Evapotranspiration and water yield of a pine-broadleaf forest are not altered by long-term atmospheric [CO2 ] enrichment under native or enhanced soil fertility.

Journal Article (Journal Article)

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.

Full Text

Duke Authors

Cited Authors

  • 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

Published Date

  • October 2018

Published In

Volume / Issue

  • 24 / 10

Start / End Page

  • 4841 - 4856

PubMed ID

  • 29949220

Electronic International Standard Serial Number (EISSN)

  • 1365-2486

International Standard Serial Number (ISSN)

  • 1354-1013

Digital Object Identifier (DOI)

  • 10.1111/gcb.14363


  • eng