Dragan Bukovec

Spatio-temporal interpolation of climatic variables over large region of complex terrain using neural networks

Empirical models for seven climatic variables (monthly mean air temperature, monthly mean daily minimum and maximum air temperature, monthly mean relative humidity, monthly precipitation, monthly mean global solar irradiation and monthly potential evapotranspiration) were built using neural networks. Climatic data from 127 weather stations were used, comprising more than 30 000 cases for each variable. Independent estimators were elevation, latitude, longitude, month and time series of respective climatic variable observed at two weather stations (coastal and inland), which have long time-series of climatic variables (from mid last century). Goodness of fit by model was very high for all climatic variables (R>0.98), except for monthly mean relative humidity and monthly precipitation, for which it was somewhat lower (R=0.84 and R=0.80, respectively). Differences in residuals around model were insignificant between months, but significant between weather stations, both for all climatic variables. This was the reason for calculation of mean residuals for all stations, which were spatially interpolated by kriging and used as a model correction. Similarly interpolated standard deviation and standard error of residuals are estimators of the model precision and model error, respectively. Goodness of fit after the averaging of monthly values between years was very high for all climatic variables, which enables construction of spatial distributions of average climate (climatic atlas) for a given period. Presented interpolation models provide reliable, both spatial and temporal estimations of climatic variables, especially useful for dendroecological analysis.

A Factor Model of the Relationship between Stream Sediment Geochemistry and Adjacent Drainage Basin Lithology, Medvednica Mt., Croatia

A mathematical model is constructed to relate the geochemical composition of recent stream material in a number of catchments on Medvednica Mt. to a broadely defined bedrock lithology which represents the parent material for the former. It is a system based factor model, which synthesizes eight lithological and 25 geochemical variables (major, minor and trace elements), reducing their relationships to six geologically meaningful factors. Five of these divulged a definite relationship between geochemistry and lithology. These are labelled as follows: factor of metamorphic rocks; factor of igneous rocks; factor of Tertiary carbonate rocks; factor of parametamorphic rocks and factor of Mesozoic carbonate rocks. Two lithologies; the Mesozoic clastic rocks and Quaternary sediments showed no clear association to any of the factors. Alternatively, one of the factors (F2) can be identified as “non-lithologic” indicating other, perhaps anthropogenic, contributions to the stream sediment geochemical composition.

Modelling groundwater regime acceptable for the forest survival after the building of the hydro-electric power plant

Abstract The reservoir of the future hydro-electric power plant ‘Novo Virje’ plant on Drava river, Croatia, could increase the absolute mean groundwater level in the nearby flood-plain forest. These changes could result in a decline of some forest species, especially the pedunculate oak ( Quercus robur L.), which is very sensitive to the groundwater level disturbance. Dendroecological study was undertaken with the objective of finding acceptable groundwater level regime from the perspective of survival of nearby flood-plain forest. The study was spatially intensive (GIS based) and executed in the following steps: (1) building of the model which describes basal area increment of the pedunculate oak as a function of environmental estimators (hydrologic, soil, climatic and tree competition variables); (2) simulation of increment by the model under different groundwater level regimes and comparison of the simulation results with predefined increment minimum; and (3) designing of the envelopes of the acceptable regimes (simulated increment is larger than predefined minimum). These results are the basis for the design of hydro-technical measures aiming at protecting of flood-plain forests after the hydro-electric power plant is built.

Corine land cover changes during the period 1990–2000 in the most important areas for birds in Croatia

The authors researched changes in specific habitat types in areas considered to be the most important in Croatia for protection of endangered bird fauna during the period 1990–2000. The analysis focused on four areas in the continental part of Croatia (Danube and Drava River alluvium, Pokupsko depression, Sava River basin, Upper Drava River basin) and four areas in the Mediterranean part (Neretva River estuary, NW part of North Dalmatia, Paško field, Lake Vrana). For the classified habitat types, changes in Corine land cover databases in 1990 and 2000 were analysed. The greatest changes in habitat were detected along the Danube and Drava River alluvium, where more than 8% of the total area changed habitat type, as well along the Sava River basin, where approximately 5% of the total area and the greatest absolute area changed habitat type. The most pronounced changes were detected in forest habitats, where forest degradation prevents the maturation of forest stands. The authors discuss which bird species listed in the Red Data Book of Birds of Croatia may be most impacted by the detected changes in habitat. Special attention was given to a comparison of habitat changes in the Nature Park Lonjsko polje between two raptor species, Aquila pomarina and Haliaeetus albicilla, according to the suitability of habitats where changes occurred.

Geochemical atlas of the Medvednica Mt.: natural distribution of geochemical elements in stream sediments

The sample catchment basin approach applying the active stream sediment as a sampling medium is a frequently used cartographic technique for mapping geochemical data. It is particularly useful in mountainous areas with developed drainage network where each individual catchment basin can be assumed to represent an elementary map unit. Stream sediments have been widely used during the last two decades as an alternative sampling medium (vs. soils and overbank sediments) for regional geochemical exploration, mineral exploration, and geochemical mapping as well as for fingerprinting purposes and provenance studies. In this study, uninhabited slopes of the Medvednica Mt. in the close vicinity of the Croatian capital Zagreb, including the whole Medvednica Nature Park, have been selected as an appropriate geochemical environment for evaluation of geochemical baselines at the local and regional scale. The single-element geochemical maps representing the spatial distribution of 21 elements (As, Ba, Ca, Co, Cu, K, La, Mg, Mn, Na, Nb, Ni, P, Pb, Sc, Sr, Th, Ti, V, Y, and Zn) reflect both natural and anthropogenic impact on the environment at the contact of urban and natural landscapes.

Harmonia axyridis (Pallas, 1773), Newly Recorded Invasive Species for Albania

ABSTRACT: The biological control agent and alien invasive ladybird Harmonia axyridis (Pallas, 1773), once introduced for pest control in Europe, is now spreading very rapidly over the European continent, especially since 2002. In this paper we give the first documented record of H. axyridis from Albania, southeastern Europe. The species was recorded in three localities in Albania.