Growth Characteristics And Main Influence Factors Of Quercus Wutaishanica Seedlings

Quercus wutaishanica is one of the advantage of tree species and zonal group of treespecies in our country’s loess plateau,which has important effects on the construction of plantcommunity, soil and water conservation,ecological regional security and so on. There are twokinds of regeneration methods including asexual and sexual reproduction for Q. wutaishanicaforest. Sexual reproduction is the basic way of breeding population to maintain the geneticdiversity, the natural regeneration has important significance on the species propagation andnatural recovery for secondary Q. wutaishanica forest. Seedling stage is the most vulnerableperiod in population growth and development process, which decides the success or failure ofpopulation reproduction。Water, illumination, temperature difference and so on of abioticfactors, will affect the seedling germination, growth and survival. To understand the laws of Q.wutaishanica seedling growth and sprout, we took Q. wutaishanica seeds as object, simulatedthe natural habitat of Q. wutaishanica forest, through the method of field experiment,weresearch the seedling growth rule as well as temperature, moisture, illumination and so oninfluence on seedling growth. The purpose of the research was to provide the basis for Q.wutaishanica secondary forest in the loess plateau.The main results were as follows:1. In natural growth conditions, the seedlig emergence rate was greater in early period. Intemperate sub-humid climate conditions, April28th to June28th is the main period of Q.wutaishanica seedling emergence. In the height growth process, the height growth rule was inline with the "S" type, the fastest period of annual seedling height growth in the LoessPlateau was in late spring to early summer. The growth law of aboveground biomass,underground biomass and total biomass conforms to "S" type curve. In terms of componentsseedling biomass, underground part root was greater than leaf wilted. Root-shoot ratio was thebiggest when20days after sowing, then decreased. In terms of components seedling biomass,underground biomass of seedling was greater than aboveground.2. Different covering thicknesses had significant impact on seedling germination rate(P<0.05),covering is useful to seedling germination; The covering depth had no significanteffect on the period of seedling growth,such as seedling height, leaf area and seedling number.Sowing date had no significant influence to seedling height and leaf number but had a significant effect to leaf area of seedlings when the seeds were sowed on surface.Characterized by the leaf area was greater sowed in November1than seedling sowed inDecember10. The interaction of covering thickness and sowing time had no significant effecton seedling emergence and growth.3. Moderate shade was advantageous to the Q. wutaishanica seedling unearthed andgrowth. Different shading treatments of seedling germination rate and vigor index weresignificantly different. Seedling emergence was best in45%shading, seedling vigor index in74%shading was significantly greater than no shading. Excessive shading and intense lightwere not conducive to seedling unearthed; Different degrees of shadinghad a significant effecton seedling height, main root length, total dry weight, leaf number, specific leaf area and rootcap ratio. The seedling height, specific leaf area and root cap ratio increased significantly withthe increase of shading degree, while the seedling root length, dry weight and total leafnumber decreased obviously with the increase of shading degree. Visibly, shading wasadvantageous to the seedling growth of seedling height, leaf area and specific leaf area; Whilethe greater of the degree shading was, the less favorable to elongation of seedlingunderground root and accumulation of organic material.4. Shading reduced the light compensation point, light saturation point and darkrespiration rate of the seedling, which improved the efficiency of light quantum. Under shadeenvironment, seedling enhanced ability to capture the light, improved the use efficiency inweak light.condition. The seedling photosynthetic rate curve was obsequent "J" type.Different shading treatments affected the maximum light intensity of seedling netphotosynthetic rate, That was to say, under different light environment, light saturation pointsof seedlings were different. As shading degree increasing, the seedling light saturation pointdecreased; Excessive shading weakened the photosynthesis of plants, strong light was alsounfavorable to the photosynthesis.So we could know that shading would reduce the lightsaturation point. Visibly, moderate shading was conductive to photosynthesis and theaccumulation of organic substance for Q. wutaishanica seedling; The seedlings could reducethe light saturation point to adapt to the weak light conditions and grow normally under shadeenvironment. So it was concluded that Q. wutaishanica seedling had certain ability on shadetolerance.