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Ward EJ, Oren R, Seok Kim H, Kim D, Tor-Ngern P, Ewers BE, McCarthy HR, Oishi AC, Pataki DE, Palmroth S, Phillips NG, Schäfer KVR. Evapotranspiration and water yield of a pine-broadleaf forest are not altered by long-term atmospheric [CO 2 ] enrichment under native or enhanced soil fertility. GLOBAL CHANGE BIOLOGY 2018; 24:4841-4856. [PMID: 29949220 DOI: 10.1111/gcb.14363] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 06/30/2018] [Accepted: 05/22/2018] [Indexed: 06/08/2023]
Abstract
Changes in evapotranspiration (ET) from terrestrial ecosystems affect their water yield (WY), with considerable ecological and economic consequences. Increases in surface runoff observed over the past century have been attributed to increasing atmospheric CO2 concentrations resulting in reduced ET by terrestrial ecosystems. Here, we evaluate the water balance of a Pinus taeda (L.) forest with a broadleaf component that was exposed to atmospheric [CO2 ] enrichment (ECO2 ; +200 ppm) for over 17 years and fertilization for 6 years, monitored with hundreds of environmental and sap flux sensors on a half-hourly basis. These measurements were synthesized using a one-dimensional Richard's equation model to evaluate treatment differences in transpiration (T), evaporation (E), ET, and WY. We found that ECO2 did not create significant differences in stand T, ET, or WY under either native or enhanced soil fertility, despite a 20% and 13% increase in leaf area index, respectively. While T, ET, and WY responded to fertilization, this response was weak (<3% of mean annual precipitation). Likewise, while E responded to ECO2 in the first 7 years of the study, this effect was of negligible magnitude (<1% mean annual precipitation). Given the global range of conifers similar to P. taeda, our results imply that recent observations of increased global streamflow cannot be attributed to decreases in ET across all ecosystems, demonstrating a great need for model-data synthesis activities to incorporate our current understanding of terrestrial vegetation in global water cycle models.
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Affiliation(s)
- Eric J Ward
- Division of Environmental Science and Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina
- Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Ram Oren
- Division of Environmental Science and Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina
- Department of Forest Sciences, University of Helsinki, Helsinki, Finland
- Department of Civil and Environmental Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina
| | - Hyun Seok Kim
- Division of Environmental Science and Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina
- Department of Forest Sciences, College of Agriculture and Life Sciences, Seoul National University, Seoul, Korea
- Institute of Future Environmental and Forest Resources, Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, Korea
- National Center for Agro-Meteorology, Seoul, Korea
- Interdisciplinary Program in Agriculture and Forest Meteorology, Seoul National University, Seoul, Korea
| | - Dohyoung Kim
- Division of Environmental Science and Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana
| | - Pantana Tor-Ngern
- Division of Environmental Science and Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina
- Department of Environmental Science, Faculty of Science, Chulalongkorn University, Bangkok, Thailand
| | - Brent E Ewers
- Department of Botany and Program in Ecology, University of Wyoming, Laramie, Wyoming
| | - Heather R McCarthy
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma
| | - Andrew Christopher Oishi
- Division of Environmental Science and Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina
- USDA Forest Service, Southern Research Station, Coweeta Hydrologic Laboratory, Otto, North Carolina
| | - Diane E Pataki
- Department of Biology, University of Utah, Salt Lake City, Utah
| | - Sari Palmroth
- Division of Environmental Science and Policy, Nicholas School of the Environment, Duke University, Durham, North Carolina
| | - Nathan G Phillips
- Department of Earth and Environment, Boston University, Boston, Massachusetts
| | - Karina V R Schäfer
- Department of Biological Sciences, Rutgers University, Newark, New Jersey
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Abstract
For several years, measures to insure healthy river functions and to protect biodiversity have focused on management at the scale of drainage basins. Indeed, rivers bear witness to the health of their drainage basins, which justifies integrated basin management. However, this vision should not mask two other aspects of the protection of aquatic and riparian biodiversity as well as services provided by rivers. First, although largely depending on the ecological properties of the surrounding terrestrial environment, rivers are ecological systems by themselves, characterized by their linearity: they are organized in connected networks, complex and ever changing, open to the sea. Second, the structure and functions of river networks respond to manipulations of their hydrology, and are particularly vulnerable to climatic variations. Whatever the scale considered, river networks represent "hotlines" for sharing water between ecological and societal systems, as well as for preserving both systems in the face of global change. River hotlines are characterized by spatial as well as temporal legacies: every human impact to a river network may be transmitted far downstream from its point of origin, and may produce effects only after a more or less prolonged latency period. Here, I review some of the current issues of river ecology in light of the linear character of river networks.
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