Branko Kramberger

Recent vegetation history of the North Adriatic grasslands: expansion and decay of an anthropogenic habitat.

A summary pollen diagram and old cartographic materials were used to reconstruct the recent vegetation history and trends of temporal dynamics of the North Adriatic Karst grasslands. Before the Roman period some evidence about grassland vegetation exists from Neolithic settlements, but deforestation, detectable on the landscape level because of pollen, started 2500-2000 years BP. A large-scale anthropogenically-driven process of clearance started in the Roman period as is reflected in the increasing pollen of grasses (Poaceae) and other herbaceous species (Apiaceae). The presence of pioneer trees (Quercus, Ostrya), juniper and grasses during 1000-400 years BP suggests that cycling processes of cultivation (strong grazing pressure), abandonment and re-cultivation were present. A 250-year-old map shows a peak of probable deforestation, where grasslands have 3.2 times larger surface area than on a recent land-use map in a 665.8 km2 large pilot area. More than 60% of grasslands changed into forest since then. On a sub-plot area of 626 ha (1% of the pilot area), where habitat mappings were performed, only 12.8% were still grasslands without tall herb invasions or scrub encroachments. Another 27.1% were grasslands with early signs of reforestation. The traditionally open landscape of the North Adriatic Karst was able to recover to forest due to almost total abandonment and sufficient mesic climate conditions.

Grassland succession is mediated by umbelliferous colonizers showing allelopathic potential

Abstract Two Umbelliferous tall herbs – Laserpitium siler and Grafia golaka tend to form monodominant stands in the montane belt of the North Adriatic Karst after grassland abandonment. The germination and development of shade-tolerant species of further successional stages could be facilitated by favorable climatic conditions, measured in the canopy, but colonization by woody species was not perceived, except for Pinus sylvestris and Pinus nigra, which are not common trees in the area. The vegetation history of the site shows rather slow reforestation after abandonment and almost exclusively with pine woodland. All organs of both Umbelliferous species showed high allelopathic potential, measured as significantly inhibited germination and early development of test plants in bioassays. Under similar treatments, the germination rate of P. sylvestris was reduced, but further development of seedlings was stable. One possible explanation for the relative persistence of Umbelliferous monodominant stands is the strong allelopathic potential of both umbellifers. They act as “succession retardants”, and only pinus is able to colonize these stands successfully; the explanation for that is based on the presence of the same essential oils (limonene, pinene) in both Pinus and L. siler.

Germination and survival of endangered Pulsatilla grandis (ranunculaceae) after artificial seeding, as affected by various disturbances

Pulsatilla grandis is a rare and endangered species in Central Europe. A field experiment was set up to test the effects of disturbances on its germination and survival rates after artificial seeding. Disturbances were simulated by the following treatments: burning, hoeing, and removal of vegetation. The germination percentage decreased rapidly with time, to only 2% in 2-year-old fruits. The germination rate of fresh fruits was the highest in hoed plots (29.2 ± 12.9%), followed by removedvegetation plots (21.8 ± 17.3%) and burned plots (1.8 ± 2.2%). No germination was observed in control plots. The survival rate of seedlings was monitored over the next 5 years. In the year following the treatment, all the seedlings survived in the burned plots; in the hoed and in removed-vegetation plots, survival rates were 38.5 ± 2 and 55 ± 27%, respectively. Approximately half of them were alive after 5 years. Grassland vegetation in burned quadrates recovered very quickly, whereas in other disturbed plots the numbers ...

Comparison of using regression modeling and an artificial neural network for herbage dry matter yield forecasting

This study presents an application of artificial neural network and regression modeling techniques for forecasting grassland dry matter yield. Using data from a field plot experiment on semi‐natural grassland in Maribor (Slovenia), the multiple regression and artificial neural network methodologies were employed to explain the patterns of dry matter yield during a 6‐year period. On the basis of the two proposed approaches forecasts were conducted for the independent, validation year (6). The results in terms of Theil inequality coefficient, mean absolute error, and correlation coefficient show a better forecasting performance for the artificial neural network (likely due to the non‐linear relationships prevailing among regressors and regressand) while relationships between observables can be better explained by regression modeling results. Copyright