Evaluation of structural diversity of yew (Taxus baccata L.) stands in Golestan Province Aliabad

Jafari Afrapoly, Mohadeseh (2017) Evaluation of structural diversity of yew (Taxus baccata L.) stands in Golestan Province Aliabad. Masters thesis, University of Mohaghegh Ardabili.

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Text (ارزیابی تنوع در ساختار توده‌های جنگلی سرخدار (Taxus bacata L.) در منطقه علی‌آباد استان گلستان) Mohadeseh Jafari Afrapoly.pdf Download (997kB) | Preview

Abstract

The study of forest structure is one of the most important prerequisites for the understanding and management of forest ecosystems. To understand the structure of the forest, researchers have divided it into three kinds of the spatial diversity, mingling diversity and tree dimension diversity (diameter and height). The English yew is native and ancient tree species of the northern forests that have been considered in recent years because of two special aspects. This tree is on the treated species list and organs of this this tree contains valuable substance called taxol. The Afratakhteh Forest reserve is one of the few English yew sites of the northern forests, in which long-lived English yew trees found in a high density and sometimes as pure stands. The aim of this research is to provide quantitative characteristics of forest stand structure using a set of indicators in the natural habitat of this species. In order to reveal the quantitative characteristics of the structure of the English yew stnads in the Afrathat forests, three one hectare study sites were selected and within sites 30×30 m gird plot were established and in the intersection point of girds (n=36), diameter at the breast height, tree height, crown diameter, distance and angle among trees were measured for the closest beech to the intersection point as reference tree and other three nearest neighbors the to the reference tree. In order to study the structure the set of indices including such mingling, diameter and height differentiation, tree to tree interval distance and Clarke and Evans index were used.Our results showed that the uniform angle index value was 0.64 and Clarke and Evans were around one this means the English yew randomly distribute in this forest. The mingling index estimated 0.61 that means English yew tends to mixed with other tree species. According to the diameter and height differentiation, English yew stands have slightly heterogeneous diameter distributions, uniform tree height, and the stems have an average distance between trees of 2.0-4.0 m. The English yew is a threatened tree species in the northern forests of Iran. The species of English yew in its natural habitat tends to be mixed with other species (often with hornbeam), have slightly heterogeneous diameter and height distributions. The reduction of young English yew trees as a result of the mortality of trees in a diameter classes less than 15 cm and the high competition of English yew with other tree species requires more consideration and effort to conservation of this species in the sites.

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