红树植物白骨壤叶片衰老过程的氮磷内吸收变化研究

Resorption Efficiencies of Nitrogen and Phosphorus of Leaves During Senescence for Two Growth Forms of Avicennia marina

对广西北海大冠沙两种生长型（矮型：成熟林树高〈1．5m；过渡型：成熟林树高1．5—2m）的红树植物白骨壤（Avicennia marina）成熟叶和衰老叶的N、P含量、N：P比及内吸收率进行研究．结果表明：（1）两种生长型白骨壤成熟叶具有较高的N含量，分别为（20．45±1．10）mg／g和（22．25±1．12）mg／g；V含量分别为（1．42±0．03）mg／g和（1．31±0．03）mg／g；叶片衰老过程中，N、P含量明显下降；（2）叶片衰老过程中，N：P有增加的趋势；两种生长型成熟叶的N：P分别为14．41±0．85和16．97±0．86，显示两种生长型白骨壤均为N、P共同限制；（3）两种生长型白骨壤的N、P内吸收率在60％以上，内吸收率的高低与生长型没有明显关系．

Nitrogen and phosphorus concentrations, N： P ratio and nutrient resorption efficiency of leaves during senescence for two growth forms （ a dwarf form with tree height of below 1.5 m, and a transition form with tree height from 1.5 m to 2 m at maturity） of Avicennia marina were studied at Daguansha,Beihai,Guangxi. The results showed as follows： （ 1 ）Mature leaves had the relatively high N concentration,with （20.45 ± 1.10） mg/g for dwarf form and （22.25 ± 1.12） mg/g for transition form; P concentration of mature leaves was （ 1.42 ±0.03） mg/g for dwarf form and （ 1.31±0.03） mg/g for transition form,respectively; N and P concentrations decreased with leaf senescence. （2） N： P ratio increased with leaf senescence, N： P ratio of two growth forms was 14.41 ± 0.85 and 16.97± 0.86, respectively. （3） Resorption efficiency of N or P was above 60% , and there was no significant effect of growth form on resorption efficiency.