Soil penetrability as a key factor affecting the nesting of burrowing birds

Soil penetrability resistance was found to be crucial for nest site selection of all three Central European burrowing bird species—Sand Martins (Riparia riparia), European Bee-eaters (Merops apiaster), and Eurasian Kingfishers (Alcedo atthis). Soil penetrability resistance measurements were used to find out whether increased hardness of unexcavated banks is the key factor affecting the presence of burrowing birds. All three species avoided banks composed of too compact or too loose soils. Birds discriminated not only between high- and low-quality breeding banks, but also between different soil strata within banks. In banks with generally low penetrability resistance, Sand Martins preferred soil strata with the highest available penetrability resistance and compactness to avoid hole collapses. There was a preference for hard soil below holes to serve as a resistant platform when birds begin to dig their holes. In Sand Martins, the penetrability resistance level affected physical characteristics of holes such as tunnel length and dimensions of the orifices. Excessive compactness—and probably not high talus presence—was a major cause of abandonment of Sand Martin localities. A high penetrability resistance is the crucial factor for site selection in Sand Martins.     

Post-fire and post-quarry rehabilitation successions in Mediterranean-like ecosystems: Implications for ecological restoration

Resilience against sudden changes in the environment is a very desirable trait in plants used for ecosystem restoration. Mediterranean-like vegetation exhibits particularly strong fire resilience. There are two main functional groups of fire-prone species among Mediterranean-like vegetation: seeders and resprouters. Our aims were to describe how the theory of succession after fire relates to rehabilitation and to use this knowledge to improve the results of rehabilitation attempts in Mediterranean-like ecosystems. Eight post-fire (PF) sites, 14 post-rehabilitated (PR) quarry sites and two woodland sites were sampled. Detrended Canonical Correspondence Analysis (DCCA) showed that PF and PR successions were quite different. Both displayed an increasing abundance of resprouters over time, but seeder density increased throughout PR succession and decreased during PF succession. Nine species were common to both successions in all studied stages. The results showed that until 15-21 years of succession, the post-rehabilitation sites had not become as resilient to fires as sites populated by indigenous vegetation due to the lack of a seeder seed bank. However, after 21 years of PR succession, the exponentially increasing seeder population may allow for seed bank formation and thus eventually improve the fire resilience of the site.