| Black locust(R.pseudoacacia)is an important tree species for ecological restoration and wood production in the world.It has good functions of maintaining water and soil and improving soil.R.pseudoacacia was afforested on Mount Tai in the 50 s and 60 s of the last century.Due to its strong root sucker reproductive capacity,it currently become shorter and thinner with more and more cutting,which seriously invades other tree species.The living space has caused serious harm to Mount Tai's biodiversity and forest landscape quality.The diffusion problem of R.pseudoacacia in Mount Tai has become a technical problem that must be solved urgently in the process of management and diversity protection of Mount Tai scenic forest.In the early stage,some studies have been conducted on the stoichiometric characteristics,physiological characteristics,individual plant diffusion distance,and its diffusion to other forest types.However,there is no systematic study on the pattern and process of the R.pseudoacacia diffusion between the generations.In this study,the second and third generation sprout forests of Gushan forest farm in Mount Tai were selected as the research object,combined with the new SSR molecular marker method and geostatistics related theory,the diffusion pattern and process of R.pseudoacacia forests with different sprout generations were investigated and analyzed to clarify the multigenerational sprout forest sprout of R.pseudoacacia.The diffusion pattern and influencing factors provide a theoretical basis for Mount Tai biodiversity conservation and reasonable management and protection of landscape forests.The main research results are as follows:1.Improved the SSR molecular labeling method for the identification of locust clones.The research group Wang Cancan used 16 pairs of primers to identify locust clones in the early stage.There were problems with the specificity of individual primers,the number of primers and the cost.In this study,in order to reduce the experimental cost and achieve a better effect of rapid identification of locust clones,on the basis of Wang Cancan,8 pairs of specific primers were used for SSR molecular labeling experiments.A total of 1,476 individuals of R.pseudoacacia were tested in this study.The results showed that the number of clones and the ratio of clones identified in the third-generation sprout forest were higher than those in the second-generation sprout forest.A total of 238 genotypes with cloned individuals were identified in 6 plots.The total number of cloned ramets was 951,of which 63.33 were in the second-generation sprout forest,and the cloned individual rate was 34.94%;253.67 were in the third-generation sprout forest.79.20%.SSR molecular labeling method for "paternity testing" can ensure the in situ investigation conditions in the wild to the greatest extent,provide theoretical basis for the origin,mutation and evolution of cloned plants,and has good application prospects.2.Root-sucker diffusion pattern of R.pseudoacacia forests in different sprout generations.The distribution pattern and intensity of clone ramets in different sprout generations varied with the sampling scale,but showed different aggregation intensity with the change of sampling scale.With the increase of generations,the type of distribution pattern of R.pseudoacacia population did not change significantly.At the six sampling scales in this study(6 m × 6 m,6 m × 12 m,12 m × 12 m,18 m × 18 m,24 m × 24 m,30 m × 30 m)All of them showed aggregation distribution,and the aggregation degree was the strongest on the sampling scale of 6 m × 6 m.With the increase of the number of sprout generations,the aggregation intensity weakened.At the minimum sampling scale,the negative binomial index(K)and Morisita index(I)of the second-generation sprout forest were 1.06 and 1.97,respectively,while the thirdgeneration sprout forest was 3.45 and 1.29.The pattern size of R.pseudoacacia populations at different sprout generations reached the maximum aggregation scale at the sampling scale of 6 m × 6 m,and decreased with the increase of the sampling scale and tended to zero.At each sampling scale,the maximum mean square value of the third-generation sprout forest was 0.58,which was far lower than the maximum mean square value of the second-generation sprout forest,12.66.Because the R.pseudoacacia in this area is mainly root sucker propagation,which is restricted by distance compared with seed propagation,it shows a phenomenon of aggregation distribution.3.The diffusion number and distance of R.pseudoacacia forests with different sprout generations are different.With the increase of sprout generations,the diffusion quantity and distance are getting larger and larger.The total number of cloned ramets in the secondgeneration R.pseudoacacia forests was 88,with a total diffusion distance of 260.49 m,of which the longest distance was 7.96 m,and the longest average annual diffusion distance was 0.24 m / year;The total number of diffused plants in all directions is 537,the total diffused distance is 1981.22 m,the longest distance is 21.05 m,and the longest average annual diffused distance is 1.75 m / year.Different generations of R.pseudoacacia sprout forests are basically consistent in the upward direction of diffusion,that is,the proportion of the number of downward diffusion is higher than that of the upward slope,and the largest number of diffusion in the direction of the farthest diffusion distance.It is speculated that with the increase of the sprout generation,the number of R.pseudoacacia spread more and more,the distance is farther and farther,and the diffusion range is larger and larger.4.The influence mechanism of the pattern and process of R.pseudoacacia root sucker.The soil elements related to the R.pseudoacacia root sucker diffusion are mainly nitrogen and phosphorus.Nitrogen may be the dominant factor in diffusion,and phosphorus may be the limiting factor.The other measured soil chemical elements in this study had no obvious correlation with the R.pseudoacacia diffusion.Comprehensive analysis shows that under human disturbance,with the increase of the number of locust sprout generations,the diffusion capacity gradually increases,which is the main reason for the decline of the landscape quality of Mount Tai's scenic forest.Large-scale tending is not in line with the concept of healthy forest management.In the future,the disturbance to pure black locust forests should be reduced,and the black locust forests should be reasonably regulated so as not to spread over a large area without seriously affecting other biodiversity.Furthermore,the quality of Mount Tai's scenic forest landscape is improved. |
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