【作者】 白尚斌；

【导师】 王政权； 张裕农； 郎南军；

【作者基本信息】 东北林业大学 ， 森林培育学， 2002， 博士

【摘要】 N和P是树木的必需营养元素，树木体内缺乏势必导致生长和发育受阻。在自然条件下，树木体内N、P主要通过根系获得，自然环境中这两种养分的供应状态极大地影响树木的生长。然而，在N和P供应不适宜时，树木能够采取相应策略进行自我调整，以适应环境胁迫，从而保证其生长和发育的正常进行。因此，研究树木在不同N和P供应条件下的适应机制对于提高树木的生产能力具有重要的理论意义。 树木的生长、林分的生产力与土壤养分具有密切的关系。如何在土壤养分贫瘠的地区进行森林培育一直是森林培育学研究的重点。西南桦和思茅松是我国西南林区重要的工业用材树种，主要分布区的土壤为红壤、棕红壤或山地黄壤，其N和P营养缺乏。它们长期生长在该土壤上，对N和P缺乏具有一定的适应能力，而北美红杉是外来树种，对西南林区N和P缺乏的土壤条件的适应情况尚不清楚。如何更好地培育这三个树种、提高其木材生产能力、缓解目前我国木材供应紧张的局面具有重要的现实意义。 在本论文研究中，采取了温室栽培试验和野外栽培试验相结合的方法。在温室栽培试验中，以一年生苗为研究对象，以砂为栽培基质，分别设置8个不同的N、P供应水平（0％、25％、50％、75％、100％、150％、200％和300％，以Hoagland溶液为100％，并作为对照）和5个不同的N素形态比例（NO₃^-／NH₄⁺的比例分别为：100:0、75:25、50:50、25:75和0:100）。野外栽培试验中，在采伐迹地上种植一年生苗木，西南桦和思茅松的株行距为1.5×1.5m，北美红杉的为2×2m。取样测定各项指标。根据试验结果，得出以下结论： （1）树木幼苗所需营养元素N、P的供应受限制时，不能满足幼苗潜在生长对养分的需求，幼苗生长会延缓；N和P供应超过幼苗代谢和生理系统的应付能力时，也会对幼苗产生伤害。在适宜的N、P养分供应水平（100％供应水平）下，幼苗生长表现最好；N、P养分供应不足或过量时，幼苗生长较差。 （2）N供应不足时，幼苗将更多的生物量分配到地下以扩大根系的生长；在N供应过量时，西南桦和北美红杉两树种减小地下部分碳水化合物的分配比例，而思茅松几乎不受影响。在低P供应时，幼苗增加生物量向地下部分的分配比例，供P过量可能引起N或其它元素的相对不足，从而导致生物量分配到根系的比例增加。在野外试验中，除西南桦的根系生物量与其P含量的关系之外，根、茎、叶生物量均与各自的N和P含量有明显的正相关关系。 （3）在低N供应条件下，幼苗细根的特定根长增加尤为明显。N供应过量时，细根的特定根长减小。低P供应引起细根的特定根长增加，从而有利于幼苗吸收更多的养分和水分，保证生长和发育的正常进行。低P供应使西南桦和北美红杉幼苗的叶面积减少，而供P过量也会使西南桦叶面积变小。 （4）低N供应时，N分配到根系的比例增加。随着供N水平的提高，根系P的浓度降低，K浓度有减少的趋势，Ca浓度增加；叶中P浓度则增加，叶中K浓度减少。过量供N使叶中Mg、Zn和Mn的浓度降低，但这些元素在茎中变化不明显。低P供应条件下，随供P水平的提高，根系P浓度增加，P在根系中的分配比例降低；叶中P的浓度增加，分配比例也增加。随供P水平的提高，根系N浓度下降，叶中N浓度则增加，但P过量后，反而降低。P供应不足时，根系K浓度有下降的趋势。 〔5)西南烨、思茅松和北美红杉根际pH与非根际pH相比二有所下降，根际水解N和有效P的含量均得到了提高，尤其是根际有效P提高的更明显。根际N和P养分的有效性可以促进根系和叶片内部养分的增加。 （6）低N供应引起幼苗叶中叶绿素含量降低，同时光合速率下降。随N水平的增加，叶绿素含量增高，增加了潜在的光合能力。当超过正常供N水平后，光合速率并不随供N水平提高而呈现相应的增加趋势。3个树种叶绿素含量与光合速率在低P供应时均降低，在高P供应时，也出现叶绿素含量和光合速率下降趋势。 （7）不同 NO。－／NH。”比例处理试验表明，西南烨和北美红杉幼苗表现出了喜 NH。”的特性，而思茅松幼苗则表现出喜NO。－的特性。但是西南烨和北美红杉在完全供NO。”处理下仍能较好的生长。西南样和思茅松幼苗对NH4”的吸收会减少K、Ca、Zn和Mn的吸收，而增加 Mg和 Fe的吸收，而北美红杉幼苗对i”的吸收会减少 K、Ca、Mn和 Mg的吸收，而增加 Zn和 Fe的吸收。西南棋和北美红杉叶中叶绿素含量均在NO。WH。”比例为so：SO（％）时最低，以NH。”为主要N源时明显增加。思茅松幼苗叶绿素含量和光合速率在NO；－／NH。”比例为50：50（o）时最高，在完全供NO。“处理的要高于完全供NH。”的处理。幼苗吸收NO／与Nfu“引起了其根际pH的变化存在差异。完全供NO。“处理的3个树种根际pH均得到上升，而完全供M山”处理的根际pH均下降。但完全供NO。’处理下根际pH上升的幅度小于完全供N山”处理的下降幅度。 总之，在低N、P供应时，树木以减少地上部的生长，扩大地下部的生长来获取受限制的N、P资源。因此，在云南山地红壤或山地黄壤严重缺N、缺P条件下进行森林培育的实践中，为使人工林能够得到迅速健康的成长，苗圃育苗?更多还原

