One part of the afforestation programme consisted of the establishment of an afforestation trial on a bog and fen site in central Newfoundland to determine growth and nutrient response of newly-planted black spruce (<I>Picea mariana</I> (Mill.) B.S.P.) and eastern larch (<I>Larix laricina</I> ((Du Roi) K.Koch). The experimental design was a split-split-plot consisting of surface treatments (untilled, tilled) as main-plot treatments, fertilization (unfertilized, PK) as split-plot treatments and four ditch spacings ( 3 m, 5 m, 7 m, and 15 m) as split-split-plot treatments. A total of 3,960 25-week old container seedlings of each species were planted on each site at spacings of 0.50 m in rows of nine trees, each row being situated at a distance of 1.0 m apart. Surfaces were tilled at 0-200 mm depth using a farm rotovater attached to the back of a tractor. Ditches were made at depths of 0.50-0.75 m with a Dondi ditcher attached to the back of a tractor, and fertilizers were broadcast at the rate of 60 kg/ha P and 50 kg/ha K. The second part of the afforestation programme was a refertilization trial of 1) Japanese larch (<I>Larix leptolepis</I> Seib and Zucc.) and black spruce trees planted on Stephenville bog in western Newfoundland in 1968; and 2) black spruce, white spruce (<I>Picea glauca</I> (Moench) Voss) and lodgepole pine (<I>Pinus contorta</I> Dougl.) planted on Millertown fen in central Newfoundland in 1973. Both sites had been ploughed with a Parkgate-Tyne plough at 1.8 m spacings 1-2 years prior to planting. Following planting of the Stephenville site in 1968, the black spruce and Japanese larch were spot-fertilized (around each tree) with a top-dressing of 57 g of ground mineral rock phosphate. This procedure was repeated in 1970 with 128 g of a mixture of phosphate and potassium (20% P₂O₂, 20% K₂O). On the Millertown site, all trees were spot-fertilized in 1973 with a mixture of 71 g urea, 99 g rock phosphate and 41 g potassium sulfate.

Consistent patterns of foliar N concentration and δ¹⁵N were found in age sequences of foliage. N concentration decreased with age and δ¹⁵N increased with age. Patterns of δ¹⁵N may be useful in studying nutrient retranslocation within the canopy because, as far as it is known, they are unaffected by contemporary changes in other leaf components. No evidence for increased efficiency of N recycling in spruce from mixed stands as compared to spruce from pure stands was found. The δ¹⁵N data appear to confirm that the amount of N retranslocated depends on the N concentration of the foliage. There was evidence that in a young site the δ¹⁵N value of externally available N in the mixed stands became increasingly enriched over time, while the δ¹⁵N value of externally available N in the mixed stands at a mature site remained constant. Foliar N concentrations and δ¹⁵N of spruce in mixtures with different nurse species and in different ratios were measured. The δ¹⁵N values of nurse foliage differed significantly between species, but no significant effects of nurse species on δ¹⁵N value of the spruce were found. Increasing the proportion of the nurse in a stand increased the foliar N concentration of spruce and caused an enrichment in the ¹⁵N abundance. Soils from one site were subjected to a series of extractions to extract N pools of different liability. N concentrations of 4 pools were measured and δ¹⁵Nvalues calculated. Total soil N in mixed stands was enriched in δ¹⁵N relative to pure stands. It was not possible to identify the pools available to spruce in pure and mixed stands because of large errors in δ¹⁵N values. Organic N pools were consistently enriched relative to largely inorganic N pools. The foliar δ¹⁵N values of spruce in pure stands were close to those of the hot K₂SO₄ extractable pool containing microbial N and amino acids, whereas in the mixed stands, the foliar δ¹⁵N values of both spruce and pine were close to those of the hot HCI extractable pool containing less labile organic N. The results are discussed in relation to the mixtures effect. It is concluded that patterns of ¹⁵N natural abundance in pure and mixed stands of spruce support the hypothesis that in mixtures, spruce has access to a source of organic N not normally available to it in pure stands.

The study analyses the evolution of Joint Forest Management (JFM) in India. The influence of historical, social, economic and cultural factors on participation in JFM is discussed with reference to the Northwest Himalayas. The history of forest use and management in the eras of Pre-British rule, British rule and post-independent period is discussed. The household level differences in six case study level village, with regard to size of landholding, livestock and trees are compared. The influence of family size, caste, literacy and occupation for its dependence on forests for timber, fuelwood, fodder, livestock grazing and non-wood forest products is analysed for implications for participation in JFM. Variation between villages due to altitude, distance from markets, socio-economic characteristics of households all influence dependence on forests. The opinions of households in villages with regard to decrease in forest and forest resources, in relation to forest management option vary. The protection and management of forest areas need to be clearly defined in relation to multiple use rights of many villages. The existence of institutions of co-operative labour, local village gods, women and youth groups and of sacred forest groves provide examples of potential co-operative development for increasing mutual understanding between communities. These can be utilised for formation of rules for forest use and forest management by Village Forest Development Committees. Forest staff have different perspectives with regard to implementation of JFM. They recognise a need for re-training of front-line forest functionaries particularly 'Forest Guards'. Social, economic and political complexities necessitate that JFM must be a process where these factors are incorporated into Forest Department activities and monitored in order to evolve effective institutions for forest use and management. The new forest policy has to be flexible and needs to be amended on the basis of efforts at implementing JFM.

