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.

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.

No description available.

No description available.

No description available.