摘要
由于NH+ 4 N和NO-3 N形态的差异 ,二者对树木养分吸收和生长发育的影响不同 .树木常表现出对NH+ 4 N和NO-3 N的选择性吸收 ,树种对NH4+ N和NO-3 N吸收的偏好特性可能与生长地的土壤pH有关 .来自于酸性土壤的树种通常具有喜NH+ 4 N的特性 ,而来自于中性或碱性土壤的树种常表现出喜NO-3 N的趋势 .由于NH+ 4 N和NO-3 N所带电荷的差异 ,通常NH+ 4 N有利于阴离子的吸收 ,而NO-3 N则促进阳离子的吸收 .在有些情况下 ,NH+ 4 N会抑制NO-3 N的吸收 ,但抑制的机制目前还不清楚 .树木吸收NH+ 4 N时 ,引起根际pH下降 ,相反吸收NO-3 N时根际pH升高 .根际 pH变化可以改变土壤养分的有效性 ,并影响树木对养分的吸收利用 .树木对NH+ 4 N和NO-3 N的生长反应不同 ,有些喜NH+ 4 N的针叶树在供应NH+ 4 N时生长较好 .多数植物在同时供应NH+ 4 N和NO-3 N时生长量最大 ,有些树种在同时供应NH+ 4 N和NO-3 N时也表现出最高的生长 ,但对于树木类似的研究还少 。
Forest tree species take up both NH 4 +-N and NO 3 --N forms of nitrogen (N) during their growth. However, the effects of N form on nutrition uptake and tree growth are different due to the different N forms. Generally, trees show preference to N source, and most conifers prefer to NH 4 +-N while the preference to N form of broadleaved trees is unclear. The preference may be correlated with the pH value of the site on which the trees grown. The trees grown on acid soil generally appear preference to NH 4 +-N while trees grown on litmusless or alkaline soil prefer to NO 3 --N. Fungus also can alter the tree uptake characteristic to NH 4 +-N and NO 3 --N. In some species, the NO 3 --N uptake capacity increased remarkably while uptake capacity of NH 4 +-N keep consistent when fungus were inoculated. NH 4 +-N and NO 3 --N have different effects on other nutrient ions uptake because of the difference charge of NH 4 +-N and NO 3 --N. In general, NH 4 +-N accelerates the anion absorption while inhibits cation absorption. The effects of nitrogen forms on nutrition uptake are related with not only the charge of NH 4 +-N and NO 3 --N, but also the restrain effects among other ions. Sometimes, NH 4 +-N inhibits NO 3 --N uptake, but the mechanism is not very clear now. The form of which nitrogen is taken up by trees will induce the change of rhizospheric pH value. Uptake of NH 4 +-N results in the decrease of rhizospheric pH value. Contrary, uptake of NO 3 --N will cause the increase of rhizospheric pH value. The change of rhizospheric pH value will affect nutrient availability and thus affect nutrition uptake and utilization by trees. Trees grow differently after NH 4 +-N and NO 3 --N uptake. When supplied with NH 4 +-N, some confers that prefer to NH 4 +-N grow better while a few ammonium-preference conifers hardly show the better growth. Nevertheless, most plants grow better when both forms of N supplied simultaneously than either of N source supplied alone. For few similar studies were carried out with tree species, it needs to do more researches.
出处
《应用生态学报》
CAS
CSCD
2003年第11期2044-2048,共5页
Chinese Journal of Applied Ecology
基金
国家自然科学基金重点资助项目 (3 0 13 0 160 )
关键词
树木营养
硝态氮
铵态氮
根际PH
Tree nutrition, Nitrate, Ammonium, Rhizosphere pH
