The Primary Reproductive Characteristics Of Artificial Pinus Tabulaeformis And Its Relationship With Neighboring Strains

Pinus tabuliformis is a kind of evergreen tree of Pinaceae,which has become one of the main tree species of artificial afforestation in the Loess Plateau region.They have a series of functions such as soil and water conservation,drought and root system developed,strong anti-barren ability and adaptability.P.tabuliformis are planted one plant in a hole,part of more than one plant in a hole,the first reproduction of P.tabuliformis saplings not only related with their own genetic characteristics,but also closely related with environment,especially closely related with neighbors.In this study,by investigating the same age P.tabuliformis saplings in the grassland of the Malan forest zone,the morphological differences between P.tabuliformis saplings with cones and P.tabuliformis saplings without cones were analyzed,including individual characteristics(plant height,DBH,crown diameter)and current-year branches characteristics(diameter,length,leaves number,leaves weight,branch weight,leaves and branch weight;the number of branches,total leaves weight,total branches weight,total branches and leaves weight of all the current-year branches in 2-year-old branches),which can reveal the characteristics of first reproduction of P.tabuliformis saplings.At the same time,the relationship between first-fruiting characteristics and individual size was studied,the relationship between first-fruiting characteristics and current-year branches was studied,as well as the relationship between cones characteristics in current-year branches and the current-year branches was studied,then the first-fruiting rule of P.tabuliformis saplings was explained.By analyzing the relationship between adjacent plants and neighborhood competition intensity,and the influence of neighborhood competition intensity on individual size,current-year branch characteristics and first-fruiting characteristics,it compared the growth of P.tabuliformis saplings that more than one plant in a hole or one plant in a hole.The differences of first-fruiting characteristics,individual size,current-year branch characteristics and adjacent plants between the specific P.tabuliformis saplings(the plant with well-grown cones)and the other P.tabuliformis saplings were analyzed.This study provides the theoretical basis for the selection of the best planting methods for artificial P.tabuliformis in the Loess Plateau,as well as the restoration and reconstruction of vegetation.Main conclusions in this paper were:(1)When the artificial P.tabuliformis saplings grow to a certain size(plant height:258.13± 34.41 cm,DBH:3.50 ± 0.58 cm,crown diameter:195.20 ± 41.81 cm),they start first reproduction,so they are the size-dependent reproductive allocation.(2)The number of leaves,leaves weight and branch weight of artificial P.tabuliformis saplings current-year branches were closely related to the diameter and length of the branches,the relation could be used to predict leaves number,leaves weight and branch weight.The traits of current-year branches reach a certain threshold(branch diameter:6.00± 2.44 mm,leaves number:94.94 ± 62.62,leaves weight:3.79 ±3.03 g,branch weight:1.88 ± 1.81 g,the weight of the branches and leaves:5.67 ± 4.84 g),the first reproduction of P.tabuliformis started.And the current-year branches biomass in 2-year-old branches were bigger,the first reproduction were earlier.(3)The size and biomass of current-year branches showed a significant positive correlation with the individual size of artificial P.tabuliformis saplings(P<0.01),and the relationship of current-year branches size and the current-year branches biomass in 2-year-old branches with crown diameter are most closely(P<0.01).(4)The number of branches with cones of P.tabuliformis saplings was positively correlated with the length of current-year branches(P<0.05),the average cone weight is positively correlated with the leaves weight and branch weight of current-year branches(P<0.05),average length-width ratio is positively correlated with the leaves number of current-year branches(P<0.05),the branches number of current-year branches in 2-year-old branches is positively correlated with the cones characteristics(cones number,cones weight and average cone weight)(P<0.01 or P<0.05),there was a positive correlation between first-fruiting characteristics(cones weight,average cone weight and average length-width ratio)and the biomass of all the current-year branches in 2-year-old branches of P.tabuliformis saplings(total leaves weight,total branches weight,total leaves and branches weight)(P<0.01 or P<0.05).(5)More than one plant in a hole planting pattern increases the neighborhood competition intensity,and the more the number of neighbors,the closer the distance between the neighbor and the target wood,the larger the neighborhood competition intensity.(6)The DBH and crown diameter of P.tabuliformis saplings without cones of more than one plant in a hole less than DBH and crown diameter of one plant in a hole(P<0.05),there is no significant difference in the branches with cones of P.tabuliformis saplings between the stronger neighborhood competition intensity of more than one plant in a hole and one plant in a hole(P>0.05).In the two different planting patterns,except for current-year branches length and the current-year branches number in 2-year-old branches,there is significant different in current-year branches characteristics and current-year branches biomass in 2-year-old branches of P.tabuliformis saplings without cones,as well as average cones weight and average length-width ratio of P.tabuliformis saplings with cones(P<0.05).In more than one plant in a hole,the greater the neighborhood competition intensity,the smaller the DBH and plant height of P.tabuliformis saplings with cones,there was a negative correlation between the number of annual shoots and the annual biomass of the 2-year-old branches in the juvenile cultivated pine trees.Except for current-year branches length and the current-year branches number in 2-year-old branches,the greater the neighborhood competition intensity,the smaller the size of current-year branches size and the annualbiomass of current-year branches biomass in the 2-year-old branches of P.tabuliformis saplings without cones.(7)In the first reproductive process,the number,average distance,average plant height,average DBH,average crown diameter and the number of P.tabuliformis.saplings with cones of neighbors were not the main reasons for the emergence of specific P.tabuliformis saplings with cones.Compared to other P.tabuliformis saplings with cones,specific P.tabuliformis saplings with cones put more biomass into reproduction,and the amount of biomass put into growth is relatively small,thereby increasing the likelihood of their initial reproductive success.