ALBERT

Description: Recent studies have revealed positive and negative trends in the radial growth of treeline white spruce ( Picea glauca ) as temperatures have warmed in recent decades. Investigators have speculated that negative growth trends reflect the increasing importance of temperature-induced drought stress, yet direct observations of drought-induced stomatal closure have not been made in white spruce near the Arctic treeline. In this study, we measured needle gas exchange, a variety of needle traits, and branch growth in contrasting growing seasons on a riverside terrace near the Arctic treeline in Noatak National Preserve, northwest Alaska. Needle gas exchange was limited by cold soils (

Description: The hydrological and geomorphic functioning of high-mountain catchments is heavily influenced by snow accumulation and melt processes, which condition the timing and characteristics of discharges, solute outputs, and suspended sediment and bedload transport. We report here the transport of suspended sediment and solutes during the snowmelt period in a small experimental catchment in the subalpine belt of the Central Spanish Pyrenees. The seasonality of hydrological and sediment responses throughout the year was investigated using daily data of discharge, suspended sediment transport and solute outputs of the hydrological years 2003/2004 and 2005/2006. The study demonstrated the importance of the snowmelt period in terms of runoff p-roduction, and solute and suspended sediment yield: whereas precipitation during the snowmelt period (2-2.5 months) represented 10-13% of annual precipitation, discharge and suspended sediment transport accounted for up to 50% and 60%, respectively, and solute output approximately 40-50%. Solute transport dominated throughout the snowmelt period, whereas suspended sediment transport mostly occurred during the second phase of the snowmelt period (June), when an expanding area of the catchment was free from snow. The moderate daily increases in discharge, which were related to day-night temperature fluctuations, were insufficient to transport bedload material. Hourly data were used for preliminary assessment of the relationships among discharge, suspended sediment, and solute concentration, which provided insights into sediment sources and delivery mechanisms. Thus, during snowmelt-related events, the sediment mobilized was most probably derived from areas near or within the channel. In contrast, during events involving both snowmelt and rainfall, the gully system near the divide contributed to sediment load. The solute concentration was inversely related to water discharge, with higher concentrations during the first half of the snowmelt period (May) than during the second half (June). The results of this study demonstrate the key role of snow accumulation and melting processes in controlling the hydrological dynamics and patterns of particulate and solute mobilization in high-mountain environments. Future changes in snow volume and duration will affect the timing of snowmeltrelated spring high flows, as well as soil erosion and transport. Content Type Journal Article Pages 213-222 DOI 10.1657/1938-4246-43.2.213 Authors Noemí Lana-Renault, Department of Physical Geography, Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, The Netherlands Bernardo Alvera, Instituto Pirenaico de Ecología, CSIC, Apdo. 64, 22700 Jaca, Spain José M. García-Ruiz, Instituto Pirenaico de Ecología, CSIC, Campus de Aula Dei, Apdo. 13034, 50080 Zaragoza, Spain Journal Arctic, Antarctic, and Alpine Research Online ISSN 1938-4246 Print ISSN 1523-0430 Journal Volume Volume 43 Journal Issue Volume 43, Number 2 / May 2011

Description: For over 100 years, mountain treelines have been the subject of varied research endeavors and remain a strong area of investigation. The purpose of this paper is to examine aspects of the epistemology of mountain treeline research—that is, to investigate how knowledge on treelines has been acquired and the changes in knowledge acquisition over time, through a review of fundamental questions and approaches. The questions treeline researchers have raised and continue to raise have undoubtedly directed the current state of knowledge. A continuing, fundamental emphasis has centered on seeking the general cause of mountain treelines, thus seeking an answer to the question, "What causes treeline?" with a primary emphasis on searching for ecophysiological mechanisms of low-temperature limitation for tree growth and regeneration. However, treeline research today also includes a rich literature that seeks local, landscape-scale causes of treelines and reasons why treelines vary so widely in three-dimensional patterns from one location to the next, and this approach and some of its consequences are elaborated here. In recent years, both lines of research have been motivated greatly by global climate change. Given the current state of knowledge, we propose that future research directions focused on a spatial approach should specifically address cross-scale hypotheses using statistics and simulations designed for nested hierarchies; these analyses will benefit from geographic extension of treeline research. Content Type Journal Article Pages 167-177 DOI 10.1657/1938-4246-43.2.167 Authors George P. Malanson, Department of Geography, University of Iowa, Iowa City, Iowa 52242, U.S.A. Lynn M. Resler, Department of Geography, Virginia Tech, Blacksburg, Virginia 24061, U.S.A. Maaike Y. Bader, Functional Ecology of Plants, Department of Biology and Environmental Sciences, University of Oldenburg, D-26111 Oldenburg, Germany Friedrich-Karl Holtmeier, Institute for Landscape Ecology, Westfälische Wilhelms-Universität, D-48149 Münster, Germany David R. Butler, Department of Geography, Texas State University-San Marcos, San Marcos, Texas 78666-4616, U.S.A. Daniel J. Weiss, Yellowstone Ecological Research Center, 2048 Analysis Drive, Bozeman, Montana 59718, U.S.A. Lori D. Daniels, Department of Geography, University of British Columbia, Vancouver, British Columbia V6T 1Z2, Canada Daniel B. Fagre, U.S. Geological Survey, Northern Rocky Mountain Science Center, Glacier National Park, West Glacier, Montana 59936, U.S.A. Journal Arctic, Antarctic, and Alpine Research Online ISSN 1938-4246 Print ISSN 1523-0430 Journal Volume Volume 43 Journal Issue Volume 43, Number 2 / May 2011

