Predicting effects of invasion processes of Eurasian floodplain willows in Patagonia
Zusammenfassung der Projektergebnisse
Among riparian invaders, species of the Salicaceae family introduced for ornamental and functional landscaping play an important role e.g. in Australia, New Zealand, South Africa, the USA and South America. In riparian ecosystems of Patagonia, they have probably been introduced by European settlers in the late 19th or early 20th century as windbreakers and source of fuel wood or timber. Nowadays, they form large gallery forests e.g. in the floodplains of the Ríos Limay, Neuquén and Negro. These forests structured by willows of the Salix alba-Salix fragilis complex, Salix babylonica and hybrids, as well as some Populus taxa, native to Europe or Asia, can also comprise Salix humboldtiana, the only native tree species in the region. The overall goal of the Argentinean-German project was to discover interaction processes between the native S. humboldtiana and invasive Eurasian Salix and Populus taxa and to assess their impact on S. humboldtiana at the Rio Negro in Patagonia. Ecological investigations comprised field studies to apply habitat distribution modeling of the taxa involved, a remote sensing study to detect land cover changes based on invasive species spread in the Rio Negro region, studies on age structures of gallery forests to reconstruct establishment processes and greenhouse experiments on resprouting capacities of native and invasive Salicaceae. Genetic investigations comprised studies on hybridization processes between native and invasive willow taxa as well as on spatial patterns of genetic diversity in Salix humboldtiana. The results revealed that invasive willow taxa have better vegetative reproduction and resprouting capacities, a better growth performance in the adult life stage and they have more or less the same optima than S. humboldtiana regarding water-level-, flood duration- and soil texture gradients in all considered life stages indicating a significant competition potential of the invasive Salix taxa. Furthermore, natural hybridizations with S. humboldtiana involved were proven in the study area, meaning that the invasive willows could expand their range by introgression. However, the native species relies more on sexual reproduction than the invasive taxa. Sexual reproduction requires open sites, which were and are still available at the Rio Negro due to intensive disturbances through floods. However, results based on remote sensing techniques show that in the last decades forest establishment was much more intensive than the removal of existing forests by floods. Therefore, it can be predicted that the space suitable for germination and establishment is decreasing due to invasion processes without being able to quantify their extent. We can conclude that ecological and genetic processes are strongly governed by willow and poplar invasions which can severely affect S. humboldtiana in Patagonian river landscapes.
Projektbezogene Publikationen (Auswahl)
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(2012). Are vegetative reproduction capacities the cause of wide spread invasion of Eurasian Salicaceae in Patagonian river landscapes? PLoS ONE 7, e50652
Thomas, L., Tölle, L., Ziegenhagen, B., Leyer, I.
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(2014). Age structure, growth performance and composition of native and invasive Salicaceae in Patagonia. Plant Ecology 215, 1047-1056
Thomas, L., Leyer, I.
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(Applications in Plant Sciences, 3,4, April 2015, 1400120). Characterization of 23 polymorphic SSR markers in Salix humboldtiana (Salicaceae) using next‐generation sequencing and cross‐amplification from related species
Bozzi J.A., Liepelt S., Ohneiser S., Gallo L.A., Marchelli P., Leyer I., Ziegenhagen B., Mengel, C.
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River dynamics and invasion: Distribution patterns of native and invasive woody vegetation at the Río Negro, Argentina. Riparian Ecology and Conservation, 2015, 2(1), pp. 45-57. Retrieved 12 Oct. 2018
Thomas, L.K., Mosner, E., Leyer, I.
