Опубликована: Янв. 1, 2021

Invasive alien plant species (IAPs) represent a major threat to biodiversity loss and ecosystem functioning globally. Alien can take advantage of changes in ecosystems brought about by natural non-natural disturbances compete with indigenous for resources. Urban areas are becoming increasingly susceptible invasions due increasing anthropogenic activity levels as urban human populations increase changing climatic conditions that favour species. If uncontrolled, IAP impacts bring the transformation habitats exclusion Given limited financial resources available monitoring control developing countries like South Africa, increased efforts monitor prevalence IAPs more efficiently identify drivers invasiveness within cities is urgently needed prioritise green spaces interventions. Frameworks invasions, their sites plants have been context, particularly such Africa. Where these frameworks developed, there challenges them not being equally effective at different geographic scales across habitats. Furthermore, often also suffer weakness capturing multi-dimensionality invasiveness. This inspired current study, which aimed inform design an evidence-based framework aids prioritising interventions carrying out set inter-related investigations addressed following research questions: (1) What environmental (particularly IAPs) distribution? (2) Are functional diversity (FD) alien-indigenous co-occurrence patterns influenced disturbance? (3) influence disturbance on soil seed bank (SB) floristics? (4) Can selected physical and/or chemical traits be used potential indicators persistence SBs? These questions were using case study approach: occurring matrix rapidly city Durban (eThekwini Metropolitan Area [EMA]), located Maputaland-Pondoland-Albany hotspot subtropical KwaZulu-Natal, Classical vegetation survey techniques quantify (in terms richness, density diversity) aliens 30 area. Levels quantified scoring matrix, SB samples collected from each site. Cumulatively, 80 identified, 35 presently categorised EMA. Once it was established richness significantly positively related level, parameters measured (viz. density) develop Index (AII), utility validated its ability discriminate between low high The findings demonstrate value integrating data generated surveys Geographic Information Systems Importantly, results suggest AII could assist identifying invasive hotspots areas. In floristic probed further comparing density, (alpha functional), relation levels. ratio 1:1.5, Asteraceae most dominant family. relationship alpha differed found higher FD, except reproductive mode. Additionally, FD levels, density. Co-occurrence showed pairs cooccur spaces. Three notable (Centella asiatica- Conyza sumatrensis, Centella asiatica-Solanum mauritianum Bidens pilosa-Commelina erecta) co-occurred than 40% sites, while two alien-alien (Solanum mauritianum-Lantana camara sumatrensis-Tagetes minuata) 50% sites. positive interactions identified here contribute growing amount evidence supports Invasional Meltdown Hypothesis (IMH). might lead facilitatory interactions. Understanding help programmes focus reducing facilitation. For examining SBs nonnatural processed modified seedling emergence method, incubated under greenhouse (with irrigation), monitored one year. Germinants quantified, comparisons made standing (SV). 70 belonging 20 families SB, presence (60%) (40%). Overall, flora dominated graminoids. Of 69 shared SV. Irrespective SB. this implications managers since exploit niches created disturbances, promoting invasions. final investigation, seeds five buried years experimental site mimic burial SBs. characterised morphological anatomical (seed mass, size, coat thickness) (estimated lipid content melting properties). designed assess whether Batches exhumed every three/six months viability (germinated + stained Tetrazolium Chloride Test). Seed size thickness species, Canna indica having biggest heaviest all thickest coat. Solanum had smallest lightest seed, thinnest coats. Results decreases four (Canna indica, Melia azedarach, Senna didymobotrya, Ricinus communis), maintained 100% throughout period. However, C. R. communis, S. didymobotrya germinable before burial, declined time, but positively. azedarach slightly, where majority viable remained germinable. longest ageing rate based P50 observed (lowest estimated content), M. shortest (highest content). Decreases germination over time led either/both enthalpy lipid, temperature melt, deterioration mechanisms when buried. did significant relationships longevity investigated. explained relatively number studied phenotypic plasticity associated post-harvest physiology wild Nevertheless, gave rise beginnings conceptual continuum longevity, which, once populated supplement criteria currently assessing As mentioned earlier, challenge countries, settings. management complicated heterogeneous combinations site-specific intensity, diverse types richness. clearly show thrive co-occur various types. able area may useful tool conservation practitioners/land managers. Lantana emerged problematic It evident play role some IAPs, notably mauritianum, persist long periods morphological, anatomical, traits. multi-disciplinary multi-dimensional methods proposed land managers, practitioners, researchers recommendations actions aid, replace, existing EMA policies/guidelines preceding planning preparation phases. new approaches

Язык: Английский