Factors affecting urea hydrolysis in several alberta soils

Summary Various parameters affecting the hydrolysis of urea in several Alberta soils were studied. The hydrolysis rate of urea in a Malmo silt loam was found to be linearly dependent on concentration, and the Arrhenius plot for soil urease was found to be linear from 2 to 45°C with an experimental activation energy of 9.8 kcal/mole. The urease activities of several soils were determined and the highest activity was found in the LH horizon of a virgin Orthic Dark Gray Luvisol (Uncas loam).Paper No. T-72-4, Alberta Institute of Pedology, University of Alberta, Edmonton, Canada.     

The tellurium content of vegetation

Vegetation growing in the Ely mining district of White Pine County, NV has been analyzed for tellurium to discover whether Te accumulator plants existed similar to those that take up Se in great quantities. In addition, the variation in Te content among species growing in different geological settings was studied. Another objective of this study was to determine the range of Te concentration in vegetation in regions where the Te content of surface materials was high, as in the Ely mining district, and low as in various areas of western CO. Trees and shrubs (480 samples) as well as flowering plants (505 samples) and their associated edaphic materials were collected from six sites in the Ely region and all plant parts were analyzed for Te, Se, Fe, S, Zn, Cu, and Pb. One hundred and five plants were collected from three areas in western CO. There is a highly significant difference between Te uptake by trees and that of perennial flowering plants. Flowers contain significantly more Te on the average than other plant parts. An examination of the Te content of tree parts reveals that leaves sorb the most and branches the least. When the Te content of edaphic materials is high, there is a corresponding increase in the Te content of plants. Shallow perennial plants were not found growing in areas where soils contained more than 10 mg kg⁻¹ Te. Seleniferous species ofAstragalus contain larger quantities of Te than plants in the Ely area, whereas nonseleniferous members of this genus contain much less. The nitrotoxin producing Astragali contain concentrations of Te greater than that encountered in nonseleniferous species but less than that in seleniferous ones. No plants contained more than 1 mg kg⁻¹ Te. Iron, Te, Se, and S are coherent in all plants and in most soils and rocks examined.     

The potential of aspen clonal forestry in alberta: breeding regions and estimates of genetic gain from selection

Background

Aspen naturally grows in large, single-species, even-aged stands that regenerate clonally after fire disturbance. This offers an opportunity for an intensive clonal forestry system that closely emulates the natural life history of the species. In this paper, we assess the potential of genetic tree improvement and clonal deployment to enhance the productivity of aspen forests in Alberta. We further investigate geographic patterns of genetic variation in aspen and infer forest management strategies under uncertain future climates.

Methodology/Principal Findings

Genetic variation among 242 clones from Alberta was evaluated in 13 common garden trials after 5–8 growing seasons in the field. Broad-sense heritabilities for height and diameter at breast height (DBH) ranged from 0.36 to 0.64, allowing 5–15% genetic gains in height and 9–34% genetic gains in DBH. Geographic partitioning of genetic variance revealed predominant latitudinal genetic differentiation. We further observed that northward movement of clones almost always resulted in increased growth relative to local planting material, while southward movement had a strong opposite effect.

Conclusion/Significance

Aspen forests are an important natural resource in western Canada that is used for pulp and oriented strandboard production, accounting for ∼40% of the total forest harvest. Moderate to high broad-sense heritabilities in growth traits suggest good potential for a genetic tree improvement program with aspen. Significant productivity gains appear possible through clonal selection from existing trials. We propose two breeding regions for Alberta, and suggest that well-tested southern clones may be used in the northern breeding region, accounting for a general warming trend observed over the last several decades in Alberta.     

The vegetation of central yacutian alases

Alases are unique grassland landscapes in Central Yacutia, their development influenced by extra-continental arid climate. Twenty three associations have been distinguished and described. These associations form an ecological series from steppe withFestuca lenensis andStipa krylovii through salt and swamp meadow (Hordeum brevisubulatum, Puccinellia tenuiflora, Alopecurus arundinaceus, Calamagrostis langsdorffii, Carex juncella) to swamp communities ofScolochloa festucacea, Glyceria triflora, Scirpus lacustris andTypha latifolia. The community complexes of specific elements of alas landscapes—baidjerakhs and bulgunnyakhs—are analysed.     

The vegetation survey of Western Australia

Summary The aims and methods of the Survey in providing vegetation map coverage for the State of Western Australia on scales of 1 : 1 000 000 and 1 : 250 000 are described. The theoretical basis of the classification of vegetation units is described and a mapping notation which was evolved to characterise precisely the units mapped. It is shown that the mapping serves to define precise boundaries for phytogeographical units (botanical districts and provinces) and has contributed to a study of palaeodrainage patterns in the arid interior.

---

Zusammenfassung Ziel und Methoden der Vegetationskartierung des Staates Western Australia in den Ma?st?ben 1 : 1.000.000 und 1 : 250.000 werden beschrieben, sowie die theoretische Grundlage der Klassifikation der Vegetationseinheiten und die zur genauen Charakterisierung der kartierten Einheiten entwickelten Kartierungsbezeichung. Es wird gezeigt da? die Kartierung dazu dienen kann die genauen Grenzen von pflanzengeographischen Einheiten (botanische Distrikte und Provinzen) festzustellen. Weiterhin hat die Kartierung zu einer Untersuchung der ‘Pal?o-Entw?sserung’-Systeme beigetragen.

