Water availability as driver of birch mortality in Hustai National Park,Mongolia |
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| Institution: | 1. Forest Ecology and Forest Management Group, Wageningen University, Wageningen, The Netherlands;2. Resource Ecology Group, Wageningen University, Wageningen, The Netherlands;3. Biodiversity and Policy, Wageningen Environmental Research, Wageningen, The Netherlands;1. Beijing Shunyi Hanshiqiao Wetland Nature Reserve Management Office, Beijing 101309, China;2. Institute of Wetlands Research, Chinese Academy of Forestry, Beijing 100091, China;3. College of Forestry, Beijing Forestry University, Beijing 100083, China;4. Chinese Society of Forestry, Beijing 100091, China;5. Wanglang Nature Reserve, Pingwu County, Mianyang, Sichuan 622550, China;6. School of Tourism Sciences, Beijing International Studies University, Beijing 100024, China;1. Tropenzentrum—Center for Research in the Tropics and Subtropics, Universität Kassel, Steinstraße 19, D-37213 Witzenhausen, Germany;2. Department of Forest Genetics and Forest Tree Breeding, Büsgen-Institute, Georg-August-Universität Göttingen, Büsgenweg 2, D-37077 Göttingen, Germany;3. Senckenberg Museum of Natural History, Department of Botany, Section Phanerogams 1, Am Museum 1, D-02826 Görlitz, Germany;4. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, D-04103 Leipzig, Germany;5. Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics (OPATS), Universität Kassel, Steinstraße 19, D-37213 Witzenhausen, Germany;1. NSERC/UQAT/UQAM Industrial Chair in Sustainable Forest Management, Université du Québec en Abitibi-Témiscamingue, 445, boulevard de l''Université, Rouyn-Noranda, Québec J9X 5E4, Canada;2. Institut des sciences de la forêt tempérée, Université du Québec en Outaouais, 58, rue Principale, Ripon, Québec, J0V 1V0, Canada;1. International Institute of Tropical Forestry, USDA Forest Service, 1201 Calle Ceiba, Jardín Botánico Sur, San Juan 00926, Puerto Rico;2. Department of Agroenvironmental Sciences, College of Agricultural Sciences, University of Puerto Rico, Mayagüez, Call Box 9000, Mayagüez 00681, Puerto Rico;3. Department of Environmental Sciences, College of Natural Sciences, University of Puerto Rico, Río Piedras, PO Box 70377, San Juan 00936, Puerto Rico;4. USDA Forest Service – Research & Development, 201 14th Street, SW: Mailstop 1115, Washington, DC 20024, United States;1. Institute of North Industrial Ecology Problems, Kola Science Centre RAS, 184209 Apatity, Russia;2. Polar Geophysical Institute RAS, 184209 Apatity, Russia;3. University of Science and Technology (AGH), 30-059 Krakow, Poland;4. Institute of Archaeology, Jagiellonian University, 31-007, Krakow, Poland |
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| Abstract: | Trees in the forest-steppe ecotones face stress due to reduced water availability as a consequence of more extreme seasonal fluctuations in precipitation and temperature. Together with browsing pressure this can hinder tree growth, tree regeneration and competition between trees and grasses. We studied the impact of both stress factors on the mortality of birch trees in two forest sites at Hustai National Park, Mongolia, by applying tree-ring research to determine growth-limiting factors and assessing browsing pressure on young and adult birch. We expected warm and dry summer conditions as main growth limiting factor. Moreover, we expected a positive relation between deer density and tree mortality with browsing mainly affecting smaller trees with a low diameter at breast height (DBH). We found that the growth in both birch populations is mainly driven by winter precipitation and – to a lesser extent – negatively affected by high summer temperature. This suggests that water availability as defined by soil moisture, especially at the beginning of the growing season is crucial for birch growth in our study area. For mortality we found significant differences between both populations, but no significant relationship with deer density. In plots with high mortality rates mean tree height of the remaining living trees decreased. These results suggest that under expected climate change with declining annual precipitation rates, the birch forest of Hustai National Park is converting into a steppe ecosystem, like described for other forest ecosystems in this ecotone. |
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| Keywords: | Climate change Forest-steppe ecotone Birch forest decline Mortality Climate-growth relationships |
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