Empirical models for tracing seasonal changes in leaf area index in deciduous broadleaf forests by digital hemispherical photography

Abstract Accurate estimation of seasonal leaf area index (LAI) variations is essential for predicting forest growth, but rapid and reliable methods for obtaining such estimates have rarely been reported. In this study, direct measurements of LAI seasonal variations in deciduous broadleaf forests in China were made through leaf seasonality observations in the leaf-out season and litter collection in the leaf-fall season. Meanwhile, indirect LAI measurements were made using a digital hemispherical photography (DHP) method. Our objectives were to explore the relationship between direct and indirect LAI measurements and to recommend a rapid and reliable method to determine the seasonal variation of LAI in forests. To achieve these objectives, we first evaluated seasonal variations of the biases due to key factors (woody materials, clumping effects and incorrect automatic exposure) known to influence the estimation of LAI by DHP. The results showed that the biases due to these factors exhibited different seasonal variation patterns, and the total contribution of these factors could explain 72% of the difference between direct LAI and DHP LAI throughout the entire growing season. Second, linear regression models between direct and DHP LAI were first constructed for each 10-day period as well as the entire growing season. Significance tests were made to the differences among the models for different dates, and models for estimating LAI based on DHP in each date were aggregated to 4 periods with R 2 and RMSE values of 0.91 and 0.22, 0.79 and 0.29, 0.81 and 0.14, 0.97 and 0.14, respectively. There was no significant difference between direct LAI and estimated LAI using the four models in each aggregated period ( p

[1]  Laurent Saint-André,et al.  Within-stand and seasonal variations of specific leaf area in a clonal Eucalyptus plantation in the Republic of Congo , 2010 .

[2]  A. Cutini,et al.  Estimation of leaf area index with the Li-Cor LAI 2000 in deciduous forests , 1998 .

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

[4]  R. McMurtrie,et al.  Estimation of leaf area index in eucalypt forest using digital photography , 2007 .

[5]  A. Cutini,et al.  Digital hemispherical photography for estimating forest canopy properties: current controversies and opportunities , 2012 .

[6]  Julio Calvo-Alvarado,et al.  Calibration of LAI-2000 to estimate leaf area index (LAI) and assessment of its relationship with stand productivity in six native and introduced tree species in Costa Rica. , 2007 .

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

[8]  J. Chen,et al.  Evaluation of hemispherical photography for determining plant area index and geometry of a forest stand , 1991 .

[9]  Modeling leaf area index from litter collection and tree data in a deciduous broadleaf forest , 2011 .

[10]  M. Huston,et al.  A comparison of direct and indirect methods for estimating forest canopy leaf area , 1991 .

[11]  Jing M. Chen,et al.  Quantifying the effect of canopy architecture on optical measurements of leaf area index using two gap size analysis methods , 1995, IEEE Trans. Geosci. Remote. Sens..

[12]  R. Küssner,et al.  Comparison of direct and indirect estimation of leaf area index in mature Norway spruce stands of eastern Germany , 2000 .

[13]  B Muys,et al.  Allometry and evaluation of in situ optical LAI determination in Scots pine: a case study in Belgium. , 2005, Tree physiology.

[14]  J. Hicke,et al.  Global synthesis of leaf area index observations: implications for ecological and remote sensing studies , 2003 .

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

[16]  Adina Tillack,et al.  Estimation of the seasonal leaf area index in an alluvial forest using high-resolution satellite-based vegetation indices , 2014 .

[17]  Youngryel Ryu,et al.  Digital canopy photography: Exposed and in the raw , 2014 .

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

[19]  Kenlo Nishida Nasahara,et al.  Two separate periods of the LAI–VIs relationships using in situ measurements in a deciduous broadleaf forest , 2013 .

[20]  A. Gonsamo,et al.  The sensitivity based estimation of leaf area index from spectral vegetation indices , 2012 .

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

[22]  Euan G. Mason,et al.  Comparison of direct and indirect leaf area index measurements of Pinus radiata D. Don , 2012 .

[23]  Richard A. Fournier,et al.  Hemispherical photography simulations with an architectural model to assess retrieval of leaf area index , 2014 .

[24]  David Y. Hollinger,et al.  Leaf area index uncertainty estimates for model-data fusion applications , 2011 .

