Growth, accumulation and partitioning of biomass, C, N and P of Sophora davidii seedlings in response to N supply in dry valley of upper Minjiang River
Abstract:The dry valley of upper Minjiang River is generally noted for their low primary productivity which is due to a combination of low, unpredictable water supply and nutrient deficiency. How to improve the efficiency in using limited resources and restore vegetation is always the problem which troubled ecosystem managers. Sophora davidii is a native perennial shrub of arid valleys, which is often predominant on eroded slopes and plays a vital role in retaining ecological stability in this region. It has been found that S. davidii was better adapted to dry environment than other shrubs, prompting its use for reclamation of arid degraded lands. But the shrub exhibits weak regeneration with poor seedling emergence and early growth in the field. In order to explore whether or not N supply could enhance the adaptation ability of S. davidii seedlings to dry and infertile environment, we investigated the growth, accumulation and partitioning of biomass, C, N, and P, and nutrient (N and P) use efficiency of S. davidii seedlings under three different N supply regimes (0, 92, and 184 mg N·kg-1 soil)over one growing period. N supply dramatically influenced the growth, biomass and resources (C, N, and P) accumulation and partitioning, and nutrient use efficiency of S. davidii seedlings. The seedlings exhibited stronger responses to low N supply (92 mg N·kg-1 soil) than to high N supply treatment (184 mg N·kg-1 soil) in this study. Low N supply facilitated seedlings growth by increasing leaf number, basal diameter, root length, biomass production, C, N and P accumulation and absorption, and enhancing the use efficiency of other limited resources as P. Compared to control, however, low N supply did little effect on altering biomass, C, N and P portioning in seedlings components. On the contrary, high N supply treatment also increased leaf number, biomass and C, N and P accumulation relative to control, but significantly decreased root length, and altered more biomass and resources to above-ground, which strongly reduced the ability of absorbing water under drought condition, and thus which might deep the drought stress. The results suggested that appropriate N supply was seemed to enhance the ability that S. davidii seedlings adapted to the xeric and infertile environment by stimulating plant growth, increasing recourses accumulation, enhancing use efficiency of other limited resources, and balancing biomass and resources partitioning. Appropriate, Nsupply, therefore, would be recommended to improve S. davidii seedling establishment in this region, but excess N supply should be avoided.