On poor peats and heathlands, satisfactory growth of Sitka spruce (<i>Picea sitchensis</i>), planted pure, can only be achieved with repeated applications of nitrogen fertilizer. However, when spruce is planted in mixture with Scots pine (<i>Pinus sylvestris</i>), Lodgepole pine (<i>P.contorta</i>), or Japanese larch (<i>Larix kaempferi</i>) it shows improved nitrogen nutrition and better growth than pure spruce. The mechanism by which the 'extra' nitrogen required to sustain improved spruce growth has not yet been elucidated. A mechanism is proposed in this thesis. The mycorrhizal community is examined in pure and mixed stands at Culloden Scotland, by recording potential mycorrhizal fruiting bodies, carrying out a seedling bioassay and characterising the mycorrhizal communities on both pine and spruce roots. Approximately 30% of the mycorrhizas on pine mixtures were formed by <i>Suillus</i> spp. but there were no <i>Suillus</i> mycorrhizas on spruce, even in mixture. In pure stands spruce mycorrhizas were mostly <i>Tylospora fibrillosa</i> (55%) or Russulaceae type (16%). In mixed stands, beneath pine canopy, the production of <i>T.fibrillosa</i> on spruce roots was lower (26%) and that of Russulaceae was higher (48%). The Sitka spruce mycorrhizal populations on younger trees in experiments at Speymouth and Shin were also examined. The results suggested that a change in mycorrhizal associations are a part of the 'mixtures effect' and that it starts before closed canopy is established. The ability of various ectomycorrhizal fungi were screened for their ability to break down and utilize protein. <i>Suillus variegatus</i> had the greatest proteinase activity whilst <i>Lactarius rufus</i>, a member of Russulaceae had little ability. The ability of <i>L.rufus</i> and <i>T.fibrillosa</i> to utilise protein hydrolysed by <i>S.variegatus</i> and a <i>Calluna</i> endophyte was examined, both isolates could utilise the filtrates as the only nitrogen source. It is suggested that in mixtures the proteolytic activity of ectomycorrhizal fungi of pine results in an extracellular pool of nitrogen for which the mycorrhizal flora of spruce compete.

Effects of N supply, water stress and the water and nitrogen interaction on assimilate partitioning in <I>Populus</I> 'Balsam Spire' hybrid (<I>Populus balsamefera var</I>. <I>Muchuxii </I>(Henery) X <I>Populus trichocarpa </I>var. <I>Hastata </I>(Dode) Farwell.) were studied through three greenhouse experiments. The seedlings in the first experiment received either 1 or 3 or 9 mol N m^-3 over almost a whole growing season. Growth of the different parts of trees increased markedly by N supply. N supply increased whole tree photosynthesis through increasing total leaf area and decreased photosynthetic nitrogen use efficiency. Total respiration also increased with increasing N supply as a result of increasing leaf respiration and below-ground respiration. Below-ground respiration as a proportion of total respiration, however, decreased with increasing N supply. Nitrogen and carbon content and concentrations in different tree components and in the whole tree increased with increasing N supply. Partitioning of nitrogen into different parts of tree, however, showed no response to N supply. The proportion of carbon allocated to the leaves increased while that allocated to the roots decreased as a result of increasing N supply through increasing the concentrations of structural carbon compounds at the expense of those of non-structural carbon compounds. The ratio of total non-structural to total structural carbon compounds, therefore, increased with increasing N supply. In the second experiment, three treatments were applied to trees in the second half of their growing season by withholding irrigation either suddenly or gradually.

No description available.

No description available.

A survey of arthropods associated with exotic multipurpose trees and food crops used in agroforestry and indigenous tree species (Tamarindus indicus) grown in the wild was conducted in 1990 and 1991. The exotic multipurpose tree species (MPTs) used were: Gliricidia septum, Leucaena leucocephala and Cassia siamea growing in an alley cropping system and the food crops were Vigna unguiculata, Zea mays, and Cajanus cajan. The consequences of growing taxonomically related plant species in agroforestry systems were considered. Insecticidal knockdown technique was used to sample arthropods from the foliage. 92 species of arthropods belonging to 48 Families were found to be associated with tree species and the crops. Of these, 27 species were on MPTs, 3 species on crops, 12 species on the chosen wild tree, 13 species were shared amongst MPTs and crops while 14 species were shared between MPTs and the wild tree. A further 19 species were shared between all the groups of plant species (MPTs, crops and the wild tree) with 4 species being shared between the wild and the crop. The effect of tree pruning on arthropod communities on trees was also investigated and the results showed that pruned trees supported a richer arthropod fauna than unpruned trees. Through simulated defoliation, the impact of insect defoliators on four MPTs was also investigated. There was a considerable reduction in overall growth rate, height and diameter increment depending on the level of defoliation. Several stress factors often predispose plants to insect attack. Pruning, as a stressing agent was investigated in relation to infestation of Cassia siamea by the stem borer Xyleutes capensis. Out of the 200 pruned trees surveyed, 90 % showed the signs of borer attack, compared with only 31.5 % of unpruned trees. The role MPTs can play in aggravating infestation of stored pulses by a bruchid beetle, Callosobruchus chinensis was investigated by comparing its survival on seeds of three MPTs and Cajanus cajan. Whereas the bruchid was able to oviposit on both the MPT and crop seeds, no larval emergence was observed in any of the MPTs showing that the MPTs may not support reproduction and development of C. chinensis in the field.

