Influence of Fertilization and Altitude on Energy Budgets for Native Meadows
1966
Grable, A. R. | Hanks, R. J. | Willhite, F. M. | Haise, H. R.
Experiments were conducted for 2 years near Gunnison, Colorado, to evaluate the influence of N fertilizer and altitude on energy budgets of native wet meadows. Measurements included evapotranspiration from lysimeters (Eₜ), evaporation from Weather Bureau pans (E), net radiation (Rₙ), total short-wave radiation (R₂), soil heat flow (S), air and soil temperatures, wind velocity, precipitation, and forage yields. During two periods of 1963, Rₙ, advected heat (A), and Eₜ were slightly but not significantly altered at one location by application of N fertilizer. S was 2% or less of Rₙ, and A to lysimeters ranged from 6 to 11% of Eₜ when data from all plots were averaged. Studies during the entire growing season of 1964 at altitudes of 2240, 2350, 2670, and 3080 m indicated that Rₙ, Rₛ, and E cannot be used to accurately predict Eₜ for high-altitude wet meadows. Although changes in Rₙ or Rₛ were generally accompanied by changes in E or Eₜ, the ratios of the values changed sharply during the season because of advected energy and crop harvest. During at least 1 or 2 weeks just before midseason harvest, S was negligible and sensible heat flux to the lysimeters (−A) was as much as 26% of Eₜ; after harvest, however, S was about 20% of Et and sensible heat flux from the lysimeters (+A) was as much as 97% of Eₜ. Eₜ, E, and A (to lysimeters) during comparable periods generally decreased as altitude increased. The greatest photosynthetic efficiency obtained was about 2% of Rₙ; usually it was much less.
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