Above-ground allometry, biomass and nutrient content of acacia mearnsii across four ages and three sites in the Kwazulu-Natal Midlands.

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dc.contributor.advisor Pammenter, Norman W.
dc.creator Dovey, Steven B.
dc.date.accessioned 2011-05-04T12:06:44Z
dc.date.available 2011-05-04T12:06:44Z
dc.date.created 2005
dc.date.issued 2005
dc.identifier.uri http://hdl.handle.net/10413/2757
dc.description Thesis (M.Sc.)-University of KwaZulu- Natal, Durban, 2005. en_US
dc.description.abstract Acacia mearnsii (black wattle) is one of the few tree crops of which both timber and bark are utilised, with branches sometimes being collected for fuel wood. There is a great potential for nutrient loss from plantations with intense harvesting practices. Allometric relationships were developed to estimate above-ground biomass across four ages and three site qualities of A. meamsii stands. The three sites were based on high, medium and low site quality classes of productivity. Differences in biomass and the distribution of biomass between the stem, bark, live branches, dead branches and foliage components are described in relation to site and age. Relationships between biomass and light interception and plant area index are investigated and show some merit. Nutrient concentrations were used with the above-ground biomass data to estimate quantities of nutrients held in the various biomass components in each of the stands. Nutrient distributions in the above-ground biomass (AGB) were examined and compared to other studies. Foliar phosphorus (P) and potassium (K) concentrations were shown to be sub optimal, agreeing with results and recommendations of South African fertilisation stupies. Some concentration differences were observed between site and age classes for certain nutrients, although these differences may have been due to seasonal effects. Biomass and nutrient quantities were adjusted to yield a wood production of 100 t ha01 and compared with adjusted calculations for similar studies on other plantation crops. Total nutrients contained in the AGB of the adjusted calculations were 540.8 kg ha01 nitrogen (N), 20.4 kg ha-I P, 200.6 kg ha01 K, 241 kg ha-I calcium (Ca), 55.7 kg ha-I magnesium (Mg), with a half to two thirds of the nutrients held in the stem and bark alone. Nutrients losses vary with harvesting intensity as bark and branches may be harvested with the stem wood. Levels of nutrient removal with harvesting intensity are discussed with reference to estimated losses and gains from natural processes and management practices. An incomplete nutrient budget calculation indicated that P, K, Ca and Mg might potentially be removed in quantities greater than replaced by natural processes under stem and bark harvesting. The budget calculations lack processes such as leaching and N-fixation. It is highly probable that these processes, once quantified, may yield more negative budget results, especially for the base cations K, Ca and Mg. en_US
dc.language.iso en en_US
dc.subject Forests and forestry--KwaZulu-Natal. en_US
dc.subject Acacia mearnsii--KwaZulu-Natal. en_US
dc.subject Logging. en_US
dc.subject Theses--Botany. en_US
dc.title Above-ground allometry, biomass and nutrient content of acacia mearnsii across four ages and three sites in the Kwazulu-Natal Midlands. en_US
dc.type Thesis en_US

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