introduction of trees on farms such that the most economically viable option can be recommended to each farmer. The validation of these models confirms the potential for farm level tree growing in Haryana.

This thesis has the aim of presenting a forest management system to be applied on small farms, especially in the settlement projects of the Brazilian Amazon, and to examine its sustainability by investigating the responses of the forest in terms of the changes in natural regeneration in felling gaps and the dynamics of the residual trees. Using the program CAFOGROM, an additional aim was to simulate the forest responses to different cycle lengths, harvesting intensities and silvicultural treatments to determine the theoretical optimum combination of these parameters. The proposed forest management system was designed to generate a new source of family income and to maintain the structure and biodiversity of the legal forest reserves. The system is new in three main characteristics: the use of short cycles in the management of tropical forest, the low harvesting intensity and environmental impact and the direct involvement of the local population in all forest management activities. It is based on a minimum felling cycle of ten years and an annual harvest of 5-10 m3 ha-1 of timber. The gaps produced by logging in PC Peixoto can be classified as small or less often medium sized (canopy openness from 10% to 25%). Differences in gap size and canopy openness produced significant differences in the growth rates, species richness and species diversity of seedlings, but no statistically significant differences could be determined according to the position of the quadrats in the gaps. Mortality rates increased and recruitment rates decreased with increasing gap size. The density and recruitment of seedlings of commercial species was not different between gap sizes, but gap creation increased the growth rate of the seedlings of these species.

Seed production and germination of some timber tree species were studied in Ghana for possible prediction of seed yield and natural regeneration. Seed phenology in 13 species was monitored for two years, using permanent seed traps in two forest sites. Seed germination tests were conducted in neutral, green shade and dark in shade houses for 20 species. In the forest, germination was tested in forest gaps receiving different irradiances. Fruiting frequency ranged from twice in each year to supra-annual fruiting. Fruiting periods for species were consistent between years. Fruiting synchrony was higher among individuals of a population than between sites for the same species. Fecundity differed between years for the majority of species and between sites for species common to both sites. Premature fruit abscission was quite common. Maximum seed weight and percentage germination occurred during peak fall of mature seeds. Seeds of the majority of species germinated equally in light and dark and also in neutral and low red: far red ratio. These included some species previously classified as pioneers. In the forest germination was depressed in a large clearing for the majority of species. The use of photoblastic germination alone to define pioneers leads to a smaller group of pioneer species than is presently recognised. Large gaps due to logging may discourage natural regeneration.

A study was carried out to investigate the effect of four tree species on the acidity and chemistry of rainwater as it passed down the forest profile. The four species, Norway spruce (Picea abies), Scots pine (Pinus sylvestris), oak (Quercus petraea) and alder (Alnus glutinosa) were all at the same site at Gisburn (Bowland Forest), north-west England. The water was collected as rain, beneath the canopy and the forest floor, at the boundary of the A and B horizons and within the B horizon. The water was collected and analysed for pH, PO43--P, NO3--N, NH4+-N, Cl, SO42--S, Na+, Ca2+ and Mg2+ every two weeks. There were occasional analyses for aluminium. Porous ceramic cups were used to collect water in the soil horizons and so volumes had to be estimated. A further correction had to be made to allow for the loss of water as runoff over the surface of the forest floor. There were consistent differences between the species. The species differed in both the processes responsible for and the location of the production of acidity. Under all species there was a great reduction in acidity in the deep soil horizons. The source and nature of the anion thought to be associated with cation leaching also differed under the species. Most of the species differences could be attributed to processes occurring in the forest floor. Of most importance were: the fixation of atmospheric nitrogen by alder and its subsequent release as NO3--N; the rate of decomposition of the various litters; and the horizon where most root uptake occurred. The differences observed in the throughfall were not reflected in the forest floor or soil horizons. There was no evidence of depletion of cations in the mineral soils after thirty years of tree growth but it was considered that the risk was greater under alder and pine than under spruce and least under oak.