Abstract
The availability of suitable native plant species for local animal husbandry development and ecological restoration is limited on the Qinghai-Tibetan Plateau. Therefore, comparisons of the ecological adaptability of native species to alternative habitats and their introduction into new habitats are of high importance. This study is aimed at identifying the alteration in morphological and physiological characteristics by measuring photosynthetic physiology, nutrient content, and growth associated with adaptation of plants to conditions at different altitudes 2450, 2950, 3100, and 3300 m above sea level (a. s. l.) on the plateau. Seeds of the dominant grass, Elymus nutans, were collected from locations at these altitudes and grown at a test location of 2950 m a. s. l. Results indicated that altitude had no significant effect on plant height and root depth. However, the leaf area and total root surface area of plants derived from 2950 and 3300 m a. s. l. showed a parabolic response, being greater than those of plants derived from the lowest (2450 m) and highest (3300 m a. s. l.). Total (root plus shoot) dry matter reduced progressively from 2450 to 3300 m a. s. l, while root : shoot ratio increased progressively with altitude. Seed yield of plants originating from the test altitude (2950 m a. s. l) was significantly higher than at any other altitude, being 20% lower at 2450 m, and 38% and 58% less in populations originating from the higher altitudes (3100 and 3300 m a. s. l.). There was also a parabolic decline in response of Elymus nutans germplasm from 3100, 3300, and 2450 m, compared with plants from 2950 m a. s. l., to photosynthetic rate, total N, soluble sugar, and starch contents. Germplasm from 2450 m a. s. l. had significantly lower shoot and higher root carbon content, lower shoot nitrogen, and lower root carbon-to-nitrogen ratio compared with plants derived from the other three altitudes. It is suggested that the stable, genetically determined morphological and physiological features of ecotypes showed parabolic responses which means these ecotypes have become adapted to local habitats, whereas parameters such as dry matter, total root : shoot ratio, photosynthetic rate, and intercellular CO2 concentration of plants reflected phenotypic linear response to current abiotic conditions. It is postulated that introduced ecotypes from 2450, 3100, and 3300 m could adapt to the environment at 2950 m a. s. l. gradually. We conclude that the increased thermal regime experienced by plants introduced from high altitude to low altitude may facilitate the increased growth of Elymus nutans subtypes. It is important to preserve local strains of native species, or ecotypes, for reintroduction into degraded environments and to maintain the greatest ecosystem stability in the northeastern Tibetan Plateau.
Highlights
Plants have the ability to alter their morphological and physiological traits in response to environmental variations [1, 2] and adjust the expression of these traits to accommodate their adaptability across multiple environments [3]
Healthy E. nutans seeds were obtained from wild plants growing in Tianzhu county of Eastern Qilian Mountains (102°23~102°78′ E, 37°11~37°18′ N), Qilian Mountains, China, which lies in the northeast margin of the Tibetan Plateau, a key site to understanding the species’ adaptation in the northeastern of Tibetan Plateau
At least 15 plants of Elymus nutans per site were cut from four sites (Dachaigou, Jinqianghe, Honggeda, Daiqian) selected randomly from habitats at 2450, 2950, 3100, and 3300 m a. s. l., in an area of 100-1000 m2 that was ecologically homogeneous for the target ecotypes
Summary
Plants have the ability to alter their morphological and physiological traits in response to environmental variations [1, 2] and adjust the expression of these traits to accommodate their adaptability across multiple environments [3]. The morphological and Journal of Sensors physiological characteristics of alpine species reflect their environmental adaption under certain altitudinal gradients [6]. Alpine plants exhibit specific morphological, physiological, and biochemical responses to an increasing altitude, such as size and increases in the leaf thickness [9,10,11]. Decreases in plant growth and a higher proportion of plant biomass in the roots usually result in a higher leaf N content and lower C : N ratio, which lead to a higher photosynthetic capacity in alpine plants [12]. The relationship between plant functional traits and environmental factors has been recently gaining increasing attention. The adaptation mechanism in response to altitude variation and climate change is largely unknown [18]
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