Lichens facilitate seedling recruitment in alpine heath

Abstract Questions How do mat thickness, physical structure and allelopathic properties of terricolous mat-forming lichens affect recruitment of vascular plants in dwarf-shrub and lichen heath vegetation?. Location The mountains of Dovrefjell, central Norway. Methods In autumn, seeds of ten vascular plant species were collected and sown in a common garden experiment with mats of six lichen species and bare-soil controls as experimental treatments. We recorded growing season soil temperature and moisture, and seedling recruitment and growth after one year. The effect of lichen secondary compounds on germination was tested in a growth chamber experiment and compared to the lichen-plant interactions detected under field conditions. Results The lichen mats buffered extreme soil temperatures and soil drying in dry weather, with soils below the thickest mats (Cladonia stellaris and C. rangiferina) experiencing the lowest temperature fluctuations. Seedling recruitment and seedling growth in the field and seed germination in the lab were species-specific. Seedling recruitment rates were overall higher within lichen mats than on bare soil, but the c. 6.5 cm thick mats of C. stellaris reduced recruitment of many species. The lab experiment suggested no overall strong effect of lichen allelopathy on seed germination, and effects on seed germination were only moderately correlated with the lichen-plant interactions observed for seedling recruitment in the field. Conclusions In harsh environments like alpine dwarf-shrub and lichen heaths, the presence of lichens and the resulting amelioration of the microclimate seems more important for vascular plant recruitment than are allelopathic effects often reported in lab experiments. We might therefore expect most terricolous lichens, depending on the plant species in focus, to facilitate rather than hamper the early stages of plant recruitment into lichen-dominated arctic-alpine heath vegetation. This article is protected by copyright. All rights reserved.Peer reviewe

Wpływ różnych metod modyfikacji skrobi ziemniaczanej, pszennej i kukurydzianej na ich cechy fizykochemiczne

The physico-chemical properties of potato, wheat and maize starch, native and modified according to three methods, were studied. It was found that mild acid or enzymatic hydrolysis resulted in an increased temperature of starch pasting, a reduction of paste viscosity, and an increase of gel syneresis after defreezing. The physico-chemical changes brought about by phosphate modification were opposite to those induced by the acid and enzymatic modification. Studies of three fractions of potato starch differing in granule size showed that the changes due to modification increase with the decrease of average granule size.Przeprowadzono badania fizykochemiczne skrobi ziemniaczanej, pszennej i kukurydzianej naturalnej i modyfikowanej metodami: kwasową, enzymatyczną i fosforanową. Skrobia ziemniaczana przed modyfikacją była rozdzielana na trzy frakcje różnicą się średnią wielkością ziarn (tab. 2). Stwierdzono (tab. 1), że w wyniku łagodnej hydrolizy kwasowej lub enzymatycznej nastąpiło - w stosunku do skrobi niemodyfikowanej - podwyższenie temperatury kleikowania skrobi, obniżenie lepkości kleiku i zwiększenie synerezy żelu po jego rozmrożeniu. Modyfikacja fosforanowa spowodowała zmiany badanych cech fizykochemicznych, ale w przeciwnym kierunku niż modyfikacja kwasowa i enzymatyczna. Stosunkowo najbardziej podatna skrobia kukurydziana i najmniej - skrobia pszenna. Badania frakcji skrobi ziemniaczanej różniących się wielkością ziarn ujawniły (tab. 3), że im drobniejsza była frakcja, tym łatwiej zachodziła hydroliza kwasowa lub enzymatyczna oraz silniej wzrastała lepkość kleików otrzymanych ze skrobi modyfikowanej metodą fosforanową. Natomiast wchłanianie wody było tym większe, im większe były ziarna skrobi