تحقیقات جنگل و صنوبر ایران (Mar 2015)
Impact of resin exploitation on diameter increment of Pistacia atlantica Trees
Abstract
The historically-established exploitation of resin from wild pistachio (Pistacia atlantica Desf.) plays a great role in the socioeconomic balance and livelihood of rural communities of Zagros forest region. The objective of this study is to assess the impact of resin exploitation on diameter increment of wild pistachio. Two stands including a 4.8 ha abandoned stand (in which resin exploitation was previously ceased between 1991 and 2013) and a 9.6 ha stand (currently undergoing resin exploitation) with similar physiographic conditions were selected in the villages Bivand-bala and Bivand-paeen in Javanroud, Kermanshah province. To evaluate the diameter increment, 18 tree samples in the abandoned stand and 16 samples in the utilized stand were taken, and increment cores were extracted from each tree at the height of 30 cm using increment borer. In the increment cores, current annual radial increment (CARI) was measured for a period between 1980 and 2013. Current annual diameter increment (CADI) and its percentage (PCADI) of all diameter classes were calculated for two periods of 1980-1991 and 1991-2013. The normal distribution of the data was tested using Kolmogorov–Smirnov test. Comparing diameter increment of trees in the two stands was performed by independent-samples t test. The results indicated no significant difference in the average PCADI values between the abandoned and utilized stands during 1980-1990 (in which both stands had undergone relatively similar level of human interferences and resin extraction). The results for the period of 1991-2013 (in which resin exploitation was ceased in the abandoned stand) the average values of PCADI in diameter classes (35-60 cm) were significantly different between the two studied stands, where the abandoned stand showed higher values than the utilized stand. However, no significant difference was observed between the two stands between 1980 and 1991. Furthermore, the averages of PCADI in wild pistachio trees were significantly different for the period of 1991 to 2013 (P< 0.01).
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