Browsing by Author "Nyarobi, Herieth"

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    The effects of extreme climate on the invasive plant Gutenbergia cordifolia: implications for its future management in savannah ecosystems
    (Heliyon, 2022) Nyarobi, Herieth; Ngondya, Issakwisa; Munishi, Linus
    The aim of this study was to assess the effects of varying water stress levels on morphological and physiological parameters of an invasive plant Gutenbergia cordifolia. The assessment was conducted in the screenhouse at the Nelson Mandela African Institution of Science and Technology following a completely randomized design (CRD). Both morphological and physiological parameters were variable under water stress levels. While the maximum (159 cm) and minimum (9 cm) plant heights for G. cordifolia were observed under flood and drought water stress respectively, its maximum root collar diameter of 5 mm and the minimum of 1.3 mm were observed under moderate flood and drought water stress respectively. Generally, the number of leaves was highest under mod erate flood stress (194 leaves/plant), and lowest under drought stress (13 leaves/plant). Similarly, the largest and smallest leaf surface area of 9 103 and 1 103 mm2 were observed under flood and drought water stress respectively due to G. cordifolia's tendency to retain water when exposed to water stress through a reduction in number of leaves and leaf surface area when under drought stress condition. While a decrease in leaf chlorophyll was observed across water stress levels with the lowest chlorophyll levels of 0.02 under drought water stress, an increase in leaf anthocyanin levels (0.29 Abs g.DM 1 ) was observed particularly under flood stress due to increased chlorophyll breakdown and plants' water stress, respectively. This study informs that extreme climatic events such as excessive floods will likely facilitate invasions by G. cordifolia leading to decreased biotic resistance of native communities in savanna rangelands. Efforts to manage G. cordifolia's effects in a changing climate must therefore include the development of strategies and action plans that account for catastrophic events like floods and drought.
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    Morphological and physiological responses of the invasive plant gutenbergia cordifolia to varying biophysical conditions
    (NM-AIST, 2022-07) Nyarobi, Herieth
    This study assessed the effects of varying water stress levels on morphological and physiological traits of an invasive plant Gutenbergia cordifolia (G. cordifolia) under field and screen house conditions and the responses of these traits on performance G. cordifolia under long and short rain seasons in the Ngorongoro Crater, Tanzania. The water stress level assessment was conducted in the screen house at the Nelson Mandela African Institution of Science and Technology (NM-AIST) following a completely randomized design (CRD) while field assessment was conducted in Ngorongoro Conservation Area (NCA). While the maximum and minimum plant heights in the screen house experiment were observed under flood and drought water stress, respectively, the maximum and minimum root collar diameter (RCD) were observed under moderate flood and drought water stress, respectively. Generally, the number of leaves was highest under moderate flood stress and lowest under drought stress. The largest and smallest leaf surface areas (LSA) were observed in flood and drought water stress conditions, respectively. While a decrease in leaf chlorophyll was observed under drought water stress, an increase in leaf anthocyanin levels was observed under flood stress. In comparing field and screen house traits; both maximum G. cordifolia height and highest number of leaves were observed under screen house. While the largest and smallest LSA were observed in the field condition and screen house respectively, both the maximum root and shoot fresh and dry weights were observed under field condition. Both leaf anthocyanin and chlorophyll were higher under field compare to screen house. While both the maximum height and the largest RCD were observed during long rain season the highest number of leaves per plant was observed during short rain. Both highest root fresh and dry weight were observed during long rain. The maximum leaf chlorophyll level was observed during short rain season while the minimum was observed during long rain season. The findings from this study indicate that the establishment and spread of G. cordifolia is likely to be favoured by projected East African rainfall (2050-2100) as suggested by Platts et al. (2015) and inform conservation and management authorities on how growth and performance is likely to be in the future under changing climate and the need of integrating this information in its future management strategies. The study further suggests that efforts to minimize impacts of an invasive G. cordifolia in a changing climate must include a good understanding of G. cordifolia behaviour under extreme events so as to prepare effective management strategies and actions.