Continuous observation of leaf area index at Fluxnet-Canada sites

Abstract Continuous observation of leaf area index (LAI) is needed in order to interpret and model carbon, water and energy fluxes measured at Fluxnet tower sites. Although remote sensing LAI products can be used in regional and global scale modelling with reasonable performance, the site level modelling of ecophysiological processes needs more accurate LAI time series than those provided by global LAI products. Here we present a semi-empirical approach using satellite measured modified soil-adjusted vegetation index (MSAVI) and sparsely sampled LAI time series measurements at 7 Canadian Carbon Program (CCP) flux tower sites to produce continuous observations of site level LAI. The results indicate that accurate and continuous observation of site level LAI time series is possible using a few ground measurements and remotely sensed MSAVI observations. In order for the semi-empirical model to work correctly, the ground LAI measurements should represent all seasons, preferably including extreme values in winter and the peak of growing season.

[1]  J. Chen.  Optically-based methods for measuring seasonal variation of leaf area index in boreal conifer stands , 1996 .

[2]  P. Treitz,et al.  Canopy chlorophyll concentration estimation using hyperspectral and lidar data for a boreal mixedwood forest in northern Ontario, Canada , 2008 .

[3]  Frédéric Baret,et al.  Review of methods for in situ leaf area index determination Part I. Theories, sensors and hemispherical photography , 2004 .

[4]  Jing M. Chen,et al.  Improved assessment of gross and net primary productivity of Canada's landmass , 2013 .

[5]  Alemu Gonsamo,et al.  Application note: CIMES: A package of programs for determining canopy geometry and solar radiation regimes through hemispherical photographs , 2011 .

[6]  G. Vourlitis,et al.  Seasonal and interannual litter dynamics of a tropical semideciduous forest of the southern Amazon Basin, Brazil , 2008 .

[7]  S. T. Gower,et al.  Leaf area index of boreal forests: theory, techniques, and measurements , 1997 .

[8]  Matthias Peichl,et al.  Above- and belowground ecosystem biomass and carbon pools in an age-sequence of temperate pine plantation forests , 2006 .

[9]  Alemu Gonsamo,et al.  Methodology comparison for slope correction in canopy leaf area index estimation using hemispherical photography , 2008 .

[10]  Oliver Sonnentag,et al.  Leaf area index measurements at Fluxnet-Canada forest sites , 2006 .

[11]  T. Carlson,et al.  On the relation between NDVI, fractional vegetation cover, and leaf area index , 1997 .

[12]  J. Clevers.  Application of a weighted infrared-red vegetation index for estimating leaf Area Index by Correcting for Soil Moisture , 1989 .

[13]  Hideki Kobayashi,et al.  Continuous observation of tree leaf area index at ecosystem scale using upward-pointing digital cameras , 2012 .

[14]  J. Chen,et al.  Defining leaf area index for non‐flat leaves , 1992 .

[15]  Alemu Gonsamo,et al.  Large-scale leaf area index inversion algorithms from high-resolution airborne imagery , 2011 .

[16]  K. Morgenstern,et al.  Net ecosystem production of a Douglas‐fir stand for 3 years following clearcut harvesting , 2005 .

[17]  T. Nilson.  A theoretical analysis of the frequency of gaps in plant stands , 1971 .

[18]  Jing M. Chen,et al.  Determining digital hemispherical photograph exposure for leaf area index estimation , 2005 .

[19]  S. T. Gower,et al.  Direct and Indirect Estimation of Leaf Area Index, fAPAR, and Net Primary Production of Terrestrial Ecosystems , 1999 .

[20]  J. Clevers,et al.  The robustness of canopy gap fraction estimates from red and near-infrared reflectances: A comparison of approaches , 1995 .

[21]  Michael Sprintsin,et al.  The effect of spatial resolution on the accuracy of leaf area index estimation for a forest planted in the desert transition zone , 2007 .

[22]  M. Weissa,et al.  Review of methods for in situ leaf area index ( LAI ) determination Part II . Estimation of LAI , errors and sampling , 2003 .

[23]  Lawrence B. Flanagan,et al.  Seasonal and interannual variation in carbon dioxide exchange and carbon balance in a northern temperate grassland , 2002 .

[24]  Jing M. Chen,et al.  Daily canopy photosynthesis model through temporal and spatial scaling for remote sensing applications , 1999 .

[25]  S. Leblanc,et al.  Derivation and validation of Canada-wide coarse-resolution leaf area index maps using high-resolution satellite imagery and ground measurements , 2002 .

[26]  T. A. Black,et al.  Late-summer carbon fluxes from Canadian forests and peatlands along an east-west continental transect , 2006 .

[27]  A. Savitzky,et al.  Smoothing and Differentiation of Data by Simplified Least Squares Procedures. , 1964 .

[28]  J. Cihlar,et al.  Plant canopy gap-size analysis theory for improving optical measurements of leaf-area index. , 1995, Applied optics.

[29]  Sylvain G. Leblanc,et al.  Methodology comparison for canopy structure parameters extraction from digital hemispherical photography in boreal forests , 2005 .

[30]  Jingfeng Xiao,et al.  A comparison of methods for estimating fractional green vegetation cover within a desert-to-upland transition zone in central New Mexico, USA , 2005 .

[31]  N. Breda.  Ground-based measurements of leaf area index: a review of methods, instruments and current controversies. , 2003, Journal of experimental botany.

[32]  F. Berninger,et al.  Simulating carbon exchange of Canadian boreal forests II. Comparing the carbon budgets of a boreal mixedwood stand to a black spruce forest stand , 2008 .

[33]  F. Baret,et al.  Potentials and limits of vegetation indices for LAI and APAR assessment , 1991 .

[34]  Alemu Gonsamo,et al.  eaf area index retrieval using gap fractions obtained from high resolution atellite data : Comparisons of approaches , scales and atmospheric effects , 2010 .