Regeneration Characteristics And Community Dynamic Prediction Of Picea Spp.+Larix Principis-rupprechtii Mixed Stand In Guandi Mountain

Picea spp.(Picea wilsonii and Picea meyeri)and Larix principis-rupprechtii are mainly distributed in mid-alpine of North China.In this paper,12 plots of mixed stand for Picea spp.+Larix principis-rupprechtii in Guandi Mountain,Shanxi Province were selected to analyze the species composition and quantitative characteristics of understory regeneration.Meanwhile,the distribution pattern and heterogeneity of understory natural regeneration was carried out by methods of adjacent grid-like,combining with the geostatistical semivariance function,fractal dimension and Kriging interpolation.The futural community was predicted by static succession analysis and Markov model.The results are as follows:(1)Community structure characteristics: the relative importance values of Picea spp.and Larix principis-rupprechtii in the community were larger,meaning the greater influences of these species on the community.Larix principis-rupprechtii trees are mostly of big trees: diameter grades of Ⅸ and Ⅹaccounted for 9.00%,height grade of Ⅸ and Ⅹ accounted for 8.84%,and age grade of Ⅹ accounted for5.87%.Picea spp.was found of a few big trees,but was of a large number of seedlings and saplings.Small diameter class of I-Ⅲ accounted for 56.70%,lower height class of I-Ⅲ accounted for 52.40%,and younger age class of I-Ⅳ accounted for 54.66%.The population of Picea spp.showed both of L-shaped pyramid and inverted J-shaped structure with abundant seedlings and saplings,which belonged to a growing population.The population of Larix principis-rupprechtii showed both of inverted J-shaped and inverted pyramid structure,with a shortage of seedlings and saplings,which belonged to a declining population.(2)The characteristics of understory regeneration: the regeneration density of the community was 450~ 1350 per hm2,which was dominated by Picea spp.,accounted for 81.74%.The regeneration density of Picea spp.was 688 per hm2,and that of Larix principis-rupprechtii was 167 per hm2,which was of poor regeneration.Most of the seedlings and saplings were clustered.With the scale increasing,the clustering intensity gradually decreased.There was a strong spatial autocorrelation between seedlings and saplings.The structural and random factors were responsible for 79.6% and 20.4% of the variation of the distribution pattern,respectively.The spatial distribution of seedlings and saplings showed anisotropy,the dominant pattern was from northeast to southwest,and the subdominant pattern was from northwest to southeast.The spatial autocorrelation range of ground diameter and tree height of seedlings and saplings are 6.37 m and13.50 m,respectively.The spatial heterogeneity was stronger in the horizontal direction,and structural factors had a greater influence on its spatial heterogeneity.(3)Community dynamic prediction: the mixed stand of Picea spp.+Larix principis-rupprechtii would eventually develop into a more stable climax community which was absolutely dominated by Picea spp.During the community regeneration of the first 150 years,the tree species composition ratio of various plots changed significantly,and Picea spp.was developed rapidly.In the 150 th year,percentage of other tree species were less than 10%.When the community had succeeded for 500 years,Picea spp.was more dominant with stable composition percentage of 81%,Larix principis-rupprechtii accounted for 15%,and other species accounted for 4%.