Comparative pollen calendars from Tucson, Arizona: Durham vs. Burkard samplers

Pollen data were compared from (1) Burkard and Durham collectors located in urban Tucson, and (2) Burkard collectors located in urban and native desert environments. Morus was the most common pollen taxon collected in urban Tucson; its presence nearly tripled annual urban pollen totals. Spearman rank correlation was. 56 (p=.05) among the annual mean value of 24 principal pollen taxa collected using the two techniques. In urban areas, several taxa (i.e., Cruciferae, Plantago, cf. Aster, Cercidium and Celtis) were collected consistently using Burkard samplers; they were infrequently collected using the Durham sampler. The Durham calendar contained spring and summer Ambrosia seasons of equal importance; whereas, the urban and desert Burkard calendars reported a dominant spring Ambrosia season accounting for over 85% of the annual Ambrosia pollen. Some pollen taxa from urban areas (i.e., Populus, Ligustrum and Tamarix) remained in the urban environment; conversely, some desert taxa (i.e., spring Ambrosia, Larrea, Ephedra and summer Celtis) reached urban areas. Montane pollen taxa (i.e., Alnus, summer Pinus, Quercus and Artemisia) reached urban and desert environments of the Tucson basin in similar amounts.