This review deals with the forest vegetation of the Himalaya with emphasis on: paleoecological, phytogeographical, and phytosociological aspects of vegetation; structural and functional features of forest ecosystem; and relationship between man and forests.

https://link.springer.com/content/pdf/10.1007/BF02858183.pdf

Forest vegetation of the Himalaya

The forest canopy is fundamentally important in biodiversity conservation and ecosystem function. Cryptogamic epiphytes are dominant tree bole and canopy elements in temperate and boreal forests, though remain neglected by mainstream forest ecology. This review makes ecological information on cryptogamic epiphytes available to a non-specialist audience, to facilitate their integration in forest biodiversity and ecosystem studies more generally. The review focuses specifically on lichen epiphytes, highlighting their diversity and ecosystem role. A principal task is to explore pattern and process in lichen epiphyte diversity – species composition and richness – therefore demonstrating the utility of lichens as an ecological model system. The review examines key themes in previous research. First, the extensive literature used to resolve species response to, and community turnover along environmental/resource gradients, consistent with the habitat niche. Second, the evidence for dispersal-limitation, which may constrain community composition and richness in isolated habitats. Third, these two processes – the habitat niche and dispersal-limitation – are used to explain stand-scale diversity, in addition to the role of neutral effects (habitat area). Fourth, the review moves from a taxonomic (pattern) to a functional (process) perspective, considering evidence for autogenic succession evidenced by competition and/or facilitation, and non-random trends in life-history traits. This functional approach provides a counter-point to an assumption that lichen epiphyte communities are unsaturated and non-competitive, a situation which would allow the long-term accumulation of species richness with temporal continuity. Finally, the review explores landscape-scale impacts on lichen epiphytes, with recommendations for conservation.

Lichen epiphyte diversity: A species, community and trait-based review

About ten percent of all vascular plant species world-wide are epiphytes and they are almost exclusively found in tropical forests. Therefore, they constitute a large part of the global plant biodiversity (10% of all species), and in tropical countries represent up to 25% of all vascular plant species. Focusing on the differences between epiphytes in the strict sense or ‘holo-epiphytes’ (non-parasitic plants that use other plants — usually trees — as growing sites all through their life-cycle) and ‘hemi-epiphytes’ (‘half’ epiphytes which only spend part of their life as epiphytes until their aerial roots become connected to the ground), horizontal and vertical distribution patterns of both in relation to some of their ecological requirements are compared. Vertical ecological gradients (i.e., insolation and humidity differences from the forest floor to the canopy surface) are relevant for the composition of the holoepiphytic vegetation. For hemi-epiphytes, however, ecological differences between distinct forest habitats (i.e., horizontal gradients) are relevant, but not primarily the canopy structure, as the individual host tree structure is more important. The scale-dependence of epiphyte diversity assessment (relatively small study areas for holoepiphytes, large study areas for hemi-epiphytes) is mainly due to the striking differences in plant sizes and related mechanical and physiological requirements.

Epiphytes and their contribution to canopy diversity

Vascular epiphytes are typically associated with tropical rainforests, whereas their occurrence in temperate forests is little appreciated. This review summarises the available information on epiphytism in the temperate zones (> 23.5 latitude), which has not been reviewed omprehensively for more than a century, and critically analyses the proposed mechanisms behind the observed biogeographical patterns. Although in the temperate zone epiphytic vascular plants are rarely as impressive as in tropical forests, there are noteworthy exceptions. Temperate rain forests of Chile and New Zealand, or montane forests in the Himalayas are comparable to many tropical forests in terms of epiphyte biomass and diversity, but differ in their taxonomic spectrum temperate epiphyte communities are generally dominated by ferns and fern-allies. Other temperate areas are not, however, necessarily barren of epiphytes, as repeatedly implied. Quite in contrast, local populations of epiphytes in a large number of other non-tropical areas in both the southern and the northern hemisphere can be quite conspicuous. The proposed reasons for the latitudinal gradients in epiphyte abundance and diversity (water scarcity or low tempera-tures). are not fully convincing and, moreover, still await experimental verification. Other factors, both historical (e.g., Pleistocene extinctions) and ecological (e.g., prevalence of conifers in the northern hemisphere), should also be taken into consideration to obtain a comprehensive explanation of the extant global distribution of vascular epiphytes.

