原始森林土壤NH_4^+/NO_3^-生境特征与某些针叶树种的适应性  

Soil NH_4^+/ NO_3^- nitrogen characteristics in primary forests and the adaptability of some coniferous species

作　　者：崔晓阳[1] 宋金凤[1] 

机构地区：[1]东北林业大学林学院,哈尔滨150040

出　　处：《生态学报》2005年第11期3082-3092,共11页Acta Ecologica Sinica

基　　金：国家自然科学基金资助项目(30371146;39770608)~~

摘　　要：在陆地生态系统中,生存地段的土壤养分环境构成了植物的“营养生境”。植物在长期进化过程中往往产生对原生营养生境的生态适应,其中对NH4+和NO3-两种无机氮源的吸收、利用特性便可能是这种适应的一个重要方面。由于硝化抑制(限制)或微生物对NO3-的强烈吸收、固持作用,酸性、弱酸性的原始森林土壤中NH4+含量大都远高于NO3-,从而形成了以NH4+占绝对优势的“氮营养生境”。很多针叶树种(尤其是演替晚期阶段占优势者)对其长期所处的NH4+优势生境产生了充分适应,以致对非还原态氮(NO3-)的吸收、利用能力严重下降。这些针叶树往往表现出典型的“喜铵性”,而在NO3-优势环境中则会引起氮代谢失调和生长下降。从氮同化酶、高耐铵性、根对NH4+和NO3-的相对吸收能力及NO3-吸收的反馈控制、养分关系与养分平衡、根部碳流失、光合作用及耐荫性等多方面阐述了喜铵针叶树适应的生理生化机制。这种生态适应可能是顶极森林群落维持长期稳定的重要机制之一,而采伐干扰后NO3-明显增加的立地条件则可能会导致喜铵的“原优势针叶树种”更新困难。在温带退化森林生态系统恢复与重建过程中,顶极针叶树种对NH4+营养生境的固有适应性是必须充分考虑的问题。In terrestrial ecosystems, soil nutrient regimes at a plant＇s living site generally represent the plant＇s “nutrition habitat”. Plant species frequently well adapt to their original “nutrition habitat” during a long process of evolution, and the apparent preference for ammonium or nitrate nitrogen source （NH4^＋ or NO3^-） might he an important aspect of the adaptation. Plants typically favor the nitrogen form most abundant in their natural habitats. Nitrate has been recognized as the dominant mineral nitrogen form in most agricultural soils and the main nitrogen source for crops, hut it is not usually the case in forest ecosystems. A large number of studies show that the “nutrition habitats” associated with primary forest soils are typically dominated by NH/rather than NO3^-, generally with N3^- content much lower than NH4^＋. Low levels of N3^- in these forest soils generally correspond to low net rates of nitrification. The probable reasons for this phenomenon include： （1） nitrification limitations and/or inhibitions caused by lower pH, lower NH/ availability （autotrophic nitrifiers can＇t successfully compete for NH＋ with heterotrophic organisms and plants）, or allelopathic inhihitors （tannins or higher molecular weight proanthocyanidins） in the soil; or （2） substantial microbial acquisition of nitrate in the soils which makes net nitrification rates substantially less than gross nitrification rates even though the latter are relatively high. Many coniferous species （especially such late successional tree species as Tsuga heterophylla, Pinus banksiana, Picea glauca, Pseudotsuga meziesii, Picea abies and etc. ） fully adapt to their original NH4^＋-dominated “nutrition habitats” so that their capacities of absorbing and using non-reduced forms of nitrogen （e. g. NO3^-） substantially decrease. These conifers typically show distinct preference to NH4^＋ and reduced growth due to nitrogen-metabolism disorder when NO3^- is the main nitrogen source. The physio

关 键 词：森林土壤 铵态氮 硝态氮 针叶树种 生态适应 生理生化机制 

分 类 号：S714[农业科学—林学]