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The relationship between carbon isotope discrimination (13Δ) of C3 vegetation and long-term (30 years) and short-term (growing period) precipitation was investigated. Different species of Stipa, a dominant grass genus in the (semi-)arid Asian steppes, and other C3 species were collected along aridity gradients in Inner Mongolia in 2005 (11 sites, 71 samples) and in the Republic of Mongolia in 2006 (40 sites, 45 samples). The data set was expanded with published and unpublished data of Stipa and other C3 species (11 studies covering 8 years, including 64 observations of Stipa, and 103 observations of other C3 species) and C3 community bulk-samples (11 samples). Weather data were geostatistically interpolated for all sampling sites and years. 13Δ of Stipa followed different relationships for the individual years when related to mean annual precipitation due to large anomalies between annual and long-term average precipitation patterns. However, the 13Δ response to rainfall converged when the (long-term) mean annual precipitation was replaced by year-specific mean daily precipitation during the growing period (PG). Remarkably, the 13Δ-response to (PG) for C3 species as a whole (including herbaceous dicots, semi-shrubs and grasses) and also the C3 community-level response were virtually identical to that of Stipa. The relation was also valid outside the geographical and climatic range where it was developed, giving proof of its robustness.

The search for predictions of species diversity across environmental gradients haschallenged ecologists for decades. The humped-back model (HBM) suggests that plantdiversity peaks at intermediate productivity; at low productivity few species can toleratethe environmental stresses, and at high productivity a few highly competitive speciesdominate. Over time the HBM has become increasingly controversial, and recent studiesclaim to have refuted it. Here, by using data from coordinated surveys conductedthroughout grasslands worldwide and comprising a wide range of site productivities, weprovide evidence in support of the HBM pattern at both global and regional extents. Therelationships described here provide a foundation for further research into the local,landscape, and historical factors that maintain biodiversity. Fil: Fraser, Lauchlan H.. Thompson Rivers University; Estados Unidos Fil: Pither, Jason. University of British Columbia; Canadá Fil: Jentsch, Anke. University Of Bayreuth; Alemania Fil: Sternberg, Marcelo. Tel Aviv University; Israel Fil: Zobel, Martín. University Of Tartu.; Estonia Fil: Cabido, Marcelo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Enrico, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Nabinger, Carlos. Universidade Federal do Rio Grande do Sul; Brasil Fil: Naseri, Kamal. Ferdowsi University of Mashhad; Irán Fil: Overbeck, Gerhard E.. Universidade Federal do Rio Grande do Sul; Brasil Fil: Palmer, Todd M.. University of Florida; Estados Unidos Fil: Parsons, Sheena. University of Kansas; Estados Unidos Fil: Pesek, Mary. University of Kansas; Estados Unidos Fil: Pillar, Valério D.. Universidade Federal do Rio Grande do Sul; Brasil Fil: Pringle, Robert M.. Princeton University; Estados Unidos Fil: Roccaforte, Kathy. University of Kansas; Estados Unidos Fil: Schmidt, Amanda. Thompson Rivers University; Canadá Fil: Shang, Zhanhuan. Lanzhou University; China Fil: Stahlmann, Reinhold. University Of Bayreuth; Alemania Fil: Stotz, Gisela C.. University of Alberta; Canadá Fil: Sugiyama, Shu-ichi. Hirosaki University; Japón Fil: Szentes, Szilárd. Szent István University; Hungría Fil: Thompson, Don. Lethbridge Research Centre; Canadá Fil: Tungalag, Radnaakhand. National University of Mongolia; Mongolia Fil: Undrakhbold, Sainbileg. National University of Mongolia; Mongolia Fil: van Rooyen, Margaretha. University of Pretoria; Sudáfrica Fil: Wellstein, Camilla. Free University of Bozen Bolzano; Italia Fil: Wilson, J. Bastow. University Of Otago; Canadá. Crown Research Institutes. Landcare Research; Nueva Zelanda Fil: Zupo, Talita. Universidad Estadual Paulista; Brasil

