J Plant Ecol ›› 2020, Vol. 13 ›› Issue (6): 785-792.DOI: 10.1093/jpe/rtaa067

• Research Articles • Previous Articles     Next Articles

Variation of morphological and leaf stoichiometric traits of two endemic species along the elevation gradient of Mount Kenya, East Africa

Antony N. Waigwa1,2,3 , Brian Njoroge Mwangi1,2 , Gituru R. Wahiti3 , Fred Omengo4 , Yadong Zhou1,5,6, * and Qingfeng Wang1,5,6   

  1. 1 Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China, 2 University of Chinese Academy of Sciences, Beijing 100049, China, 3 Sino-Africa Joint Research Center (SAJOREC), Jomo Kenyatta University of Agriculture and Technology, Juja, Nairobi 00200, Kenya, 4 Department of Biodiversity Research, Kenya Wildlife Service, Nairobi 00100, Kenya, 5 Center of Conservation Biology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan 430074, China, 6 Sino-Africa Joint Research Center (SAJOREC), Chinese Academy of Sciences, Wuhan 430074, China

    *Corresponding author. E-mail: zhouyd@wbgcas.cn
  • Received:2020-08-24 Revised:2020-09-09 Accepted:2020-10-04 Online:2020-12-10 Published:2020-12-01

Abstract:

Aims

The aim of this paper is to assess morphological and leaf stoichiometric responses of Dendrosenecio keniensis and Lobelia gregoriana to extreme environmental conditions along an elevation gradient in tropical mountains.

Methods

In this study, we assessed the variation of the morphological traits, including plant height, leaf area, leaf thickness, leaf dry weight, specific leaf area and the leaf stoichiometry traits nitrogen, carbon and phosphorous of the two endemic species D. keniensis and L. gregoriana. We further explored the relations of these morphological traits to soil organic carbon, soil total nitrogen, soil phosphorous, annual mean temperature, annual mean precipitation, annual total solar radiation, water vapor pressure and the topographic variables aspect, slope and hill shade along the elevation gradient. Ninety 10 m × 10 m sampling plots were set up along the elevation gradient ranging from 3500 to 4300 m. We used 1 km × 1 km grid cells to rasterize our study area in ArcGIS 10.5 for easy access to data pertaining to the climate of each elevation band. We performed linear regression of the morphological and leaf stoichiometric traits with elevation as explanatory variable. We conducted correlation analysis on the morphological and leaf stoichiometric traits with climatic, soil and topographic variables along the elevation gradient.

Important Findings

Dendrosenecio keniensis had wool-like pubescent leaves while L. gregoriana had mucilage packed succulent and waxy cuticle leaves to avoid freezing. Both species exhibited reduced metabolic rates as shown by the low leaf phosphorous content. Our results also showed that changes in morphology and leaf stoichiometry were determined by a combination of climate, soil and topographic variables that change along elevation on Mount Kenya. The observed variations in the morphological and leaf stoichiometric traits of D. keniensis and L. gregoriana, which grow side by side along the elevation gradient, were interpreted as adaptation to the harsh environmental conditions.

Key words: Africa, elevation gradient, functional traits, adaptability, climate change

摘要:

环境能一定程度上影响和改变植物的形态结构和生理生化。本文旨在拟研究热带东非高山不同海拔梯度下两 种代表植物Dendrosenecio keniensisLobelia gregoriana的形态结构和生理生化的变化。我们沿海拔梯度在海拔3500 m至4300 m的范围内 建立了90个10 m × 10 m的样方,使用1 km × 1 km网格单元在ArcGis 10.5 中栅格化研究区域并获取每个样方的气候数据,包括年平均气温、 年平均降水量、年总辐射量、水汽压,同时获取了每个样方的地形变量,包括坡向、坡度和阴影等。我们收集了每个样方两种植物的形态性状,包括株高、叶面积、叶厚、叶干重、比叶面积,以及叶化学计量性状,包括氮、碳、磷的含量,同时收集了样方的土壤有机碳、 土壤全氮、土壤有机氮和土壤磷数据。我们将海拔高度设为解释变量,对两种植物的形态性状和叶片化学计量性状进行线性回归分析,同时,在海拔梯度上对叶片形态和化学计量性状与气候、土壤和地形变量进行了相关分析。我们的研究发现,D. keniensis 有羊毛状的短柔毛叶, 而L. gregoriana则有粘液填充的肉质和蜡质的角质层叶子,以避免冻害。这两个物种都呈现出了降低的代谢率,表现在叶片磷含量较低。我 们的研究结果还表明,形态和叶片化学计量的变化是由气候、土壤和地形变量共同决定的,这些变量随肯尼亚山海拔的变化而变 化。我们推测,沿海拔梯度两种植物的形态和叶片化学计量性状的变异是对恶劣环境条件的适应。

关键词: 非洲, 海拔梯度, 功能特性, 适应性, 气候变化