Surveying of Trees Outside Forest Using Sector Sampling: A Case Study of Kasetsart University, Bangkhen Campus
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Abstract
The objectives of this study were to estimate the basal area of trees and compare them with the basal area estimated using sector sampling. The study area was located in the Bangkhen campus of Kasetsart University, in an area of 707.740 rai. The area was divided into four sub areas labeled as 1, 2, 3, and 4, which had an area of 55.810, 127.560, 256.550, and 267.820 rai, respectively. In each sub area, data was collected using sector sampling with three angles of 3, 5, and 7 degrees, to ensure that the center of a sector (pivot- point) was in the middle of each area and random directions were sampled starting with drawing lottery and aligning the next sector with a right angle, to obtain a total of four sectors. Within these sectors, the basal area was estimated, and the data was analyzed through ANOVA analysis.
We found 284 trees belonging to 57 species with a diameter at breast height of more than 4.5 cm. The basal areas of sub area 1 estimated through sector sampling with varying angles of 3, 5 and 7 degrees were 69.685, 45.640, and 35.350 m2, respectively. Similarly, for sub area 2, the basal areas were 80.732, 52.370, and 39.625 m2, respectively, in sub area 3, they were 23.955, 30.278 and 29.310 m2, respectively, while in sub area 4, the basal areas were 80.688, 53.691 and 49.839 m2, respectively. The results of ANOVA analysis found that the basal areas estimated using sector sampling with differing angles of 3, 5 and 7 degrees in each sub area were not significantly different at a level of P > 0.05. As such, the suitable angles for sector sampling in sub areas 1, 2, 3, and 4 were selected based on the lowest value of the standard errors. Hence, the suitable angle sizes for the respective sub areas were 7, 7, 3, and 7 degrees, respectively with the standard errors in estimated basal areas of 28.123, 26.651, 6.633, and 28.836 respectively. The results of this study can be used as a guideline when choosing the appropriate angle size and while doing studies in other areas.
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ข้าพเจ้าและผู้เขียนร่วม (ถ้ามี) ขอรับรองว่า ต้นฉบับที่เสนอมานี้ยังไม่เคยได้รับการตีพิมพ์และไม่ได้อยู่ในระหว่างกระบวนการพิจารณาตีพิมพ์ลงในวารสารหรือสิ่งตีพิมพ์อื่นใด ข้าพเจ้าและผู้เขียนร่วม (ถ้ามี) ยอมรับหลักเกณฑ์และเงื่อนไขการพิจารณาต้นฉบับ ทั้งยินยอมให้กองบรรณาธิการมีสิทธิ์พิจารณาและตรวจแก้ต้นฉบับได้ตามที่เห็นสมควร พร้อมนี้ขอมอบลิขสิทธิ์ผลงานที่ได้รับการตีพิมพ์ให้แก่วารสารวนศาสตร์ คณะวนศาสตร์ มหาวิทยาลัยเกษตรศาสตร์ กรณีมีการฟ้องร้องเรื่องการละเมิดลิขสิทธิ์เกี่ยวกับภาพ กราฟ ข้อความส่วนใดส่วนหนึ่ง หรือ ข้อคิดเห็นที่ปรากฏในผลงาน ให้เป็นความรับผิดชอบของข้าพเจ้าและผู้เขียนร่วม (ถ้ามี) แต่เพียงฝ่ายเดียว และหากข้าพเจ้าและผู้เขียนร่วม (ถ้ามี) ประสงค์ถอนบทความในระหว่างกระบวนการพิจารณาของทางวารสาร ข้าพเจ้าและผู้เขียนร่วม (ถ้ามี) ยินดีรับผิดชอบค่าใช้จ่ายทั้งหมดที่เกิดขึ้นในกระบวนการพิจารณาบทความนั้น”
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