Browsing by Author "Keet, Jan‑Hendrik"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Hooker’s or warty barberry? physiological background analysis for choosing the right one into ornamental plantations endangered by drought
    (Mendel University Press, 2017) Ferus, Peter; Bosiakova, Dominika; Konopkova, Jana; Hotka, Peter; Keet, Jan‑Hendrik
    Barberries as undemanding shrubs with high aesthetic value are often planted in city parks and street greeneries. However, severe urban environment combined with climate change puts pressure on these plants in terms of their ability to cope with drought. In order to avoid plantation fall‑offs, a common garden experiment was carried out on the drought tolerance of two Asian barberry species, namely Hooker’s barberry (Berberis hookeri Lem.) and warty barberry (Berberis verruculosa Hemsl. and Wils.). Higher leaf relative water content, postponed but more sensitive stomatal closure (decrease in stomatal conductivity for water) as well as osmotic adjustment (free proline accumulation) and antioxidant defence onset (total antioxidant activity of the hydrophilic phase), and faster photosynthetic pigment decomposition in Hooker’s barberry transplants compared to warty barberry, point to better water management and advanced protection of leaf structures in this species under limited soil moisture. Moreover, warty barberry plants with half total leaf area suffered from drought earlier, because of enhanced soil water loss through evaporation. Thus, Hooker’s barberry can be taken as more drought tolerant than its counterpart, therefore making it more suitable for plantings in areas that are prone to this environmental constraint.
  • Thumbnail Image
    Item
    The invasive cactus Opuntia stricta creates fertility islands in African savannas and benefits from those created by native trees
    (2021-10-21) Novoa, Ana; Foxcroft, Llewellyn C.; Keet, Jan‑Hendrik; Pysek, Petr; Le Roux, Johannes J.
    The patchy distribution of trees typical of savannas often results in a discontinuous distribution of water, nutrient resources, and microbial communities in soil, commonly referred to as “islands of fertility”. We assessed how this phenomenon may affect the establishment and impact of invasive plants, using the invasion of Opuntia stricta in South Africa’s Kruger National Park as case study. We established uninvaded and O. stricta-invaded plots under the most common woody tree species in the study area (Vachellia nilotica subsp. kraussiana and Spirostachys africana) and in open patches with no tree cover. We then compared soil characteristics, diversity and composition of the soil bacterial communities, and germination performance of O. stricta and native trees between soils collected in each of the established plots. We found that the presence of native trees and invasive O. stricta increases soil water content and nutrients, and the abundance and diversity of bacterial communities, and alters soil bacterial composition. Moreover, the percentage and speed of germination of O. stricta were higher in soils conditioned by native trees compared to soils collected from open patches. Finally, while S. africana and V. nilotica trees appear to germinate equally well in invaded and uninvaded soils, O. stricta had lower and slower germination in invaded soils, suggesting the potential release of phytochemicals by O. stricta to avoid intraspecific competition. These results suggest that the presence of any tree or shrub in savanna ecosystems, regardless of origin (i.e. native or alien), can create favourable conditions for the establishment and growth of other plants.