I am analysing ecological data for relationships using PCA. Data have been grouped according to signs (-/+) of PC1, 2 and 3 that explained 85% of the variance.

Do data that have negative signs need to be transformed (i.e. watertable below the soil surface) and by what method??

Correlation analysis and multiple regression analysis suggest that watertable was negatively correlated with respiration and yet in PCA the results show apposing signs in both PC1 and PC2. Thus does this suggest negative correlations?

Also what are the most important factors to consider: signs, closeness of coefficients to 1, the number of PCs with the same signs??