Spatial Pattern And Association Of Spruce-fir Seedlings And Saplings In Secondary Forests In The Changbai Mountains Area In Northeastern China

Spatial pattern of seedlings is an important factor affecting the dynamic changes of forest communities.Spatial pattern of Picea jezoensis and Abies nephrolepis seedlings at different developmental stages is analyzed and spatial association between their seedlings and surrounding trees is also studied in this paper in order to explore the spatial change in a Picea jezoensis and Abies nephrolepis forest and to find the impact of spatial structure on Picea jezoensis and Abies nephrolepis seedlings.In this study,the survey data of the cloud and fir-coniferous mixed forest sample(0.36hm2)established in Jingouling Forest Farm in 2017 and 2018 were used to analyze the different developmental stages of Picea jezoensis and Abies nephrolepis space distribution pattern and spatial association by the SADIE spatial analysis method at the 5m and 10m spatial scales in the two plots.The research results show that:(1)In the both stands,the diameter structure roughly presented inverted "J" curve,and the stands structure are relatively stable.(2)Individual spatial structure and spatial correlation vary with different plant density,developmental stage and spatial scale.In the stands with small plant density,spruce seedlings grow more closer to the large trees,and as the plant density increased,Picea jezoensis seedlings and trees gradually separated in space..With the growth process of seedlings to adult trees,the spatial distribution also tends to be random and eventually reaches uniform distribution.In different spatial scales,the species showed different spatial distribution patterns,and the spatial pattern significance decreases(or strengthens)with the changes of scale.(3)Abies nephrolepis seedlings and saplings have strong shade tolerance,which is positively correlated with the big tree,and grow well under the canopy.Picea jezoensis seedlings showed mainly spatially unrelated or negatively correlated with the top layer,so its makes not easy to regeneration in the closed forest and more distributed in the forest edge.(4)In the stand with lower density,because of the light condition is better,Picea jezoensis mainly distribute under the shelter of the large trees in the range of 10m-15m when they are growing.For the closed forest stand,the distance between Picea jezoensis seedlings and large trees is around 10m and 20m-25m due to the poor light condition in some areas under the forest.Therefore,at the management stage of the forest stand,the implementation measures should be established according to the business purpose and combination with the actual situation of forest stand.And the appropriate replanting or harvesting measures should be formulated according to the stand density,forest development and spatial pattern to adjust the spatial structure of the stand,which will enable the forest stand to achieve sustained and stable development.