【作者】 陈琳；

【导师】 曾杰；

【作者基本信息】 中国林业科学研究院 ， 森林培育， 2010， 硕士

【摘要】 苗期营养诊断与施肥研究对于指导壮苗培育,从而提高苗木质量和造林成活率至关重要;氮素是植物体内分布最广的营养元素之一,植物氮素需求以及氮素施用的有效性一直是植物营养学家或生理学家的研究重点。西南桦是我国热带、南亚热带地区大规模发展的一个珍贵乡土阔叶树种,其养分需求尚未见报道。因此,本研究进行了西南桦苗期大量元素的缺素试验,并应用指数施肥法进行了西南桦苗期氮素施肥试验。通过叶片的症状观察、生长调查、光合色素测定以及叶片养分分析,探究西南桦苗期叶片主要营养元素的缺素症状以及各种大量元素缺乏对西南桦幼苗生长及养分状况的影响;分析了不同氮素供应水平下西南桦幼苗生长及全株养分的动态变化,并应用临界浓度法和养分供应量与生物量及养分的关系模型确定西南桦幼苗的适宜施氮量;旨在为完善西南桦育苗技术,促进西南桦人工林持续、健康发展提供理论依据。1.以平均高度约14.5cm的西南桦组培苗为材料,设置全素（Control）、缺氮（-N）、缺磷（-P）、缺钾（-K）、缺钙（-Ca）、缺镁（-Mg）和缺硫（-S）等7个处理,采用砂培法开展西南桦苗期缺素试验。结果表明:（1）-N、-K和-Mg幼苗的叶片症状最为明显,表现出叶片黄化、褐斑、叶片卷曲或脉间失绿等。（2）-Mg和-S处理对西南桦幼苗的各生长指标影响相对较小,而其他缺素处理幼苗的高、地径、分枝数、叶面积和生物量与对照相比均显著下降,根冠比则明显升高。（3）缺磷对西南桦幼苗的光合色素的影响不显著,而其他各缺素处理均导致西南桦幼苗的光合能力显著下降。（4）应用向量分析揭示出在各种缺素处理下,西南桦幼苗中各养分元素间存在明显的协同与拮抗作用。2.以平均高度约4cm的西南桦幼苗为材料,设置0、50、100、200、300、400、600 mgN·株^-1等7个氮素处理,运用指数施肥法开展西南桦幼苗氮素施肥试验。结果表明:（1）不同氮素处理西南桦幼苗的地径、高、生物量以及全株N、P、K含量均随着时间的变化呈指数递增,而根冠比基本呈递减趋势;不同处理西南桦幼苗全株P浓度随着时间的变化一直增大,而全株N和K浓度则先下降后上升或一直呈上升趋势。（2）各处理间西南桦幼苗的地径、高、生物量以及叶面积差异显著,200 mgN·株^-1是满足西南桦幼苗生长的临界点。（3）西南桦幼苗对N、P、K的需求程度不一致,全株N和K浓度在施氮量大于300 mg·株^-1时趋于稳定,叶片N和K浓度在施氮量大于200 mg·株^-1以后仍持续增加,而全株和叶片P浓度在施氮量大于100 mg·株^-1时即趋于稳定,表明幼苗对P素的需求远远小于其对N和K素的需求。（4）综合采用临界浓度法以及养分供应量与生物量和养分状况的关系模型,确定出西南桦幼苗的适宜施氮范围为200～400 mgN·株^-1,说明西南桦是一个速生、喜肥的树种。更多还原

【Abstract】 Nutrient diagnosis and fertilization for seedlings plays an important role in guiding to grow robust seedling, thus improve seedling quality and enhance survival rate of plantations. The requirement and efficiency of nitrogen in plants has always been a focal issue of nutritionists and physiologists since nitrogen is one of the elements widely distributed in plant. Betula alnoides Buck. -Ham. ex D. Don is a valuable indigenous hardwood species with large-scale development in tropical and warm subtropical areas, while less study has been reported on its nutrient requirement and fertilization. Therefore, trials of macronutrient deficiency and nitrogen exponential fertilization were conducted for its seedlings. We determined the responses of B. alnoides seedlings to deficiencies of these nutrients in terms of foliar symptoms, growth attributes, pigment composition concentration and mineral element contents, examined the growth and nutrient dynamics of B. alnoides seedlings under different nitrogen addition levels, and to determine the optimum nitrogen amount based on critical level method and the relationship between nutrient supplied quantity, biomass and nutrient condition. The findings provide a theoretical foundation for plantation forestry of B. alnoides and optimizing techniques for growing its seedlings.Macronutrient deficiency trial was carried out using healthy tissue cultured seedlings of B. alnoides with almost uniform height of 14.5 cm in sand culture with seven treatments: i.e., complete nutrient mixture （Control）, minus nitrogen （-N）, minus phosphorus （-P）, minus potassium （-K）, minus calcium （-Ca）, minus magnesium （-Mg）, and minus sulfur （-S） nutrient solutions. It was indicated that: （1） The foliar symptoms of no-N, no-K, and no-Mg seedlings were most apparent including leaf discoloration, bronze patches, leaf twisting, and interveinal chlorosis; （2） Apart from no-Mg and no sulfur （no-S） treatments, seedlings lacking other nutrients showed significant decreases in the height, root collar diameter, number of branches, leaf area as well as biomass of B. alnoides seedlings, but an increase in root/shoot ratio; （3） Phosphorous deficiency had no significant effect on all fractions of pigments, while the other nutrient deficiency treatments resulted in significant reductions of photosynthetic ability of seedlings; and （4） Vector analyses showed that there was obvious synergism or antagonism between different nutrients in B. alnoides seedlings under different treatments of nutrient deficiency.An exponential fertilization trial was conducted with seven dose levels involved (applying a total of 0, 50, 100, 200, 300, 400, 600 mg N seedling^-1 in the experiment), using healthy seedlings of B. alnoides with almost uniform height of 4cm. It was showed that: （1） The root collar diameter, height, biomass and whole plant nutrient contents of all nitrogen treatment seedlings followed an exponential function as the time advanced, while the root and shoot ratio gradually reduced; As for the whole plant nutrient concentrations, P concentration increased with time, while N and K concentrations decreased followed by increasing or consistently raised; （2） There were significant differences in the root collar diameter, height, biomass and leaf area of B. alnoides seedlings between treatments, and 200 mg N seedling^-1 was the critical amount meeting growth of B. alnoides seedlings; （3） The extent of requirements for N, P and K were different, the leaf and whole plant phosphorus concentrations became stable when nitrogen supply was more than 100 mg N seedling^-1, whole plant N and K concentrations were stable as nitrogen supply more than 300 mg N seedling^-1, while leaf N and K concentrations kept on increasing when nitrogen supply more than 200 mg N seedling^-1, suggesting that the requirement for P was less than N and K; and （4） Based on critical level method and relationship between nutrient supply and biomass and nutrient conditions, it could be inferred that 200 - 400 mg N seedling^-1 was the optimal nitrogen amount for B. alnoides seedlings, indicating that B. alnoides is grow-fasting and fertilizing species.更多还原