This was my final data project for my isotopes class at Purdue, and one of my first R projects. It might not be perfect and difficult to understand because it has been 4 years ago.
How water availability affects C3 and C4 differ in their response to changes in precipitation, and if there is a species-specific difference in isotopic signatures along a precipitation gradient on arid and semi-arid climate in Norther China.
Carbon and nitrogen isotopes can be used as tracers to help understand how water controls the ecosystem elements. It is well studied the negative correlations between mean average precipitation and the d13C of value C3; however, there is not common to see a relationship between the mean average precipitation with d13C of C4. In addition, nitrogen isotopic composition is related to water availability and it can be used as an indicator of ecosystem N cycling because an enrichment of d15N in soil has been observed on gradient precipitation on arid environments.
For analyze the plant carbon and nitrogen stable isotope composition, a scatterplot will be used to determinate if there is a correlation between carbon and nitrogen isotopes values of C3 and C4 with the precipitation gradient. It is expected that C4 might be less sensitive to water stress. Also, the four more frequent dominant C3 species were identify with presence along the gradient on the dataset and they will be used for identifying correlation between plant stable isotope composition and precipitation. For the nitrogen isotope values on plants, plants with N2 fixing and mycorrhizal symbiosis will be used to determinate if there is a relationship or not with nitrogen isotope values. Furthermore, a linear regression will be performed to get the R2 and P values to stablish a correlation.
- Ma J-Y, Sun W, Liu X-N, Chen F-H (2012) Variation in the Stable Carbon and Nitrogen Isotope Composition of Plants and Soil along a Precipitation Gradient in Northern China. PLoS ONE 7(12): e51894. This is the main paper that provides the data set of sample location, mean annual precipitation, vegetation type and collected species. There is no information about the isotopes of the soil organic matter.