氮磷添加对巨桉幼苗生物量分配和C:N:P化学计量特征的影响

Effect of nitrogen and phosphorus fertilization on biomass allocation and C:N:P stoichiometric characteristics of Eucalyptus grandis seedlings

巨桉(Eucalyptus grandis)是一种优良的速生用材树种,了解氮(N)和磷(P)对巨桉生长、养分限制、化学计量特征的影响对于科学合理施肥具有重要意义。该实验以巨桉无性系组培苗为研究对象,通过在酸性紫色土中设置不同施N或施P梯度,研究巨桉幼苗各器官(根、茎、叶)生物量及碳(C)、N、P的分配和化学计量特征以及巨桉生长的养分限制状况。结果表明:施N处理对巨桉根茎叶及总生物量的影响极显著,增加了地上部分的生物量比例而显著降低了根系的生物量比例;施P对巨桉幼苗总生物量影响不显著,但显著提高了根的生物量分配比例,对茎和叶的生物量分配没有显著影响。施N或施P显著改变了巨桉幼苗的N、P含量和化学计量比,同时也显著影响了土壤与植物N:P的关系。施N可以促使酸性紫色土条件下巨桉对N的吸收而抑制对P的吸收,施P则促进巨桉幼苗对P的吸收。施N对巨桉幼苗根茎叶的C、N、P分配特征有极显著影响,而施P对巨桉幼苗根茎叶的C、N、P分配没有显著影响。施N极显著降低了巨桉幼苗N的利用率,显著提高了P的利用率,而施P处理极显著降低了巨桉幼苗P的利用率。从巨桉生物量沿施肥梯度和N:P的变化规律可以判断,当叶片N:P<15时,巨桉的生长主要受到N的限制作用。施N可以显著地提高根茎叶的N:P比值,缓解巨桉缺N的现象,施P则进一步加剧了N元素的缺乏。

Aims Eucalyptus grandis is an excellent, fast-growing timber species. It is important to understand the effect of nitrogen and phosphorus addition on E. grandis growth, nutrient limitation and stoichiometric characteristics. Our objectives are to test 1） biomass of organs （roots, stems and leaves） and allocation proportion, 2） C, N and P content and allocation in different organs and 3） elements that restrict the growth ofE. grandis as well as N and P use efficiency and C：N：P stoichiometry. Methods We grew E. grandis clone tissue culture seedlings using a pot experiment with acidic purple soil and N and P fertilizer additions. We measured the biomass and C, N and P content of roots, stems, leaves and soils. Important findings Roots, stems, leaves and total biomass orE. grandis seedlings were significantly affected by application of N, which increased the aboveground biomass ratio and significantly reduced the root biomass ratio. Total biomass was not significantly affected by application of P, root biomass allocation ratio increased significantly and stem and leaf biomass allocation were not significant affected. N or P fertilization significantly changed N and P content and the stoichiometric ratio, as well as significantly affected the soil and plant N：P relationship. N fertilization can promote N uptake and inhibit the absorption of P in acid purple soil, and then P fertilization can promote P uptake ofE. grandis seedlings. C, N and P distribution in roots, stems and leaves were significantly affected by N fertilization while not significantly affected by P fertilization. N-use efficiency was reduced and P-use efficiency improved significantly by N addition; however, P-use efficiency was reduced significantly by P addition. N：P of roots, stems and leaves can be significantly improved by N fertilization to alleviate the phenomenon of lack of N, but it is further exacerbated by the lack of N element by P fertilization.