Natural Regeneration Characteristics And Adaptive Mechanism Of Larix Principis-rupprechtii

Natural forest regeneration is a process of restoring the ecological environment through selfreproduction,a process of forest resource reproduction,and an important link in the succession of forest ecosystems.Therefore,understanding the mechanism of environmental factors in the process of natural forest regeneration can better understand its regenerated features and adaptation mechanisms.However,the research on the influencing factors of natural forest regeneration mostly focuses on the single type of factor,and insufficient consideration of indirect effects of multifactorial interactions on natural regeneration.At present,the natural regeneration of Larix principis-rupprechtii is difficult to achieve,and its ecological and economic benefits cannot be well realized.The goal of forest management and tending is difficult to achieve,and the sustainable development of forest ecological resources is affected.In this study,by analyzing the distribution and growth characteristics of understory regenerated seedlings in the typical distribution area of Larix principis-rupprechtii,and the adaptive mechanism of soil nutrients,climatic environment and geographical conditions of Larix principis-rupprechtii.The purpose of this study was to explore the natural regeneration characteristics and influencing factors of Larix principis-rupprechtii.It can provide a theoretical basis for the formulation of natural forest regeneration management and tending management measures.In this study,the density,number,height,ground diameter,height of diameter at breast and the relative position coordinates of the natural regenerated seedlings and adult trees in the distribution area of Larix principis-rupprechtii were measured through the sample plot survey.Soil physical and chemical properties,topography and the climate environment in the forest also were recorded.Using the spatial point pattern analysis method,the spatial distribution pattern of natural regenerated seedlings of Larix principisrupprechtii and the influence of Larix principis-rupprechtii adult trees on the distribution of natural regenerated seedlings were analyzed.The relationship between density,height and ground diameter was explored,and their mutual influence was explored.Fisher’s discriminant method was established to discriminate the distribution of natural regenerated seedlings under different community structures,climatic environments and geographical conditions.Using artificial neural networks to analyze the response of natural regenerated seedlings to climate.Redundancy analysis was used and structural equation model to study the main factors affecting the natural regeneration of Larix principis-rupprechtii.Research indicates:(1)There is spatial heterogeneity in the distribution of natural regenerated seedlings of Larix principisrupprechtii in the study area.Natural regenerated seedlings are clustered in a small scale(0-2m),and randomly and regularly distributed in a large scale.Adult trees showed a promotion effect on natural regenerated seedlings on a small scale(0-4m),and showed no effect on natural regenerated seedlings on a large scale.(2)Soil nutrients(water content,organic content,total nitrogen,alkali-hydrolysable nitrogen,available phosphorus and available potassium)in the sample plots in the study area showed obvious horizontal and vertical spatial distribution heterogeneity.According to the second national soil nutrient evaluation standard,the soil nutrient of the sample plot was judged to be at the medium level.When comparing soil physical and chemical properties at different soil depths,it was found that with the increase of soil depth,soil water content,organic matter,alkali-hydrolysable nitrogen and available potassium showed a downward trend,and soil total nitrogen showed a trend of increasing first and then decreasing.With the increase of altitude,soil water content and available phosphorus decreased first and then increased,and other nutrients showed a downward trend.With the increase of slope,soil water content,organic matter,total nitrogen,alkali-hydrolysable nitrogen,available phosphorus and available potassium showed a downward trend.With the decline of the slope position,the soil water content and alkali-hydrolysable nitrogen first decreased and then increased,and the other soil physicochemical properties showed a continuous increase trend.In terms of the slope aspect,the contents of soil water content,organic matter,total nitrogen,alkali-hydrolysable nitrogen,available phosphorus and available potassium in the north-west orientation were higher than those in the western orientation of these six soil nutrients.(3)In the fitting of soil nutrients and the density,height and ground diameter of natural regenerated seedlings of Larix principis-rupprechtii,it was found that the relationship between soil nutrients and the growth of natural regenerated seedlings was mostly logarithmic and linear functions.Then,the fitting of the nonlinear mixed model was carried out,and it was found that the determined coefficients of the final fitting of the three basic models were all high,which could be used as the theoretical basis for the later tending management.(4)In the study on the habitat adaptability of natural regenerated seedlings of Larix principis-rupprechtii,it was found that the three climatic factors of temperature,humidity and precipitation had a significant impact on the growth and distribution of natural regenerated seedlings of Larix principis-rupprechtii.A number of community factors have an impact on the growth of natural regenerated seedlings.Longitude,latitude,slope and slope position are the main geographical factors affecting the natural regeneration of Larix principisrupprechtii.(5)Among the results of the research on the effects of environmental factors on the natural regeneration process of Larix principis-rupprechtii,litter thickness,stand density,herb coverage,slope,soil total nitrogen,water content and shrub coverage are the most important factors affecting the natural regenerated seedlings growth of Larix principis-rupprechtii.The main factors of poor natural regeneration in Larix principis-rupprechtii distribution area in Guandi Mountain,including insufficient germplasm resources,understory vegetation and litter affecting the habitat of natural regenerated seedlings.Based on the findings of this study,we propose some tending measures to improve the natural regeneration of Larix principis-rupprechtii.Increasing the distance between natural regenerated seedlings of Larix principis-rupprechtii and adult trees,and at the same time ensure that there is a small amount of aggregation of natural regenerated seedlings of Larix principis-rupprechtii.Removing the herbs and shrubs next to the natural regenerated seedlings to improve the space environment for the growth and development of the seedlings.The thickness of the litter under the small forest can improve the settlement rate of seedlings after seed germination.At the same time,the collected litter is incinerated and buried in the soil to increase the return of nutrients and improve the circulation rate of nutrients in the soil.Cutting down some dead trees in forest land and pruning the dead branches of the forest trees,increasing the amount of light radiation and soil moisture,and improve the space environment for the vertical growth of seedlings.Because some natural regenerated seedlings will grow in positions with large slopes,but the root system does not have a strong grip on the soil.And which affect by many environmental factors,these seedlings will be dead,and the roots are exposed to the air,eventually lead to the death of the natural regenerated seedlings.Therefore,transplanting the natural regenerated seedlings distributed in the steeper slope area to the gentler slope area,which can well guarantee the quantity and quality of the natural regenerated seedling community.The above-mentioned tending measures can well eliminate the obstacle mechanism of natural regeneration of Larix principis-rupprechtii,creating favorable environmental conditions for the growth and distribution of natural regenerated seedlings,and promote the sustainable development of Larix principis-rupprechtii.