Effect Of Thinning On The Sexual Reproduction And Regeneration Of Quercus Liaotungensis Forest In Huanglong And Qiaoshan Mountains

Taking the Quercus liaotungensis middle-aged forests in Huanglong and Qiaoshan mountains(in the south of the Loess Plateau)as study object,the reproductive module,the seeding update,as well as effects of litter on early growth and development were investigated which were under the guidance of close-to-natural management of five years after thinning at different intensities(CK,10%,20% and 30%),in order to demonstrate the impact of thinning intensity on sexual reproduction and regeneration of Q.liaotungensis.These studies were able to reveal the effect of thinning intensities on the reproduction of Q.liaotungensis and the regeneration of woodland.And provide the basis for high yield,high quality and sustainable management of Q.liaotungensis forest.The main conclusions were as follows:1.Thinning intensities promoted the growth of Q.liaotungensis forest,the average treeheight and DBH increased with the increase of thinning intensity.There was a significantpositive correlation between the crown area,the crown volume and the thinning intensity.The vegetative branches,male inflorescence,male flowers,male flowers,female flowers,yield of generative shoots,young fruits and mature fruits also increased with the increase ofthinning intensity.And the yield of generative shoots,young fruits and mature fruits haveraised significantly under 20% and 30% thinning intensity,30% reached the maximum.Theratio of generative shoots and fruit setting rate increased with thinning intensity,andreached significant level under 20% or 30% thinning intensity.About three-quarters of thegenerative shoots,female and male flowers centered in the upper canopy,with the rest inthe lower part;sunny side numbers of reproductive modules accounted for about 65%,shaded side accounted for only 35%.The lower of crown,shaded generative shoots,pistillate flowers and staminate inflorescence increase with increasing thinning intensity.2.Percent of seed trees,seeds number per sample tree and percent of developed seeds ofQ.liaotungensis forests would increase with the increasing intensity,and show up as 30%>20%> 10%> CK.Seeds number per area had reached the maximum number under 20%thinning intensity,and show up as 20%> 30%> CK> 10%.From the seeds spatialdistribution in the canopy,the upper accounted for 73.6%,while the lower had 26.2%.Thesunny side of canopy layer set relatively the most fruits of 65.8%,shady side only had34.2%.For further improving lower of canopy greater than upper of canopy and shady side greater than sunny side under thinning intensity;seed long diameter,seed short diameter and 1000-seeds mass of Q.liaotungensis forests would increase with the increasing intensity,which reached to the maximum under 30% thinning intensity.The thinning intensity of 20%was most conducive to the seed quantity and quality improvements of Q.liaotungensis,when continuously add the thinning intensity to 30%,it did not improve the fruiting,but the unit area of stand fruits dropped.3.The number of seedlings per unit area of Q.liaotungensis increased with the increase of thinning intensity,and the seedling density reached the maximum at 30% intensity.The conversion rate decreased with the increase of seedling age,and the conversion rate of the same seedling age increased with the increase of thinning intensity.Among them,the conversion rate of the control group was the lowest between 4 years and 5 years,only(44.3± 3.0)%.The height,basal diameter and length of main root of seedling had significant positive correlation with seedling age.And the height,basal diameter and length of main root at same seedling age increased with thinning intensity,and have significant difference under 30% thinning intensity.Average biomass,leaf,root and total of them positively related to thinning intensity.The seedlings tend to store more dry matter in the roots when the period is 1 ~ 3 years.After 3 years,the ratio of aboveground biomass was higher than that of underground,and the growth of seedling was dominated by aboveground growth.4.The litter thickness had a significant effect on the germination time of Q.liaotungensis seeds.The earliest germination when the litter thickness was 0 cm.The longer the litter thickness was,the longer the initial germination time was.The litter thickness had a significant effect on seed germination at the bottom.The final germination rate and germination potential of the seeds was significantly reduced,germination rate is only 41.8%,37.3% and 34.0%.And the root length,stem length and biomass of the seedling were significantly reduced.The greater the thickness was,the smaller the germination rate and the biomass were.The inhibition in germination of Q.liaotungensis seeds increased significantly when lay the litter in the bottom,and the greater the thickness,the more obvious inhibition.Water immersion liquid of different litter type had no significant influence on Q.liaotungensis seed germination and the early growth of seedlings.