Relationship between leaf traits of Melica przewalskyi and slope aspects in alpine grassland of Qilian Mountains, China

Aims Variations in leaf characteristics can reflect plant acclimation to environments. We aimed to examine the relationship between leaf traits of Melica przewalskyi and slope aspect. Methods In alpine grassland of Qilian Mountains, Gansu Province, China, 80 plots were sampled at intervals of 20 m along eight aspects. Latitude, longitude and altitude of each plot were recorded by GPS. At each plot, 10 individuals of M. przewalskyi were random selected and harvested for measurements of leaf mass, leaf area, and leaf volume. A digital elevation model (DEM) was constructed to extract elevation, aspect, and slope for each plot by ArcGIS. The 80 plots were divided into groups of north, east, west and south aspect. Values for leaf traits were log-transformed. the standardized major axis (SMA) estimation method, was used to examine the covariation among leaf traits. Important findings Leaf area and leaf volume decreased significantly as aspect turns from north to east, from east to west, and from west to south, but not so for leaf mass, suggesting that leaf thickness increased as slope aspect changes, and thus led to the smaller and thicker leaves on the south-facing slope than that on north-facing slope. A clear allometric relationship between leaf mass and leaf area was found only on the south-facing slope where increase in leaf mass was greater than that in leaf area. While on other slope aspects, an isometric relationships between them was observed. The allometric relationship between leaf mass and leaf volume was found on all four aspects, with the growing speed of leaf volume greater than that of leaf mass, and a rising SMA slope. We can conclude that variations in leaf traits of M. przewalskyi with slope aspect could reflect plant acclimation.