## 3 Results  
### Crop Classification  
To assess the performance of crop identification using the fuzzy decision tree algorithm, area proportions of the four major crops estimated from the classification were compared with those reported by OMAFRA at the county level for all 14 years (Figure 2). Area proportions were calculated on the basis of the total areas of the four major crops because only these four crops were identified in the study area. Given that the four crops constitute more than 85% of the total crop area in the region, we consider the results acceptable, although the approximation could induce bias. For most counties, the proportions of winter wheat area were around 13%, and could approach 30% in some counties (Figure 2a). There was a large overestimation of winter wheat in many counties. Identification of corn was better, although discrepancy was still observed (Figure 2b). There was a persistent underestimation of soybean due to a large omission error in classification (Figure 2c). Estimated area proportions of forage crops correlated well with the reported proportions; however, overestimation was also observed for most of the counties (Figure 2d). As reported by [PERSON] et al. [1], there was large confusion between winter wheat and forage crops, and between corn and soybean in the classification. The phenological patterns of soybean and corn were similar, with only a slightly shorter peak growth duration for soybean. Winter wheat and forage crops also have a similar pattern with a quick and early growth phase in early spring, and undergo a complicated procedure in summer, either due to mechanical harvest and then volunteer regrowth for forage crops, or harvest of winter wheat followed by reseeding with cover crops to protect soil in winter [30]. These factors bring additional challenges for crop identification using coarse resolution satellite data such as MODIS imagery. Figure 2e, f shows the comparison of the two pairs of crops combined. Areal proportions for  
Figure 2: Comparison of county level crop area proportions estimated annually using the fuzzy decision tree classifier and reported by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) for the period between 2003 and 2016.  
corn and soybean combined were mostly underestimated in most cases, and forage and winter wheat were mostly overestimated. Classification results can also be assessed using average seasonal growth profiles of the three annual crops represented by time-series EVI2. Figure 3a-c shows growth curves of winter wheat, corn, and soybean in three counties, Chatham-Kent in Southern Ontario, Perth County in Western Ontario, and Durham in Central Ontario, as examples. The growth profiles were constructed using extracted EVI2 from \"pure\" pixels identified by the classification algorithms for the three crops in 2016. Growth profiles extracted using a general cropland mask for the three counties are shown in Figure 3d. It was observed that EVI2 of winter wheat reached peak stage from late May to early June, and declined to minimum at the end of July when the crop is senescent and ready for harvest. Corn and soybean started to grow from late May, reaching peak growth status between late July and end of August. Because most areas in these three counties were seeded with soybean and corn combined, seasonal vegetation growth profiles extracted using a general cropland mask showed a typical pattern of the two summer crops (Figure 3d), that is, reach peak stage in late July. In 2016, the area seeded with corn and soybean was about 80% in Chatham-Kent, whereas only about 60% in Perth and Durham. Another factor causing the discrepancy could be associated with variability of phenological cycles pertaining to different crop varieties that could not be specified in this study.