     

The significance of pattern in vegetation

Résumé A l'encontre de Scurfield (1956), il est inexact d'attribuer le pattern (écart à une distribution au hasard des espèces et des individus) dans les groupements végétaux, exclusivement ou principalement à la concurrence. Il peut être dû à la modification du régime physique ou à la morphologie, ou au comportement reproductif des espèces en question. L'hypothèse de Scurfield d'une tendance à une régularité croissante, inhérente à la végétation en évolution, n'est pas confirmée, Au contraire, il semble qu'il y ait une tendance à une diminution de l'intensité de pattern, et un accroissement de l'échelle de pattern au cours de la succession. L'étude du pattern peut constituer un instrument écologique utile.     

The theoretical basis of vegetation science

There are two distinct research approaches to a theoretical framework for vegetation science. One involves critical analysis of observed patterns of multi-species community composition; the other entails experimental examination, at the population level, of processes in a multi-species context. Each approach is currently incomplete, but has questions in common with the other. Light, nitrogen and disturbance have been identified as critical factors determining vegetation composition by researchers using different theoretical frameworks. The increasing communication between vegetation analysts concerned with community pattern and experimental ecologists concerned with community processes may lead to a convergence in their theoretical concepts.     

The Circumpolar Arctic vegetation map

Abstract. Question: What are the major vegetation units in the Arctic, what is their composition, and how are they distributed among major bioclimate subzones and countries? Location: The Arctic tundra region, north of the tree line. Methods: A photo‐interpretive approach was used to delineate the vegetation onto an Advanced Very High Resolution Radiometer (AVHRR) base image. Mapping experts within nine Arctic regions prepared draft maps using geographic information technology (ArcInfo) of their portion of the Arctic, and these were later synthesized to make the final map. Area analysis of the map was done according to bioclimate subzones, and country. The integrated mapping procedures resulted in other maps of vegetation, topography, soils, landscapes, lake cover, substrate pH, and above‐ground biomass. Results: The final map was published at 1:7 500 000 scale map. Within the Arctic (total area = 7.11 × 106 km²), about 5.05 × 10⁶ km² is vegetated. The remainder is ice covered. The map legend generally portrays the zonal vegetation within each map polygon. About 26% of the vegetated area is erect shrublands, 18% peaty graminoid tundras, 13% mountain complexes, 12% barrens, 11% mineral graminoid tundras, 11% prostrate‐shrub tundras, and 7% wetlands. Canada has by far the most terrain in the High Arctic mostly associated with abundant barren types and prostrate dwarf‐shrub tundra, whereas Russia has the largest area in the Low Arctic, predominantly low‐shrub tundra. Conclusions: The CAVM is the first vegetation map of an entire global biome at a comparable resolution. The consistent treatment of the vegetation across the circumpolar Arctic, abundant ancillary material, and digital database should promote the application to numerous land‐use, and climate‐change applications and will make updating the map relatively easy.     

The influence of coppicing on vegetation

In the Netherlands and adjacent countries on old (non-holocene) soils the relation was studied between high forest dominated by Fagus sylvatica, and coppice derived from it, with Quercus spp. and Betula spp. or Carpinus betulus. From place-names a shift Fagus > Quercus > Betula is found, caused by cutting and coppicing. An analysis of relevés of the vegetation yielded more detailed information.The occurrence and rejuvenation of Fagus and other climax tree species decrease, while most other trees and shrubs show an increase. The mean total number of species in 1396 relevés increases from 22.0 to 24.4. Decreasing species include widely distributed species as well as character species. Increasing species include shrubs, woodedge species of heathland or limestone grassland, and nitrophilous species.The light-indication according to Ellenberg increases considerably, most of all in the types on poor soils. Moisture seems hardly involved, but pH-indication is divergent: decreasing in acid types, increasing in alkaline types. For the latter erosion is held responsible. N-indication follows the same trend. All ecological shifts remain within the framework of each association concerned.The Sørensen index for floristic composition shows a mean of 68% correlation, of the same order as variants within one association. The ecological correlation is even higher. So coppice can be considered as management variants, not deserving an association status, as often was given in the past.     

The structure of the vegetation of Khakasia

A diagram of the vegetation structure of Khakasia, made up with the use of a generalized large-scale map, shows the main variety of the phytocoenoses. It is particularly important for the analysis of the vegetation of mountaincous regions.Differentiated areas of phytocoenoses are used to distinguish the region borders in fractional geobotanical regionalization.Khakasia belongs to three geobotanical provinces of the Altal-Saijan geobotanical region — provinces of Minusinsk depression, West Saijan and Kuznetsk Alatau. In Khakasia, geobotanical districts are distinguished by altitudinal zonation and phytocoenotic structure. The vegetation cover is comprehensively described in a special monograph.Nomenclature follows (Flora USSR. Ed. Acad. Sc. Leningrad Vol. I–XXX, 1934–1960). This paper was presented at the International Botanical Congress, USSR, Leningrad, July 1975.