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Interannual Invariability of Forest Evapotranspiration and Its Consequence to Water Flow Downstream

Publication ,  Journal Article
Oishi, AC; Oren, R; Novick, KA; Palmroth, S; Katul, GG
Published in: Ecosystems.
April 2010

Although drought in temperate deciduous forests decreases transpiration rates of many species, stand-level transpiration and total evapotranspiration is often reported to exhibit only minor interannual variability with precipitation. This apparent contradiction was investigated using four years of transpiration estimates from sap flux, interception-evaporation estimates from precipitation and throughfall gauges, modeled soil evaporation and drainage estimates, and eddy covariance data in a mature oak-hickory forest in North Carolina, USA. The study period included one severe drought year and one year of well above-average precipitation. Normalized for atmospheric conditions, transpiration rates of some species were lower in drought than in wet periods whereas others did not respond to drought. However, atmospheric conditions during drought periods are unlike conditions during typical growing season periods. The rainy days that are required to maintain drought-free periods are characterized by low atmospheric vapor pressure deficit, leading to very low transpiration. In contrast, days with low air vapor pressure deficit were practically absent during drought and moderate levels of transpiration were maintained throughout despite the drying soil. Thus, integrated over the growing season, canopy transpiration was not reduced by drought. In addition, high vapor pressure deficit during drought periods sustained appreciable soil evaporation rates. As a result, despite the large interannual variation in precipitation (ranging from 934 to 1346 mm), annual evapotranspiration varied little (610-668 mm), increasing only slightly with precipitation, due to increased canopy rainfall interception. Because forest evapotranspiration shows only modest changes with annual precipitation, lower precipitation translates to decreased replenishment of groundwater and outflow, and thus the supply of water to downstream ecosystems and water bodies.

Duke Scholars

Published In

Ecosystems.

DOI

ISSN

1432-9840

Publication Date

April 2010

Volume

13

Issue

3

Start / End Page

421 / 436

Related Subject Headings

  • Ecology
  • 3109 Zoology
  • 06 Biological Sciences
  • 05 Environmental Sciences
 

Citation

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Oishi, A. C., Oren, R., Novick, K. A., Palmroth, S., & Katul, G. G. (2010). Interannual Invariability of Forest Evapotranspiration and Its Consequence to Water Flow Downstream. Ecosystems., 13(3), 421–436. https://doi.org/10.1007/s10021-010-9328-3
Oishi, A Christopher, Ram Oren, Kimberly A. Novick, Sari Palmroth, and Gabriel G. Katul. “Interannual Invariability of Forest Evapotranspiration and Its Consequence to Water Flow Downstream.” Ecosystems. 13, no. 3 (April 2010): 421–36. https://doi.org/10.1007/s10021-010-9328-3.
Oishi AC, Oren R, Novick KA, Palmroth S, Katul GG. Interannual Invariability of Forest Evapotranspiration and Its Consequence to Water Flow Downstream. Ecosystems. 2010 Apr;13(3):421–36.
Oishi, A. Christopher, et al. “Interannual Invariability of Forest Evapotranspiration and Its Consequence to Water Flow Downstream.” Ecosystems., vol. 13, no. 3, Apr. 2010, pp. 421–36. Epmc, doi:10.1007/s10021-010-9328-3.
Oishi AC, Oren R, Novick KA, Palmroth S, Katul GG. Interannual Invariability of Forest Evapotranspiration and Its Consequence to Water Flow Downstream. Ecosystems. 2010 Apr;13(3):421–436.
Journal cover image

Published In

Ecosystems.

DOI

ISSN

1432-9840

Publication Date

April 2010

Volume

13

Issue

3

Start / End Page

421 / 436

Related Subject Headings

  • Ecology
  • 3109 Zoology
  • 06 Biological Sciences
  • 05 Environmental Sciences