sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDÜ ORMAN FAKÜLTESİ DERGİSİ
samples. Samples were mixed for each plot, sieved to pass 2 mm after air drying,
and physical and chemical properties were determined in laboratory.
2.3. Needle samples
Prior to sampling, every tree was labelled and their health condition was
recorded. Five healthy and 5 unhealthy trees were chosen for foliar sampling in
each plot (Figure 1). 40 fascicles were taken from each tree with a shotgun.
Samples were dried at 70°C for 24 hours. The dry weights were measured and the
needles ground, then chemical analysis was performed for nutrients.
2.4. Plant water potential
We assumed that water potential of the trees may have played a role in
development of this fungal disease. Five trees were chosen in each plot for water
potential measurements. From each tree, representative needle samples were taken
from the bottom 1/3 of the canopy, and needle water potentials were measured with
a pressure bomb. However, the data was not conclusive, so the initial results were
not included here.
3. RESULTS
3.1. Fungal survey
Figure 1. Healthy (a) and unhealthy (b) pine needles.
Since start of the fungal disease in 2004, the rate of the disease has decreased
over time. In 2006, the ratio of samples with Diplodia was 20 %, while in 2008 the
ratio fell down to 5.5 %. As of today, the stand looks quite healthy.
3.2. Soil samples
On average, soil texture was sandy clay loam (Table 1). Soil reaction was relatively
neutral. Organic matter and nutrient concentrations were moderate. However, soil
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