Long-lived sustainable microhabitat structures in arable ecosystems, and Skylarks (Alauda arvensis)

To slow down the decline of skylark populations, in agri-environment schemes within-field microhabitat structures with stunted growth of the vegetation (“scrapes”, “plots”) are created artificially for one year each. However, in arable land comparable microhabitat structures may develop spontaneously, and exist over long periods, caused by microgeological features, and traditional cultivation practices. Skylarks, and other species of arable ecosystems, may adhere strongly to such structures. In two study areas in southwestern Germany, with fairly high densities of 0.26-0.42 skylark territories/ha, 80.2% of the territory centres were situated near such structures; 32.4% were re-used in different years. In combination with the observation of further farmland species, e.g. arthropods, at these locations, it is suggested that short-lived structures with stunted vegetation may promote predominantly species with shorter life-cycles, while the longer-lived naturally forming structures may be attractive also for species with higher site-fidelity, or with multi-annual life-cycles. In many regions, at least traces of these structures are present in fields to date, but rapidly vanishing under use of modern agro-machinery, and thus becoming less effective in causing patchy, stunted vegetation. Yet, protection of such quasi self-preserving, sustainable microhabitat structures, adapted to local conditions, could benefit biodiversity. More studies are needed to understand in more detail the ecological role of these undervalued elements of arable ecosystems.