Description: In exploring geographical distribution of mountain altitudinal belts (e.g., snowline, timber line, etc.), many unitary or dibasic fitting models have been developed to depict the relationship between altitudinal belts' elevation and longitude or latitude, or both. However, most of these models involve small scales and could not be applied to other regions, while those established for the northern hemisphere or the whole globe, are of very low precision. The reason is that these models neglect one of the most important factors controlling the distribution of altitudinal belts—mass elevation effect ( massenerhebungseffect , short as MEE in the following text). This concept (MEE) was introduced more than 100 years ago by A. de Quervain to account for the observed tendency for temperature-related parameters such as tree line and snowline to occur at higher elevations in the central Alps than on their outer margins. Although it has been widely observed and its effect on the elevation of mountain vegetation belts recognized, this phenomenon has not been quantitatively studied. We compiled 143 snowline descriptions from literature covering the Tibetan Plateau and its surrounding areas. Snowline elevation is related to longitude, latitude, and mountain base elevation (MBE), to construct a multivariate linear regression equation. These three factors could explain 83.5% of snowline elevation's variation in the Tibetan plateau and its surrounding areas. Longitude, latitude, and MBE (representing MEE to some extent) contribute 16.14%, 51.64%, and 32.22%, respectively, to the variability of snowline elevation. North of latitude 32°N, the three factors' contribution amounts to 18.72%, 44.27%, and 37.01%, respectively; to the south, their contribution is 28.12%, 15.37%, and 56.51%, respectively. A nonlinear model was also constructed, but it only enhances the ability slightly in fitting of snowline's distribution. Our analysis reveals that latitude and MBE are significant controlling factors of snowline elevation. Longitude, which stands for precipitation to a great extent, has limited impact on snowline's distribution. MEE should be further studied, or directly quantified so that it can be adequately incorporated into the development of spatial models for altitudinal belts, whereby the precision of such models could be greatly enhanced. Content Type Journal Article Pages 207-212 DOI 10.1657/1938-4246-43.2.207 Authors Han Fang, State Key Laboratory of Resource and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, No. A-11, Datun Road, Chaoyang District, Beijing, 100101, People's Republic of China Zhang Baiping, State Key Laboratory of Resource and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, No. A-11, Datun Road, Chaoyang District, Beijing, 100101, People's Republic of China Yao Yonghui, State Key Laboratory of Resource and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, No. A-11, Datun Road, Chaoyang District, Beijing, 100101, People's Republic of China Zhu Yunhai, Shandong Institute for Development Strategy of Science and Technology, No. 19, Keyuan Road, Jinan, Shandong Province, 250014, People's Republic of China Pang Yu, State Key Laboratory of Resource and Environment Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, No. A-11, Datun Road, Chaoyang District, Beijing, 100101, People's Republic of China Journal Arctic, Antarctic, and Alpine Research Online ISSN 1938-4246 Print ISSN 1523-0430 Journal Volume Volume 43 Journal Issue Volume 43, Number 2 / May 2011

Description: Tree Rings and Natural Hazards: a State-of-The-Art, by Markus Stoffel, Michelle Bollschweiler, David R. Butler, and Brian H. Luckman (eds.) Content Type Journal Article Category Book Review Pages 161-162 DOI 10.1657/1938-4246-43.1.161b Authors Jeff Lukas, Western Water Assessment, Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, Colorado 80309, U.S.A. Journal Arctic, Antarctic, and Alpine Research Online ISSN 1938-4246 Print ISSN 1523-0430 Journal Volume Volume 43 Journal Issue Volume 43, Number 1 / February 2011