Reconstructing past structure and nitrogen accumulation of free populations, and test of its accuracy

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We tested accuracy of the method for structural and functional reconstruction of tree populations from the existing samples, by applying this technique to a 26-year-old plantation of Todo-fir, and comparing the estimated and observed structures of the forests. Sampling was done in Oct. 2000, at a fertilization experiment plots in Hitsujigaoka Exp. Forest in Sapporo. Tree dbh, height and crown length etc. were measured in both control and annually fertilized plots. Then ten trees were felled, and their plant-part biomass values were measured. Stem discs were taken for estimation of sapwood areas. Discs were also collected for stem analysis for estimation of stem volume and growth. Additional sampling was done in Oct. 2001. Then, all samples were analyzed together to develop allometric relationships between tree size and plant part, growth, etc. Tree samples were also collected for analysis of nitrogen concentration: they were dried, ground, then analyzed with the N-C analyzer for N concentration. Time series data of dbh exists for individual trees in the studied stands. With the additional information of tree allometry, we estimated for the total stands, plant-part biomass, leaf area, their growth etc. For the years without plot data, we applied the stand reconstruction method of Osawa et al. (2000), and total stand structure and nitrogen content were estimated. Also analyzed for this calculation were relationships between stem nitrogen concentration vs. sapwood volume, sapwood volume vs. tree size, and stem size distribution. We published two original papers on accuracy of estimates in the theory of stand reconstruction.