This paper presents the results of the preliminary testing of the selected trace elements in the soils of several parks in the city of Zagreb, Republic of Croatia. In each park, the samples were taken from several points-at various distances from the roads. The samples were taken at two different depths: 0-5 and 30-45 cm. Composite samples were done for each sampling point. Microwave-assisted wet digestion of the soil samples was performed and the determination by ICP-AES technique was done. Results obtained for Al, As, Ba, Mn, Ti, V, and K are in a good agreement with the results published in the scientific literature so far. The mass fraction values of Cd, Cr, Cu, Ni, Pb, and Zn are somewhat higher than the maximum values given in the Croatian Directive on agricultural land protection against pollution. Be, Mo, Sb, Se, and Tl in the samples were present in the concentrations that are lower than their method detection limit values.

The quantity and quality of seedlings in the nursery has an impact on the success of re-establishment and later growth. High germination rates enable a sufficient number of seedlings, and their quality is assessed using a number of parameters, including seedling height and root collar diameter. These parameters are influenced in some species by seed size, but the correlation between them is species-specific. The model species in this research was sweet chestnut (Castanea sativa Mill.), and seeds from 12 populations from two distinct biogeographical regions of Croatia were collected. We examined the influence of seed size on four parameters: germination rate, seedling height, root collar diameter and sturdiness quotient. Seed size has been shown to have a positive influence on both seedling height and root collar diameter, whereas no such correlation was noted for germination rate and sturdiness quotient. Significant differences in nut size and seedling growth parameters were found between the Mediterranean and continental populations, with higher values observed in the coastal Mediterranean populations. We concluded that seed origin and seed size have a significant impact on seedling growth and are important factors to consider when choosing seed material. Further nursery operations should consider seed origin and local environmental conditions when choosing seedlings for reforestation efforts and general forest operations.

There are many various environmentally hazardous substances, but researchers around the world are especially interested in heavy metals. Heavy metals are naturally occurring elements that have a high atomic weight and a density at least 5 times greater than that of water [1]. From a biological point of view, Nieboer and Richardson [2] have classified heavy metals into three groups: (i) elements essential to some organisms (V, Cr, Mn, Fe, Co, Zn, and Mo), (ii) elements necessary for growth and development of plants (Mn, Fe, Cu, Zn, Mo, and Ni), and (iii) phytotoxic elements (Cd, Hg, and Pb). World Health Organization (WHO) has classified As, Cd, Hg, and Pb among 10 groups of hazardous chemicals. Those are elements which have toxicological characteristics. Moreover, when their concentrations increase, Mn, Co, Ni, Cu, Zn, Se, Ag, Sb, and especially Cr and Ti are also considered toxic [3]. Since the pollution of soil by heavy metals is one of the possible causes of a decrease in forest ecosystem vitality and degradation of the whole habitat, there is a significant scientific interest in research of the connection of heavy metal concentration values in the environment to their degradation effect [4]. In higher concentrations heavy metals

U radu su prikazani rezultati ispitivanja laboratorijske klijavosti i morfoloških značajki klijanaca europskoga pitomoga kestena (Castanea sativa Mill.). Uzorci za istraživanja sakupljeni su u submediteranskom području Hrvatske, a radni uzorak za ispitivanje klijavosti iznosio je 8×25 sjemenki. Sjeme je do ispitivanja klijavosti čuvano tri mjeseca u hladnjaku na temperaturi od 3 °C. Postotak laboratorijske klijavosti utvrđen je prema postotku pravilnih klijanaca koji su normalno proklijali nakon 27 dana ispitivanja. Ispitivanje je provedeno u laboratoriju prema uvjetima koje propisuje ISTA (International Seed Testing Association). Izrađen je katalog sa slikama i opisom nepravilnih klijanaca. Na osnovi definiranih kodova nepravilnih klijanaca moguće je preventivno djelovati kako bi se reducirale nepoželjne jedinke. Rezultati ovog istraživanja od velike su koristi za razumijevanje složenoga procesa klijanja sjemena, kako u laboratoriju, tako i šumskim rasadnicima.

Odumiranjem stabala mijenjaju se stanišne prilike u šumskom ekosustavu, uslijed čega dolazi do promjene mikroklime i mikrobiološke aktivnosti tla. Cilj ovoga istraživanja je utvrditi razlike u mikroklimi staništa te u enzimatskoj aktivnosti šumskog tla u trima šumskim progalama i trima šumskim sastojinama obične jele s rebračom (Blechno-Abietetum Ht. 1950). Od mikroklimatskih elemenata mjerene su temperatura zraka, temperatura tla, relativna vlažnost zraka i volumetrijska vlažnost tla. Za određivanje kemijskih svojstava tla te dehidrogenazne i proteolitičke aktivnosti tala prikupljeni su kompozitni uzorci tla s dubine od 0 do 10 cm. U šumskim progalama utvrđene su značajno više vrijednosti temperatura zraka i tla te značajno niže vrijednosti relativne vlažnosti zraka i volumetrijske vlažnosti tla nego u šumskoj sastojini. Provedenim istraživanjem nisu utvrđene značajne razlike u kemijskim svojstvima tala između šumskih progala i sastojina. Zbog nesignifikantnih promjena kemijskih karakteristika tla, nisu utvrđene značajne promjene u enzimatskoj aktivnosti tala u progalama u odnosu na šumske sastojine. Temperatura zraka i temperatura tla povezane su s dehidrogenaznom aktivnosti tala, dok su temperatura tla i volumetrijska vlažnost tla povezane s proteolitičkom aktivnosti tala u šumskim progalama. Kemijska su svoj­stva tla također imale značajan utjecaj na enzimatsku aktivnost, jer se povećanjem udjela organske tvari, dušika, humusa i ugljika u tlu povećava i enzimatska aktivnost šumskih tala. Najveće korelacije enzimatske aktivnosti i kemijskih svojstava tla utvrđene su za proteolitičku aktivnost šumskih tala. Enzimatska aktivnost šumskih tala bila je najveća na početku vegetacijskog razdoblja u uvjetima optimalne temperature i vlažnosti tla.