Estimating Mortality Dynamic Of Pine-Oak Stands With Empirical And Process-based Methods

This research uses multi-source inventory data to explore the main stand factor affecting the mortality at the individual-tree level;study the differences of tree survival in over-storey and under-storey in Pine-Oak forests at DBH class level;select biological and ecological models,then model self-thinning model of dominant forest stands in Qinling mountains.Stand Density Management Diagrams of Pine-Oak forests were developed according to the general rule of density effect with suitable equations.Based on CROBAS and QUASSI 1.0,the parameters of CROBAS-PT(Pinus tabulaeformis)were calibrated.The effects of stand site and density on mortality predictions were analyzed,based on a 20 years simulation of 9 plots to compare the empirical model and process based model on mortality predictions.Mean error,mean absolute error and mean relative error were calculated to compare the results from CROBAS-PT and QUASSI 1.0.(1)In Pine-Oak forests,survival of the dominant storey is obviously higher than depressed storey,that reveals the complexity of spatial distribution and structural of Pine-Oak forests.The larger of diameter at breast height,the better the individual competition for scarce resources,Mortality shows a trend of decrease after increase first with the intensification of environment competition conditions,increase of the BAL.(2)The SDMD's well demonstrates the dynamic relationship between stand density and other stand factors which is the basis of reasonable management over forest resource.(3)Mortality predictions are sensitive to different initial density,but insensitive to site.CROBAS-PT model predicts lower level of mortality than QUASSI 1.0 model.The process-based CROBAS-PT model can be used for mortality predictions,as its results match the statistical test.Since processed model explains the theory of forest mortality,it can be an effective method to predict the mortality of Pinus tabulaeformis in the region where data is lacking.