Abstract
Despite the relevance of leaf area index (LAI) to forest productivity, few studies have focused on the interannual variability of LAI of an evergreen stand and its relationship with stand growth and meteorological factors. We estimated the change in LAI of an evergreen conifer (Chamaecyparis obtusa) stand over 19 years from a dataset using allometric methods. The LAI varied between 7.1 and 8.8 m2 m−2, with a 95% confidence interval of <1.1 m2 m−2 over the 19 years. This LAI range was maintained such that the gradual increase in leaf area (LA) of the largest trees counterbalanced the gradual loss in LA of the smallest trees. Meanwhile, more trees showed a temporary decrease in LA in years with low summer precipitation. The LAI and current-year mean temperature for July and August (TJA) were weakly correlated, whereas the correlation coefficient increased (r = 0.93) when LAI was correlated with the moving average TJA over the previous 6 years, which agreed with the estimated turnover time of canopy foliage. The annual stem biomass growth rate was significantly positively correlated with summer precipitation, but not with LAI. These results will be useful for refining models in studies on forest growth and global climate change.
Highlights
The leaf area index (LAI) of a forest is an important factor for estimating the primary productivity of the stand[1,2,3,4,5]
The difference between current-year LAI and previous-year LAI of a stand is calculated by the difference between the amount of leaf area newly produced in the current year and the one lost between the previous and current years as e.g. leaf fall and grazing
This decrease in tree LA was accompanied by reduction in crown length (Fig. 1c); crown length reduction occurs when the growth rate of tree height is smaller than the rate of the rise of crown base that results from the death of the lowest living branches in the crown
Summary
The leaf area index (LAI) of a forest is an important factor for estimating the primary productivity of the stand[1,2,3,4,5]. An among-stand comparison conducted by Smith et al.[27] showed that net photosynthetic production did not strongly depend on LAI in evergreen conifer forests in which LAI had reached a certain level. Within an even-aged stand, trees can have increasing or decreasing crown sizes[30,31], suggesting that the competitive status of a tree affects the pattern of changes in its leaf area (hereafter ‘tree LA’) over time. The effects of meteorological factors on population dynamics have seldom been studied for evergreen stands through long-term observations of a given stand
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