No description available.

No description available.

Thesis (M. Sc.)--University of Hong Kong, 1972. / Mimeographed.

Thesis (M.Sc.) --University of Adelaide, 1953? / Typewritten copy.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 149-156).

No description available.

Ten two hectare forest plots were established on two distinct reserves, one mainly on volcanic deposits and the other on sedimentary and alluvial soils. These were investigated for their site carrying capacity and species diversity in relation to edaphic factors, using accumulated basal area as the growth indicator. A soil survey was conducted in each reserve to classify the soil types at the series level. Five two hectare sites each reflecting different soil types were chosen from each reserve. All trees of 10 cm dbh and over were enumerated on each soil type and identified to species level. Fourteen tree species were selected for foliage sampling. A representative soil pit was dug for each soil type and the different horizons were sampled. In addition, ten composite samples were randomly selected to represent soil depths 0-15 cm and 15-30 cm. A complete physical and chemical analysis was carried out on the samples. The results clearly exhibited the influence of parent material on particle size distribution, soil colour, bulk density, porosity, moisture retention and soil chemical compositions. In addition the phosphate fixation problem was discussed. Soil fertility is governed by the parent material from which the soil is derived and is parallelled by the site carrying capacity of the tropical rain forest. Reserve of K was demonstrated to be the main growth limiting nutrient. This was well supported by both soil and foliage analyses data. The nutrients N and P also influence growth but in these cases consistent relationships with basal area were only established after removing some out-lying points. The available and exchangeable soil nutrients were found to be poor indicators of growth. There appears a possibility of using Shorea leprosula as indicator species for foliar analysis in order to assess site fertility. Certain physical properties such as bulk density, clay content, site gradient and available water also exerted some influence on the growth of the trees. Fertile sites contained less species than nutritionally poorer sites. The competition-domination-suppression phenomenon is put forward in explanation. The geological body from which soil is derived is more dominant in determining species diversity than is the soil series per se. On poor sites dipterocarp species are more diverse and they also grow better on lower gradients. Chance factor plays more of an indirect role in species diversity and is believed to be very critical (especially on fertile sites) in the regeneration of dipterocarp species.

Thesis (M.S.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references (leaves 68-75). Also available online.

Thesis (M.S.)--University of Kentucky, 2006. / Title from document title page (viewed on August 22, 2006). Document formatted into pages; contains: vi, 79 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 71-78).

At the heart of long term sustainable soil management is chemical fertility through the retention of exchangeable cations. Many current concepts of cation exchange and its relationship with base cation availability remain unchanged over the past century. Despite considerable advancements in analytical techniques many methods used today would be familiar to our forefathers. Comparative studies were undertaken in this thesis to understand how techniques to measure exchangeable soil ions could be enhanced and matched to defined scenarios. The total amount of cations that can be retained electrostatically on soil surfaces is termed the cation exchange capacity (CEC). An ability to systematically and consistently measure CEC is an essential step in soil characterisation. Compulsive exchange methods (using either 1.0 M NH4OAc or 0.05 M BaCl2) at a fixed pH value for determining CEC were scrutinised but acknowledged to be prone to systematic artefacts. The relationship between soil pH, soil texture and CEC was soil specific. When the batch method was compared with the column leach method, the former was more consistent for all soils. For calcareous soils BaCl2 was more suitable but NH4OAc was more generally applicable. The CEC was consistently significantly greater by the compulsive technique when compared with the effective method. The NH4OAc extraction method was applied to soils contaminated with potentially toxic elements (PTEs). The exchangeable concentration of PTEs correlated with total PTE loading. However, the exchangeable Ca decreased with amendment rate confirming an exchange of sites by PTEs. The compulsive technique extracted PTEs that were significantly 2 negatively correlated with soil basal respiration, phosphatase activity, potential nitrification rate (PNR) and the soil microbial biomass carbon. This confirms that of this method is evaluating the bioavailable/bioreactive fraction. Soil cation exchange capacity and exchangeable base cations increased commensurate with the amendment loading of bentonite and charcoal. The exchange capacity was also soil specific. Following amendments, the exchange capacity was higher after six weeks than after thirty weeks. This means that the amendment performance became impaired with time perhaps as the fine soil particles coated the ameliorant causing a decline in CEC. The difference between the effective and compulsive CEC was described as the calculated CEC. This was very sensitive to soil pH and was confirmed in a detailed study at a site where pH plots were amended over a five decade period. As pH rose, so did the exchangeable fraction of Ca, Mg and K. As the pH declined, Al, Fe and Mn exchangeability increased. Extraction techniques must be sympathetic of the soil pH value. The quantification and characterisation of exchangeable cations remains as fundamental a component of soil science today as it was a century ago.