Study On Effects Of Altitude On The Structure And Physio-ecological Characteristics Of Moso Bamboo Forest

In the dissertation,the author has investigated changes of main weather factors, soil properties,population structure,economic characters,photosynthetic physiology of Moso bamboo forest at different altitudes.The growth and regeneration characteristics,effects of main environmental factors and adaptive mechanism were also revealed.The main results were described as follows:1.With the increase of the altitude,Tair definitely decreased.When the altitude increased for 100m,there is no notable decrease range of temperature in three altitude grads among different seasons.RH has a bigger increment with the humidity increasing most obviously both in Autumn and Winter.PAR is also high in some scale.With the increase of altitude for 100m.Tair decreased at a range from 0.61℃to 0.69℃,RH increased at a range from 1.42%to 2.47%,and PAR increased at an extent from 23.61μmol·m^-2·s^-1 to 60.36μmol·m^-2·s^-1.The weather is more suitable for the growth of Moso bamboo forest when the altitude increased.2.At the same altitude,with the increase of soil depth,soil bulk density,total porosity,non-capillary porosity,capillary porosity,saturated water capacity,field water-holding capacity,clay and sand particle content increased,but silt content decreased.There existed a negative correlation between total porosity and soil bulk density.Altitude had no significant effect on soil bulk density,capillary porosity, field water-holding capacity.With the increase of altitude,total porosity, non-capillary porosity,saturated water capacity increased significantly.Particle composition of soil in different altitudes varied in such a sequence:sand＞silt＞clay particle.With the increase of altitude,clay and silt particle content decreased,but sand content increased gradually.3.There were a highly significant negative correlation among altitude and soil pH,total nitrogen and available nitrogen content,and a significant positive correlation between altitude and organic matter,but there was no significant effect on the contents of total phosphorus,available phosphorus,total potassium,and available potassium.There was a positive correlation between altitude and soil enzyme activities.At middle level of altitude,the great changes took place in phosphatase,urease and invertase.With the increase of altitude,protease activities slightly increased,and calatase activities also rise smoothly.Soil physical properties had no significant effect on soil enzyme activities.Soil enzyme activities had significant or definitely significant correlation with organic matter,total nitrogen and available nitrogen,and no significant correlation with total phosphorus, available phosphorus,total potassium,available potassium.There was a significant correlation among soil enzyme activities with specifiying and concomitant characteristics.4.With the increase of altitude,the density,DBH,height under branch and total height increased significantly,but uniformity and evenness decreased significantly. Individual growth showed egoistic behavior to some extent.With increasing altitude, the time of beginning and termination of shooting were backward,whereas,the time of duration and degenerated shoot ratio decreased.The duration of earlier stage and later stage of shoot emergence was similar both at middle and lower altitude,but longer than that of at higher altitude.Height growth period from shoot to young culm could be divided into four stages,such as initial stage,rising stage,rapid growth stage and telophase,which showed a rhythm of slow growth followed by fast growth.With the increasing altitude,the difference of height growth existed mainly in the increase of mean height growth increment at rapid growth stage.The height growth period of shoot at the same stage was delayed and the duration of height growth shortened.Among all shooting stages,the earlier stage was longest,and the later stage was shortest at the same altitude.The high growth nearly ended in the same time which exhibited ecological adaptive mechanism of altruism.5.There was a negative correlation between altitude and cell wall thickness at DBH,wall thickness ratio.With the increasing altitude,the weight and timber volume of Moso bamboo with the same DBH decreased,while the timber yield and volume increased.There was no significant difference in timber volume between middle and higher altitude due to multiple changes of structure factors of bamboo stands.With the increasing altitude,taper increased greatly.The corresponding table was established which could reflected the relationship between timber volume and DBH of bamboo in different altitude grads.With increase of altitude,the yield and quality of shoots enhanced.Eeffects of altitude on the quality of bamboo shoots depended on the rise of total sugar content,soluble sugar content,P,Fe,water content and edible proportion of shoot.But heat,fibre content,ash content and Ca all decreased with increasing altitude.6.With the increasing altitude,the leaf chlorophyll content of Moso bamboo with different ages represented a small increasing trend,and Pn also increased in the sequence of Summer＞Autumn＞Winter＞Spring.At lower and middle altitude,Pn showed a double-peak curve,and midday depression of photosynthesis rate took place.But at higher altitude,Pn showed a single-peak curve in Spring and Autumn. Tr showed a single-peak curve in Spring,Autumn and Winter,but double-peak curve in Summer and its value was in a sequence of Summer＞Autumn＞Spring＞Winter. With the increasing altitude,Tr decreased in Summer and Spring,but increased in Autumn and Winter.WUE increased in Summer and Spring,but did not significantly varied in Autumn and Winter.Seasonal drought could improve WUE.7.Main environmental factors that influenced photosynthetic rate were PAR, Tair and RH.There was a highly significant negative correlation between Tair and Ci and Cond.RH represented a highly significant positive correlation with Ci and Cond. PAR had a highly significant positive correlation between Pn,Tr and Vpdl,and a highly significant negative correlation between Ci.Environmental factors influenced Moso bamboo photosynthesis due to Cond variation.High temperature in Summer and seasonal drought in Autumn and Winter had significant effects on Cond and caused midday depression of photosynthetic rate decline by means of stomatal limitation.Seasonal variation of LCP was in the sequence of Spring＞Summer＞Autumn＞Winter,and that of LSP was in the sequence of Autumn＞Summer＞Winter＞Spring.With the increasing altitude,LCP and LSP both decreased.Seasonal variation of P_max was in the sequence of Summer＞Autumn＞Winter＞Spring.With the increasing altitude,annual average P_max increased.P_max and annual average P_max increased in Summer and Autumn,but decreased in Winter and Spring.AQY in Summer and Autumn was higher than that both in Winter and Spring.With the increasing altitude,seasonal drought and leaf aging in Spring were the main reason affecting AQY.