Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Ant community responses to fertiliser application and disturbance in a mistbelt grassland, KwaZulu-Natal.

Auteur :

Université de soutenance : University of KwaZulu-Natal

Grade : Master of Science (MS) Ecology 2021

Résumé partiel
Land transformation and land-use intensification are major threats to biodiversity and ecosystem functions. Most of the land transformations are linked to habitat loss and disturbance. Grasslands are one of the most threatened biomes in South Africa due to disturbance. Ants are a dominant taxon in terrestrial ecosystems. They are frequently used to understand faunal responses to disturbance because they are sensitive to environmental change. Fire, mowing disturbances, and fertilization are important management practices for maintenance and grassland management in Southern African. These grass management practices are also known to influence ant community responses, but responses vary with habitat type and vegetation structure. However, the factors that drive these responses are not well understood. This study aimed to investigate ant community responses to burning/mowing disturbances and fertilizer application using the long-term (>60years) veld fertilizer and burning/mowing grassland experimental trials at Ukulinga research farm, South Africa. Therefore, the objectives of the current study were to (1) determine the effects of burning frequency and burning/mowing season on ant species richness and composition, and to determine soil correlates of these effects, and (2) to determine how ant species richness and composition vary with two different types of nitrogen fertilization ; and (3) to assess whether these responses are related to grassland structure and composition. Ant sampling was conducted during wet (March 2019) and dry (July 2019) seasons using standardized pitfall traps in a long-term veld fertilizer trial (VFT) and burning and mowing trial (BMT) and grassland experiments, each replicated into three blocks. The VFT treatments consisted of control and two forms of N, limestone ammonium nitrate (LAN, 28%N) and ammonium sulphate (AS, 21%N), each separately applied annually at two levels (high and low) : LAN (0.21 and 63.2 g m-2 ), and AS (33.6 and 100.8 g m-2 ). The BMT included two fully crossed fire treatments : frequency (annual, biennial, and triennial) and season (August and after spring rains) along with annual mowing in August and after spring rains and an undisturbed control. In BMT trials, burning frequency and burning/mowing season did not affect ant species richness nor composition. None of the soil variables were correlated with ant assemblage composition. This suggests that ant assemblage composition in the BMT is resistant to the regimes of burning and mowing.

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