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  • Author: Hana Habrová x
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Abstract

The study describes main biotopes of Socotra Island. The biotopes were distinguished and described during complex field observations on more than 250 localities of Socotra between years 1999-2004. Classification of biotopes is based on differences in physiognomy, structure and species composition of the vegetation component of present biocoenoses. Groups of biotope types differ, above all, in the physiognomy and structure of vegetation. Biotope types are divided according to composition of dominant species. In this manner, 13 groups of biotopes and 39 biotope types were distinguished and described

Abstract

The landscape differentiation on seed regions is used in the Czech forestry industry for purposes of seed transfers. The seed regions are created for main commercial tree species and the rules for transfer among these regions are described. The geobiocoenological landscape differentiation and differences among tree species populations were used as main approaches. The same principle is used for Boswellia seed regions differentiation on Socotra island. Eight species of Boswellia genus were determined on the island, all species being endemic. The differentiation is based on Boswellia populations field survey. All populations were described in morphological signs. The vegetation zones and geomorphological differentiation were also taken into account. The result is a map of seed regions for every Boswellia species on Socotra island presented in the article.

Abstract

Within the area of Central Europe, and especially in the Czech Republic (and former Czechoslovakia), geobiocoenological landscape differentiation has been applied for more than 40 years to create a spatial model of the natural (potential) condition of geobiocoenoses in the landscape. Because long-term objective of geobiocoenology is to contribute to the creation of harmonic cultural landscape by gradual development of a comprehensive system of groundworks for sustainable landscape use, and as Mendel University experts work in various countries, adaptions of geobiocoenology were used also outside Europe, in tropical areas. Examples of such a work could be shown on islands such as Socotra (belonging politically to Yemen), Tasmania, and Cuba.

Abstract

Between 2010 and 2011 a field survey dedicated to Dracaena cinnabari (DC) population was conducted in Firmihin, Socotra Island (Yemen). It’s main goal was to collect data that would make it possible to unbiasedly estimate main characteristics of the local DC population. Our motivation was to provide reliable information to support decision-making processes as well as other research activities. At the same time we were not aware of a survey which could provide this kind of statistical-sound estimates for the whole population covering an area of almost 700 ha.

This article describes how the survey has been planned and carried out in practice. In addition, we also provide a set of preliminary estimates of the main DC population figures - totals and per hectare densities of stems, overall and partitioned according to predicted crown age. Among estimated parameters there are also mean crown age and proportions of predefined age classes on the total number of living DC stems. These estimates provide an explicit information on age structure of the whole DC population in Firmihin.

Although we collected data on more than one hundred randomly located plots, the reported accuracy of our estimates is still rather limiting. We discuss several possibilities to obtain more accurate results or at least to approach the supposedly lower true variance that can’t be calculated by approximate techniques applied here.

The design and concept of our survey makes it possible to evaluate changes over time on stem by stem bases and to generalize these stem-level details to the whole population. Mortality, regeneration and even change of population’s mean crown age can be estimated from a future repeated survey, which would be extremely useful to draw firm conclusions about the dynamic of the whole DC population in Firmihin.