Previous work in animal nutrition has focused on single feeds and assumed additivity in ration systems. In the tropics, farmers are likely to feed mixtures of feeds, including tree fodders, which may not be simply additive in nutritional terms. This study has increased our understanding of the mechanisms that determine the associative effects on the in vitro fermentation of mixtures of fodder tree leaves. Associative effects are governed by a synchronisation in the fermentation rates of the components of the mixture. This is in turn dependent on the fermentability of their chemical constituents. Effects were demonstrated by changes in the fermentation kinetics of gas production curves. The chemical components of fodder tree leaves that affect the fermentation, and the time at which the effect occurs, were identified, using two media of different nitrogen contents. The fermentation of mixtures of pure chemical entities in various combinations was then examined. The greatest associative effects were found when the mixture had components of similar fermentability. It is proposed that associative effects are a function of the synchronisation of fermentation of the different components and was shown to occur at the point when the rate was maximal. With two types of protein (casein and bovine serum albumin (BSA)), utilisation of a protein by rumen microbes was shown to be a function of its fermentability and not of its solubility. This is also influenced by the type of associated carbohydrate. Fodder tree leaves were then combined with different pure chemical entities. Associative effects between fodder tree leaves and carbohydrates were shown to occur and the responses were similar to those obtained with mixtures of pure carbohydrates and proteins. The effect of tannins and phenolic compounds was studied using quebracho tannin as a model, and in five of the tree species. They were shown to affect the fermentability of both carbohydrates and proteins. The effect was greater with carbohydrates of medium to low fermentability. They also reacted with both soluble and insoluble protein. Forages with phenolic compounds showed both positive and negative effects. The effects were possible due to a synchrony or asynchrony in the release of protein. In mixtures of leaves from different species, associative effects were related to their fermentability. Again, this appeared to be the result of the synchronisation of the release of nutrients. Associative effects with fodder tree leaves were of a composite nature and can be both positive and negative. The implications of these findings in relation to in vivo digestion and animal production are discussed. Due to the diversity of fodder trees, there is the potential to develop feeding systems based on mixtures which make better use of available resources. This will also contribute to improved efficiency in the management and use of natural resources, and take advantage of natural plant diversity in the tropics.

The ITE biogeochemistry group monitoring solute movement at Beddgelert Forest provided an opportunity to study the hydrology of a steep section of hillslope in a high rainfall environment. The aim of the experiment was to characterise and compare the hillslope hydrologies of one forested and one whole tree harvested site. Particular attention was paid to the influence of trees both directly on soil water pathways and indirectly on soil characteristics. Atmospheric inputs were monitored for the slope and individual plots for one year. In spite of high rainfall volumes, the slope was not waterlogged indicating a soil with high conductivity. However, frequent macropore flow was not observed at the site. Tensiometer results showed that the mineral soil remained unsaturated. Therefore, a type of preferential flow dominates at both sites. A one dimensional modelling approach to soil water movement confirmed that mesopores within the soil could conduct a large volume of water rapidly. Modelling demonstrated the importance of soil structure especially a large pore size distribution. Analyses of active soil water pathways based on tensiometer results were inconclusive. Downslope moisture gradient combined with high conductivity suggested that large quantities of water could be transmitted. Similarly, the well structured surface soil and marked horizon development also indicate lateral flow may be dominant. The study showed that saturated hydraulic conductivity was highly variable at both the forest and whole tree harvested sites. Analysis of semi-variograms indicated that most of the variance occurred at a sampling distance of 50 cm (i.e. individual tree roots and slate fragments were causing variations in Kg). Investigations of soil structure found more vertical cracks in the forest soil compared to the whole tree harvested site. At the more detailed ped scale, fractal dimensions of both sites were similar. Based on these results combined with temporal moisture content data the research has demonstrated that first, the hydrologicai regime at both sites were similar. Second, the direct impact of trees was limited. Third, the large cracks at the forest site were not significant. The major result of this research was that at both sites vertical flow in the Ah/Ea horizon dominates and a significant amount of water moved laterally within the Eag, Bs and C horizons. This result has major implications for the solute chemistry and movement of acid deposition in that soil water born solutes will tend to enter water courses more rapidly than if vertical flow predominated.