Detecting and Mapping Forest Nutrient Deficiencies: Eucalyptus Variety (Eucalyptus grandis x and Eucalyptus urophylla) Trees in KwaZulu-Natal, South Africa = Ukuthungatha nokubekisa ukuntuleka kwemisoco yamahlathi: uhlobo lwezihlahla eziyindlulamithi (Eucalyptus grandis x kanye ne-Eucalyptus urophylla) KwaZulu-Natali, eNingizimu Afrika.

Abstract

Abstract Nutrient deficiencies in commercial forestry environments stunt plant growth and reduce survival, resulting in a loss of time, resources, and trees that can become more susceptible to a host of infections. Ineffective and inefficient nutrient screening methods could lead to the release of unhealthy trees for in-field planting, wasting functional space and inevitably impeding forest production. Therefore, the early detection and continuous monitoring of nutrient deficiencies are essential to support management decisions for an effective nutrient management regime. This research aimed to develop and explore innovative detection techniques to map nutrient deficiencies in commercial forest plantations. The first part provides a synopsis of the application of near-infrared spectroscopy (NIRS) for detecting foliar nutrients, focusing on the best spectral noise removal methods, data pre-processes, and statistical models. The research methodology entailed creating a pot trial experiment to acquire full-waveform hyperspectral data (350nm-2500nm) from 135 young trees in a controlled forestry nursery environment. This research quantified nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), and boron (B) in a commonly planted commercial hybrid variety. In the final part the focus was to test the capabilities of unmanned aerial system (UAS) imagery using a very high resolution Micasense sensor and satellite imagery (PlanetScope) in conjunction with an ANN to classify four nutrient regimes in live standing forestry compartment. Overall, this research advocates for the potential use of advanced remote sensing technology to detect and map nutrient deficiencies in commercial forestry environments, at nursery and compartment levels. The results from this study provide an alternative nutrient screening framework for the commercial forestry industry that require quality planting material for long- and short-term resource sustainability on a large scale.

Iqoqa Ukuntuleka kwemisoco ezindaweni zokulinywa kwamahlathi amakhulu okuhweba kudala ukuthi izihlahla zingakhuli ziphakame kanti futhi ezinye ziyafa, okuholela ekuthini kuchitheke isikhathi esiningi kanye izinsizakusebenza kanye nezihlahla ezisengozini yokutheleleka ngezifo. Izindlela ezingasebenzi zokuhlola imisoco zingaholela ekuthini kugcine sekutholakala izihlahla ezingaphilile ezingase zitshalwe kanti sekungukukwenzela phansi indawo ebingatshalwa izihlahla ezifanele kanye nokuthikameza ukukhiqizwa kwamahlathi. Ngakho-ke ukuthungatheka kanye nokuqashwa kokuntuleka kwemisoco ngezikhathi zonke kubalulekile ukuze kwelekelele ekuthathweni kwezinqumo ezimayelana nokwenganyelwa kwemisoco efanele. Lolu cwaningo lwaluhlose ukuthuthukisa nokuhlola amaqhinga obuchwepheshe obusha bokubekisa izindawo ezintula imisoco emahlathini amakhulu okuhweba. Ingxenye yokuqala iveza ubufakazi bokusetshenziswa kwe-near-infrared spectroscopy (NIRS) ekuthungatheni imisoco yezitshalo ngokugxila kwizindlelakwenza eziphambili zokuqeda umsindo, nokulungiselela izinhlelo zemininingo, kanye namamodeli ezibalomidanti. Indlelakwenza yocwaningo yaqala ngokwenza ilinge elaziwa nge-pot trial ukuze kutholakale imininingo ephelele ngakho konke okuthungathwayo (350nm-2500nm) ezihlahleni ezisencane eziyi-135 ngaphansi kwesimo samahlathi esilawuliwe. Lolu cwaningo lwakala ubungako be-nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), kanye neBoron (B) ohlotsheni olufanayo nalolu olutshalelwe ukuhweba. Esigabeni sokugcina kwagxilwa ekuhloleni ukusebenza kohlelo lokuhlolwa kwemifanekiso kusetshenziswa into endizayo ingagitshelwe muntu olwaziwa nge-unmanned aerial system (UAS) eneMicasense ekwazi ukuthola imininingwane esezingeni eliphezulu, kanye nemifanekiso ethathwe ngama-satellite (Planetscope). Lokhu kwakuhambisana ne-ANN ukuze kuhlelwe ngezigaba izinhlobo ezine zemisoco ezitholakala emahlathini amilile. Sekukonke, lolu cwaningo luphakamisa ukuba kungasetshenziswa ubuchwepheshe bokuhlola nokuthungatha bukude nalapho kuhlolwa khona ukuze kubekiswe lezo zindawo ezingenawo kahle umsoco odingekayo emahlathini, ezindaweni okukhuliswa kuzo izithombo zezihlahla, kanye nasezindaweni ezisekelwe ukutshala amahlathi. Imiphumela yalolu cwaningo iveza enye indlela engasetshenziswa njengohlaka lokuhlola imisoco emahlathini amakhulu adinga ukutshalwa izihlahla zohlobo oluphezulu esikhathini eside ngaphandle kokuthikanyezwa komkhiqizo.