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δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa
Thesis (MSc (Forest and Wood Science))--University of Stellenbosch, 2011.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : University of Stellenbosch
2011
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| _version_ | 1867613807520514048 |
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| access_status_str | Open Access |
| author | Fischer, Phillip Murray |
| author2 | Jarmain, Caren |
| author_browse | Fischer, Phillip Murray Jarmain, Caren |
| author_facet | Jarmain, Caren Fischer, Phillip Murray |
| author_sort | Fischer, Phillip Murray |
| collection | Thesis |
| dc_rights_str_mv | University of Stellenbosch |
| description | Thesis (MSc (Forest and Wood Science))--University of Stellenbosch, 2011. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/6588 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:42:01.161Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2011 |
| publishDateRange | 2011 |
| publishDateSort | 2011 |
| publisher | Stellenbosch : University of Stellenbosch |
| publisherStr | Stellenbosch : University of Stellenbosch |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/6588 δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa Fischer, Phillip Murray Jarmain, Caren University of Stellenbosch. Faculty of AgriSciences. Dept. of Forest and Wood Science. δ13C Pinus radiata -- Drought stress -- South Africa Pinus radiata -- Water availability -- South Africa Dissertations -- Forest and wood science Theses -- Forest and wood science Thesis (MSc (Forest and Wood Science))--University of Stellenbosch, 2011. ENGLISH ABSTRACT: This study investigated the use of carbon isotopes as a potential measure for water availability and drought stress in Pinus radiata in the Western and Southern Cape, South Africa. An understanding of water availability and its variation in space is fundamental to the implementation of increasingly site-specific management regimes that have the potential to greatly improve productivity across sites in the region. Fifteen plantation compartments situated on water shedding sites were identified where good weather data existed and a water balance model could be run. In addition, late wood samples were analysed from four co-dominant trees in the same stand to determine the δ13C values of five tree rings, each representing a specific growth year before first thinning. Detailed water balances were constructed for each trial site and drought stress indicators (a) relative canopy conductance (after Granier et al., 2000) and (b) the ratio of actual to potential evapotranspiration (supply / demand ratio), were related to δ13C values in latewood. Maximum available soil water ranged from 52 to 313 mm across trial sites. The water balance model used adequately described soil water availability throughout each growing season and indicated that stand stress due to the lack of available soil water mainly occurred during the summer months of the study period (November to April). The supply / demand ratio for this period as well as the relative canopy conductance proved to be good measures of drought stress. The six-month supply demand ratio (calculated for the period November to April) ranged from 0.04 to nearly 1 (winter rainfall zone) and 0.35 to 1 (all-year rainfall zone) and were strongly related to δ13C values (p < 0.001; r2 = 0.7822). It appears that using δ13C values, it may be possible to classify sites into three water availability classes. This classification may assist in the implementation of intensive silvicultural operations on an increasingly site-specific basis. Where sites are enriched with water from lateral flow or upslope positions, δ13C may be the only reliable technique to quantify soil water availability. AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die gebruik van koolstof isotope as 'n moontlike maatstaf vir die beskikbaarheid van water en droogtestremming in Pinus radiata in die Wes-en Suid-Kaap, Suid-Afrika. 'n Begrip van die beskikbaarheid van water en die ruimtelike variasie daarvan is fundamenteel vir die implementering van groeiplek-spesifieke bestuur sisteem wat die potensiaal het om baie verbeterde produktiwiteit oor persele in die streek teweeg te bring. Vyftien plantasievakke, geleë op waterskeidingsterreine is geïdentifiseer waar goeie weer data bestaan en 'n water balans model uitgevoer kon word. Daarmee saam is laathout monsters vanuit vier ko-dominante bome in dieselfde kompartement geanaliseer en die δ13C waardes van laathout in vyf jaarringe bepaal wat elk 'n spesifieke jaar van groei voor die eerste dunning verteenwoordig. Gedetailleerde water balanse is vir elke proef perseel bereken en aanwysers van droogtestremming, nl.: (a) relatiewe kroon geleiding (na Granier et al., 2000) en (b) die verhouding van die werklike teenoor potensiële evapotranspirasie (vraag / aanbod verhouding) is gekorreleer met 13C waardes in laat hout. Die maksimum hoeveelheid water beskikbaar op die verskeie proefpersele wissel van 52 tot 313 mm. Die water balans model wat gebruik is beskryf die beskikbare grondwater met genoegsame akkuraatheid. vir die hele groeiseisoen. Die model dui ook aan dat die kompartemente droogtestremming as gevolg van die gebrek aan beskikbare grond water ervaar gedurende die somer maande van die studie tydperk (November tot April). Die vraag / aanbod verhouding vir hierdie tydperk, asook die relatiewe kroon geleiding is geskik om as maatstawwe van droogtestremming gebruik te word. Die vraag / aanbod verhouding (bereken vir die tydperk November tot April) het gewissel van 0,04 tot byna 1 (Winter reënval gebied) en 0,35 tot 1 (die heel jaar reënval sone) en is sterk verwant aan 13C waardes (p <0,001; r2 = 0,7822). Dit blyk dat met die gebruik van δ13C waardes, dit moontlik kan wees om kompartemente te klassifiseer in drie klasse van water beskikbaarheid. Hierdie klassifikasie kan help met die implementering van intensiewe boskultuur bedrywighede op 'n meer vak-spesifieke basis. Waar vakkeverryk is met water vanuit laterale vloei of hoër liggende posisies, mag δ13C dalk die enigste betroubare tegniek wees om die beskikbaarheid van water te kwantifiseer. Masters 2011-02-28T20:33:50Z 2011-03-14T08:21:59Z 2011-02-28T20:33:50Z 2011-03-14T08:21:59Z 2011-03 Thesis http://hdl.handle.net/10019.1/6588 en_ZA University of Stellenbosch 108 p. : ill., maps application/pdf Stellenbosch : University of Stellenbosch |
| spellingShingle | δ13C Pinus radiata -- Drought stress -- South Africa Pinus radiata -- Water availability -- South Africa Dissertations -- Forest and wood science Theses -- Forest and wood science Fischer, Phillip Murray δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa |
| title | δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa |
| title_full | δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa |
| title_fullStr | δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa |
| title_full_unstemmed | δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa |
| title_short | δ13C as indicator of soil water availability and drought stress in Pinus radiata stands in South Africa |
| title_sort | δ13c as indicator of soil water availability and drought stress in pinus radiata stands in south africa |
| topic | δ13C Pinus radiata -- Drought stress -- South Africa Pinus radiata -- Water availability -- South Africa Dissertations -- Forest and wood science Theses -- Forest and wood science |
| url | http://hdl.handle.net/10019.1/6588 |
| work_keys_str_mv | AT fischerphillipmurray d13casindicatorofsoilwateravailabilityanddroughtstressinpinusradiatastandsinsouthafrica |