Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks

Réjou-Méchain, M.; Muller-Landau, H.C.; Detto, M.; Thomas, S.C.; Le Toan, T.; Saatchi, S.S.; Barreto-Silva, J.S.; Bourg, N.A.; Bunyavejchewin, S.; Butt, N.; Brockelman, W.Y.; Cao, M.; Cárdenas, D.; Chiang, J.-M.; Chuyong, G.B.; Clay, K.; Condit, R.; Dattaraja, H.S.; Davies, S.J.; Duque, A.; Esufali, S.; Ewango, C.; Fernando, R.H.S.; Fletcher, C.D.; Gunatilleke, I.A.U.N.; Hao, Z.; Harms, K.E.; Hart, T.B.; Hérault, B.; Howe, R.W.; Hubbell, S.P.; Johnson, D.J.; Kenfack, D.; Larson, A.J.; Lin, L.; Lin, Y.; Lutz, J.A.; Makana, J.-R.; Malhi, Y.; Marthews, T.R.; McEwan, R.W.; McMahon, S.M.; McShea, W.J.; Muscarella, R.; Nathalang, A.; Noor, N.S.M.; Nytch, C.J.; Oliveira, A.A.; Phillips, R.P.; Pongpattananurak, N.; Punchi-Manage, R.; Salim, R.; Schurman, J.; Sukumar, R.; Suresh, H.S.; Suwanvecho, U.; Thomas, D.W.; Uríarte, M.; Thompson, J. ORCID: https://orcid.org/0000-0002-4370-2593; Valencia, R.; Vicentini, A.; Wolf, A.T.; Yap, S.; Yuan, Z.; Zartman, C.E.; Zimmerman, J.K.; Chave, J.. 2014 Local spatial structure of forest biomass and its consequences for remote sensing of carbon stocks. Biogeosciences, 11 (23). 6827-6840. 10.5194/bg-11-6827-2014

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Abstract/Summary

Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+. Though broad scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of field measurements and calibration procedures. The mismatch in spatial scales between field inventory plots and larger pixels of current and planned remote sensing products for forest biomass mapping is of particular concern, as it has the potential to introduce errors, especially if forest biomass shows strong local spatial variation. Here, we used 30 large (8–50 ha) globally distributed permanent forest plots to quantify the spatial variability in aboveground biomass (AGB) at spatial grains ranging from 5 to 250 m (0.025–6.25 ha), and we evaluate the implications of this variability for calibrating remote sensing products using simulated remote sensing footprints. We found that the spatial sampling error in AGB is large for standard plot sizes, averaging 46.3% for 0.1 ha subplots and 16.6% for 1 ha subplots. Topographically heterogeneous sites showed positive spatial autocorrelation in AGB at scales of 100 m and above; at smaller scales, most study sites showed negative or nonexistent spatial autocorrelation in AGB. We further show that when field calibration plots are smaller than the remote sensing pixels, the high local spatial variability in AGB leads to a substantial "dilution" bias in calibration parameters, a bias that cannot be removed with current statistical methods. Overall, our results suggest that topography should be explicitly accounted for in future sampling strategies and that much care must be taken in designing calibration schemes if remote sensing of forest carbon is to achieve its promise.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.5194/bg-11-6827-2014
UKCEH and CEH Sections/Science Areas:	Watt
ISSN:	1726-4170
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link
Additional Keywords:	carbon, forest biomass, spatial scale, remote sensing
NORA Subject Terms:	Ecology and Environment
Related URLs:	Discussion paper
Date made live:	05 Jul 2016 11:39 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/513915

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