Frydoon Ferydoony-Nasry; Ismaeil Rahbar; Orujali karimi
Volume 13, Issue 4 , February 2007, , Pages 385-393
Abstract
Based on a general model, estimated number of population density for ten years old Haloxylon plantation in Gonabad was 150 trees per hectar; therefore, six density treatments were selected around the estimated density; two density treatments over estimated number, two under it, and existing density as ...
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Based on a general model, estimated number of population density for ten years old Haloxylon plantation in Gonabad was 150 trees per hectar; therefore, six density treatments were selected around the estimated density; two density treatments over estimated number, two under it, and existing density as the control treatment. The treatments consisted of T1=120, T2=135, T3=150, T4=165, T5=180, and the existing density (control) T6=250 trees per hectar. The treatment have been compared in a Randomized Complete Block Design, with four replications, since the spring 1996. After thinning, height (H) and crown diameter (CD) of the remained trees were measured. This measurement was repeated during the growth period in ten years. A size index (SI) model of the form H ×CD2 was founded to distinguish the best among the 6 treatments. The growth percentage of H, CD, and SI, between first and the last measurement were calculated. The analysis of variance of the growth percents showed that there is significant difference between treatments. The highest growth belonged to T1 and lowest belonged to T6 (control). This result show that optimized population density for ten years old Haloxylon stands in Gonabad is 20 (and or 10)% less than the estimated number based on the general model.
Mohammad javad Ahmadian yazdi; Esmaeil Rahbar; Orujali Karimi
Volume 14, Issue 3 , January 2007, , Pages 313-322
Abstract
A general model was developed to explain the interrelationships between soil saturation percentage, mean annual precipitation, and population density on growth and vigority of planted Haloxylon trees. Based on the model, estimated number of population density for 7 years old Haloxylon plantation in Sabzevar ...
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A general model was developed to explain the interrelationships between soil saturation percentage, mean annual precipitation, and population density on growth and vigority of planted Haloxylon trees. Based on the model, estimated number of population density for 7 years old Haloxylon plantation in Sabzevar was 309 trees per hectar; therefore, six density treatments were selected around the estimated density; two density treatments over estimated number, two under it, and existing density as the control treatment. The treatments consisted of T1=247, T2=278, T3=309, T4=340, T5=371, and existing density(control) T6=500 trees per hectar. The treatments have been compared in a Randomized Complete Block Design, with four replications, since winter of 1994. After thinning practices, height(H) and crown diameters(CD) of the remained trees were measured. This measurement was repeated during the growth period in ten years. Since the CD increment between the first and the 10th measurement was 3 times more than H increment; therefore, a size index(SI) model of the form H×(CD)2, which was constructed by trial and error, was found to distinguish the best among the 6 treatments. The growth percentage of H, CD, and SI between first and the last measurement were calculated. The analysis of variance of the growth percents showed that there is significant differences between treatments for H, CD, and SI. The highest growth belonged to T2 and lowest belonged to T6(control). The results show that optimized population density of seven years old Haloxylon stands in Sabzevar is 10% less than the estimated number based on the general model.