African Journals Online
Southern African Forestry Journal

Issue 197, March 2003
ABSTRACTS

Using chlorophyll fluorescence to determine stress in Eucalyptus grandis seedlings: scientific paper

Rolando, Carol A.; Little, Keith M.

Abstract: Since several environmental factors affect the functioning of the photosynthetic system, the status of the photosynthetic apparatus is a good indicator of the plant in terms of stress and stress adaptation. The measurement of chlorophyll fluorescence with a portable fluorimeter has been shown to be a useful non-destructive method for the investigation of the structure and function of the photosynthetic apparatus. A quantitative analysis of fluorescence emission, called the JIP-test, has also been introduced by which the behaviour of the photosynthetic system in response to environmental changes can be monitored. A pilot trial was conducted to determine the effect of light, water and nutrient stress on the fluorescence emission of Eucalyptus grandis seedlings. Flourescence measurements were made on potted plants with a Hansatech Plant Efficiency Analyser, every one to two days from stress initiation until trial termination. The results indicate that water and light stress in E. grandis seedlings can be detected using chlorophyll fluorescence data. The quantum efficiency of primary photochemistry (F_v/F_m) is a good indicator of water stress, while a more detailed analysis of the JIP-test parameters is required for detection of light stress. These results indicate that nutrient stress may have to be severe before photosynthesis and growth are affected. As a practical tool to detect unhealthy plants this technique could be useful to the forestry industry particularly in the fields of establishment and tree breeding where drought or temperature stressed seedlings could be detected before mortality occurs. More detailed studies are required to confirm this.

Genetic improvement of Eucalyptus grandis using breeding seedling orchards and the multiple population breeding strategy in Zimbabwe: scientific paper

Gapare, W.J.; Barnes, R.D.; Gwaze, D.P.; Nyoka, B.I.

Abstract: Eucalyptus grandis is commercially important in Zimbabwe and a breeding program has been in progress since 1962. A classical breeding strategy was used initially but, in 1981, the Multiple Population Breeding Strategy (MPBS) was implemented and the concept of the Breeding Seedling Orchard (BSO) became central to the MPBS in Zimbabwe. Two-year height data from five BSOs established at Mtao and Mukandi in Zimbabwe over two successive generations under the MPBS were used to determine the extent of genetic gain and the implications for future breeding strategy. Four genetic checks, three of which were common to all BSOs, were included by which to monitor the possible onset of inbreeding and against which to measure genetic gain. Significant differences between families were detected for height in the third generation BSOs but no significant differences were detected in one-fourth generation BSO. Genetic checks had average ranking at Mtao where they were selected but had very low ranking at Mukandi. Ranking among genetic checks was fairly similar in the BSOs at Mtao, suggesting that the design of the BSOs is satisfactory for producing a ranking of families at two years at this site. However ranking among the genetic checks at Mtao differed from those at Mukandi. Genetic correlation between height at two years and volume at age five years was favorable (0, 81) suggesting that height at two years is a good predictor of volume at five years. There was no genetic progress in second year height in the fourth generation compared to third generation BSOs. To ensure gain in advanced BSOs, larger numbers of families should be included in the BSOs and a Best Linear Unbiased Prediction methodology should be used for selecting candidates for advanced breeding.

Foliar nutrient levels as indicators of site quality for Pinus patula in the Mpumalanga escarpment area: scientific paper

Louw, J.H.; Scholes, M.C.

Abstract: The South African forest industry is based on intensively managed monoculture systems, and requires diagnostic tools for the development of site-related nutrient management policies. Worldwide, the evaluation of foliar nutrient concentrations is one of the most widely used techniques in forest nutrition research, with many different applications. This paper forms part of a comprehensive study of the differential nutrient supply of forest sites in the study area, as well as the effect thereof on the growth of Pinus patula. The aim of this paper is to investigate the complex interactions between site factors, absolute foliar nutrient levels and tree growth. The levels recorded in this study indicate that most elements are in adequate supply, with possible exceptions being nitrogen and calcium. A range of site factors was found to correlate significantly with foliar nutrient levels, including climatic parameters, topsoil cation levels, N mineralization rate and soil texture. The season of sampling was identified as an important source of variation in foliar nutrient concentrations, partly due to seasonal accumulation of carbohydrates in foliar tissue, causing a dilution effect. Correlations between foliar nutrient levels and tree growth were generally low in this study. Nutrient concentrations recorded during winter were found to be a more accurate indicator of tree growth than summer concentrations. However, the normalization of summer nutrient concentrations after correction for carbohydrate levels, provided an improved correlation with the growth of P. patula. This study can therefore contribute to the interpretation of foliar nutrient concentrations, and has the potential to form part of integrated systems for diagnosing nutrient-supply limitations.

Determination of land and tree values of hybrid poplar plantations: a case study for Turkey: research note

Engindeniz, Sait; Olgun, Aysen

Abstract: Valuation of poplar plantations is important in condemnation, taxation, loan, insurance, inheritance, and purchase-sale cases. In general, for the appraisal of land value of poplar plantations, sales comparison and income capitalization approaches can be used. In appraisal of tree values sales comparison, income capitalization, and cost approaches are used. The approach to be used may vary according to the purpose of appraisal, age of the establishment, obtainable data, and according to the current regulations. In this study, approaches that could be applied in valuation of hybrid poplar plantations (PopulusxEuramericana Guiner cv. I-214) are theoretically examined and a survey has been done in a selected region.