Climate-tree growth relationship

Examine how climate change affected tree growth

Data

You will need to get the orginal data from Yong Luo. The data were not put into repo for two reasons: 1. data size is too large to upload; 2. restriction of data usage

Data preparation

The data were selected using

source(file.path(".", "Rcodes", "MBdataselection.R"))

The independent variables (IDVs) were incorporated into the data using

source(file.path(".", "Rcodes", "IDV preparation.R"))

For Hegyi index, a CItable(in data folder) had been prepared using function HeghyiCICalculation.R in Rfunctions folder. The climate anomalies is in data folder

Data inspection

The data was inspected for the normality of depedendt variable (visually check), linearity between dependent variable and independent variables (visually check), and variance inflaction factor (VIF).

The inspection was processed using dataInspection.R. The VIF was checked using method proposed by Zuur, A.F., et al. (2010)

Data analyses

Examine temporal trends of tree growth

For each species among Jack pine, Trembling aspen and Black spruce, mixed models that account for both random slope and random intercept had been developed using lme function in nlme package.

For each species, a best model was determined based on smallest AIC and was considered as the final model that was reported in the results.

Examine climate changes and their associations with tree growth

Tables and figures presentations