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Forest edges created by scattered-patch clear-cutting have become a common landscape feature in tropical montane forests, including pine-oak and evergreen cloud forests. Forest-edge-pasture gradients were characterised with respect to changes in vegetation structure and ecological function in the Highlands of Chiapas, Mexico. In this study two edge types were recognised by assessing vegetation structure and floristic composition along a gradient from adjacent clearings into the forest interior. The influence of edge type (either “hard” or “soft”) was investigated with respect to acorn production, predation, dispersal and germination, seedling establishment and abundance of small mammals during two consecutive years. There was no significant difference between the forest interior and the edge in plant density and basal area. Floristic richness and composition did not vary with depth-of edge influence. Edge type influenced the relationship between probability of acorn removal by small mammals and distance from the edge in both mast fruiting and non-mast fruiting years. Movements of metal-tagged acorns supported the hypothesis that soft edges are permeable to acorn predators and/or dispersers, and that rodents move acorns up to 15 m into the grasslands in soft edges. In hard edges, acorn dispersal and removal was greater within the forest. Peromyscus spp. were the main acorn predators and/or dispersers of acorns. The intensity and rate of acorn removal varied with the year, demonstrating that in mast-fruiting years some seeds may escape predation by animals, according to the predator satiation hypothesis. Grasslands presented fewer insect damaged acorns and higher seedling emergence than the edge and the forest, emphasising the importance of acorn dispersal. Seedling survival and growth were higher for 12 m into grassland from the soft edges, suggesting that the probability of oak expansion into the grassland increases when the grasslands have been abandoned and have a scattered cover of shrubs. The results indicate that edge structure alters edge function (edge permeability), which determines the probabilities of tree invasion into old-fields. These findings have implications for the conservation of montane forest in Mexico where scattered patch clear-cutting is widespread. Recommendations are made for different restoration practices to accelerate tree colonisation into the grasslands across hard and soft edges.

Tree breeders worldwide have highlighted the importance of wood quality within the juvenile core in determining final timber strength. The potential for improving timber strength by estimating genetic parameters of certain wood properties of Sitka spruce (Picea sitchensis) within the outer zone of the juvenile core was investigated. Fifteen trees were sampled from each of 33 families selected from a 20 year old open pollinated progeny trial. A number of wood properties critical to wood strength were measured; namely, density, grain angle, microfibril angle and branching characteristics. Clearwood stiffness and strength along with indirect measures of stiffness using acoustics and density using Pilodyn measurements were assessed. All wood properties were moderately heritable, wood density and acoustic velocity were the most heritable traits (h2 i 0.71 and 0.67 respectively). Genetic correlations showed that wood strength and stiffness were strongly correlated with wood density (0.86 and 1.04 respectively) and microfibril angle (-0.79 and -0.62 respectively). Acoustic velocity was strongly correlated with wood stiffness (0.81) and microfibril angle (- 0.83). The ability to select trees for wood stiffness with the use of acoustics along with the moderate inheritance of this trait should enable improvements in the wood quality of Sitka spruce. Despite the unfavourable correlation between growth rate and some key wood quality traits associated with timber strength, selection of certain families would enable modest gains to be made in both growth rate and wood quality.

I assessed forest dynamics, stand structure and composition using repeated measurements of permanent plots over twelve years, in areas logged according to RIL guidelines and areas logged conventionally (CL) in Sabah, Malaysia. I compared successful pathways between treatments and used stand dynamics data to estimate carbon fluxes and pools over twelve years. Matrix models were used to generate projections of carbon emissions, sequestration and storage over a thirty-year logging cycle. Stem density (439 stems ha^-1 (95% CI = 358 – 477), basal area (32 m² ha^-1 (95% CI = 23-44) ) and carbon stored in above ground biomass (AGB, 1160 Mg C ha^-1 (95% CI = 97 – 232)) did not differ from prelogging levels twelve years after RIL. There was no recovery of these years variables after CL (246 stems ha^-1 (95% CI = 200 – 303), basal area 20 m² ha^-1 (95% CI = 13-28), carbon in AGB 101 Mg C ha^-1 (95% CI = 58 – 157)). Mortality, growth and recruitment rates remained elevated throughout the study. Both damaged and undamaged trees experiencing high mortality, especially after CL. Stalled, tree-less gaps and vine-covered building phase forest covered 54% of the CL area and appeared to have increased over time. Closed canopy and tree-dominated building phase forest dominated the RIL areas (81%). Total carbon storage over a thirty year logging cycle after RIL is projected to be 40% higher than after CL and result in reduced emissions of 88 Mg C ha^-1 and increased sequestration of 27 Mg C ha^-1. The total carbon benefit of using RIL instead of CL in lowland dipterocarp forest is projected to be 196 Mg C ha^-1 over a cutting cycle. My comparisons and projections of emissions, sequestration and storage in above-ground biomass show that the carbon benefit of reduced-impact logging exceeds previous projections. RIL areas are likely to provide substantial co-benefits in timber stocking, biodiversity conservation and resilience to climate change compared with CL areas.

