Figure 2
From: Effect of long-term fertilisation on the weed community of a winter wheat field
RDA analysis of effects of different fertilisation treatments on weed species and density growth in wheat field. (C0 = no fertiliser application; CN = nitrogen fertiliser only; CNP = nitrogen plus phosphorus fertiliser; CNK = nitrogen plus potassium fertiliser; CPK = phosphorus and potassium fertiliser; CNPK = combined fertiliser with nitrogen, phosphorus, and potassium). Redundancy analysis (RDA), also called reduced-rank regression, the canonical form of PCA. Special cases are simple and multiple regression, analysis of variance and the log-ratio form of reduced-rank regression principal components analysis (PCA). The arrow represents the environmental factor, the quadrant where the arrow is located represents the positive and negative correlation between the environmental factor and the ordination axis, and the length of the arrow connection represents the degree of correlation between an environmental factor and the distribution of the research objects. The longer the connection, the impact of this environmental factor on the distribution of objects is greater. The angle between the arrow connection and the ordination axis represents the correlation between the certain environmental factor and the ordination axis. The smaller the angle is, the higher the correlation is.
