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The aim of this study was to quantify, both spatial and temporal variations of maximum leaf area index (LAI) and to interpret LAI variation according to stand characteristics and meteorological conditions. We have compared maximum LAI, measured using the LI-COR LAI-2000 PCA, throughout 4 years and over 420 ha of a temperate forest across a range of stand structure (density, biomass, age) and site fertility (soil nutrient and water availability). LAI values ranged from 0.5 to 8 m2 m−2. This study has shown that maximal LAI was relatively stable between years. However, although the water stress did not affect LAI development in the current year, it reduced LAI of the following year only in stands with high LAI (above 5.5 m2 m−2). Spatial variations of maximal LAI were mainly dependent on forest management which affected tree density and stand diameter at breast height (DBH) through thinning and harvesting. Among the 34 deciduous stands studied, maximal LAI increased with tree density up to a value of about 1000 stems per ha and then it reached a plateau between 6 and 8 m2 m−2. Total leaf area per tree has a strong correlation to DBH for species with different sap conducting system (r2 = 0.94). Decreases of maximal LAI with humus quality were observed, suggesting that, although forest management appears to be the main cause of LAI variations between stands and between years, soil fertility may be a determinant of stand LAI. |
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