Disturbances of Biological Soil Crust by fossorial birds increase plant diversity in a Peruvian desert

Abstract. The Lomas Formation are fog-dependent oases within the hyper arid band of the Peruvian coast. Biological soil crusts (BSC) form in the Lomas and interact with their fauna and flora. Here we asked if natural disturbances – biopedturbations – made by fossorial birds have an effect on seedlings emergence in the Lomas Formations in the National Reserve of Lachay in Lima, Peru. We analysed active and inactive avian biopedturbations, BSC and bare soil field samples for moisture content. Soil chemical properties were also analysed including organic matter, phosphorus, potassium, electrical conductivity (EC), pH and CaCO₃ content, from BSC, the soil beneath the BSC and soil from biopedturbations. Furthermore, we looked into the seedbank and the field emergence of seedlings in plots with BSC and with active and inactive biopedturbations. The results revealed that active biopedturbations had the highest soil moisture content and BSC showed the lowest values. Moreover, organic matter and potassium content were significantly higher in the BSC than the soil beneath it and the bare soil. On the other hand, CaCO₃ content and EC were higher in bare soil than the other treatments, and no significant differences were found in soil pH or phosphorus content between treatments. In the seedbank experiment, 13 herbaceous plant species were found; furthermore, biopedturbations had a higher diversity but lower abundance than the BSC. However, in the field observations biopedturbations had a higher diversity and abundance of seedlings than BSC and only 8 herbaceous species were found. The species Fuertesimalva peruviana (L.) Fryxell, Exodeconus prostratus (L'Hér.) Raf., Cryptantha granulosa I. M. Johnst. Solanum phyllanthum Cav. and Calandrinia alba (Ruiz & Pav.) D. C increase their abundance in some type of biopedturbations. Our results showed the positive effect on seed germination and diversity of vascular plants by the natural disturbances made by fossorial birds in a unique ecosystem of the Peruvian desert, and remarks the importance of spatial and temporal heterogeneity for ecosystem structure and functioning.