Evaluating environmental factors & fire disturbance influencing species diversity in a mountainous protected area

Abstract

Mountain Zebra National Park (MZNP) is a unique conservation area occurring at the interface of three Biomes, i.e., Grassland, Nama karoo, and thicket. Grassland is the least protected biome in South Africa, with only approximately 2% of the biome being protected. It is estimated that 60% of the Grassland biome has been permanently transformed, while as little as 15% remains natural Grassland. Majority of the remaining natural Grassland is highly fragmented, and most is poorly managed. Grasslands and savannas are shaped by several factors, including climate change and fire. Fire plays a crucial role, particularly in influencing the structure and composition of vegetation which does have an influence on ecosystem functionality. Globally, there is a noticeable increase in the abundance of woody plants observed in Grasslands and savannas. This change in plant functional types has been ascribed to several factors, including reduced fire frequency, intense grazing pressures and elevated atmospheric CO2. Although several ecological studies have explored different aspects of vegetation within MZNP, there still exists a considerable knowledge gap regarding the driving factors that influence this vegetation. Soil is a vital environmental factor that influences ecosystem processes and the distribution and characteristics of plant communities. The relationship between plant productivity and species richness is a fundamental focal point in community ecology, as it provides the basis for understanding plants’ responses or adaptive strategies. The main objectives of this study were 1. To determine the influence of fire on woody/shrub plant species richness, diversity, and composition. 2. To determine the influence of fire on grass species richness, diversity, and composition. 3. To determine the influence of environmental factors on the species diversity and richness.4. To determine the effects of absence and presence of Fire on Woody species recruitment in a mountainous grassland. This was done using satellite imagery; the park’s fire history was c between 2000 and 2020. Eighty plots (approximately 20 × 20 metres; >100 metres apart) were laid out purposively across the different fire regimes. Vegetation data was obtained using the step-point method. Biomass measurement was collected using a disc pasture meter on the transects. Environmental data except the rainfall data were extracted for each sample site using Quantum GIS 2.18.0 (Las Palmas de G.C.). All layers applied in the QGIS used the geographic coordinate system WGS84 and EPSG:4326 as spatial reference. This was done using Worldclim which allows the extraction of raster values to points. There was no significant difference in both species’ richness and diversity in burned and unburned sites (p>0.05) There was a significant difference in species cover for the Type B fire (2010 and 2019) compared to the Site A fire (2002 and 2010) fire. The unburned site had higher moribund material and unpalatable grasses than the burned area. The results show that the absence of fire for a prolonged period changes woody species cover in Grassland. Only one of the soil properties, soil pH, influenced plant biomass. Although soil nutrients are highly important in plant biomass production, it was found their influences on Above Ground Biomass (AGB) and plant to be insignificant. The study’s main findings indicate that the chemical properties of soil (nitrogen and soil organic carbon) significantly impacted species richness and diversity and that clay and sand content (i.e., soil texture) positively affected species diversity. In contrast, the physical properties of soil (silt) did not affect plant species richness and diversity. Nitrogen showed an inversely proportional relationship with species richness. Sand content was the only physical property of soil which positively affected species diversity.