氮素形态处理下水曲柳幼苗养分吸收利用与生长及养分分配与生物量分配的关系

Relationships between nutrient uptake,use efficiency and growth, and between nutrient partitioning patterns and biomass partitioning patterns in Fraxinus mandshurica seedlings supplied with different ratios of nitrogen forms

森林土壤中NO-3-N和NH+4-N的比例不平衡,造成森林树木对养分的吸收与利用、生长以及生物量分配格局发生变化。采用沙培技术,以不同NO-3-N和NH+4-N的比例对水曲柳播种苗木进行处理,研究养分吸收利用与生长的关系以及养分分配格局与生物量分配格局的关系。实验结果表明,虽然水曲柳幼苗偏好NO-3-N,但NNUR、NPUR、NUE、PUE、RGR、NAR以及单株总生物量均没有随NO-3-N的比例增加而增加。在8～9月份水曲柳幼苗生长旺盛时期,NNUR和NUE之间以及NPUR和PUE之间的关系显著,而在9～10月份这两组关系不显著。在水曲柳旺盛生长的8～9月份,NUE和PUE对水曲柳幼苗的NAR具有很大的影响,而在生长较弱的9～10月份,这两者对其NAR影响不大。在8～9月份和9～10月份两个时段内,NUE和RGR之间以及PUE和RGR之间的关系非常显著。在8月份和9月份,在不同氮素形态处理下,水曲柳幼苗体内的氮分配格局决定了其生物量的分配格局,而磷分配格局与生物量分配格局无关。

In forest soils, there are often imbalance between nitrate and ammonium,resulting in changes in nutrient uptake and use by forest trees, tree growth, and biomass partitioning pattern. In this present paper, sand culture technique was used Relationships between Nutrient Uptake,Use Efficiency and Growth, and between Nutrient Partitioning Patterns and Biomass Partitioning patterns in Fraxinus mandshurica Seedlings Supplied with Different Ratios of Nitrogen Forms. Seed seedlings were planted in plastic barrels (d. 30 cm, h. 27 cm), 4 seedlings per barrel. After a month the seedlings were supplied with complete nutrients, these seedlings were treated with nitrogen forms:0 NO-_3-N∶100%NH+_4-N, 25%NO-_3-N∶75%NH+_4-N, 50%NO-_3-N∶50%NH+_4-N, 75%NO-_3-N∶25%NH+_4-N, and 100%NO-_3-N∶0%NH+_4-N. The plants were harvested on 3 August, 12 September, 2 October. The results showed that NNUR of seedlings supplied with 75% NO-_3-N was the highest during the period from 3 August to 12 September. In the same period, NNUR reduced 40% when seedlings were only supplied with NO-_3-N. NNUR of seedlings supplied with 75% NO-_3-N was 0.34 mg/(g DW·d) during the period from 12 September to 2 October, but when seedlings were only supplied with NO-_3-N, NNUR increased about 3 times. During the two periods, NPUR of seedlings supplied with 50% NO-_3-N reached the highest value, and changes of NUE and PUE were irregular. As time changed, for all treatments of nitrogen forms, nitrogen partitioning to roots increased, but nitrogen partitioning to stems didn't changed significantly, nitrogen partitioning to leaves reduced. Phosphorus partitioning to roots, stems and leaves changed irregularly, but when plants were harvested on 3 August, phosphorus partitioning to roots reached the lowest value, and the partitioning to leaves reached the highest value. When seedlings were supplied with nitrogen forms, the growth of their organs changed as the ratios of NO-_3-N to NH+_4-N changed. At the three time plants were harvested, SLA increased as the ratios of NO-_3-N to NH+_4-N increased from 0 to 25%. But when ratios of NO-_3-N to NH+_4-N increased to 100%, SLA reduced. For all treatments, LMR reduced as time changed, and RMR increased. During the two periods (from 3 August to 12 September and from 12 September to 2 October), NAR of seedlings supplied with 50% NO-_3-N reached the highest peaks. From 3 August to 12 September, RGR of seedlings supplied with 50% NO-_3-N reached the highest peaks, but from 12 September to 2 October, RGR was the highest when seedlings were supplied with 25% NO-_3-N. For the seedlings harvested on 3 August and 12 September, total biomass of a single seedling supplied with 50% NO-_3-N was the highest. But when seedlings were harvested on 2 October, the total biomass didn't change significantly as ratios of NO-_3-N to NH+_4-N changed.