内蒙古荒漠草原植物叶片功能性状关系及其经济谱分析

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

气候变化和人为干扰导致草原荒漠化加剧,引发了严重的环境问题。因此,对荒漠草原植物与环境变化关系的研究愈加迫切,分析比较荒漠草原不同功能型物种叶片经济谱具有重要意义。该研究通过测定内蒙古荒漠草原生态系统不同功能型植物叶片的光合及叶绿素荧光参数、比叶面积和叶片氮素含量,验证了荒漠草原植物叶片经济谱的存在,明确了各功能型植物叶片性状间的关系及其在叶片经济谱中的位置。荒漠草原不同功能型植物叶片性状差异明显,草本植物的比叶面积(SLA)、单位质量叶氮含量(Nmass)分别是灌木的2.39倍和1.20倍;一年生植物单位面积最大净光合速率(Aarea)、SLA、光合氮利用效率(PNUE)分别是多年生植物的1.93倍、2.13倍和4.24倍;C4植物的Aarea、SLA、PNUE分别是C3植物的2.25倍、1.73倍和3.61倍。除Aarea与单位面积叶氮含量(Narea)、PSII的实际光化学效率(ΦPSII)与SLA之间不存在显著相关关系外,叶片性状间存在广泛的相关关系,且均达到极显著水平。这验证了叶片经济谱在内蒙古荒漠草原植物中也同样存在。进一步分析表明,一年生植物、草本植物、C4植物叶片在叶片经济谱中位于靠近薄叶、光合能力强、寿命短的一端;而多年生植物、灌木、C3植物叶片靠近厚叶、光合能力弱、寿命长的一端。这说明荒漠草原中不同功能型植物可通过权衡其经济性状间的关系而采取不同的适应策略,对于荒漠草原生态系统管理具有重要的理论指导意义。

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.