Analysis of relationships among leaf functional traits and economics spectrum of plant species in the desert steppe of Nei Mongol

Abstract

Aims Grassland desertification is being accelerated because of adverse climate change effects and unsustainable land uses, resulting in several major environmental problems. However, there are few studies on the economics spectrum of different plant functional types in desert steppe. The objectives of the current study are to examine the relationships among leaf functional traits of native plant species, to compare the functional traits among different plant functional types, and to determine whether an economic spectrum exists for the majority of species in the desert steppe of Damao Banner, Nei Mongol, China. Methods Photosynthetic and chlorophyll fluorescence parameters, specific leaf area(SLA), and leaf nitrogen contents across 24 species of different functional types were measured in situ in the desert steppe ecosystem. Non-parametric tests were used to analyze leaf trait differences in plant species of different functional types. Linear regression analysis was used to determine the relationships among leaf traits in different plant species. Finally, a comprehensive analysis on these leaf traits in different plant species was conducted using the principal component analysis. All data analyses were performed using SPSS 16.0(SPSS, Chicago, USA). Important findings Significant differences among plant functional types were found in most of the leaf traits. SLA and mass-based nitrogen concentration(Nmass) in grasses were 2.39 and 1.20 folds, respectively, of that in shrubs; area-based photosynthetic capacity(Aarea), SLA, and photosynthetic nitrogen use efficiency(PNUE) in annual species were 1.93, 2.13, and 4.24 folds, respectively, of that in perennial species; and Aarea, SLA, and PNUE in C4 species were 2.25, 1.73, and 3.61 folds, respectively, of that in C3 species. Almost all relationships signifi-cantly differed(p 0.01) among the leaf traits, with exception of the relationships between Aarea and area-based nitrogen concentration(Narea) and between quantum yield of PSII electron transport(ΦPSII) and SLA, implying that an economic spectrum may exist in the desert steppe ecosystem. The relationships of Narea, mass-based photosynthetic capacity(Amass), and PNUE with SLA were most significantly strong(R2 = 0.54, 0.62, 0.60, respectively; p 0.01). Results in this study suggest that the annuals, grasses, and C4 species might be located at the end of the leaf economic spectrum with high area-based photosynthetic rate, high nitrogen concentration on mass basis, short leaf lifespan, and high SLA; whereas the perennials, shrubs, and C3 species could be located at the another end of the economic spectrum with contrasting traits.