Hardseededness and the accuracy of seed bank estimates obtained through germination

The seed content of soils is often estimated through germination tests, though these methods are always somewhat inaccurate due to the presence of dormant seeds in the samples. The researcher thus faces the question of whether to continue the germination test or to stop it in the search for an accuracy-to-effort balance. In this paper I analyze the accuracy of seed content estimates obtained after a first-year germination test, by comparison to the germination recorded after three-year cultivation, in 48 soil seed bank samples and 389 from herbivore dung. After the first 9-month cultivation, I recorded 85 ± 1% seedlings and 90 ± 1% species in soil samples, while the accuracy in those of dung was significantly lower, 48 ± 1% seedlings and 65 ± 1% species. The accuracy of estimations varied among samples within experiments, with significant differences in the estimation of species richness in both cases. I did not find consistent differences in the accuracy of estimations linked to seedling densities in growing pots, but the taxonomic composition of samples was a major source of bias. Thus, 22% and 36% of the most frequent species showed germinabilities in the first year significantly different from the rest, and some generalities arose, like the high germinability of grasses and the hardseededness of legumes. I would thus recommend the use of at least two germination cycles for seed bank estimations and a cautious approach when comparing samples with very different origin and/or taxonomic composition

The potential role of drove roads as connecting corridors for birds between Natura 2000 sites

Ecological connectivity among protected Natura 2000 sites is a priority for conservation in Europe due to the increasing pressure on biodiversity from human activities and climate change. Drove roads, the traditional paths used to move livestock through the territory, have been proposed as potential ecological corridors due to their large extent, continuous nature and centennial protection from ploughing and urbanization, which allows the persistence of some tree cover and natural habitats in them. Bird communities were sampled during the reproductive season along 19 drove road transects in agrarian landscapes between Natura 2000 sites, all of them around the conurbation of Madrid (Madrid Region, Spain). Bird community nestedness was assessed by NODF computation followed by significance estimation by aleatorization, and factors explaining species richness and bird abundance were analyzed through General Linear Models fitted with environmental variables measured on official vegetation maps and orthophotos. Bird communities in drove roads were significantly nested, showing high predictability in the order of species loss from better preserved sites to those under stronger environmental pressures. Accordingly, Poisson regression showed bird richness to decrease strongly with distance from the closest Natura 2000 site and to increase with forest cover at the landscape and at the drove road scales. Bird abundance increased strongly with distance from urban areas and motorways, and it was slightly higher in areas with more forest cover and in transects with less bare ground. These results, and the higher relevance detected for landscape scale variables (500 m around transects) than for those at the drove road (50 m) scale, show that (i) they can only play a secondary role as habitat for nesting birds but (ii) they may add to the Green Infrastructure strategy as facilitators or stepping stones for bird communities if the surrounding landscape is favorable for the

Bird flight behavior, collision risk and mitigation options at high-speed railway viaducts

High-speed railway (HSR) networks are rapidly expanding and are predicted to continue to grow over coming decades. However, there is scant knowledge of their environmental impacts. Their possible effects on bird mortality, particularly at viaducts, gives especial cause for concern. This work presents the results of a nine-month monitoring of bird activity in the vicinity of three HSR viaducts in Central Spain. The study focused on the effects of the infrastructure regarding bird frequentation of the site and on bird flight activity in the danger zone for collision with passing trains. The findings show (i) that bird communities may differ markedly between sites and (ii) that bird activity increases near the railway together with changes in relative species abundances. Furthermore, (iii) birds show a significant tendency to avoid flying across the danger zone, but (iv) all kinds of birds are at a real risk of collisions with trains at viaducts. The greatest danger is at viaduct extremes rather than in their central section, particularly during gusts of wind and for small or medium-sized birds. It also appears that relatively low viaducts might pose greater risk. In practical terms, these results (i) emphasise the need for thorough prior prospection of bird species present, and their flight patterns, where new viaducts are to be built, (ii) show that there is a real risk of bird collisions with trains at viaducts, which should be mitigated, with particular attention due to viaduct extremes and areas where their height is not much above the surrounding vegetation and (iii) strongly indicate the need to minimise viaduct features that may attract birds to them, for example as potential nest sitesThis study is derived from research into the ecology and mortality of birds at highspeed railways done under project EU LIFE+ Impacto Cero (LIFE 12 BIO/ES/000660). JEM and JH form part of the REMEDINAL TE-CM research network, funded by the Comunidad de Madrid (P2018/ EMT-4338). Comments by two anonymous reviewers improved the final tex