Juan Gaitán, a researcher form INTA in Argentina who has been a graduate student in the lab for the past four years, has succesfully completed his PhD, which will be defended soon in the Faculty of Agronomy of the University of Buenos Aires. The title of his PhD is "Structural and functional attributes of arid and semiarid ecosystems of Patagonia and its relation with abiotic factors and the anthropic use" and the abstract of this PhD is:
The advance of desertification is one of the major environmental problems affecting the Argentinian Patagonia. Overgrazing and recurrent droughts are the main drivers of desertification in this region. According to climate models, the occurrence of drought will increase in the future in drylands worldwide, including those from Patagonia. However, little is known on the mechanisms and interactions of climate change and desertification, and how they will affect the ecosystems of the Patagonian steppe. A better understanding of these aspects can help to monitor desertification processes, project their changes and assess their impact under climate change. The objective of this thesis was to analyze the relationship between structural and functional attributes of ecosystems and their interaction with climate and anthropogenic use (grazing) in dryland ecosystems from Argentinian Patagonia. The study was conducted on 320 sites of the MARAS (acronym of “Monitoreo Ambiental para Regiones Áridas y Semiáridas”) network, installed and maintained by INTA researchers since 2007. The main findings found were: The NDVI index derived from MODIS sensor is a good estimator of structural (plant cover) and functional (surrogates of soil functioning) attributes of ecosystems. Vegetation structural attributes such as species richness and cover explained a significant and unique portion of the variability found in ecosystem functioning at the regional scale, which is as important as that explained by climate. The occurrence of drought causes a decrease in the primary productivity of ecosystems, which is higher as temperatura and drought severity increase. Drought effects were attenuated in those sites having higher species richness and shrub cover. Species richness and grass cover (especially palatable species) had a positive effect on functional attributes of the ecosystem such as primary productivity and precipitation-use efficiency. Grazing decreased species richness and thecover of palatable grasses, increased the cover of unpalatable grasses and did not promote shrub encroachment. The effects of grazing on the structure and functioning of ecosystems converged with the expected effects induced by warming and increasing aridity due to ongoing global climate change.
The PhD has four chapters, and three of them have already been published (two of the articles are Open Access):
Gaitán, J.J., D. Bran, G. Oliva, F.T. Maestre, M. R. Aguiar, Esteban G. Jobbágy, G. Buono, D. Ferrante, V. Nakamatsu, G. Ciari, J. Salomone, V. Massara. 2014. Plant species richness and shrubcover attenuate drought effects on ecosystem functioning across Patagonianrangelands. Biology Letters 10, 20140673.
Gaitán, J.J., D. Bran, G. Oliva, F.T. Maestre, M. R. Aguiar, E.G. Jobbágy, G. Buono, D. Ferrante, V. Nakamatsu, G. Ciari, J. Salomone, V. Massara. 2014. Vegetation structure is as important as climate for explainingecosystem function across Patagonian rangelands. Journal of Ecology 102: 1419-1428.
Gaitán, J.J., D. Bran, G. Oliva, G. Ciari, V. Nakamatsu, J. Salomone, D. Ferrante, G. Buono, V. Massara, G. Humano, D. Celdrán, W. Opazo, F.T. Maestre. 2013. Evaluating the performance ofmultiple remote sensing indices to predict the spatial variability of ecosystemstructure and functioning in Patagonian steppes. Ecological Indicators 34: 181–191.
Gaitán, J.J., D. Bran, G. Oliva, F.T. Maestre, M.R. Aguiar, G. Buono, D. Ferrante, V. Nakamatsu, G. Ciari, J.M. Salomone, V. Massara, G. García Martinez. Warming and overgrazing have convergent effects on ecosystem structure and functioning in Patagonian rangelands. Under review
Many congrats Juan! We are all very happy of what you have acomplished in your PhD!