[25]  S. T. Gower,et al.  Rapid Estimation of Leaf Area Index in Conifer and Broad-Leaf Plantations , 1991 .

[26]  S. T. Gower,et al.  Measurements of branch area and adjusting leaf area index indirect measurements , 1998 .

[27]  S. Leblanc.  Correction to the plant canopy gap-size analysis theory used by the Tracing Radiation and Architecture of Canopies instrument. , 2002, Applied optics.

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

[29]  Miina Rautiainen,et al.  An assessment of ground reference methods for estimating LAI of boreal forests , 2013 .

[30]  A comparison of four methods for determining leaf area index in successional hardwood forests , 1985 .

[31]  Jan Pisek,et al.  Estimation of foliage clumping from the LAI-2000 Plant Canopy Analyzer: effect of view caps , 2014, Trees.

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

[33]  R. Myneni,et al.  Intercomparison and sensitivity analysis of Leaf Area Index retrievals from LAI-2000, AccuPAR, and digital hemispherical photography over croplands , 2008 .

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

[35]  Jianchu Xu,et al.  On the exposure of hemispherical photographs in forests , 2013 .

[36]  J. Topping,et al.  Errors of Observation and Their Treatment , 1957 .

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

[38]  Miina Rautiainen,et al.  Seasonal variation in MODIS LAI for a boreal forest area in Finland , 2012 .

[39]  R. Shaw,et al.  Leaf area measurements based on hemispheric photographs and leaf-litter collection in a deciduous forest during autumn leaf-fall , 1989 .

[40]  G. Russell,et al.  Leaf area index estimates obtained for clumped canopies using hemispherical photography , 1999 .

[41]  J. Tenhunen,et al.  On the relationship of NDVI with leaf area index in a deciduous forest site , 2005 .

[42]  J. M. Chen,et al.  Effects of clumping on estimates of stand leaf area index using the LI-COR LAI-2000 , 1993 .

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

[44]  J. Reynolds,et al.  On definition and quantification of heterogeneity , 1995 .

[45]  E. Dufrene,et al.  Estimation of deciduous forest leaf area index using direct and indirect methods , 1995, Oecologia.

[46]  S. Nagai,et al.  Vertical integration of leaf area index in a Japanese deciduous broad-leaved forest , 2008 .

[47]  A. Gonsamo,et al.  The computation of foliage clumping index using hemispherical photography , 2009 .

[48]  Hu Gang,et al.  Spatial heterogeneity of soil nutrients and its impact on tree species distribution in a karst forest of Southwest China , 2011 .

[49]  T. A. Black,et al.  Characteristics of shortwave and longwave irradiances under a Douglas-fir forest stand , 1991 .

[50]  Hugh J. Barclay,et al.  Assessing bias from boles in calculating leaf area index in immature Douglas-fir with the LI-COR canopy analyzer. , 2000 .

[51]  M. Kalacska,et al.  Calibration and assessment of seasonal changes in leaf area index of a tropical dry forest in different stages of succession. , 2005, Tree physiology.

[52]  Guangjian Yan,et al.  Woody-to-total area ratio determination with a multispectral canopy imager. , 2009, Tree physiology.

[53]  Andrea Cutini,et al.  Estimation of canopy properties in deciduous forests with digital hemispherical and cover photography , 2013 .

[54]  Michael Sprintsin,et al.  Long term and seasonal courses of leaf area index in a semi-arid forest plantation , 2011 .

[55]  J. Ross.  The radiation regime and architecture of plant stands , 1981, Tasks for vegetation sciences 3.

[56]  J. Chen,et al.  On improving the accuracy of digital hemispherical photography measurements of seasonal leaf area index variation in deciduous broadleaf forests , 2015 .

[57]  G. Jin,et al.  Optical and litter collection methods for measuring leaf area index in an old-growth temperate forest in northeastern China , 2013, Journal of Forest Research.

[58]  Jb Miller,et al.  A formula for average foliage density , 1967 .

[59]  Lars Eklundh,et al.  Estimating LAI in deciduous forest stands , 2005 .

[60]  Jiquan Chen,et al.  Seasonality of soil CO2 efflux in a temperate forest: Biophysical effects of snowpack and spring freeze-thaw cycles , 2013 .