Investigating the potential of GIMMS and MODIS NDVI data sets for estimating gross primary productivity in Harvard Forest

Author(s):  
Xiaolei Yu ◽  
Zhaocong Wu ◽  
Xulin Guo
2010 ◽  
Vol 7 (1) ◽  
pp. 1445-1487 ◽  
Author(s):  
V. Yadav ◽  
K. L. Mueller ◽  
D. Dragoni ◽  
A. M. Michalak

Abstract. A coupled Bayesian model selection and geostatistical regression modeling approach is adopted for empirical analysis of gross primary productivity (GPP) at six AmeriFlux sites, including the Kennedy Space Center Scrub Oak, Vaira Ranch, Tonzi Ranch, Blodgett Forest, Morgan Monroe State Forest, and Harvard Forest sites. The analysis is performed at a continuum of temporal scales ranging from daily to monthly, for a period of seven years. A total of 10 covariates representing environmental stimuli and indices of plant physiology are considered in explaining variations in GPP. Similar to other statistical methods, the proposed approach estimates regression coefficients and uncertainties associated with the covariates in a selected regression model. However, unlike traditional regression methods, the presented approach also estimates the uncertainty associated with the selection of a single "best" model of GPP. In addition, the approach provides an enhanced understanding of how the importance of specific covariates changes with temporal resolutions. An examination of trends in the importance of specific covariates reveals scaling thresholds above or below which covariates become significant in explaining GPP. Results indicate that most sites (especially those with a stronger seasonal cycle) exhibit at least one prominent scaling threshold between daily to 20-day temporal scale. This demonstrates that environmental variables that explain GPP at synoptic scales are different from those that capture its seasonality. At shorter time scales, radiation, temperature, and vapor pressure deficit exert most significant influence on GPP at most examined sites. However, at coarser time scales, the importance of these covariates in explaining GPP declines. Overall, unique best models are identified at most sites at the daily scale, whereas multiple competing models are identified at larger time scales. In addition, the selected models are able to explain a larger fraction of the observed variability for sites exhibiting strong seasonality.


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pp. 1189-1204 ◽  
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N R Patel ◽  
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