Scots pine (Pinus sylvestris L.) represents around 16% of the area of commercial conifer plantations in Great Britain, but around 30% in north and north-eastern Scotland. Most of the timber produced from these forests goes into lower-value markets such as fencing and panel products, and only a small proportion is converted into high-value structural timber. In order to maximise financial returns from this resource in the medium and long term, it will be necessary to increase the outturn of structural timber. However, this requires knowledge of the variation in those wood properties that influence structural timber performance and of the effects of silviculture on wood quality. Changes in silvicultural practices in recent decades—wider initial spacings, a preference for artificial regeneration, and an increased use of mechanised thinnings, have led to concerns about the suitability of Scots pine timber for use in structural applications due to potentially poorer stem form, a greater proportion of juvenile wood and larger, more numerous knots. As part of the research presented here, novel predictive equations were developed for the key physical, mechanical and branching properties that determine structural timber quality in Scots pine, namely: microfibril angle, wood density, clearwood bending strength and stiffness, and branch number, size, insertion angle and status (alive or dead). Simulations were carried out using these equations to examine the effects of different silvicultural regimes on each wood and branch property of interest. Based on these simulations it is recommended that in order to produce high quality Scots pine timber, trees are planted at narrower initial spacings and grown on longer rotations than currently prescribed, and, where appropriate, thinnings should be delayed. Together, these measures will restrict final branch size and the amount of mechanically inferior juvenile wood in the final crop.

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.

Shortage of timber input for processing industries is the main issue facing the Malaysian forest sector. The need to implement policies which will ease the pressure on timber shortage and induce the expansion of forest sector industry, development of rubberwood sector in Malaysia is becoming increasingly urgent. The Malaysian government has announced and implemented three main policies: timber market restriction, encourage utilisation of rubberwood and promotion of lesser-known timber species (LKS). Application of timber market restriction policies has a considerable dispute; firstly because of widespread disagreement over the effect on efficiency of utilisation of timber that lead to timber harvest and deforestation and secondly it will undermine the government effort to promote utilisation of rubberwood and lesser known species. In this thesis, an attempt has been made to enlarge the available empirical knowledge of such effect through a. multi-sectoral forest - rubberwood sector model simulation. An analytical framework is developed, focusing on three major product of the forest sector; log, sawnWood and plywood, and two major products of rubberwood sector; rubberwood log and sawn rubberwood. The framework is used to developed an empirical model of forest-rubberwood and analysed the effect of market restriction policy on forest harvest behaviour, sawnwood and plywood development, rubberwood sector development and change in forest cover. The production, consumption and export of timber, sawnwood, plywood, rubberwood and sawn rubberwood, and change in forest cover have been examined in relation to a number of market policies: export taxes, export ban and import ban, and other alternative policies; royalty, exchange rate, wood utilisation efficiency and subsidies. A series of simulations was undertaken to describe the effect of these policies. The analysis suggests that export restriction on processed timber product will reduced the timber harvest and improved the forest cover but will hinder or distort the development of rubberwood sector and utilisation of less timber species. Related to the deforestation, the notion of environmental Kuznets curve is also examined. The results does not support the existence of this notion for Malaysia. In addition to sectoral analysis, an extended analysis using species harvest was undertaken, as a new approach to investigate efficiency of utilisation of wood resource and forest cover. The results show that promotion of species utilisation will not be achieved with the implementation of market restriction policy on forest products. Species analysis also indicate that in the absence of full data on the quantity of forest harvest, species harvest data would be a good alternative to estimate the effect of policies on forest cover.

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.