Long Term Effects And Optimization Mode Of Larch Plantation Thinning Based On FORCAST Model

Larch(Larix olgensis) plantation was studied in east forest region of northeast China bymethods of simulation and prediction using Forest Ecosystem ManagementModel(FORECAST model) based on the research of practice effect of thinning at immobilizedfield in one management cycle, focus on the problem of thinning could promote the growth ofproductivity in short term but hard to predict the long term effect to ecosystem. FORECASTmodel was calibrated by collecting the data of soil and tree growth, researching biomass andanalyzing nutrient concentration of shrub and herb of larch plantation, then using it to study thelong term effect of thinning no biomass of truck timber, available N, P, K storage in ecosystembetween cutting rotation. Discuss the reasonable mode of thinning of larch plantation, in orderto provide basis for maintaining its long term productivity.Results showed that:(1) Average diameter at breast height (DBH) of larch plantation increasing following thedecreasing of management density index at same site conditions. Average DBH of preservingtrees when management density index is 0.7, 0.8, 0.9 or 1 is increased 16.33ï¼…, 10.41ï¼…, 7.05ï¼…,3.87ï¼…than controls respectively. Individual stem volume increased 14.90ï¼…, 24.24ï¼…, 12.28ï¼…,9.23ï¼…than controls respectively. Synthesis perspective yields the appropriate managementdensity index of 0.7 and 0.8. However, the effect of different management density index tototal volume of woodland is not evidence.(2)Variety of shrub and herb biomass in larch plantation has a trends of increasing-decreasing-increasing-stable following the forest age, maximum appears at 5-8 years, stabilizeat about 20 years. Variety trends of nutrient concentration in composing portions of shrub(root,branch, leaf) and herb (aboveground, underground) has large difference, but it get to stable atabout 20 years after a series of fluctuations.(3)Predictive results of FORECAST model showed that thinning can promote the growthof productivity of larch plantation in short term, but increasing quantity decreased followingthe increasing generations of continuous cultivation, at last, it get to identical to nomanagement forest gradually. Productivity does not decline in 5-10generations by usingmoderate thinning intensity. Synthesis perspective showed that moderate or light thinningmode is suitable to larch plantation.