Temporal Dynamics And Application Of Seed Rain Characteristics Of Quercus Variabilis In Beijing Jiufeng Area

Quercus variabilis has high economic value and ecological protection value.Previous scholars have excavated the seed rain of Quercus variabilis in terms of time and space,but whether the quality of the seeds is consistent during different seed rain periods,and whether there are many and good periods of seed drop,is still lack of research.At present,the main research object is the population,and the difference in the individual level of the single mother tree is unknown,so the seed rain mechanism of the group is still unclear.In this experiment,a individual tree was taken as the research object.Seed rain started at the beginning of August and finished at the end of September,we collected followed seeds every 3 days,collected 29 times.Analyzing the temporal dynamics and inter-annual differences in the number of seeds,bad seed rate,nutrient content,seed rain composition,etc.,the following results are obtained in this paper:1 The duration of individual seed rain of Quercus variabilis varies from 3 to 30 days,and the drop curve is usually single-peaked.The drop curve may be interrupted or no peak when it encounters a strong young year.The overall seed rain time of the 15 mother trees lasted for two months from the beginning of August to the end of September.The occurrence time,duration and peak time of the overall seed rain for two years were similar.The individual seeding period,number and weight of individual mother trees vary greatly.The lower the number of mother trees,the later the start of seeding.2 Quercus variabilis species also have the masting phenomenon in different years.Relative synchronization of seed rain number dropped between the trees may be the cause of the guild masting.In 2019,the seeding number of 10 mother trees decreased significantly at the same time,among which 7 trees had a drop of 60%to 90%.It is speculated that 2019 will be the non-masting year of these trees.On the guild level,the number of seeds dropped by 25.4%,and the synchronous change in the seeding of nearly half of the trees increased the interannual variation of the guild seeding.The change in the overall seed size composition of the two years is also presumed to be due to the change in the number of seeds dropped.3 The total seed rain period of 15 trees lasts 43 days.The peak drop period is concentrated from August 28 to September 5 in 2018 and August 25 to September 2 in 2019,which lasting only 9 days;the peak drop period only accounts for 20%of the seed rain process.The amount of seeds has reached 50%of the total,and the number of seeds is 2.5 times the average level.The bad seed rate in the peak period is about 10%,and the bad seed rate in the initial and late stages of seed rain is about 30%-70%.Seed collection at the peak period from the end of August to the beginning of September not only has high efficiency,but also has the best seed quality than other periods.4 The peak seeding period of individual plant implementation is widely distributed.The earliest peak seeding period is August 19 to August 25,and the latest peak seeding period is September 15 to September 17.In 2018 and 2019,the duration of the peak seeding period coverage of the individual trees were 19 days and 22 days,respectively.The peak seeding period of Quercus variabilis individual was staggered to avoid extreme weather loss,and it was conducive to seed diffusion and population renewal.5 There is no specific trend for the content of N,P and K in seeds of single mother tree at different planting time.During seeding period,the range of N concentration is 6.24-14.90mg/g,the range of P concentration is 0.91-5.49mg/g,and the range of K concentration is 5.19-12.69mg/g.6 The rate of bad seed which has a large number of dropped seeds is low,and the rate of individual plant with a small number of dropped seeds is high.The total number of dropped seeds per plant is negatively correlated with its bad seed rate（correlation coefficient is-0.541）.The result of the quantitative relationship between the two is y=0.288*e^-0.01x（R²=0.619）.Therefore,when calculating the number of seeds to be collected,the number of seeds per plant and the rate of bad seeds should be considered.There is a similar normal curve between the good seed rate and time of the population in 2019.The relationship curve between the two:y=-0.0163x²+0.2247x +0.2222（R²=0.8867）.Therefore,during the peak period,not only the number of seeds dropped, but also the number of good seeds,the use of this relationship can also guide the selection of seed production time.7 The classification thresholds of large,medium and small seeds of Quercus variabilis in Jiufeng area are 3.92g and 3.54g,respectively.It is not easy to use the weight of the seed as a criterion for judging the size of the seed,but it is simple and easy to use the width of the seed as the screening standard.After the study,it was found that the seed width was significantly related to the seed weight.The equation relationship between the seed weight and the seed width of some seeds was established as y=1.454x+11.349（R²=0.797）.Substitute the data of the individual- seed weight of more than 30,000 seeds for two years to obtain their corresponding seed widths. After clustering analysis,the critical values for the width classification of the three seed-level seeds are:17.05mm and 16.50mm.The concept of the seed classifier can easily distinguish the seeds of different particle grades,which provides a technical idea for the grading production of large-size seeds in the future.