Tredennick et al. criticize one of our statistical analyses and emphasize the low explanatory power of models relating productivity to diversity. These criticisms do not detract from our key findings, including evidence consistent with the unimodal constraint relationship predicted by the humped-back model and evidence of scale sensitivities in the form and strength of the relationship. Fil: Pither, Jason. University of British Columbia; Canadá Fil: Fraser, Lauchlan H.. Thompson Rivers University; Canadá Fil: Jentsch, Anke. University of Bayreuth; Alemania Fil: Sternberg, Marcelo. Tel Aviv University; Israel Fil: Zobel, Martín. University of Tartu; Estonia Fil: Cahill, James. University of Alberta; Canadá Fil: Cabido, Marcelo Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Enrico, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Carlyle, Cameron N.. University of Alberta; Canadá Fil: Chelli, Stefano. University of Camerino; Italia Fil: Cserg, Anna Maria. The University of Dublin; Irlanda Fil: Ensing, David. Queen’s University; Canadá Fil: Fidelis, Alessandra. Universidade Estadual Paulista; Brasil Fil: Garris, Heath W.. Thompson Rivers University; Canadá Fil: Henry, Hugh A. L.. University of Western Ontario; Canadá Fil: Höhn, Maria. Corvinus University of Budapest; Hungría Fil: Klironomos, John. University of British Columbia; Canadá Fil: Koorem, Kadri. University of Tartu; Estonia Fil: Lawrence Lodge, Rachel. University of Otago; Nueva Zelanda Fil: Manning, Peter. Senckenberg Gesellschaft für Naturforschung; Alemania Fil: Mitchell, Randall J.. University of Akron; Estados Unidos Fil: Moora, Mary. University of Tartu; Estonia Fil: Pillar, Valerio D.. Federal University of Rio Grande do Sul; Brasil Fil: Stotz, Gisela C.. University of Alberta; Canadá Fil: Sugiyama, Shu-ichi. Hirosaki University; Japón Fil: Szentes, Szilárd. Szent István University; Hungría Fil: Tungalag, Radnaakhand. National University of Mongolia; Mongolia Fil: Undrakhbold, Sainbileg. Free University of Bozen-Bolzano; Italia Fil: Wellstein, Camila. Free University of Bozen-Bolzano; Italia Fil: Zupo, Talita. Universidade Estadual Paulista; Brasil

Wahrend der im August 2005 von Zoologen der Georg-August-Universitat Gottingen durchgefuhrten 4. “Gobi Desert Vertebrates”-Expedition in den Omnogov Aimak der Mongolei, an der wir teilnehmen konnten, wurden von uns Vegetationsuntersuchungen in den pflanzengeographischen Bezirken Ost-Gobi und Alasan-Gobi durchgefuhrt. Dabei widmeten wir uns im Wesentlichen den weitverbreiteten zonalen Pflanzengesellschaften der Wusten und Halbwusten. Aber auch der Vegetation der grundwassernahen Standorte und der anthropogenen Vegetation wurde Beachtung geschenkt. Einige floristische Neunachweise fur die genannten Bezirke konnten erbracht werden. Solanum physalifolium wurde in der Mongolei neu gefunden. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Geobotanical research in the Borzongiyn- and Galbyn-Gobi (Omnogov Aimak, Mongolia) In August 2005 we joint the 4th “Gobi Desert Vertebrates”-Expedition of zoologists from the Georg-August-University Gottingen to the Omnogov Aimak of Mongolia. During the expedition we made geobotanical studies in the plantgeographic regions East-Gobi and Alashan-Gobi. Generally we worked on the widespread zonal plant communities of desert and semi-desert. But consideration was paid also to the vegetation of habitats close to groundwater and to the anthropogenic vegetation. We could find some new additions to the flora of the above mentioned regions. Solanum physalifolium was found new for Mongolia.

We tested whether the abundance of C(4) vegetation in grasslands of the Mongolian plateau is influenced by grazing conditions. The analysis exploited the politically originated contrast that exists between Mongolia (low stocking rate, transhumant system) and the district of Inner Mongolia, China (high stocking rate, sedentary system). We estimated the proportion of C(4) carbon (P(C4)) in grazed vegetation from the relative carbon isotope ratio (δ(13)C) of sheep wool sampled from 298 annual shearings originating from 1996 to 2007. Annual stocking rates varying over time and between the districts of both countries were taken from regional statistics. The P(C4) pattern within the 0.7 million km(2) sampling area was geostatistically analyzed and related to stocking rates and temperature gradients. For similar climatic conditions, P(C4) was the same in both countries. Further, a unique relationship was found between P(C4) and July temperature on both sides of the border, which explained 71% of the pattern. Stocking rate and grazing system had no significant influences on present-day C(3)/C(4) abundance ratio. This finding suggests that recent changes in the C(3)/C(4) ratio of these grasslands are mainly a consequence of regional warming, not overgrazing.