An Investigation And Evaluation Of Torreya Grandis Populations In Yixian County

Torreya grandis is a rare and precious economic tree species in China.A large number of Torreya grandis trees distributed in Yixian County,Anhui Province,with abundant germplasm resources.In order to utilize the resources of Torreya grandis tree efficiently and scientifically,the quantity distribution,genetic diversity and soil nutrient status of Torreya grandis in Yixian County were systematically investigated and analyzed.The population structure of Torreya grandis and its dynamic regularity and evolution trend were also analyzed.The main results are as follows.（1）There are abundant germplasm resources of Torreya grandis in Yixian County.A total of 32 types with special germplasm were collected,among which 8 types were excellent for utilization.（2）The physical parameters of fruit for Torreya grandis,including vertical and horizontal diameters of fruits,vertical and horizontal diameters of seed,fresh fruit and seed weights and fresh seed rate,were measured and analyzed.There were significant differences in these parameters amongst the different types.The fresh seed weight had significant positive correlation with vertical and horizontal diameters of fruit and seed,and significant negative correlation with fruit index and seed index.（3）The age structure of Torreya grandis poplation was typical inverted J-curve.The dynamic index Vp of age structure of the whole population was 39.25%.When considering external interference,V_p,i’=0.04%>0,indicating a stable growth population.（4）The results from static and survivability analysis,the survival curve of Torreya grandis poplation tended to Deevey-II pattern.With the increase of age,the mortality rate increased gradually during the early growth period of the poplation due to the environmental selection,and then the mortality rate decreased.After the age class VII,the death rate of the poplation increased due to the declination of physiological function.（5）The individual numbers of Torreya grandis population showed an increasing trend from age classⅡtoⅨ.The individual numbers at age classⅩshowed monotonical decrease in 2 to 4 years and showed monotonical increase afterward.From the time series prediction map of Torreya grandis population at age 2,4,6 and 8,an inverted J-type distribution was appeared,indicating that the population was a stable increase pattern.This result was in agreement with the results from the age class curve and survivability analysis.（6）The result from the spectral analysis of the Population regeneration was made to revel the renewal process and stability of Torreya grandis the results showed that there was a clear dynamic pattern of periodic fluctuation of Torreya grandis population.The maximum fundamental wave was A1=1.863,which was the most basic periodic fluctuation of the Torreya grandis population.There appeared a clear multiple harmonic overlap for minor cycles in the large cycle of Torreya grandis population.However,the fluctuation in the minor cycle had little effect on the large cycle.（7）Based on the standards of soil nutrient grades of cropland in southern China and of the green food production area of the Ministry of Agriculture,the soils of Torreya grandis forest were rich in organic matter and total nitrogen,and lack in total phosphorus and potassium.The average fertility indices of 0¹0 cm and 10³0 cm soil layers were,respectively,0.95 and 0.85.The comprehensive fertility was medium for 0¹0cm soil layer and low for 10³0 cm soil layer.（8）The correlation analysis showed that the physical parameters of Torreya grandis fruits and seeds had correlated to altotude and soil factor without significant correlation.The parameters of Torreya grandis fruit and seed are controled by genetic factors.