Somogyi Múzeumok Közleményei 18. (Kaposvár, 2008)

DÉNES ANDREA, JUHÁSZ MAGDOLNA & SALAMON-ALBERT ÉVA: A szibériai nőszirom {Iris sibirica L.) egy Dráva menti állományának változásai 2000-2007 között

Population changes of Siberian Iris (Iris sibiríca L.) in a habitat along river Drava, between 2000-2007 ANDREA DÉNES, MAGDOLNA JUHÁSZ & ÉVA SALAM ON-AL BE RT Studied Ins sibiríca stand is situated in the neighbourhood of village Gyékényes, on former flood area of river Drava, on a swamp meadow (Carici-Alopecuretum pratensis) mowed in every year. Population changes were monitored between 20002007 in a study plot of 20*20m, using micro-area mapping and yearly shoot and flowering shoot counting. Surveys were made every year at middle or late May. This study is part of an environmental monitoring survey, started in 2000, for studying environmental effects in Hungary of a planned hydroelectric power plant in Novo Virje, Croatia. In the first yearof the study (2000) 33, more or less distinguishable clones were marked. 9 appearing new clones were registered during following years, so for 2007 there were 42 numbered clones on the study site. In the first year shoot number of clones varied between 15 and 233, total number of shoots were 3842. Shoot number of clones in most cases increased year to year in all clones. Increase of total shoot number from 2000 to 2007 is 369% (from 3842 to 14264). Shoot number by clones varied between 52 and 2604. Total number of flowering shoots in the first year was 251 (0-26 by clones). Number of flowering shoots did not show an increasing trend. In the best flowering year (2006) number of flowering shoots varied between 7 and 169 by clones. Total number of flowering shoots were 1546 this year, which decreased to 698 in next year (2007). Percentage of flowering shoots varies from year to year. Flowering peaks were observed in years which were driest in the vegetation period: in 2002 (10,8% of shoots flowering) and in 2006 (13,3% flowering). Weak flowering were observed in 2001 and 2007 (3,32% and 4,89%, accordingly). The planned hydroelectric plant have not been built and no other anthropogenic effects on water levels were observed. Intensive growth of Iris sibiríca clones cannot be explained by abiotic changes. Knowing local situation, in this phase of study we can assume even that this is a stand replanted from a neighbouring meadow, whose population increases because of proper conditions. From data of eight study years we draw the conclusion that water supply has a strong effect on percentage of flowering shoots: physiological drought stimulates flowering of Iris sibirica. It seems sure that mowing after fruit ripening has a positive effect on propagation by seeds. Year-to year monitoring of Iris sibirica at the Gyékényes site was suspended in 2007. Further monitoring is planned in longer intervals. Fig.1. Position of Iris sibirica clones on the 20x20m study site (micro-area map). Fig.2. Percentage of flowering shoots. Table 1. Short description of Iris sibirica clones of the study area. Table 2. Shoot number and flowering shoot number by sites during Iris sibirica monitoring in 2000-2007. Table 3. Total number of shoots, of flowering shoots and percentage of flowering shoots yearly.