J Plant Ecol ›› 2020, Vol. 13 ›› Issue (2): 204-212.DOI: 10.1093/jpe/rtaa001

• Research Articles • Previous Articles     Next Articles

Effect of nitrate supply on the facilitation between two salt-marsh plants (Suaeda salsa and Scirpus planiculmis)

Hua Ma1,2, Li-Juan Cui1,2,3, *, Xu Pan1,2,3, Wei Li1,2,3, Yu Ning1,2 and Jian Zhou4   

  1. 1Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China, 2 Beijing Key Laboratory of Wetland Services and Restoration, Beijing 100091, China, 3 Beijing Hanshiqiao National Wetland Ecosystem Research Station, Beijing 101309, China, 4 School of Nature Conservation, Beijing Forestry University, Beijing 100083, China

    *Corresponding author. E-mail: lkyclj@126.com
  • Received:2019-07-08 Revised:2019-12-21 Accepted:2020-01-06 Online:2020-01-07 Published:2020-04-01

Abstract:

Aims

In estuarine salt-marshes, nitrate supply and soil salinity, which are known as two main environmental drivers, simultaneously affect the interspecific interactions between plant species. However, to date, their interactive effects on interspecific interactions have not been closely examined for salt-marsh plant species.

Methods

Juvenile plants of Suaeda salsa L. (Chenopodiaceae) and Scirpus planiculmis Fr. (Cyperaceae) were grown in rinsed river sand to conduct a greenhouse experiment with three treatment categories: interspecific interaction (mixed culture or monoculture), three salinity levels (1, 50 and 100 mmol L−1) and three nitrate levels (0.5, 5 and 10 mmol L−1). First, height and biomass of all plants were measured. Then, the growth data, relative interaction index and competitive important index of the two species were analyzed.

Important Findings

The interspecific interactions between S. salsa and S. planiculmis were facilitation across the salinity gradients. The promotion of S. salsa growth with high nitrate supply did not enhance the facilitative effect of the species, especially at low salinity. However, high nitrate supply significantly shifted the interspecific interactions of S. planiculmisfrom facilitation to competition at high salinity. Our results suggest that excessive nitrate application changes the prediction of the stress-gradient hypothesis along a salinity gradient, leading to collapse of the two species coexistence in the salt-marshes. These findings make a contribution to the understanding of how S. salsaand S. planiculmis, as well as salt-marsh communities, respond to the human modification of estuarine nutritional levels.

Key words: nitrate supply, salinity gradient, salt-marsh plants, facilitation, stress-gradient hypothesis

摘要:

在河口盐沼中,硝酸盐浓度和土壤盐分是两个主要的环境驱动因素,它们同时影响着植物物种之间的相互作用。然而,迄今为止,它们的交互作用对盐沼植物种间相互作用的影响还没有得到针对性的研究。在被漂洗过的河沙中种植盐地碱蓬(Suaeda salsa L.)和扁秆藨草(Scirpus planiculmis Fr.)的幼株,实验中设置三种处理:种间相互作用处理(混合培养或者单独培养)、三个盐度水平处理(1、50和100 mmol L-1) 以及三个硝酸盐水平处理(0.5、5和10 mmol L-1)。首先测量了所有植物植株的高度和生物量,然后分析了这两个物种的生长数据、种间相对关系指数和竞争重要性指数。在三个盐度处理中,盐地碱蓬和扁秆藨草的种间相互作用为种间促进。高浓度的硝酸盐促进了盐地碱蓬的生长,但并没有增强该物种的种间促进作用效果,特别是在低盐度处理中。然而,在高盐度处理中,高浓度的硝酸盐显著地将扁秆藨草的种间相互作用从促进转变为竞争。我们的结果表明,过量施用硝酸盐会在盐度梯度中改变胁迫梯度假说的预测,从而导致在盐沼中这两个物种共存的崩溃。这些发现有助于人们理解盐地碱蓬和扁秆藨草以及盐沼植物群落如何响应由人类活动导致的河口营养水平的改变。

关键词: 硝酸盐浓度, 盐度梯度, 盐沼植物, 促进作用, 胁迫梯度假说