Influencing Factors And Quantitative Model Of Regeneration For Natural Larix Gmelinii Secondary Forest In Central Great Xing’an Range

The natural regeneration of forests is the process that forming a new generation of young forests on woodlands or forest relics by self-reproduction and recovery ability of forest trees,which is the reproduction of resources in the forest ecosystem Natural regeneration is one of the important ways of ecosystem restoration and reconstruction,and it is also one of the hot issues studied by ecologists.It is of great significance to the sustainable management of forests.The Great Khingan is one of the national key state-owned forest areas and natural forest distribution areas,and is also the only cold temper zone bright conifer forest area in China.Taking the survey data of 57 larix gmelinii secondary forest sample plots in the Great Khingan from 2018 to 2019 as the research object,to understand the renewal pattern,renewal influencing factors and renewal density of natural larix gmelinii secondary forest in The Great Khingan area.Analyze the spatial pattern distribution and scale effect law of regeneration seedlings of natural Larix olgensis secondary forests in the Great Khingan from the three aspects of spatial pattern,regeneration limiting factor and counting model,and establish the regeneration seedling density counting model based on the key factors.The results of the study are as follows:(1)The aggregation intensity of renewal seedlings is the largest on the 5m×5m scale.As the sampling size increases,the renewal seedling aggregation intensity decreases.On the whole,the population pattern scale of regeneration seedlings is:larix gmelinii>betula platyphylla,The population pattern intensity of seedlings is significantly greater than that of plantlets and saplings,and the pattern intensity of seedlings is 58 times that of plantlets,which is saplings 130 times.As the sampling scale increases,the intensity of the population pattern gradually decreases.(2)The main influencing factors of forest renewal in the Great Khingan are:average stand height,stand canopy density,litter thickness,herb coverage,and total nitrogen content of the humus layer.The contribution rate of these five environmental factors to forest renewal density is 57.1%.From the results of variable decomposition,the forest stand factor(contribution rate 72.28%)has a greater impact on the forest stand regeneration density than the soil factor(contribution rate 13.14%).The main tree species in the Great Khingan area are poorly renewed and lack of seedling renewal.here was no significant difference in the renewal of the three regions(P=0.175).The renewal density of larix gmelinii and betula platyphylla had significant differences(P=3.28E-07).The renewal density of seedlings,plantlets,and saplings had significant differences(P=0.0153).On the whole,the regeneration density of the main tree species in the Greater Khingan is negatively correlated with the average forest stand height and herb coverage,and positively correlated with the thickness of litter,the total nitrogen content of the humus layer,and the canopy closure.(3)The fitting effect of the count-data model of the updated seedlings is ranked from good to bad,ZINB model,NB model,ZIP model,and Poisson model;the predictive effect of the counting model is from good to bad,ZINB model,ZIP model,NB model,Poisson model.On the whole,the fitting effect and prediction accuracy of the ZINB model are better than those of the other three types of models.The fitting effect and prediction accuracy of the updated seedling counting model for larix gmelinii and betula platyphylla at different height levels are sorted from good to bad,larix gmelinii>betula platyphylla,seedlings>plantlets>saplings.