DIGITALNA ARHIVA ŠUMARSKOG LISTA
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|ŠUMARSKI LIST 5-6/2014 str. 46 <-- 46 --> PDF|
The number of prepupae, in the year 2009, found in the 25 x 25 x 20 cm soil samples taken from the middle of the circular plots varied from 10 to 59 individuals/sample, or, calculated per m2 of soil, from 160 to 944 individuals/m2 of soil, while in 2010 the number of prepupae varied from 4 to 20 individuals/sample, from 64 to 320 individuals/m2 of soil. The average number of prepupae on the plot ranged from 37 ± 16,8 to 595 ± 269,5 individuals/m2 of soil in 2009, while in 2010 the average number of prepupae on the plot ranged from 12 ± 5,5 to 189 ± 87,3 individuals/m2 of soil. The average number of prepupae in the soil in 2010 was lower for 68%, according to the number of prepupae in the soil in 2009.
Soil and air temperature are important factors that affect the bionomy of Cephalcia spp. The duration of the development of Cephalcia spp. depends on the temperature of the soil and the temperature in the crowns of the trees. Table 1 present general temperature conditions (average max., min., and year soil and air temperature) for a wider area of the research location Prevalje over the period 2007–2010. For the air and soil temperature the data were obtained from ARSO, from the meteorological station Šmartno pri Slovenj Gradcu over the period 2007–2010, however for the year 2010, the data about the average max. and min. soil temperature were not available, because the method of measuring was changed. For the year 2010, soil temperatures were measured with ‘T-button’ thermometers on the location Prevalje.
If we look air and soil temperature through period 2007 -2010, there are differences in average max., min. and year temperature. These temperatures play an important role in eclosion of adults.
The influence of air and soil temperature on the time of occurrence of adult forms of the C. arvensis in 2011 is shown on Figure 4.
Figure 4 shows the average daily air temperature and average soil temperature (measured with ‘T-button’ thermometers) at a depth of 20 cm over the period from 19.4.2011 to 19.5.2011. In 2011, the emergence of Cephalcia was noted in large number on the 23rd of April (Figure 4), when the average daily air temperature at a height of 2 meters above the ground was 14.7 °C, the temperature of the soil at a depth of 20 cm was 8.7 °C, and the weather was clear and sunny. The emergence of Cephalcia was strong until the 9th of May, when the weather was clear to moderately cloudy, with an average daily air temperature between 7 to 14 °C and an average soil temperature between 8 to 10 °C. After this date, only individual Cephalcia adults were observed until the 19th of May, when they were no longer observed.
The average defoliation of the trees found in the selected sample plots was 28% in the autumn of 2009, 32% in the autumn of 2010. Our study has shown, that tree defoliation increased within the two years of monitoring (Figure 5).