Pollen–vegetation–rainfall relationships in the Gebel al-Akhdar, Northeast Libya

Abstract

Very little work has been done on vegetation–pollen relationships in Northeast Africa, which presents barriers for interpreting pollen diagrams in this region. This paper therefore investigates rainfall-vegetation–pollen relationships in the Gebel al-Akhdar in Northeast Libya. The Gebel al-Akhdar is an unique upland habitat island, isolated between the Mediterranean Sea and the Sahara Desert, characterised by a high degree of endemicity amongst its flora and invertebrate fauna, and with an extremely long history of human activity. Orographically-driven rainfall supports dry Mediterranean woodland and maquis on the northern slopes of the Gebel, with scrub-steppe passing into steppe and then pre-desert on the dryer southern slopes. Here we document rainfall/vegetational/pollen relationships along North–South transects across the Gebel al-Akhdar. Vegetation around pollen sample sites was recorded. Precipitation was interpolated from ERA5 satellite data, and from the local meteorological network. Surface pollen assemblages allow us to distinguish habitats with higher effective moisture on the northern slopes of the Gebel from those with lower effective moisture on the southern slopes. Coastal garrigue is characterised by high Pinus pollen, reflecting the very low pollen productivity of this habitat. Despite complexities in the relationship between vegetation and surface pollen, most parts of the rainfall distribution in the Gebel al-Akhdar can be characterised palynologically, giving confidence in the use of palynology to characterise past rainfall regimes in the region.