Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forests
Since N-tree sampling methods produce biased estimate, bias evaluation should be applied to N-tree estimator. The purpose of this study is to assess the N tree distance sampling method bias with modified estimator Kleinn and Vilcko in estimating number per hectare and canopy cover in Zagros forests....
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| Format: | Article |
| Language: | fas |
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Iranian Society of Forestry
2016-09-01
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| Series: | مجله جنگل ایران |
| Subjects: | |
| Online Access: | http://www.ijf-isaforestry.ir/article_38841_ae2e747c40ce23a294d3e8be9185d6df.pdf |
| _version_ | 1818742970769211392 |
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| author | حمدالله صادقی سودابه گراوند ایمان ظفریان |
| author_facet | حمدالله صادقی سودابه گراوند ایمان ظفریان |
| author_sort | حمدالله صادقی |
| collection | DOAJ |
| description | Since N-tree sampling methods produce biased estimate, bias evaluation should be applied to N-tree estimator. The purpose of this study is to assess the N tree distance sampling method bias with modified estimator Kleinn and Vilcko in estimating number per hectare and canopy cover in Zagros forests. For this purpose, 6-10 trees from real forest map were tested with full inventories. For comparing the results of characteristics in different trees in N-tree method with full inventories, ANOVA was used. Evaluation of N tree distance sampling method was done by using accuracy criterion and standard error of mean. Bias was also evaluated via one-sample t-test and relative bias. Results showed that in estimating number per hectare and canopy cover, there is no significant difference between tree numbers with full inventory. Bias test for six and seven trees per hectare was significant, but it was not significant for eight, nine and 10 trees. Canopy cover for all tree numbers showed no significant difference. So, in order to achieve a maximum accuracy (minimum bias), at least eight trees within sample plot should be measured. Finally, this study implies that in forests with lower density and cluster pattern, bias change in N tree distance method does not follow a predictable decreasing pattern. |
| first_indexed | 2024-12-18T02:20:59Z |
| format | Article |
| id | doaj.art-265b3f0fea864be58528e89827fecd56 |
| institution | Directory Open Access Journal |
| issn | 2008-6113 2423-4435 |
| language | fas |
| last_indexed | 2024-12-18T02:20:59Z |
| publishDate | 2016-09-01 |
| publisher | Iranian Society of Forestry |
| record_format | Article |
| series | مجله جنگل ایران |
| spelling | doaj.art-265b3f0fea864be58528e89827fecd562022-12-21T21:24:11ZfasIranian Society of Forestryمجله جنگل ایران2008-61132423-44352016-09-018223925038841Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forestsحمدالله صادقی0سودابه گراوند1ایمان ظفریان2دانشجوآزادازادSince N-tree sampling methods produce biased estimate, bias evaluation should be applied to N-tree estimator. The purpose of this study is to assess the N tree distance sampling method bias with modified estimator Kleinn and Vilcko in estimating number per hectare and canopy cover in Zagros forests. For this purpose, 6-10 trees from real forest map were tested with full inventories. For comparing the results of characteristics in different trees in N-tree method with full inventories, ANOVA was used. Evaluation of N tree distance sampling method was done by using accuracy criterion and standard error of mean. Bias was also evaluated via one-sample t-test and relative bias. Results showed that in estimating number per hectare and canopy cover, there is no significant difference between tree numbers with full inventory. Bias test for six and seven trees per hectare was significant, but it was not significant for eight, nine and 10 trees. Canopy cover for all tree numbers showed no significant difference. So, in order to achieve a maximum accuracy (minimum bias), at least eight trees within sample plot should be measured. Finally, this study implies that in forests with lower density and cluster pattern, bias change in N tree distance method does not follow a predictable decreasing pattern.http://www.ijf-isaforestry.ir/article_38841_ae2e747c40ce23a294d3e8be9185d6df.pdfcrown coverforest inventoryrelative biasspatial patterntree per hectare |
| spellingShingle | حمدالله صادقی سودابه گراوند ایمان ظفریان Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forests مجله جنگل ایران crown cover forest inventory relative bias spatial pattern tree per hectare |
| title | Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forests |
| title_full | Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forests |
| title_fullStr | Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forests |
| title_full_unstemmed | Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forests |
| title_short | Bias analysis of modified estimator of N-tree method for estimating stand density and crown cover area in Zagros Forests |
| title_sort | bias analysis of modified estimator of n tree method for estimating stand density and crown cover area in zagros forests |
| topic | crown cover forest inventory relative bias spatial pattern tree per hectare |
| url | http://www.ijf-isaforestry.ir/article_38841_ae2e747c40ce23a294d3e8be9185d6df.pdf |
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