Albert et al. (2014) Applied Vegetation Science

Ágnes-Júlia Albert, András Kelemen, Orsolya Valkó, Tamás Miglécz, Anikó Csecserits, Tamás Rédei, Balázs Deák, Béla Tóthmérész & Péter Török (2014): Secondary succession in sandy old-fields: a promising example of spontaneous grassland recovery. Applied Vegetation Science, DOI: 10.1111/avsc.12068, PDF itt

Abstract
Question: Based on the spontaneous vegetation development of old-fields in the Nyírség and Kiskunság sand regions (Hungary), we aimed to answer the following questions using the chronosequencemethod: (1) how do the proportions of different functional groups change during succession; (2) which target species establish successfully in the old-fields during the course of succession; and (3) how successful is spontaneous succession in the recovery of target grasslands?
Location: Two sand regions of the Great Hungarian Plain: (1) the Nyírség sand region (East Hungary, acidic sand, moderately continental climate) and the Kiskunság (Central Hungary, calcareous sand, continental climate).
Methods: Altogether 24 old-fieldswere classified into young (<10-yr-old),middle-aged (10–20-yr-old) and late-succession (20–40-yr-old) old-fields; four fields in each age category. For baseline vegetation reference, three open and three closed sand grassland stands in both regions were sampled in the vicinity of the old-fields. The percentage cover of vascular plants was recorded in five 2 9 2-m plots in each field, in early May and late June 2012. We used life forms, clonal spreading traits and Ellenberg indicator values for nutrients in the analysis. Species of Festuco-Brometea class were considered as target species.
Results: The cover of hemicryptophytes and geophytes increased, the cover of short-lived species decreased with time. Cover of species without clonal spreading ability decreased, while cover of species with clonal spreading ability increased with increasing field age. The cover of invasive species decreased with increasing field age. The majority of target species had established already in the young and middle-aged old-fields, although their cover was significantly higher in the two older age groups.
Conclusion: Spontaneous succession can be a vital option in recovery of sand grassland vegetation in Central Europe; the majority of the species pool of sandy grasslands can be recovered in the first 10–20 yrs. However, the success of grassland recovery can be strongly influenced by the surrounding species pool and can be slowif seed dispersal is limited. Spontaneous succession ismost promising when the target species of grasslands immigrate at the very beginning of the succession, within the first few years.


Keywords
abandonment, acidic sand, calcareous sand, clonal traits, grassland restoration, invasion, spontaneous succession

Møller et al. (2012) Oecologia

Anders Pape Møller, Mario Diaz, Einar Flensted-Jensen, Tomas Grim, Juan Diego Ibáñez-Álamo, Jukka Jokimäki, Raivo Mänd, Gábor Markó, Piotr Tryjanowski (2012): High urban population density of birds reflects their timing of urbanization. Oecologia 170(3): 867-875.

Abstract
Living organisms generally occur at the highest population density in the most suitable habitat. Therefore, invasion of and adaptation to novel habitats imply a gradual increase in population density, from that at or below what was found in the ancestral habitat to a density that may reach higher levels in the novel habitat following adaptation to that habitat. We tested this prediction of invasion biology by analyzing data on population density of breeding birds in their ancestral rural habitats and in matched nearby urban habitats that have been colonized recently across a continental latitudinal gradient. We estimated population density in the two types of habitats using extensive point census bird counts, and we obtained information on the year of urbanization when population density in urban habitats reached levels higher than that of the ancestral rural habitat from published records and estimates by experienced ornithologists. Both the difference in population density between urban and rural habitats and the year of urbanization were significantly repeatable when analyzing multiple populations of the same species across Europe. Population density was on average 30 % higher in urban than in rural habitats, although density reached as much as 100-fold higher in urban habitats in some species. Invasive urban bird species that colonized urban environments over a long period achieved the largest increases in population density compared to their ancestral rural habitats. This was independent of whether species were anciently or recently urbanized, providing a unique cross-validation of timing of urban invasions. These results suggest that successful invasion of urban habitats was associated with gradual adaptation to these habitats as shown by a significant increase in population density in urban habitats over time.


Keywords
Adaptation, Birds, Cross-validation, Invasion, Population density