Ganéjtúró bogarak trágyalebontásban betöltött szerepének vizsgálata Bugacon

Egy nemzetközi vizsgálathoz csatlakozva kísérletesen arra kerestük a választ, hogy a hazai ganéjtúró-közösségek (Geotrupidae, Scarabaeidae) milyen mértékben végzik el a három legjelentősebb legeltetett patás állatfajunk (ló, marha, juh) trágyájának lebontását. A kiskunsági Bugacpusztán a ganéjtúrók 5 funkcionális csoportjának (nagy és kis alagútásók, nagy és kis galacsinhajtók, társbérlők) egyenkénti és kombinált kizárásával vizsgáltuk azok trágyafogyasztásban és -elhordásban való részvételét. A különböző trágyákhoz kötődő ganéjtúró-közösséget kétféle talajcsapda-típussal mintáztuk meg. A vizsgálat során talajcsapdákkal 23 faj 744 egyedét gyűjtöttük, kiegészítő egyelő gyűjtésekkel pedig további 11 fajt mutattunk ki. Az előkerült fajok 3 funkcionális csoportot képviseltek: kis alagútásók (12 faj), nagy alagútásók (3 faj) és trágyalakók (19 faj). Galacsinhajtókat nem, ugyanakkor a nálunk nagyon ritka sokfoltos trágyatúrót (Euoniticellus pallipes) sikerült kimutatnunk a területen. A különböző ganéjtúró fajok eltérő mértékben preferálták az egyes trágyafajtákat. A kizárások esetében a trágyafogyás mértéke 10-40 % között változott, a legjelentősebb trágyafogyasztónak a kis alagútásók bizonyultak

The effect of light, soil pH and stand heterogeneity on understory species composition of dry oak forests in the North Hungarian Mountains

Dry oak forests have one of the richest understory vegetation in Europe, but the environmental drivers of this community have been scarcely revealed. In this study, we assessed whether the amount of light, soil pH or stand heterogeneity affect primarily the species composition of this community. We investigaed 332 sampling plots in 40-165 year old managed and abandoned Quercus cerris and Q. petraea dominated forests in North Hungary. Presence-absence data of herbaceous species and seedlings of woody species were recorded in 28 subplots within each sampling plot. Stand structure, canopy openness and soil pH were also measured in each plot. The relationships between stand characteristics and the species assemblage were explored by redundancy analysis, while the individual responses of species and species groups were studied by generalized linear mixed models. Multivariate methods and individual species response analyses provided similar results, the amount of light and soil pH were equally important variables (both of them explained 2.8% of species variance), while stand heterogeneity had a bit lower, albeit still significant role in determining understory species composition (1.9% of species variance explained). Seedlings of woody species preferred shaded (half-shaded) conditions, while many herbaceous species were positively related to light. The effect of the three explanatory variables was hard to separate, since they influenced each other as well. Sessile oak seedlings and herbs typical of dry forests, forest edges, grasslands and acidic soil habitats preferred light rich habitats with homogeneous stand structure and low soil pH. Mesic forest herbs and seedlings of other woody species were related to relatively high soil pH, heterogeneous stand structure and closed canopy. These two understory types were clearly separated regarding composition. This study emphasizes the importance of heterogenous light conditions and mosaic, diverse forest structure (presence of homogeneous and heterogeneous forest patches) during forest management for the maintenance of understory biodiversity

Weak evidence of long-term extinction debt in Pannonian dry sand grasslands

Habitat loss is one of the major drivers of the reduction in biological diversity worldwide. European dry grasslands are particularly endangered. However, the persistence of populations can temporarily mitigate species loss - a process referred to as 'extinction debt'. We test this hypothesis using historical and present day habitat maps and current plant biodiversity data collected in the forest-steppe zone of Europe. In 16 5 km × 5 km study sites, representing the landscape heterogeneity of the Kiskunság region (Hungary), 86 20 m × 20 m vegetation plots were surveyed in open and closed calcareous sand grasslands. Grassland diversity was measured as the number of specialist species, defined by statistical fidelity measures using primary and secondary grassland plots. Landscape context was quantified using the areal extent of semi-natural forest-steppe vegetation in a 300 m neighborhood of the plots, based on recent and historical maps (1783, 1860, 1950s, 1987-1989 and 2005). The number of specialist species was estimated with Poisson generalized linear models using the present landscape context, climatic conditions, and a proxy of soil type as covariates. To test for the effect of historical legacies, Pearson residuals from the present models were tested for significant relationships between the residuals and the historical landscape contexts using linear models. We found that the present landscape context had no significant relationship with the specialist species richness of the primary grassland fragments. However, we found a significant relationship between the historical landscape context of the 19th century and the residuals of the present model. Even though the extent of natural vegetation in the 20th century showed more drastic changes, the landscape context in 1950s and 1987-1989 exhibited no significant statistical relationship with the residuals. This delay of species loss is consistent with the extinction debt hypothesis. © 2013 Elsevier B.V. All rights reserved