Evaluation of Indirect Measurement Method of Seasonal Patterns of Leaf Area Index in a High-Density Short Rotation Coppice Culture of Poplar

Abstract

Leaf area index (LAI) is an important determinant of biomass production and yield of short rotation bio-energy plantation. An accurate measurement of LAI is critical for quantifying light interception and penetration within the canopy, and subsequently understanding its influence on the stand carbon and energy balance. The aim of the current study is validation of the Sunscan Plant Canopy Analyzer which serves as an indirect method for the evaluation of the seasonal patterns of LAI, relation between LAI and above ground woody dry biomass and to determine the specific leaf area in short-rotation poplar hybrid clone J-105 (Populus nigra × P. maximowiczii) in uncoppiced (1st rotation) and coppiced (2nd rotation), respectively. LAI was measured in uncoppiced and coppiced by two different methods using indirect (SunScan Plant Canopy Analyzer) and direct (litterfall collection). Sunscan Plant Canopy Analyzer was compared against litterfall collection (only way to retrieve the actual LAI). Simple regression (R2 = 0.82) model was fitted to validate indirect measurement method and a very good agreement (82%) was observed in LAI values estimated from SunScan Plant Canopy Analyzer and from litterfall collection. Seasonal variability of LAI in a short rotation coppice (SRC) culture of poplar clone J-105 was evaluated over six years period (2008–2013), for uncoppiced (2008 and 2009) and coppiced (2010, 2011, 2012 and 2013) culture. The maximum canopy LAI (LAImax) reached 7.3 (uncoppiced) and 9.5 (coppiced). The linear regression (R2 = 0.93) for average LAI and above ground woody dry biomass was determined, and it was found that LAI acts an indicator of biomass productivity. Specific leaf area (SLA) was estimated in both uncoppiced and coppiced culture of poplar. The maximum SLA was found to be 138.9 cm2g−1 in uncoppiced and 126.9 cm2g−1 in coppiced. To conclude, the evaluated indirect LAI measurement method is portable, reliable and faster than direct LAI measurement in high density poplar short-rotation coppice culture.