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Title: Forest productivity varies with soil moisture more than temperature in a small montane watershed

Mountainous terrain creates variability in microclimate, including nocturnal cold air drainage and resultant temperature inversions. Driven by the elevational temperature gradient, vapor pressure deficit (VPD) also varies with elevation. Soil depth and moisture availability often increase from ridgetop to valley bottom. These variations complicate predictions of forest productivity and other biological responses. We analyzed spatiotemporal air temperature (T) and VPD variations in a forested, 27-km 2 catchment that varied from 1000 to 1650 m in elevation. Temperature inversions occurred on 76% of mornings in the growing season. The inversion had a clear upper boundary at midslope (~1370 m a.s.l.). Vapor pressure was relatively constant across elevations, therefore VPD was mainly controlled by T in the watershed. Here, we assessed the impact of microclimate and soil moisture on tree height, forest productivity, and carbon stable isotopes (δ 13C) using a physiological forest growth model (3-PG). Simulated productivity and tree height were tested against observations derived from lidar data. The effects on photosynthetic gas-exchange of dramatic elevational variations in T and VPD largely cancelled as higher temperature (increasing productivity) accompanies higher VPD (reducing productivity). Although it was not measured, the simulations suggested that realistic elevational variations in soil moisture predicted the observedmore » decline in productivity with elevation. Therefore, in this watershed, the model parameterization should have emphasized soil moisture rather than precise descriptions of temperature inversions.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [3] ;  [6] ;  [7]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Idaho, Moscow, ID (United States). Dept. of Forest, Rangeland, and Fire Sciences
  2. Descartes Labs, Inc, Santa Fe, NM (United States); Univ. of Idaho, Moscow, ID (United States). Dept. of Geography
  3. Univ. of Idaho, Moscow, ID (United States). Dept. of Forest, Rangeland, and Fire Sciences
  4. Texas A & M Univ., College Station, TX (United States). Dept. of Ecosystem Science and Management
  5. West Virginia Univ., Morgantown, WV (United States). Inst. of Water Security and Science, Davis College, Schools of Agriculture and Food
  6. United States Forest Service, Moscow, ID (United States). Rocky Mountain Research Station
  7. Univ. of Idaho, Moscow, ID (United States). Dept. of Forest, Rangeland, and Fire Sciences; Swedish Agricultural Univ., Skogmarksgrand, Umea (Sweden). Dept. of Forest Ecology and Management
Publication Date:
Report Number(s):
Journal ID: ISSN 0168-1923
Grant/Contract Number:
AC52-06NA25396; EPS-0447689; 2003-35102-13675; 2006-35102-17689
Accepted Manuscript
Journal Name:
Agricultural and Forest Meteorology
Additional Journal Information:
Journal Volume: 259; Journal Issue: C; Journal ID: ISSN 0168-1923
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program; National Science Foundation (NSF)
Country of Publication:
United States
OSTI Identifier: