Spanner, M., L. Johnson, J. Miller, R. McCreight, J. Freemantle, J. Runyon and P. Gong (1994)
Remote sensing of seasonal leaf area index across the Oregon transect. Ecological Applications 4, 258-271.
We acquired remotely sensed data from four remote-sensing instruments on three different
aircraft platforms over a transect of coniferous forest stands in Oregon, and analyzed
them with respect to seasonal leaf area index (LAI). Data were corrected for the varying seasonal
and geographic atmospheric conditions present along the transect. Strong logarithmic relationships
were observed between seasonal maximum and minimum LAI and the simple ratio (SR)
(near infrared/red reflectance) calculated from the broad-spectral-band Thematic
Mapper Simulator (TMS), as well as from the narrow-spectral-band Airborne
Visible/Infrared Imaging Spectrometer (AVIRIS), the Compact Airborne Spectrographic
Imager (CASI), and a Spectron SE590 spectro-radiometer (r2=0.82-0.97).
The TMS SR reached an asymptote at an LAI of nearly 7-8.
However, the SE590 and the CASI SR continued to increase up to the
maximum LAI of 10.6. The variability of the relationship between the AVIRIS SR and
LAI increased for stands with LAI >7, making a trend in the AVIRIS
SR-LAI relationship for LAI >7 difficult to discern. The SRs of the coniferous
forest stands measured by the narrow-spectral-band instruments were higher than
they were from the broad-spectral-band TMS. We attributed this partially to the
integration of the TMS over a broad wavelength region in the red and more strongly
to calibration differences between the sensors. Seasonal TMS SR trends for four time
periods for some of the stands deviated from the expected seasonal LAI
trends, possibly because of smoke and very low sun angles during some of
the acquisition periods. However, the expected SR differences for the seasonal minimum
and maximum LAI were observed for all of the sensors for nearly all of the forest
stands. We demonstrated that remotely sensed data from both broad- and
narrow-spectral-band instruments can provide estimates of LAI for use in forest
ecosystem simulation models to estimate evapotranspiration, photosynthesis, canopy
turnover, and net primary production over large areas.
Waring, R.H. and S.W. Running (1998) Forest Ecosystems: analysis at multiple scales.
Second edition, Academic Press, San Diego. 370 pp. with supplemental CD-ROM.
McGuire, A.D., J.M. Melillo, L.A. Joyce, D.W. Kicklighter, A.L. Grace, B. Moore III, and C.J. Vorosmarty (1992)
Interactions between carbon and nitrogen dynamics in estimating net primary productivity for potential vegetation
in North America. Global Biogeochemical Cycles 6, 101-124.
- The terrestrial ecosystem model (TEM), a process-based model, was used to investigate how interactions
between carbon (C) and nitrogen (N) dynamics affect predictions of net primary productivity (NPP) for potential
vegetation in North America. Data on pool sizes and fluxes of C and N from intensively studied field sites were
used to calibrate the model for each of 17 non-wetland vegetation types. Information on climate, soils,
and vegetation was used to estimate for each of 11,299 non-wetland, 0.5° lat/long grid cells in North America.
The potential annual NPP and net N mineralization (NETNMIN) of North America are estimated at 7.032 x 10^15 g C/yr
and 104.6 x 10^12 g N/yr, respectively. Both NPP and NETNMIN increase along gradients of
increasing temperature and moisture in northern and temperate regions of the continent, respectively. Nitrogen
limitation of productivity is weak in tropical forests, increasingly stronger in temperate and boreal forests,
and very strong in tundra ecosystems. The degree to which productivity is limited by the availability of N also
varies within ecosystems. Spatial resolution in estimating exchanges of C between the atmosphere and the
terrestrial biosphere is improved by modeling the linkage between C and N dynamics. A factorial
experiment was performed with TEM on temperate mixed forest in North America to evaluate the importance of
considering interactions between C and N dynamics in the response of NPP to an elevated temperature of 2° C.
Uncoupling the C cycle from the N cycle caused NPP to decrease primarily because of higher plant respiration.
NPP increased with the C and N cycles coupled because productivity that is due to increased N availability more than
offsets the higher costs of plant respiration. Process-based models need to consider linkages between the C and N cycles
in order to investigate how global change will affect biosphere-atmosphere interactions.
Melillo, J.M., A.D. McGuire, D.W. Kicklighter, B. Moore, C.J. Vorosmarty, and A.L. Schloss (1993)
Global climate-change and terrestrial net primary production. Nature 363, 234-240.
- Global patterns of net primary production (NPP) and soil nitrogen (N) cycling were estimated using a
process-based model for contemporary climate conditions and current atmospheric CO2 concentration. More than 50%
of global annual NPP was estimated to occur in the tropics, with most of this attributable to
tropical evergreen forest. The effects of CO2 doubling and associated climate changes were also explored. Responses
in tropical and dry temperate ecosystems were dominated by CO2, whereas those in northern and moist temperate ecosystems
reflected the effects of temperature on N availability.
Pan, Y., A.D. McGuire, D.W. Kicklighter, and J.M. Melillo (1996) The importance of climate and soils for estimates
of net primary production: a sensitivity analysis with the terrestrial ecosystem model. Global Change Biology
- The Terrestrial Ecosystem Model (TEM) was used to investigate how alternative input data sets of climate
(temperature/precipitation), solar radiation, and soil texture affect estimates of net primary productivity (NPP)
for the conterminous United States. At the continental resolution, the climates of Cramer and Leemans (C&L) and
of the Vegetation/ Ecosystem Modelling and Analysis Project (VEMAP) represent cooler and drier conditions for the
United States in comparison to the Legates and Willmott (L&W) climate, and cause 5.2% and 2.3% lower estimates of
NPP. Solar radiation derived from C&L and given in VEMAP is 32% and 60% higher than the solar radiation data derived
from Hahn cloudiness. These differences result in 8-10% lower NPP because of radiation-induced water
stress. In comparison to the FAO/CSRC soil texture, which represents most biomes with loam soils, the soil textures
are finer (more silt and clay) in the Zobler and VEMAP data sets. The use of VEMAP soil textures instead of FAO/CSRC
soil textures causes about 3% higher NPP because enhanced volumetric soil moisture results in higher rates of
nitrogen cycling, but use of the Zobler soil textures has little effect. Overall, NPP estimates of TEM are more
sensitive to alternative data sets at the biome and grid cell resolutions than at the continental resolution. At all
spatial resolutions, the sensitivity of NPP estimates represents the impact of uncertainty among the alternative data
sets we used in this study. Input data sets need to reduce their uncertainty to improve the spatial
resolution of NPP estimates by process-based ecosystem models. This is especially important for improving assessments
of the regional impacts of global change.