INVASIVE VASCULAR FLORA OF POŽEGA VALLEY, REPUBLIC OF CROATIA: DIVERSITY AND RISK ASSESSMENT

Non native, and especially invasive plants, often have a negative impact on biodiversity, economy, and even on human health. They have rapid reproduction potential and are capable for dispersal over significat areal. They have a negative impact on biological diversity, economy and even on human health. Therefore, the spread of invasive plant species is consider as one of the biggest problems in nature protection. Research on prevalence and risk assesment of invasive vascular flora in Požega valley were conducted during the summer months from 2017 to 2019 using the Br. –Bl. (1964.) cover/abundance method. A thirty four invasive species were detected during the study period. Analysis according to family affiliation, life form, geographic origin and invasion stage were made. Multivariate statistical technique –CCA were use to analyse relation between elevation and cover values of invasive flora of Požega valley. The most numerous families are Asteraceae and Poaceae. Life-form analysis showed the predominance of therophytes, but also presence of hemicryptophytes, phanaerophytes, geophites and hydrophyte. Regaridng origin, majority of invasive alien species come from American continent, particularly from North America, followed by those from Asia and Africa. Most of them (47%) are in the stage of invasion i.e. colonisation. Many of them are already naturalised, and in invasion phase. Lowlands (elevation up to 200 m) are favorable sites for most of the invasive plants, and just small amount of them, like Phytolacca americana L. and Ailanthus altissima (Mill.) Swingle are positively correlated with the hilly areas. The most affected by the invasion are ruderal and agricultural habitats.