Variation in root biomass for clonal eucalypts as a function of regime and site quality

Van Heerden, Benjamin (2019-03)

Thesis (MScFor)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: The South African forestry industry may reduce imposed carbon taxation by accounting for the industry’s carbon sequestration. This study investigates the potential of Eucalyptus grandis x urophylla root systems to fix carbon and the factors that influence the growth of these roots. A two-way factorial design was used to compare the relative and upscaled belowground biomass of stands under planted regimes and coppiced regimes, as well as high and low site qualities (based on site index). Allometric models were developed to predict the bulk belowground biomass for both management regimes combined and for each management regime (planted or coppiced) separately, as well as root size class models (coarse, medium and fine) for each of the treatments, based on above ground variables. This study shows that the absolute belowground biomass is greater for high quality stands, while low quality stands have greater relative belowground biomasses. This study also shows that both the relative and absolute belowground biomass of coppiced stands are greater than that of planted stands. A novel finding of this study is that there may be a net belowground biomass and carbon accumulation over multiple rotations for planted stands, and this accumulation can be increased by implementing a regime consisting of a planted crop followed by a single coppice rotation.

AFRIKAANSE OPSOMMING: Die Suid Afrikaanse bosbedryf mag koolstof belasting verminder deur rekening te hou van koolstof wat deur die bedryf gesekwestreer word. Hierdie studie ondersoek die potensiaal van Eucalyptus grandis x urophylla wortelstelsels om koolstof te sekwestreer, asook die faktore wat die groei van hierdie wortels beïnvloed. ʼn Tweerigting-faktoriaal ontwerp is gebruik om die relatiewe asook opgeskaalde ondergrondse biomassa van opstande wat slegs geplant is, met opstande wat stomploot-verjonging ondergaan het te vergelyk asook die relatiewe en opsgeskaalde ondergrondse biomassa van opstande op hoë en lae groeiplek bonniteite. Allometriese modelle is ontwikkel om totale ondergrondse biomassa te voorspel vir hierdie twee bestuurspraktyke (gesamentlik en afsonderlik). Allometriese modelle is ook ontwikkel om die biomassa van die gegewe wortel grootteklasse (grof, medium en fyn) vir elk van die behandelings te voorspel. Hierdie studie wys dat die absolute ondergrondse biomassa van hoë-bonniteit opstande groter is as die van lae-bonniteit opstande, maar dat die relatiewe ondergrondse biomassa groter is vir lae-bonniteit opstande. Hierdie studie wys ook dat beide die relatiewe en absolute ondergrondse biomassa van opstande wat stomploot-verjonging ondergaan het groter is as vir opstande wat bloot aangeplant is. ʼn Noemenswaardige bevinding van hierdie studie is dat daar ’n akkumulasie van ondergrondse biomassa na veelvoudige rotasies mag wees vir geplante opstande, en dat hierdie akkumulasie verder vermeerder kan word deur ’n regime te implementeer waar ʼn geplante rotasie gevolg word deur ʼn enkele stomploot-verjongingsrotasie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105589
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