Abstract booklet - gtö – Society for Tropical Ecology

220 SCIENTIFIC POSTER SESSION | FOYERSCIENTIFIC POSTER SESSION | FOYER221WEDNESDAY | FOYERTopic: Ecological networks and ecosystem functioningSOIL NUTRIENTS AND WATER AVAILABILITY SHAPING SPECIESDISTRIBUTIONS IN TROPICAL FORESTSDelicia Rayda Pino Garay 1 , Richard Condit 2 , Ben Turner 2 , BettinaEngelbrecht 1 , Rolando Perez 21University of Bayreuth, Bayreuth, DE, delicia.pino@gmail.com, 2 SmithsonianTropical Research Institute, Balboa, Panama,Identifying patterns of tree distributions across species, and understandingthe underlying mechanisms is challenging in tropical forests due to their highspecies diversity. Rainfall and the subsequent variation in soil water availability,as well as soil nutrient availability have been shown to be associated withspecies distribution and forest diversity. However it remains difficult todisentangle the role of either soil nutrients or moisture because commonlyboth co-vary, and the strength and shape of their relationship vary spatially in acomplex manner. In this study we analyzed the occurrence of 440 tree speciesin 44 1-ha plots across a strong rainfall gradient at the Isthmus of Panama.Soil nutrients were analyzed, and soil moisture deficit during dry seasonwas modelled for every plot. Logistic regressions of species occurrences as afunction of soil nutrients and moisture were carried out and univariate modelswere applied using individual nutrients. Soil nutrients and soil moisture showedtremendous variation in the area as plots locations encompass a wide rangeof geological substrates. Most nutrients were correlated among each otherhowever phosphorous remained most significant in the models when testedagainst species occurrences. In addition, phosphorous and soil moisture werestrongly negatively correlated. Phosphorous and moisture both contributedsignificantly to explaining species occurrence. Species showed three distinctivepatterns of distribution with respect to phosphorous and moisture. Individualspecies related characteristically to particular combinations of moisture andphosphorous concentrations. 10% of the species correlated negatively withboth phosphorous and moisture, 8% of the species correlated positively withphosphorous and negatively with moisture while 5% showed the inversepattern. Our results strongly suggest that differential resource requirementsfor both moisture and phosphorous are important in shaping tree distributionpatterns in these tropical forests. To conclusively evaluate the underlyingmechanisms, experimental studies will be carried out to quantitatively linkplant species responses to different nutrients with their distribution patterns.Topic: Ecological networks and ecosystem functioningINFLUENCE OF CLIMATIC CONDITIONS ON THE NUTRIENT STATUSOF TREES IN A HUMID FOREST IN SOUTHERN ECUADORDarwin Pucha Cofrep 1,2 , Achim Bräuning 1 , Wolfgang Wilcke 31University of Erlangen, Erlangen, DE, darwinalexander@gmail.com, 2 UniversidadNacional de Loja, Loja, Ecuador, 3 University of Berne, Berne, SwitzerlandSo far, little is known about how climatic variations influence the availabilityand the uptake of nutrients in tropical trees and which implications climaticchanges may have on the future growth potential of different ecological foresttypes. It has been shown that the nutrient input by dry and moist depositioninto the humid lower montane rainforest of the RBSF in southern Ecuador variesconsiderably between different years as a consequence of varying climaticconditions. We combine dendrochemical analyses with the variations of thestable carbon isotope content to obtain information about how different climaticconditions influence the short-term and the long-term uptake of nutrients.We present the first preliminary results of the distribution and concentrationof immobile elements in individual growth rings of Cedrela montana andcompare these data with the ENSO index. We aim for a reconstruction of thevariation of humidity conditions during the past decades derived from stablecarbon isotopes and ring-width measurements. Finally, we try to evaluate howthe uptake of immobile elements in the wood is influenced by the climaticconditions during the time of nutrient uptake.Wednesday WEDNESDAY 16:00 | FOYER | FoyerMerian Award Winner 2011gtöSociety for Tropical Ecology | Gesellschaft für Tropenökologie e.V. Status and future of tropical biodiversity | Frankfurt, 21 - 24 February 2011gtö