@article{KahmenSachseArndtetal.2011, author = {Kahmen, Ansgar and Sachse, Dirk and Arndt, Stefan K. and Tu, Kevin P. and Farrington, Heraldo and Vitousek, Peter M. and Dawson, Todd E.}, title = {Cellulose delta O-18 is an index of leaf-to-air vapor pressure difference (VPD) in tropical plants}, series = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {108}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, number = {5}, publisher = {National Acad. of Sciences}, address = {Washington}, issn = {0027-8424}, doi = {10.1073/pnas.1018906108}, pages = {1981 -- 1986}, year = {2011}, abstract = {Cellulose in plants contains oxygen that derives in most cases from precipitation. Because the stable oxygen isotope composition, delta O-18, of precipitation is associated with environmental conditions, cellulose delta O-18 should be as well. However, plant physiological models using delta O-18 suggest that cellulose delta O-18 is influenced by a complex mix of both climatic and physiological drivers. This influence complicates the interpretation of cellulose delta O-18 values in a paleo-context. Here, we combined empirical data analyses with mechanistic model simulations to i) quantify the impacts that the primary climatic drivers humidity (e(a)) and air temperature (T-air) have on cellulose delta O-18 values in different tropical ecosystems and ii) determine which environmental signal is dominating cellulose delta O-18 values. Our results revealed that e(a) and T-air equally influence cellulose delta O-18 values and that distinguishing which of these factors dominates the delta O-18 values of cellulose cannot be accomplished in the absence of additional environmental information. However, the individual impacts of e(a) and T-air on the delta O-18 values of cellulose can be integrated into a single index of plant-experienced atmospheric vapor demand: the leaf-to-air vapor pressure difference (VPD). We found a robust relationship between VPD and cellulose delta O-18 values in both empirical and modeled data in all ecosystems that we investigated. Our analysis revealed therefore that delta O-18 values in plant cellulose can be used as a proxy for VPD in tropical ecosystems. As VPD is an essential variable that determines the biogeochemical dynamics of ecosystems, our study has applications in ecological-, climate-, or forensic-sciences.}, language = {en} } @article{LoefflerAnschlagBakeretal.2011, author = {Loeffler, J{\"o}rg and Anschlag, Kerstin and Baker, Barry and Finch, Oliver-D. and Diekkrueger, Bernd and Wundram, Dirk and Schroeder, Boris and Pape, Roland and Lundberg, Anders}, title = {Mountain ecosystem response to global change}, series = {Erdkunde : archive for scientific geography}, volume = {65}, journal = {Erdkunde : archive for scientific geography}, number = {2}, publisher = {Geographisches Inst., Univ. Bonn}, address = {Goch}, issn = {0014-0015}, doi = {10.3112/erdkunde.2011.02.06}, pages = {189 -- 213}, year = {2011}, abstract = {Mountain ecosystems are commonly regarded as being highly sensitive to global change. Due to the system complexity and multifaceted interacting drivers, however, understanding current responses and predicting future changes in these ecosystems is extremely difficult. We aim to discuss potential effects of global change on mountain ecosystems and give examples of the underlying response mechanisms as they are understood at present. Based on the development of scientific global change research in mountains and its recent structures, we identify future research needs, highlighting the major lack and the importance of integrated studies that implement multi-factor, multi-method, multi-scale, and interdisciplinary research.}, language = {en} } @article{GeyerKieferKreftetal.2011, author = {Geyer, Juliane and Kiefer, Iris and Kreft, Stefan and Chavez, Veronica and Salafsky, Nick and Jeltsch, Florian and Ibisch, Pierre L.}, title = {Classification of climate-change-induced stresses on biological diversity}, series = {Conservation biology : the journal of the Society for Conservation Biology}, volume = {25}, journal = {Conservation biology : the journal of the Society for Conservation Biology}, number = {4}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0888-8892}, doi = {10.1111/j.1523-1739.2011.01676.x}, pages = {708 -- 715}, year = {2011}, abstract = {Conservation actions need to account for and be adapted to address changes that will occur under global climate change. The identification of stresses on biological diversity (as defined in the Convention on Biological Diversity) is key in the process of adaptive conservation management. We considered any impact of climate change on biological diversity a stress because such an effect represents a change (negative or positive) in key ecological attributes of an ecosystem or parts of it. We applied a systemic approach and a hierarchical framework in a comprehensive classification of stresses to biological diversity that are caused directly by global climate change. Through analyses of 20 conservation sites in 7 countries and a review of the literature, we identified climate-change-induced stresses. We grouped the identified stresses according to 3 levels of biological diversity: stresses that affect individuals and populations, stresses that affect biological communities, and stresses that affect ecosystem structure and function. For each stress category, we differentiated 3 hierarchical levels of stress: stress class (thematic grouping with the coarsest resolution, 8); general stresses (thematic groups of specific stresses, 21); and specific stresses (most detailed definition of stresses, 90). We also compiled an overview of effects of climate change on ecosystem services using the categories of the Millennium Ecosystem Assessment and 2 additional categories. Our classification may be used to identify key climate-change-related stresses to biological diversity and may assist in the development of appropriate conservation strategies. The classification is in list format, but it accounts for relations among climate-change-induced stresses.