Arable weed vegetation and germination traits of frequent weeds in Kosovo

摘要

Research on changes in Europe’s arable weed flora and vegetation, which resulted from changes in agricultural practices, has been conducted since about 1970, but has concentrated on Central and Northern Europe. Thus, only few data on changes in the arable weed flora and vegetation have been available from Southern Europe including the Republic of Kosovo, located in the centre of the Balkan Peninsula, Europe’s major hotspot of biodiversity. In general, Kosovo is known for its rich flora and vegetation. However, the knowledge on Kosovo’s flora and vegetation is still incomplete or might be outdated due to pronounced land-use changes in the last two decades. With respect to the arable weed flora and vegetation of Kosovo, no comprehensive research has been conducted since about 1980 and is thus of interest from a vegetation and landscape ecological perspective and the perspective of biodiversity conservation. Moreover, knowledge on Kosovo’s arable weed flora and vegetation and on weed species traits is valuable from an agronomic perspective, since arable production is among the region’s main economic activities contributing to the gross domestic product.Against this background, empirical and experimental studies conducted in this thesis (i) contribute to the ongoing floristic mapping of Kosovo, (ii) provide a reference database for future studies on land-use change and its effects on the regional arable weed flora and vegetation, (iii) provide information on the relationships between the vegetation of the arable land and both environmental features and agricultural management measures, (iv) elucidate within-region differentiations of weed species’ frequencies, cover and germination characteristics, and (iv) analyse region-specific germination traits of three frequent weed species, namely A. retroflexus, E. crus-galli and D. stramonium.Based on the results of an empirical study in 432 cultivated arable fields in 2006, today’s arable weed flora and vegetation of Kosovo is characterised by a low alpha-species richness with mean species numbers between 8 (in vegetables) and 10 (in winter wheat) per 25 m², the predominance of few nitrophilic and often herbicide-resistant species at the plot and regional scale, a low cover (at the plot scale) and low occurrence frequencies (at the regional scale) of the larger fraction of weed species (187 of 235 species), decreased frequencies of some arable weeds s. str. compared to the situation around 30 years ago, a nearly total lack of differences in species composition due to site conditions (e.g. altitude above sea level, soil base-richness, soil moisture), marginal differences in the weed flora between two sub-regions of Kosovo that differ in climate and land use, and pronounced differences in species composition between fields that differ in crops (summer vs. winter crops) and weed control (chemical vs. mechanical measures).As it may be concluded from an empirical study conducted in 41 recently abandoned arable fields in 2007, the alpha-species richness (in average 18.8 species per 25 m²) and the frequencies of arable weed species are higher in recently abandoned than in cultivated arable fields. This result indicates a potential for future development of species rich weed communities, provided by the soil seedbanks of the arable land.Based on the results of a climate chamber experiment and a field experiment conducted in 2007, the germination behaviour of three problematic arable weeds of Kosovo, namely Amaranthus retroflexus, Echinochloa crus-galli and Datura stramonium, is found to be as follows: The temperature-dependent germination behaviour is species-specific and, for one species, the germination behaviour differs for seeds originating from different provenances within Kosovo, indicating ecological adaptation at the population level.The results of the empirical and experimental studies are discussed against the need to develop and implement sustainable agricultural systems considering the multifunctionality of agriculture. Moreover, shortcomings in the availability of spatially-explicit databases on the geometry and pattern of Kosovo’s agricultural land parcels and land use types are discussed in the context of relationships between biodiversity and landscape structure. Finally, suggestions for future research in the arable land of Kosovo and on traits of the region’s problematic weed species are presented.