|Aerobiological behaviour of Urticaceae in Mediterranean Climate (Southern Spain)
F. Alba (1), C. Díaz de la Guardia (1), D. Nieto (1), C. De Linares (1), S. Schiaffino-Ortega (1), M.M. Trigo (2), M. Recio (2), L. Ruiz (3), P. J. Hidalgo (4), P. Candau (5), F. González-Minero (5),
H. García-Mozo (6) & C. Galán (6)
(1) Dpto. de Botánica. Universidad de Granada. Campus de Fuentenueva. 18071 Granada.
(2) Dpto. de Biología Vegetal. Universidad de Málaga. Apdo. 59. 29080 Málaga.
(3) Dpto. de Biología Animal, Biología Vegetal y Ecología. Universidad de Jaén. 23071 Jaén.
(4) Dpto. Biología Ambiental y Salud Pública. Fac. Ciencias Experimentales. Universidad de Huelva. 21071 Huelva
(5) Dpto. de Biología Vegetal y Ecología. Universidad de Sevilla. Apdo. 874. 41080 Sevilla.
(6) Dpto. de Botánica, Ecología y Fisiología Vegetal. Universidad de Córdoba. 14071 Córdoba.
INTRODUCTION. In Andalusia region, Urticaceae pollen is, together with Chenopodiaceae/Amaranthaceae and Poaceae, the most frequent morphotype from herbaceous plants in the aerobiological samples. This taxon is represented by species of the genera Parietaria and Urtica common in somewhat moist substrates on croplands edges. It is also frequent in urban wall fissures. Urticaceae pollen is constantly present throughout the year and its highest levels are recorded between late winter and spring. In Mediterranean climate, water availability is one of the limiting factors for pollen production and phenological patterns, which in turn depends on total annual precipitation and the annual rainfall distribution. In the current context of global warming, to knowledge of the aerobiological behaviour of herbaceous taxa subjected to extreme episodes in Mediterranean climate (water limitation, concentration of precipitations in extreme events and lack of rainfall predictability), is of the most importance to estimate the aerobiological behaviour of Urticaceae in future climatic scenarios.
METHODOLOGY. This study was carried out in nine localities of southern Spain (Almería, Cádiz, Córdoba, Granada, Huelva, Jaén, Málaga, Motril and Sevilla). In climate terms, these cities belong to the Mediterranean climate type, but they do show some diversity regarding total annual precipitation and temporal rainfall distribution. A volumetric Hirst-type spore-trap was used at all the sampling sites, the sampling period ranging between 1991 and 2007. The inter-annual evolution and trend of pollen production were evaluated taking into account meteorological factors (temperature and total rainfall). In addition, the main pollen season (MPS) or the variation in the onset and duration of the pollination period (nº of days) was determined at 85% using GAIA procedure (Torrecilla, 2008). Furthermore, modelling based upon geostatiscal mapping has enabled the construction of a spatial model to estimate the values of Urticaceae pollen at a regional scale.
RESULTS AND DISCUSSION. Most species of the genera Urtica and Parietaria presented a long flowering season in the study area. In consequence, Urticaceae pollen remained in the air continually, practically appearing every day of the year. The highest levels were reached in the months of March and April, while lower concentrations were registered in summer. Strong fluctuations of pollen production appeared from year to year and sampling site, being the lowest quantities registered in Malaga (average annual values: 850 grains) and the highest in Motril (22800 grains). The beginning of MPS generally occur in October and the length is fairly uniform, ranging between 200 and 280 days. Both the pollen production as well as the length of the flowering period appeared to be linked to the periods of precipitation, increasing when rainfall conditions were favourable. In addition, the maps generated present a two-dimensional vision of the study area, showing that bioclimatic diversity of this region promotes a step-wise flowering of Urticaceae.
In conclusion, Urticaceae adjusted their flowering-onset date and pollen emission to the availability of soil-water resources, responding positively to rainfall of the previous early spring and autumn.
ACKNOWLEDGEMENTS. RAA and the authors wish to thank the Junta de Andalucía Government funding for this study through the project “RNM 02034. 2007-20, Análisis del polen atmosférico como bioindicador de la calidad del aire y de los efectos del cambio climático en la fenología y biodiversidad de los ecosistemas andaluces” and to the Spanish Government (DGICYT) for supporting the project “GGL2006-12648-CO3-02”.
Torrecilla Salinas, C. J. (2008). Gestor Automático de Información Aerobiológica – GAIA. Universidad de Granada, Granada.