Doctoral Degrees (Forest and Wood Science)

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Browsing Doctoral Degrees (Forest and Wood Science) by Author "Crowe, N. D"

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    Growth, yield and economics of Pinus patula in the Natal Midlands
    (Stellenbosch : Stellenbosch University, 1965) Crowe, N. D; Wicht, C. L.; Becking, J. H.; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: This thesis deals with the mensurational and economic studies in plantations of Popatula in the Natal Midlands o In Chapter I the climate of P.patula areas in Natal I is classified with the Thornthwaite method. The present silvicultural practice in the Natal Midlands is surmnarised o In Chapter II the construction of Volume Yield tables is discussed. These tables are based on the measurement of stand characteristics of temporary sample plots which have been measured once. The past diameter and the basal area i ncrement is determined from increment cores o A multiply regression analysis is used to determine the relationship between basal increment as dependent variable, stand density» age, sit e index and their interactions as independent variableso Site index is deleted l::lltage and stand density are retained as explaining variables . Site index curves, based on temporary sample plots are constructed, but the yield tables are based on the mean site index of 81 . 9 feet at 20 years. The volume increment is estimated from separately determined height and basal area increment equations., Four thinning models are introduced and for each of them a yield table is constructed., For these thinning regimes the diameter- = , volume--, and log class volume distributions are investigated . In Chapter IV the results of the economic analysis are presented.,Production costs have been investigated through questionnaires. Various types of rotations are calculated for each of the four thinning regimes. The profitability of different rotations and thinning regimes are compared. The implications of these calculations on the practice of silviculture and management are discussed.