J Plant Ecol ›› 2020, Vol. 13 ›› Issue (6): 693-703.DOI: 10.1093/jpe/rtaa060

• Research Articles • Previous Articles     Next Articles

Ecophysiological responses of two poplar species to intraspecific and interspecific competition under different nitrogen levels

Yan Li1 , Jieyu Kang2 , Zhijun Li3 , Helena Korpelainen4 and Chunyang Li2   

  1. 1 Ecological Security and Protection Key Laboratory of Sichuan Province, Mianyang Normal University, Mianyang 621000, China, 2 Department of Ecology, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou 311121, China, 3 Key Laboratory of Protection and Utilization of Biological Resources in Tarim Basin of Xinjiang, College of Life Sciences, Tarim University, Alar 843300, China, 4 Department of Agricultural Sciences, Viikki Plant Science Centre, University of Helsinki, PO Box 27, FI-00014 Helsinki, Finland

    *Corresponding author. E-mail: licy@hznu.edu.cn
  • Received:2020-03-02 Revised:2020-07-29 Accepted:2020-08-21 Online:2020-08-27 Published:2020-12-01

Abstract:

Aims

Populus deltoides and P. euramericana are widely used in China as major forestry species. At present, little is known about their responses to nitrogen (N) deficiency when grown in monocultures or mixed plantations. The aim of this investigation was to analyze the growth, and morphological and physiological responses of P. deltoides and P. euramericana to different N levels under competition conditions.

Methods

We employed two Populus species (P. deltoides and P. euramericana) to discover how N deficiency affects plant traits under different competition types (P. deltoides × P. deltoides, intraspecific competition; P. euramericana × P. euramericana, intraspecific competition; P. deltoides × P. euramericana, interspecific competition). Potted seedlings were exposed to two N levels (normal N, N deficiency), and nitrogen- and competition-driven differences in growth, morphology and physiology were examined.

Important Findings

Under normal N conditions, interspecific competition significantly decreased the total root weight, root mass fraction (RMF), root–shoot ratio (R/S) and carbon/nitrogen ratio (C/N), and increased the leaf dry weight, leaf mass fraction and total leaf area of P. euramericana compared with intraspecific competition. The same conditions significantly affected the growth and morphological variables of P. deltoides, except for the dry weight of fine roots, R/S, specific leaf area, RMF, total nitrogen content and C/N compared with intraspecific competition. In addition, chlorophyll a (Chla), total chlorophyll (Tchl), carotenoid contents (Caro) and the carbon isotope composition (δ 13C) of P. deltoides were significantly lower in interspecific competition than in intraspecific competition, but no difference was detected in P. euramericana. The effects of N deficiency on P. deltoides under intraspecific competition were stronger than under interspecific competition. In contrast, the effects of N deficiency on P. euramericana between intraspecific and interspecific competition were not significantly different. These results suggest that under normal N condition, P. deltoides is expected to gain an advantage in monocultures rather than in mixtures with P. euramericana. Under N deficiency, the growth performance of P. euramericana was more stable than that of P. deltoides under both cultivation modes.

Key words: competition, nutrient resorption efficiency, photosynthesis capacity, competition intensity index, N deficiency

摘要:

美洲黑杨(Populus deltoides)和欧美杨(P. euramericana)在中国是广泛应用的造林树种。目前,有关这两种树种在纯林和混栽林条件下对氮缺乏的响应研究还较少。本研究的目的是分析这两种植物在不同竞争条件及氮水平下的生长,形态及生理响应。以美洲黑杨和欧美杨为研究材料,以盆栽实验模拟不同竞争方式(美洲黑杨×美洲黑杨,种内竞争;欧美杨×欧美杨,种内竞争;美洲黑杨×欧美杨,种间竞争),研究不同竞争方式和氮水平(正常氮添加和氮缺乏)对两种植物特征的影响,分析其在竞争和氮缺乏条件下生长,形态及生理特性的 变化。研究结果表明,在正常氮素水平下,与种内竞争相比,种间竞争显著降低了欧美杨的根重、根分配、根冠比、碳氮比,增加了其叶重、叶分配以及总叶面积;同时除了细根重、根冠比、比叶面积、根分配、总氮含量和碳氮比未受影响外,种间竞争也显著影响了美洲黑杨的生长和形态特征。此外,在正常氮水平下,美洲黑杨的叶绿素a含量、总叶绿素含量、类胡萝卜素含量以及碳同位素组成在种间竞争条件下都显著低于种内竞争,但是在欧美杨中未发现显著的种间和种内竞争差异。在种内竞争下,氮缺乏对美洲黑杨的影响比在种间竞争下更强;但对于欧美杨,氮缺乏的影响在两种竞争条件下差异并不显著。因此,在正常氮素水平下,美洲黑杨纯林栽培比与欧美杨混合栽培生长表现更好;但在氮素缺乏时,欧美杨在纯林和混合栽培条件下的表现比美洲黑杨更稳定。

关键词: 竞争, 营养吸收效率, 光合能力, 竞争强度指数, 氮缺乏