ALBERT

Description: Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from unmanaged old forests in the western United States showed that background (noncatastrophic) mortality rates have increased rapidly in recent decades, with doubling periods ranging from 17 to 29 years among regions. Increases were also pervasive across elevations, tree sizes, dominant genera, and past fire histories. Forest density and basal area declined slightly, which suggests that increasing mortality was not caused by endogenous increases in competition. Because mortality increased in small trees, the overall increase in mortality rates cannot be attributed solely to aging of large trees. Regional warming and consequent increases in water deficits are likely contributors to the increases in tree mortality rates.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉van Mantgem, Phillip J -- Stephenson, Nathan L -- Byrne, John C -- Daniels, Lori D -- Franklin, Jerry F -- Fule, Peter Z -- Harmon, Mark E -- Larson, Andrew J -- Smith, Jeremy M -- Taylor, Alan H -- Veblen, Thomas T -- New York, N.Y. -- Science. 2009 Jan 23;323(5913):521-4. doi: 10.1126/science.1165000.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉U.S. Geological Survey, Western Ecological Research Center, Three Rivers, CA 93271, USA. pvanmantgem@usgs.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19164752" target="_blank"〉PubMed〈/a〉

Description: Crimmins et al. (Reports, 21 January 2011, p. 324) attributed an apparent downward elevational shift of California plant species to a precipitation-induced decline in climatic water deficit. We show that the authors miscalculated deficit, that the apparent decline in species' elevations is likely a consequence of geographic biases, and that unlike temperature changes, precipitation changes should not be expected to cause coordinated directional shifts in species' elevations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stephenson, Nathan L -- Das, Adrian J -- New York, N.Y. -- Science. 2011 Oct 14;334(6053):177; author reply 177. doi: 10.1126/science.1205740.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉US Geological Survey, Western Ecological Research Center, Three Rivers, CA 93271, USA. nstephenson@usgs.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21998371" target="_blank"〉PubMed〈/a〉

Description: Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stephenson, N L -- Das, A J -- Condit, R -- Russo, S E -- Baker, P J -- Beckman, N G -- Coomes, D A -- Lines, E R -- Morris, W K -- Ruger, N -- Alvarez, E -- Blundo, C -- Bunyavejchewin, S -- Chuyong, G -- Davies, S J -- Duque, A -- Ewango, C N -- Flores, O -- Franklin, J F -- Grau, H R -- Hao, Z -- Harmon, M E -- Hubbell, S P -- Kenfack, D -- Lin, Y -- Makana, J-R -- Malizia, A -- Malizia, L R -- Pabst, R J -- Pongpattananurak, N -- Su, S-H -- Sun, I-F -- Tan, S -- Thomas, D -- van Mantgem, P J -- Wang, X -- Wiser, S K -- Zavala, M A -- England -- Nature. 2014 Mar 6;507(7490):90-3. doi: 10.1038/nature12914. Epub 2014 Jan 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉US Geological Survey, Western Ecological Research Center, Three Rivers, California 93271, USA. ; Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama. ; School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA. ; Department of Forest and Ecosystem Science, University of Melbourne, Victoria 3121, Australia. ; 1] School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA [2] Mathematical Biosciences Institute, Ohio State University, Columbus, Ohio 43210, USA (N.G.B.); German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig, 04103 Leipzig, Germany (N.R.). ; Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK. ; Department of Geography, University College London, London WC1E 6BT, UK. ; School of Botany, University of Melbourne, Victoria 3010, Australia. ; 1] Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama [2] Spezielle Botanik und Funktionelle Biodiversitat, Universitat Leipzig, 04103 Leipzig, Germany [3] Mathematical Biosciences Institute, Ohio State University, Columbus, Ohio 43210, USA (N.G.B.); German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig, 04103 Leipzig, Germany (N.R.). ; Jardin Botanico de Medellin, Calle 73, No. 51D-14, Medellin, Colombia. ; Instituto de Ecologia Regional, Universidad Nacional de Tucuman, 4107 Yerba Buena, Tucuman, Argentina. ; Research Office, Department of National Parks, Wildlife and Plant Conservation, Bangkok 10900, Thailand. ; Department of Botany and Plant Physiology, Buea, Southwest Province, Cameroon. ; Smithsonian Institution Global Earth Observatory-Center for Tropical Forest Science, Smithsonian Institution, PO Box 37012, Washington, DC 20013, USA. ; Universidad Nacional de Colombia, Departamento de Ciencias Forestales, Medellin, Colombia. ; Wildlife Conservation Society, Kinshasa/Gombe, Democratic Republic of the Congo. ; Unite Mixte de Recherche-Peuplements Vegetaux et Bioagresseurs en Milieu Tropical, Universite de la Reunion/CIRAD, 97410 Saint Pierre, France. ; School of Environmental and Forest Sciences, University of Washington, Seattle, Washington 98195, USA. ; State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110164, China. ; Department of Forest Ecosystems and Society, Oregon State University, Corvallis, Oregon 97331, USA. ; 1] Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama [2] Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California 90095, USA. ; Department of Life Science, Tunghai University, Taichung City 40704, Taiwan. ; Facultad de Ciencias Agrarias, Universidad Nacional de Jujuy, 4600 San Salvador de Jujuy, Argentina. ; Faculty of Forestry, Kasetsart University, ChatuChak Bangkok 10900, Thailand. ; Taiwan Forestry Research Institute, Taipei 10066, Taiwan. ; Department of Natural Resources and Environmental Studies, National Dong Hwa University, Hualien 97401, Taiwan. ; Sarawak Forestry Department, Kuching, Sarawak 93660, Malaysia. ; Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331, USA. ; US Geological Survey, Western Ecological Research Center, Arcata, California 95521, USA. ; Landcare Research, PO Box 40, Lincoln 7640, New Zealand. ; Forest Ecology and Restoration Group, Department of Life Sciences, University of Alcala, Alcala de Henares, 28805 Madrid, Spain.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24429523" target="_blank"〉PubMed〈/a〉

Description: Skeletal muscle ventricles (SMVs) were constructed from canine latissimus dorsi and connected to a totally implantable mock circulation device. The SMVs, stimulated by an implantable pulse generator, pumped continuously for up to 8 weeks in free-running beagle dogs. Systolic pressures produced by the SMVs, initially of 139 +/- 7.2 mmHg and after 1 month of continuous pumping of 107 +/- 7 mmHg, were comparable to normal physiologic pressures in the adult beagles (114 +/- 21 mmHg). After 2 weeks of continuous pumping, the mean stroke work of the SMVs was 0.4 X 10(6) ergs, a performance that compares favorably with the animal's cardiac ventricles. This study shows that canine skeletal muscle which has not received prior training or electrical conditioning can perform sustained work at the high levels needed for an auxiliary cardiovascular pump. It might be possible eventually to use such muscle pumps in humans to assist the failing circulation and to provide support in children with certain types of congenital heart defects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Acker, M A -- Hammond, R L -- Mannion, J D -- Salmons, S -- Stephenson, L W -- HLBI 34778/HL/NHLBI NIH HHS/ -- New York, N.Y. -- Science. 1987 Apr 17;236(4799):324-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2951849" target="_blank"〉PubMed〈/a〉