Fig. 6
Effect of beech mast index with different time lags (2 years versus 1 year) for the spring and fall peak (BM[2,1]) on the density of nymphs (DON) is shown for the (a) spring peak and (b) fall peak. The beech mast index (BM[2,1]) assumes a 2-year time lag for the spring nymphal peak and a 1-year time lag for the fall nymphal peak. The relationship shows that the DON increases with the beech mast index at each of the four elevation sites for both the (a) spring peak and (b) fall peak. The DON is an estimate of the number of questing I. ricinus nymphs per 100 m2 sampled by the dragging method each month. Beech mast indices have values of 1, 2, 3, 4, and 5, which refer to very poor mast, poor mast, moderate mast, good mast, and full mast, respectively. The predicted values were calculated using model 2 in Table 5. The reference conditions were as follows: year = 2004, and calendar days were 105 (15 April) and 288 (15 October) for the spring and fall peak, respectively. Increasing the beech mast score from 1 (poor mast) to 5 (full mast) increased the DON by 166% at each of the four elevation sites