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1. K-Step Adaptive Cluster Sampling with Horvitz-Thompson Estimator | |||
Zhu Guangyu | |||
Forestry 06 June 2016 | |||
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Abstract:Adaptive cluster sampling (ACS) has widely been used for data collection of environment and natural resources. However, the randomness of its final sample size often impedes the use of this method. To control the final sample sizes, in this study a k-step ACS based on Horvitz-Thompson (HT) estimator was developed and an unbiased estimator was derived. The k-step ACS Horvitz-Thompson (ACS-HT) was examined first using a simulated example and then using a real survey for numbers of plants for three species that were characterized by clustered and patchily spatial distributions. The effectiveness of this sampling design method was assessed in comparison with ACS Hansen-Hurwitz (ACS-HH) and Horvitz-Thompson (ACS-HT) estimators, and k-step ACS-HT estimator. The effectiveness of using different k-step sizes was also compared. The results showed that k-step ACS-HT estimator was most effective and ACS-HH was least. Moreover, stable sample mean and variance estimates could be obtained after a certain number of steps, but depending on plant species. K-step ACS without replacement was slightly more effective than that with replacement. In K-step ACS, the variance estimate of 1-step ACS is more big than other K-step ACS (k>1), but it is more small than ACS. This implies that -step ACS is more effective than traditional ACS, besides, the final sample size can be controlled easily in population with big clusters. | |||
TO cite this article:Zhu Guangyu. K-Step Adaptive Cluster Sampling with Horvitz-Thompson Estimator[OL].[ 6 June 2016] http://en.paper.edu.cn/en_releasepaper/content/4695965 |
2. Deriving merchantable volume in poplar through non-destructive terrestrial laser scanning | |||
SUN Yuan,LIANG Xinlian,LIANG Ziyu,LI Weizheng,WELHAM Clive | |||
Forestry 18 April 2016 | |||
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Abstract:Timber volume is an important ecological component in forested landscapes. The application of Terrestrial Laser Scanning (TLS) to volume estimation has been widely accepted though few species have well-calibrated taper functions. This research uses TLS technology in poplar (Populus × canadensis Moench cv. 'I- 72/58') to extract stem diameter at different tree heights and establish the relationship between point cloud data and stem curve, which constitutes the basis for volume estimation of single trees and the stand. Eight plots were established and scanned by TLS. Stem curve functions were then fitted after extraction of diameters, DBH and tree heights from the point cloud data. Lastly, six functions were evaluated by R2 and RMSE. A modified Schumacher equation was the most suitable taper function. Volume estimates from the TLS-derived taper function were better than those derived using the stem-analysis data. Finally, regression analysis showed that predictions of stem size were similar when data were based on TLS versus stem analysis. Its high accuracy and efficiency indicates that TLS technology can play an important role in forest inventory assessment. | |||
TO cite this article:SUN Yuan,LIANG Xinlian,LIANG Ziyu, et al. Deriving merchantable volume in poplar through non-destructive terrestrial laser scanning[J]. |
3. Technical, Environmental & Social Feasibility Analysis For Indian Forestry Sector | |||
TAKLE Shrinidhi Sunil,Jiang Zhihong | |||
Forestry 04 December 2009 | |||
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Abstract:The rapidly growing Indian economy has implications for all sectors of the economy, including forestry. The societal demands on forests are becoming more diversified and rising faster than the capacity of forests to supply them on a sustainable basis. The widening gap is one of the main causes of forest degradation and loss of forest biodiversity that is taking place on an unprecedented scale, fast eroding the very basis of the livelihood of forest璬ependent communities. The existing administrative structure and functions, planning and control system, and research and training methods are all geared toward securing a sustained supply of timber, mainly from state forest reserves. A move toward more comprehensive multiple璾se forestry would require reorientation of forestry institutions by bringing within their mandate the production of goods and environmental services, both in and outside forests. A mismatch between the changing societal demands on forests and non璫hanging forestry institutions could slow down the growth or even allow the sector to stagnate, thereby accelerating forest degradation. The themes are: The future of Indian forestry will depend on the provision of reliable data and inventories covering all aspects of the Indian forestry system. New data and inventories must be based on integrated assessments that take account of issues far beyond traditional forest璼ector analysis and map the root causes of the degradation and depletion of forest resources. These integrated assessments can then feed into an ongoing, institutionalized strategic planning process that result in integrated strategies and policies. The successful implementation of this strategic plan will require the restructuring of existing governance and institutions with respect to the forest sector. In essence, Indian forestry experts point to the need for an integrated concept for analysis, planning, and management of the Indian forest sector. | |||
TO cite this article:TAKLE Shrinidhi Sunil,Jiang Zhihong. Technical, Environmental & Social Feasibility Analysis For Indian Forestry Sector[OL].[ 4 December 2009] http://en.paper.edu.cn/en_releasepaper/content/37245 |
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