【Abstract】 Nitrogen and phosphorus are the very important elements that are vital to plants. In plants, ’many chemicals that contain nitrogen and/or phosphorus, such as proteins, phospholipids and nucleotides, play very important roles in physiology and biochemical functions. The deficiency of nitrogen and phosphorus in plants must induce the impedance of growth and development, and reduce plant products. Plants get nitrogen and phosphorus from soils by the activities of roots under natural conditions. Therefore, the environmental supplies of nitrogen and phosphorus to plants affect plant products to a great extent. However, plants adapt to environmental stresses by many mechanisms, ensuring their normal growth and development. Studies on the adaptive mechanisms to nutrition environment are of significance to plant physiology and practice.Tree growth and stand productivity are greatly related to nutrient availability in soils. This has been very important for silviculture to cultivate trees under the deficiency of nitrogen and phosphorus. Betula alnoides and Pinus kesiya are two kinds of important woody species for industry in southwestern China. At present, the soils in the distribution regions of B. alnoides and P. kesiya are red soil, brown soil and yellow mountain soil. Nitrogen and phosphorus is deficient in these soils. The two species have been adaptive to the deficiency of nitrogen and phosphorus because of their long habit. Sequoia sempervirens, coming from USA, is not native to southwestern China. Its adaptation to deficiency of nitrogen and phosphorus in soils of southwestern China is still unclear. It is very important to cultivate the three species in order to improve their productivity and to resolve the current crisis of short supply of wood in China.In this present dissertation, experiments were carried out in greenhouse and in field. In greenhouse, one-year-old seedlings were potted in sand. The nutrient solution was prepared as Hoagland receipt. The concentration gradients were designed as follow: 0%, 25%, 50%, 75%, 100%, 150%, 200%, 300%, 100% as control. Five different ratios of NO3-/NH4+ were 100:0, 75:25, 50:50, 25:75, and 0:100. In field experiments, experimental materials were one-year-old seedlings planted in harvest areas: 1.5X1.5 m for Betula alnoides and Pinus kesiya, and 2 X 2 m for S. sempervirens. Then all indexes were determined from sample. The results suggested:(1) When seedlings were supplied with deficient nitrogen and phosphorus, growth of seedlings was slow; When supply of nitrogen and phosphorus to seedlings was over the metabolic and physiological capacity, oversupply of nitrogen and phosphorus did harm to seedlings. According to the results of the experiments under different levels of nitrogen and phosphorus, when the seedlings of B .alnoides, P. kesiya, and S sempervirens were supplied with normal levels of nitrogen and phosphorus, they grew well; when they were oversupplied with nitrogen and phosphorus or supplied with less nitrogen and phosphorus, they grewslowly.(2) When the seedlings of the three species grew under the conditions of deficient nitrogen, partitioning of biomass to roots was more in order to increase root growth. Biomass partitioning to roots was less when the seedlings of B.alnoides and S sempervirens were oversupplied with nitrogen, but biomass partitioning of seedlings of P. kesiya hardly changed. Biomass partitioning to roots increased when the seedlings of the three species were supplied with less phosphorus. Oversupply of phosphorus caused relative deficiency of nitrogen, leading to increase of biomass partitioning to roots. In field experiments, there were positive relationships between biomass of roots, stems and leaves with their own contents of nitrogen and phosphorus, but there was an exception of biomass of B. alnoides roots.(3) When the seedlings of the three species were supplied with less nutrients, these seedlings changed below-ground and above-ground structures by regulating partitioning of photosynthates between them, and utilize更多还原