Modelling the spatio-temporal distribution of dichrostachys cinerea in Queen Elizabeth National Park

Abstract

This study was conducted in March 2022 in QENP. Dichrostachys cinerea (L.) Weight and Arn. Shrub has been reported to be on the increase threatening other native plant species in Queen Elizabeth National Park. However, the spatial distribution, response to climate patterns, and relationship with woody plants diversity remain largely undocumented. This study covered three objectives, i) to simulate the historical spatial distribution of D. cinerea in the QENP, ii) to model the potential distribution of Dichrostachys cinerea under future climate change scenarios for the year 2030, and iii) to assess the relationship between D. cinerea and woody plant diversity. To assess the historical distribution, and effect of climate change, 528 points data for D. cinerea, and 10 predictors (e.g., Euclidean distance from the road, Maximum temperature, Elevation, Euclidean distance from water sources, Minimum temperature, Slope angle, Precipitation, and bushfire) were used in a maximum entropy (MaxEnt) model. The climate data included both historical and future (near term) data for scenarios SSP2-4.5, and 5-8.5. The Pearson correlation coefficient (r) was used to study the effects on species diversity and abundance. The results showed that human influenced factors need to be qualified ie. Soil (46.5%), Road (25.4%), and water (17.4%) were the most important factors for historical spread of D. cinerea in QENP, even in isolation from other factors. In terms of spatial spread, 1.5%, 2.92%, and 9.7% and of QENP were highly, moderately, and suitable. Under future climate, the effect of rainfall was observed to change by 228%, while that of maximum temperature changed by 188%, while minimum temperature effect declined. Areas of high and moderate suitability increased by 42.5%, and 75% for SSP2-45, and by 33.0% and 90.1% for SSP5-8.5. Further D. cinerea caused a 4-, 10-, and 3-fold decrease in species diversity, abundance and richness. This study found out that Soil types exhibited characteristics (e.g., high fertility, good drainage, high moisture retention, and nutrient availability), favourable for the invasive species. Roads serve as pathways for introduction of invasive species and spread. Human activities near roads facilitate seed dispersal contributing to its invasive success. Waterlogged conditions inhibited the species, while low water conditions supported the growth of D. cinerea. The effect of climate change was significant for invasion. The relationship on diversity, abundance and richness is evident, due to allopathic, competition and fast growth characteristics of D. cinerea. The study recommends prioritization of management and control efforts in areas categorized as highly suitable and moderately suitable, early detection and rapid response to identify and address new invasions, and timely intervention to avoid the observed expansions with climate change and other influencing factors, education of local communities about the risks associated with invasive species and the importance of preventing its spread