The potential of Eucalyptus hybrids in farm forestry in the semi-arid winter rainfall region of South Africa

Lambrechts, Hugo Amos (2018-12)

Thesis (MScFor)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: The aim of this study was to investigate Eucalyptus hybrids as a source of woody biomass in the semi-arid winter rainfall region of South Africa. The study focuses on an experimental planting at 10 years of age and the coppice crop from this experiment grown for nine months after clear felling. The trial investigated the survival, potential production (growth) and coppicability of several Eucalyptus hybrids, namely E. grandis x camaldulensis, E. grandis x resinifera, E. grandis x tereticornis and E. saligna x urophylla, which were compared to the control of E. cladocalyx and commercial controls of E. dunnii and E. grandis x camaldulensis. The survival and potential production were explored on a taxa and provenance, genotype and stand level, while the coppice results were ranked on a genotype level. Overall, the survival on the site was above 75 %, excluding the controls of E. cladocalyx and E. dunnii, which did not perform well. At 10 years of age, the experimental stand achieved a mean annual increment (MAI) of 17.24 m3.ha-1.a-1. Basal area growth was used to rank the growth response of the tested genotypes. The basal area was upscaled from single tree plots which meant that the mean value yielded a useful estimate, however, the upscaled value of individual genotypes from the single tree plots were only reliable to rank genotypes and not to estimate growth potential in field. The upscaled basal area ranged between 12 m2.ha-1 and 55 m2.ha-1. Several of the tested hybrids were well suited to the semi-arid site, namely: E. gxc Albacutya CSS01659 (9), E. gxc Albacutya CSS01682 (13), E. gxt (AUS) seed SR0046xT32 (84) and E. gxt (AUS) seed AG049xT08 (83) and E. gxc (SA) seed SGR1231xC42 (76). Slightly less than 50% of the genotypes had good coppicability. The biomass produced in coppice shoots was not significantly different among the taxa at nine months of age. The potential for deploying the newly tested genotypes in farm forestry projects in semi-arid climates of the Western Cape is discussed

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om Eucalyptus-hibriede te ondersoek as ‘n bron van houtagtige biomassa in die halfdorre winterreënvalgebied van Suid-Afrika. The studie fokus op ʼn 10-jaar-oue eksperimentele aanplanting, asook die stomplootverjonging en daaropvolgende groei tot en met nege maande na kaalkap. Die proef ondersoek die oorlewing, potensiële produktiwiteit (groei) en vermoë van stomplootverjonging van verskeie Eucalyptus-hibriede, naamlik E. grandis x camaldulensis, E. grandis x resinifera, E. grandis x tereticornis en E. saligna x urophylla. Dit word vergelyk met die E. cladocalyx-kontrole en kommersiële E. dunnii- en E. grandis x camaldulensis-kontroles. Die oorlewing en potensiële produktiwiteit is ondersoek op ’n takson-, herkoms-, genotipe- en opstandsvlak, terwyl die resultate van die stomplootverjongings gerangskik is van groot na klein op ’n genotipe-vlak. Oor die algemeen was die oorlewing op die eksperimentele eenheid bo 75 %, behalwe vir die kontroles van E. cladocalyx en E. dunnii, wat nie goed gevaar het nie. ’n Gemiddelde jaarlikse aanwas van 17.24 m3.ha-1.jaar-1 is behaal op die opstand oor die 10 jaar periode. Basale oppervlakte was gebruik om die rang van die groei respons van die genotipes te toets. Die basale oppervlakte was van enkelboomplotte opgeskaal wat beteken dat die gemiddelde waarde ‘n goeie indikator van groei was. Die opgeskaalde basale oppervlakte van individuele genotipes was egter net betroubaar vir rang en nie vir die skatting groei potensiaal in die veld nie. Die opgeskaalde basale oppervlakte het gewissel van 12 tot 55 m3.ha-1. Verskeie van die getoetste hibriede is skynbaar goed aangepas by die groeiplek, naamlik: E. gxc Albacutya CSS01659 (9), E. gxc Albacutya CSS01682 (13), E. gxt (AUS) seed SR0046xT32 (84) and E. gxt (AUS) seed AG049xT08 (83) and E. gxc (SA) seed SGR1231xC42 (76). Amper 50% van die genotipes het ’n goeie stomplootverjongingsvermoë gehad. Die resultate vir die stomplootbiomassa het nie beduidend tussen taksa verskil op nege-maande-oue ouderdom nie. Die potensiaal vir die ontplooïng van die nuut getoetsde genotipes in plaasbosbouprojekte in die semi-ariede Wes-Kaap word bespreek.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/104806
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