Fractal analysis of yield variability of some cereals between 1938 and 2016

Characterization of temporal variability of crop yield is important in evaluation of sustainability of farming systems. We used fractal analysis to evaluate temporal variability of wheat (Triticum L.), barley (Hordeum vulgare L.), rye (Secale cereale L.), oat (Avena sativa L.), and rice (Oryza sativa L.), which are widely grown cereals in Turkey. Fractal dimension (D) was calculated from time series of annual mean yields for the crops. D-values for all five crops were below 1.50, which suggested anti-persistence of the temporal variability of the annual yields. Highest D-values occurred for rye (1.417) and lowest for wheat (1.255), which suggested that wheat has the least and rye has the most short-term variability among the studied crops. The D-values also indicated that both of short-term and long-term temporal variability were the case. Further research is needed for understanding the factors featuring the crop specific fractal characteristics of yield temporal variability across different crops and temporal scales to ensure food security under changing climate.