SlideServe
Télécharger Obtenir Pro
Menu
Accueil Pro
Préférences
ApparenceLight Aide et commentaires
© SlideServe · v2026

Error estimates for biometric measurements of NEP

gilda avatar
gilda
11 diapositives · 249 Views · Sep 29, 2014

This study discusses methods for estimating Net Ecosystem Production (NEP) using biometric measurements, focusing on factors such as age, fertility, and species variation. It compares NEP estimation with Eddy Flux NEE and highlights common myths, including the perceived variability of estimates. Two approaches are analyzed: replicate plots for landscape inference and single sites for localized studies. Results indicate a significant coefficient of variation for NEP estimates (CV ~40%) in Eucalypt plantations and identify methods to enhance estimation precision, emphasizing the importance of standardized methodologies.

#error estimates for biometric measurements of nep #error estimates for biometric measurements of nep ppt #powerpoint #presentation
Error estimates for biometric measurements of NEP - slide 1
01 / 11Error estimates for biometric measurements of NEP
1 / 17

Télécharger la présentation

Error estimates for biometric measurements of NEP
Une image / un lien ci-dessous est fourni (tel quel) pour télécharger la présentation

Politique de téléchargement : le contenu du site vous est fourni TEL QUEL pour votre information et votre usage personnel ; il ne peut être vendu, concédé sous licence ni partagé sur d’autres sites sans l’accord de son auteur.Le contenu vous est fourni TEL QUEL, pour votre information et votre usage personnel uniquement. Téléchargez la présentation en cliquant sur ce lien. Lors du téléchargement, si vous ne parvenez pas à télécharger une présentation, l’éditeur a peut-être supprimé le fichier de son serveur.Pendant le téléchargement, si vous ne parvenez pas à obtenir une présentation, le fichier a peut-être été supprimé par l’éditeur.

F I N

Plus de contenu associé

Transcription de la présentation

  1. Error estimates for biometric measurements of NEP Mike Ryan and Rudy King USDA Forest Service Motivation: Understand how age, fertility, species change NEP; compare with Eddy Flux NEE

  2. One Method of Estimating NEP from Biometric Measurements NEP = GPP – RH - RA = Annual change in ecosystem C storage = [CDW (dead wood) + CW (live biomass)+ CS (soil) + CR (Roots) + CL (fine litter)]

  3. Myths • Variability is too large to do this accurately • Compounding error will give very uncertain estimates of NEP • However, most variability is local (scale of m2) and not important for our questions (scale of ha or larger)

  4. Two Cases • Replicate Plots: Inference at a landscape or experiment scale • Single site: Inference at a site scale (for example Ameriflux tower footprint)

  5. Replicate Plots • Sub-sample variance not included in replicate plot is negligible and does not have to be propagated (n/N ~ 0): • Poor sub-sampling will give larger variance among replicate plots, and good sub-sampling will give smaller variance among replicate plots, but you do not need to propagate any additional sub-sample variance.

  6. Replicate Plots • Cumulative Error: NEP calculated using plot-level estimates of all components contains cumulative (S variance + covariance) and sub-sample variance. • Allometric equations? Working on it.

  7. Results • For Eucalypt plantation in Hawaii: CV for NEP ~40%. 95% CI = 20 – 30% of mean for n=6. Larger plots for biomass sampling would probably lower CV. • 50% higher NEP in high fertility plots

  8. Results • CV for lodgepole pine chronosequence suggests similar variance for NEP: Biomass C 12-20% Dead Wood C 17-45% Forest Floor C 8-12% Soil C 5-25%

  9. Single Site • CI and SE will decrease with sqrt(sample size). • Plots (with sub-sampling) can be used to minimize small-scale variability. • Cumulative Error: NEP calculated using plot-level estimates of all components contains cumulative (S variance + covariance) and sub-sample variance.

  10. What can improve precision? • Replicate sample units • Time (Precision of D increases linearly with number of years) • Increased subsamples/replicate plot will decrease overall variance--especially important with small n.

  11. Needs for Ameriflux • Commitment to measuring C stocks at all sites • Commitment to measuring NEP based on changes in C stocks over some standard interval (5-10 years). • Development of standard methodology for measuring C stocks and changes at sites. • Research into efficient sampling methods.