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Title: Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration

Mountains are vital to ecosystems and human society given their influence on global carbon and water cycles. Yet the extent to which topography regulates montane forest carbon uptake and storage remains poorly understood. To address this knowledge gap, we compared forest aboveground carbon loading to topographic metrics describing energy balance and water availability across three headwater catchments of the Boulder Creek Watershed, Colorado, USA. The catchments range from 1800 to 3500 m above mean sea level with 46–102 cm/yr mean annual precipitation and -1.2° to 12.3°C mean annual temperature. In all three catchments, we found mean forest carbon loading consistently increased from ridges (27 ± 19 Mg C ha) to valley bottoms (60 ± 28 Mg C ha). Low topographic positions held up to 185 ± 76 Mg C ha, more than twice the peak value of upper positions. Toe slopes fostered disproportionately high net carbon uptake relative to other topographic positions. Carbon storage was on average 20–40 Mg C ha greater on north to northeast aspects than on south to southwest aspects, a pattern most pronounced in the highest elevation, coldest and wettest catchment. Both the peak and mean aboveground carbon storage of the three catchments, crossing an 11°Cmore » range in temperature and doubling of local precipitation, defied the expectation of an optimal elevation-gradient climatic zone for net primary production. These results have important implications for models of forest sensitivity to climate change, as well as to predicted estimates of continental carbon reservoirs.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Univ. of Arizona, Tucson, AZ (United States). BIO5 Inst.
  2. Univ. of Utah, Salt Lake City, UT (United States). Dept. of Geology and Geophysics
  3. Univ. of Colorado, Boulder, CO (United States). Dept. of Geography. Inst. of Arctic and Alpine Research (INSTAAR)
  4. Univ. of Nevada, Reno, NV (United States). Dept. of Natural Resources and Environmental Science
  5. Univ. of Arizona, Tucson, AZ (United States). Dept. of Hydrology and Water Resources
Publication Date:
Grant/Contract Number:
SC0006968; NSF-0724960; EAR-1043051; DBI-0735191; DBI-1265383; NSF-1331408
Type:
Accepted Manuscript
Journal Name:
Ecosphere
Additional Journal Information:
Journal Volume: 8; Journal Issue: 4; Journal ID: ISSN 2150-8925
Publisher:
Ecological Society of America
Research Org:
Univ. of Colorado, Boulder, CO (United States); Univ. of Arizona, Tucson, AZ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; carbon; climate change; eco-hydrology; forests; lidar; microclimate; topography
OSTI Identifier:
1425484

Swetnam, Tyson L., Brooks, Paul D., Barnard, Holly R., Harpold, Adrian A., and Gallo, Erika L.. Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration. United States: N. p., Web. doi:10.1002/ecs2.1797.
Swetnam, Tyson L., Brooks, Paul D., Barnard, Holly R., Harpold, Adrian A., & Gallo, Erika L.. Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration. United States. doi:10.1002/ecs2.1797.
Swetnam, Tyson L., Brooks, Paul D., Barnard, Holly R., Harpold, Adrian A., and Gallo, Erika L.. 2017. "Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration". United States. doi:10.1002/ecs2.1797. https://www.osti.gov/servlets/purl/1425484.
@article{osti_1425484,
title = {Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration},
author = {Swetnam, Tyson L. and Brooks, Paul D. and Barnard, Holly R. and Harpold, Adrian A. and Gallo, Erika L.},
abstractNote = {Mountains are vital to ecosystems and human society given their influence on global carbon and water cycles. Yet the extent to which topography regulates montane forest carbon uptake and storage remains poorly understood. To address this knowledge gap, we compared forest aboveground carbon loading to topographic metrics describing energy balance and water availability across three headwater catchments of the Boulder Creek Watershed, Colorado, USA. The catchments range from 1800 to 3500 m above mean sea level with 46–102 cm/yr mean annual precipitation and -1.2° to 12.3°C mean annual temperature. In all three catchments, we found mean forest carbon loading consistently increased from ridges (27 ± 19 Mg C ha) to valley bottoms (60 ± 28 Mg C ha). Low topographic positions held up to 185 ± 76 Mg C ha, more than twice the peak value of upper positions. Toe slopes fostered disproportionately high net carbon uptake relative to other topographic positions. Carbon storage was on average 20–40 Mg C ha greater on north to northeast aspects than on south to southwest aspects, a pattern most pronounced in the highest elevation, coldest and wettest catchment. Both the peak and mean aboveground carbon storage of the three catchments, crossing an 11°C range in temperature and doubling of local precipitation, defied the expectation of an optimal elevation-gradient climatic zone for net primary production. These results have important implications for models of forest sensitivity to climate change, as well as to predicted estimates of continental carbon reservoirs.},
doi = {10.1002/ecs2.1797},
journal = {Ecosphere},
number = 4,
volume = 8,
place = {United States},
year = {2017},
month = {4}
}