Abstract:

To elucidate the driving factors behind plant functional traits, especially in mountainous areas, we explored how variation in topography and soil characteristics affects ecophysiological and morphological traits of woody plants within the Gutianshan 24-ha plot in Zhejiang Province. This site is in a typical subtropical broad-leaved forest. During the summers of 2008 and 2009, we measured three ecophysiological traits (chlorophyll content, chlorophyll fluorescence parameters F_v/F_m and PI_ABS, and stem sapwood xylem specific hydraulic conductivity) and four morphological traits (stomata density, specific leaf area, leaf thickness, and ratio of leaf length to leaf width) among 115 woody species in the field. Redundancy analysis was conducted to identify the most influential environmental factors from our topographical factors (mean elevation, convexity, slope, and aspect) and five soil parameters (moisture, total nitrogen content, total phosphorus content, total carbon content, and pH). Leaf chlorophyll content was negatively correlated with elevation and convexity, but positively correlated with soil moisture and total nitrogen content. The two chlorophyll fluorescence parameters (F_v/F_m and PI_ABS) were strongly negatively correlated with soil total nitrogen and phosphorus content; these variables were likely interrelated with low soil pH values. Stem sapwood xylem specific hydraulic conductivity was positively correlated with soil moisture and specific leaf area was positively correlated with elevation. Topographical variables explained 10.4% of total variation in functional traits; mean elevation was the most powerful explanatory variable, followed by convexity, slope and finally, aspect. Soil parameters explained 13.9% of the total functional trait variation; and soil moisture was the most powerful factor, followed by total nitrogen content, pH value, total phosphorous content, total carbon content and the ratio of nitrogen and phosphorous. At this scale and at this site elevation and convexity were the two most influential topographical factors, and moisture and nitrogen were the most influential soil factors, on plant functional traits. However, because of a lack of phosphorous in the soil, some important physiological processes including photosynthesis may have been limited, thereby leading to some confusing trait/environment relationships.

Key words: functional traits, elevation, convexity, soil moisture, soil phosphorus