Abstract
Aims The relationship between stem and leaf growth is a strategy that plant canopy enhances photosynthetic efficiency and competitiveness through configuration adjustments; this relationship indicates the ratio between xylem and photosynthetic area in a heterogeneous environment. Our objective was to examine how Melica przewalskyi modulated leaf and stem traits in adaptation to changes in slope. Methods In the alpine grassland of Qilian Mountains, Gansu Province, China, 80 plots were set up along four transects corresponding to contrasting aspects with 20 m distance between adjacent plots. A GPS was used to record latitude, longitude and altitude of each plot and Arc GIS software was used for constructing a digital elevation model(DEM) and extracting information on elevation, aspect, and slope. Community characteristics were investigated and 10 random individuals of M. przewalskyi were cut at the soil surface in each plot, and leaf mass, leaf area and stem mass were measured in laboratory. The 80 plots were grouped into 0°–10°, 10°–20°, 20°–30° slope gradients. Stem and leaf traits were log-transformed and then standardized major axis(SMA) estimation method was used to examine the allometric relationships of stem mass with leaf area or leaf mass. Important findings The stem mass, leaf mass and leaf area of M. przewalskyi gradually decreased, but the leaf number increased, with slope gradient. An isometric relationship was found between stem mass and leaf area in plots within each slope gradient, whereas an allometric relationship was found between stem mass and leaf mass. Melica przewalskyi grown on steeper slopes tended to have smaller leaf area and greater leaf number at a given stem mass, and leaves with greater stem mass had greater leaf mass. A significant difference in the SMA slope among the three slope gradients of the plots suggested that the slope of the growth site constrained leaf area and leaf mass by stem mass, reflecting plant adaptation to heterogeneous environment.
Published Version
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