Plant Functional Traits And Functional Diversity Response To Topographical Changes In An Alpine Meadow Of Tibetan Plateau

Plant functional traits are characterized as the “morpho-physio-phenological” traits that influence the individual performance- “growth, reproduction and survival” – and also plant functional diversity represents the range and value of functional traits within a community. Among topographical changes, plant functional traits and functional trait diversity were studied, which is of great significance to better understand the community assembly, ecosystem function and structure in a Tibetan alpine meadow.We measured four important functional traits of plant leaves: specific leaf area(SLA), leaf dry matter content(LDMC), leaf nitrogen concentration(LN)and leaf phosphorus concentration(LP)in the community of the Tibetan alpine meadow. Community functional traits were identified as community weighted means(CWM), and functional diversity of traits were calculated singly(FDrao) and in aggregate(functional richness, FRic; functional evenness, FEve; functional divergence, FDiv), respectively. Furthermore, the response patterns of plant functional traits and functional diversity to topographical changes were clarified, and the correlation between plant functional traits, single-trait functional diversity and functional diversity for the suite of leaf functional traits and soil physical-chemical properties were explored, respectively.The main results are as following:(1) Soil physical-chemical propertiesSoil moisture and available phosphorus content increased along summit, south-facing slope, north-facing slope and gully; soil available nitrogen content had the highest value in north-facing slope, followed by gully, and the lowest in the summit and south-facing slope; soil with the highest p H occurred in the south-facing slope.(2) The CWM values of plant functional traitsThe CWM values for SLA、LN and LP tended to increase, but LDMCCWM showed a decreased trend along topographical changes(summit, south-facing slope, north-facing slope and gully). The CWM values for SLA、LN and LP significantly increased and LDMCCWM decreased with increasing soil moisture、soil available nitrogen and available phosphorus content.(3) Plant single-trait functional diversity(FDrao)The FDrao of LDMC in the south-facing slope and gully was higher than in the summit and north-facing slope, and it significantly decreased with increases in soil available nitrogen and increased with increasing soil available phosphorus. The FDrao of SLA tended to increase when responded to topographical changes, consistently with increases in soil moisture content, available nitrogen and available phosphorus. The FDrao of LN and LP were both highest in the north-facing slope. There were a negative association between FDrao of LN, FDrao of LP and soil p H, but a positive relationship between FDrao of LN、LP and soil available nitrogen.(4) Plant functional diversity for the suite of leaf functional traits(FD)Plant functional diversity of leaf functional traits in aggregate response to topographical changes indicated that FRic and FDiv significantly increased, whereas FEve did not significantly changed. The correlation between plant functional diversity and species diversity showed FRic and FDiv increased with species diversity.In conclusion, this study suggested that soil physical-chemical properties were significantly different along topographical changes, and these properties had significantly effects on plant functional traits and functional diversity in a Tibetan Alpine Meadow.