Self-adaptability To Main Ecological Factors Of Oligostachyum Lubricum

Oligostachyum.lubricum, one of high quality and high-yield shoot use bamboo species with a long shooting period from May to October, has great value for cultivation and extension. To provide theoretical basis for promotion O.lubricum cultivation in regional scale, relationship between ramet component factors and organ biomass, phenotypic plasticity to the changes of population density were investigated, self-adaptability of O.lubricum to soil salt, water, N and P content were analyzed by determineing growth and physiological metabolism of ramet to salt, water and N, P stress. The main results were showed as follows:1. Relationships among ramet component factors and organ biomass of O.lubricumPresent above-ground biomass allocation pattern of 1-year-old O.lubricum ramets was stem(43.72%)﹥foliage(31.49%)﹥twig(24.79%) and that of 2-year-old ramets was foliage(46.35%)﹥stem(27.09%)﹥twig(26.56%). Increase of allocation proportion of foliage biomass was beneficial for O. lubricum to develop new habitat and consolidate present habitat. There were significant or very significant correlation between component factors and most component biomass of 2-year-old ramets. The total height(TH),height under branch(HB) and round of branchs(RB) were subordinate factors of the diameter at breast-height(DBH) of 2 year-old ramets. DBH had decisive effects on the biomass of each component and above-ground part of ramets and the relationships between them could be simulated with cubic function very significantly.2. Responses of O.lubricum phenotypic plasticity to the variation of population densityPrincipal component analysis of ramets component factors of O.lubricum in different ramet densities(17500²7500 stems·hm^-2, D1; 37500⁴2500 stems·hm^-2, D2; 55000⁶2500 stems·hm^-2, D3; 72500⁸2500 stems·hm^-2, D4) indicated that phenotypic vharacteristics was correlated most closely with ramet'stem, secondly it was twig and the next was foliage. Through path analysis we got the result that the phenotypic comprehensive scores in different ramet densities was: D3>D4>D2>D1. It was considered that the density of 55000⁶2500 stems ·hm^-2 was the density threshold value between cost and benefit of physiological integration and appropriate population density for growing of O.lubricum at the current DBH of ramets in experimental forest.3. Self-adaptability of O.lubricum to water stressThe variation of physiological metabolism in leaves of 2-year-old ramets planted in different soil water content for 56 days indicated that O.lubricum was injured seriously and died after stressed for 14 days in soil with less than 30% relative moisture content. Under 40%⁹0% relative moisture content, O.lubricum grew well and all physiological characteristics in leaves fluctuated and stabled at the level before treatment finally after changed for some days. Under root-flooding stress, O.lubricum had no stress reaction when stressed within 14days, and then injured more serious with the increasing of treated time untill died after treated for 14 days. O.lubricum had strong water self-adaptive capacity and exhibited some resistance to drought and flooding.4. Self-adaptability of O.lubricum to salt stressThe variation of physiological metabolism in leaves of 2-year-old ramets planted in different soil salinity for 45 days in summer(May to June) and winter(November to December) indicated that no seasonal variation in tolerance to low salinity(1‰²‰) existed, and O. lubricum seedlings under high soil salt concentration (3‰⁵‰) were injured more serious in summer than during winter under the same soil NaCl concentration. O. lubricum seedlings had higher salt tolerance in winter than in summer. so in order to improve survival rate, the best time of afforestation was autumn and winter.In summer, soil with 1‰²‰NaCl concentration was beneficial to growth of O.lubricum seedings. With the increasing of soil NaCl concentration in 3‰⁵‰, Na⁺ and Cl^- in all organs of O.lubricum ramets increased, K⁺ in root, culm and branch decreased and Ca²⁺ changed slightly, the ion content in leaf was higher than that in other organs, Chloroplast, vacuole and other organelles in leaves disintegrated and deformed gradually, the injury of O.lubricum ramets was more serious but was reversible. The ion leakage of leaf was more than 50% and leaf abscission was 47% under 6‰NaCl concentration stress for 15 days. Cell structure became fuzzy and organelles became degraded seriously in leaves treated by 6‰NaCl concentration for 45 days, so 6‰was the threshold concentration. With the enhancing of ion transporting ability from branch to leaves, O.lubricum stored more salt ion in leaves and could reduced salt ion content in palnt by leaf abscission, so salt-residence and salt-avoid both were mechanisms of self-adaptability for O.lubricum.5. Self-adaptability of O.lubricum to soil N, P contentThe relationships among soil and leaf N, P stoichiometric characteristics and chlorophyll content of O.lubricum planted in soil with different total N and P content which were achieved by adding different anount of NH₄NO₃ and NH₄H₂PO₄ indicated that soil total N concentration had significant positive correlation with leaf total N concentration and leaf N:P ratio, whereas soil total P concentration had no significant correlation with leaf total P concentration and leaf N:P ratio. Leaf N:P was the main factor that effect leaf chlorophyll content. The adequate supply of soil total N leaded to luxury uptake of N by leaf of O.lubricum. The growth of O. lubricum were limited by low soil total N concentration(421.76 mg·kg^-1) before N and P addition.