/pdf/vascular-epiphytes-in-the-temperate-zones-a-review-4w3a0zgar5.pdf

Vascular epiphytes in the temperate zones–a review

This paper describes vegetation changes on cultivation terraces after abandonment, considered as secondary succession, and vegetation responses after clear-cutting, considered as regeneration. Species were grouped in life form and dynamic categories in order to infer dynamic patterns. By applying the Shannon diversity index to these characteristics, an index of functional diversity is obtained. Regenerative succession is considered here as a particular case of secondary succession, characterized by a fast vegetative regeneration of the dominant woody species, which controls the succession of the understorey species. Post-agricultural succession and forest regeneration succession show a similar relation between the diversity index and a forest index, indicating the relative amount of forest species. It appeared that the old-field dynamics resemble the deciduous oak-forest regeneration after the woody species have established. The species diversity at the end of the post-agricultural succession and in the forest is controlled by the nature of the dominant tree species.

Comparison of old‐field and forest revegetation dynamics in Provence

Some results from an analytic study of reliability and availability of the crystallizer system in sugar plants are presented. The analytic model was developed in a study of an actual plant. The crystallizer system consists of five basic repairable subsystems in series. Each subsystem is considered as being: good, reduced, or failed. Some subsystems can fail together due to a common cause. The model is based on the Chapman-Kolmogorov equations. Steady-state availability and various state probabilities are derived using Laplace transforms. The usefulness of the study is demonstrated through illustrations. >

Availability of the crystallization system in the sugar industry under common-cause failure

This paper is devoted to the analysis and computation of overall as well as various subsystem availabilities of a urea fertilizer plant. Based on the analysis, appropriate maintenance strategies for different situations have been developed. Using Lagrange's multiplier technique the cost of maintenance and manpower is analysed. By minimizing the maintenance cost allocation to various subsystems, the optimum repair policy is determined.

Maintenance planning and resource allocation in a urea fertilizer plant

Spectra on life form, leaf size, leaf persistence, flowering season, and shade tolerance of trees in different vegetation types occurring within the north-western catchment of the river Gola in Kumaun Himalaya are presented. The flora of Quercus leucotrichophora, Quercus lanuginosa and Quercus floribunda forests is phanerophytic, that of Pinus roxburghii and mixed forests therophytic. The grassland vegetation is characterized by the largest percentage of hemicryptophytes. The flora of the whole area, is therophytic. The biological spectrum for the entire Kumaun Himalaya is characterized as therohemigeophytic. Among the various altitudinal zones, the tropical has a preponderance of phanerophytes, the temperate and the alpine of hemicryptophytes. The observations on leaf size indicate that with the exception of Pinus roxburghii forest, in all vegetation types, the species with microphylls are greater in number. In this region, the vegetation expression is evergreen, although the tree flora has a considerable content of deciduous elements. In all the forests, the flowering period in most of the trees is vernal. On the basis of relative density, the greatest proportions of adult trees in the Pinus roxburghii and Quercus lanuginosa forests are shade intolerant, while in the mixed and Quercus leucotrichophora forests maximum trees are intermediate in shade tolerance. With the exception of the Pinus roxburghii forest, all the forests exhibit the dominance of trees which are shade tolerant at the seedling stage. On the basis of relative density, all forest types, except for Pinus roxburghii forest, have 74.5 to 100% trees with the potentiality of vegetative reproduction.

Biological spectrum and other structural functional attributes of the vegetation of Kumaun Himalaya

The epiphytes present at about breast height on trunks of different size were studied for three major tree species in a seasonally wet forest at 2050 m altitude in the Kumaun Himalaya: Cedrus deodora, Quercus floribunda and Q. leucotrichophora. The total biomass and species number per unit trunk area, were found to increase with trunk size. It was supposed that the results indicated a succession in the type of epiphytic cover from young trunks to older trunks. The amount of loose material (plant remains and ‘soil’) per unit area of trunk increased with increasing girth. The C:N ratio in this material was initially very high on the oaks (129–197) and declined with increasing trunk size (to 73–78); the ratio was constant across girth classes in the cedar (86–87). Bryophytes produced most biomass on most trunks; next to them were lichens on the smallest trunks, and flowering plants on the largest. The number of species of epiphytes was similar on all three host species. The results are discussed in relation to contemporary ideas on diversity and ‘strategies’.

P. C. Pandey

Papers

Availability of the crystallization system in the sugar industry under common-cause failure

Maintenance planning and resource allocation in a urea fertilizer plant

Biological spectrum and other structural functional attributes of the vegetation of Kumaun Himalaya

Epiphytic succession on tree trunks in a mixed oak-cedar forest, Kumaun Himalaya

Operational behaviour and profit function for a bleaching and screening system in the paper industry