Sex-related Spatial Distribution And Dynamic Changes Of Populus Cathayana Populations In Xiaowutai Mountains

Populus cathayana Rehd.,a widely distributed deciduous tree species in the temperate hemisphere with fast-growing,appearance and other characteristics,is often used as a landscape,greening and afforestation species widely cultivated in the world.This work investigated the sexual spatial distribution and dynamic changes of P.cathayana population in the Xiaowutaishan nature reserve of Hebei Province,northern China.The average nearest neighbor index,kernel density estimation,Kriging interpolation and single factor variance analysis methods were used to estimate the poplar population and its female and male spatial distribution and dynamic changes,and the relationship with its habitat factors.The results are followed:(1)In general,P.cathayana populations are aggregated distribution along the narrow belt river bank;while the male and female trees showed cross distribution,but the concentrated distribution of the two areas is closely adjacent.And the aggregation degree of males was slightly higher than that of females.(2)The distribution of plant number and density is increased first and then decreased with the increase of altitude.The highest density at 1500 m but the lowest at 1700 m and 1300 m was found.In addition,the plant number and density decreased with the distance increasing to river.(3)The average diameter at breast height(DBH)of P.cathayana population and its male and female are also affected by altitude and distance from the river.It was the characteristic of "first decrease then increase" with elevation altitudes like "U",the maximum at 1300 m and 1700 m,the lowest 1400 m and 1500 m.The average DBH of the male and female and population of P.cathayana gradually decreased with the distance increasing to river.And male is slightly larger than the female at the altitudes and distance from the river.(4)There is different distribution between sexes with change of altitude and distance to river.Female-biased population was found at 10-30 m from the river at the altitude of 1300 m,10-30 m and for more than 60 m from the river at 1500 m and 30-60 m from the river at 1600 m,while male-biased population found 0-60 m from the river at the altitude of 1400 m,0-10 m and 30-60 m from the river at 1500 m and >60 m from the river at 1600 m.And the sex ratio tended to 1:1 in other area.At all altitudes,the population was slightly male-biased(1:1.06)but the sex ratio tended to 1:1.(5)the distribution of male and female is also affected by the physical and chemical properties of soil.Female prefers to be more prone to the distribution that it is high soil of physical and chemical properties,such as water content,organic matter,total N(TN)and available P(AvP),while the male adapt wider range of physical and chemical properties such as pH,water content,organic matter,TN,total P(TP),total K(TK),available N(AvN),AvP and available K(AvK).In summary,the distribution and dynamic changes of P.cathayana population under the synthetic effect of ecological factors at altitude,river and soil physical and chemical properties.Females tended to distribute in favour soil habitat with high soil water content,organic matter,TN and AvP compared to the males.Males has a wider range of tolerance to soil physical and chemical properties,such as pH,water content,organic matter,TN,TP,TK,AvN,AvP and AvK.