Tien jaar bijen bijeen in een stadstuin in Appingedam: een methodologische en ecologische analyse

An inventory of the solitary bee community in a small garden in Appingedam, The Netherlands, was made from 2003 to 2012. In total 48 species were found. Number of species per year was positively correlated with the observation effort. Even after 10 years from the start of the inventory still one to two new species were found yearly. Two years after the beginning of the inventory all 21 species that were found in more than three years of the ten year period had been established. During the inventory period nineteen species were found in one year only. Most species only visited the garden to forage. Four species have been found to nest. Only Osmia bicornis had nests every year. Eight species that were found belong to the Dutch Red List. The garden represented 35,0% of the species that have been found in the province of Groningen. If only species of the clay region of Groningen province were considered, 50,0% of the species were found in the garden. Moreover, if species were excluded that are only known from large artificial raised land areas within the clay region, 81,4% of the clay region species were found in the garden. Of all species 62,5% were polylectic and 29,2% were parasites of other solitary bees. Of all species 50,0% of the species build their nests underground, whereas 23,5% and 26,5% build their nests above ground or are able to do both respectively. Of all species 68,8% have one generation per year. There was a strong correlation between the sum of the number of years of host species presence (mostly Andrena spp.) and the number of years that their parasitic bee (mostly Nomada spp.) was present.