}, language = {en} } @article{DeFrenneBrunetShevtsovaetal.2011, author = {De Frenne, Pieter and Brunet, Jorg and Shevtsova, Anna and Kolb, Annette and Graae, Bente J. and Chabrerie, Olivier and Cousins, Sara Ao and Decocq, Guillaume and De Schrijver, An and Diekmann, Martin and Gruwez, Robert and Heinken, Thilo and Hermy, Martin and Nilsson, Christer and Stanton, Sharon and Tack, Wesley and Willaert, Justin and Verheyen, Kris}, title = {Temperature effects on forest herbs assessed by warming and transplant experiments along a latitudinal gradient}, series = {Global change biology}, volume = {17}, journal = {Global change biology}, number = {10}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/j.1365-2486.2011.02449.x}, pages = {3240 -- 3253}, year = {2011}, abstract = {Slow-colonizing forest understorey plants are probably not able to rapidly adjust their distribution range following large-scale climate change. Therefore, the acclimation potential to climate change within their actual occupied habitats will likely be key for their short-and long-term persistence. We combined transplant experiments along a latitudinal gradient with open-top chambers to assess the effects of temperature on phenology, growth and reproductive performance of multiple populations of slow-colonizing understorey plants, using the spring flowering geophytic forb Anemone nemorosa and the early summer flowering grass Milium effusum as study species. In both species, emergence time and start of flowering clearly advanced with increasing temperatures. Vegetative growth (plant height, aboveground biomass) and reproductive success (seed mass, seed germination and germinable seed output) of A. nemorosa benefited from higher temperatures. Climate warming may thus increase future competitive ability and colonization rates of this species. Apart from the effects on phenology, growth and reproductive performance of M. effusum generally decreased when transplanted southwards (e. g., plant size and number of individuals decreased towards the south) and was probably more limited by light availability in the south. Specific leaf area of both species increased when transplanted southwards, but decreased with open-top chamber installation in A. nemorosa. In general, individuals of both species transplanted at the home site performed best, suggesting local adaptation. We conclude that contrasting understorey plants may display divergent plasticity in response to changing temperatures which may alter future understorey community dynamics.}, language = {en} } @article{WischnewskiKramerKongetal.2011, author = {Wischnewski, Juliane and Kramer, Annette and Kong, Zhaochen and Mackay, Anson W. and Simpson, Gavin L. and Mischke, Steffen and Herzschuh, Ulrike}, title = {Terrestrial and aquatic responses to climate change and human impact on the southeastern Tibetan Plateau during the past two centuries}, series = {Global change biology}, volume = {17}, journal = {Global change biology}, number = {11}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {1354-1013}, doi = {10.1111/j.1365-2486.2011.02474.x}, pages = {3376 -- 3391}, year = {2011}, abstract = {Rapid population growth and economic development have led to increased anthropogenic pressures on the Tibetan Plateau, causing significant land cover changes with potentially severe ecological consequences. To assess whether or not these pressures are also affecting the remote montane-boreal lakes on the SE Tibetan Plateau, fossil pollen and diatom data from two lakes were synthesized. The interplay of aquatic and terrestrial ecosystem response was explored in respect to climate variability and human activity over the past 200 years. Nonmetric multidimensional scaling and Procrustes rotation analysis were undertaken to determine whether pollen and diatom responses in each lake were similar and synchronous. Detrended canonical correspondence analysis was used to develop quantitative estimates of compositional species turnover. Despite instrumental evidence of significant climatic warming on the southeastern Plateau, the pollen and diatom records indicate very stable species composition throughout their profiles and show only very subtle responses to environmental changes over the past 200 years. The compositional species turnover (0.36-0.94 SD) is relatively low in comparison to the species reorganizations known from the periods during the mid-and early-Holocene (0.64-1.61 SD) on the SE Plateau, and also in comparison to turnover rates of sediment records from climate-sensitive regions in the circum arctic. Our results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem in our study area. Synergistic processes of post-Little Ice Age warming, 20th century climate warming and extensive reforestations since the 19th century have initiated a change from natural oak-pine forests to seminatural, likely less resilient pine-oak forests. Further warming and anthropogenic disturbances would possibly exceed the ecological threshold of these ecosystems and lead to severe ecological consequences.}, language = {en} }