Научная литература
booksshare.net -> Добавить материал -> Экология -> Протасов А.А. -> "Биоразнообразие и его оценка. Концептуальная диверсикология" -> 43

Биоразнообразие и его оценка. Концептуальная диверсикология - Протасов А.А.

Протасов А.А. Биоразнообразие и его оценка. Концептуальная диверсикология — Киев, 2002. — 105 c.
Скачать (прямая ссылка): bioraznoobrazie2002.pdf
Предыдущая << 1 .. 37 38 39 40 41 42 < 43 > 44 45 46 .. 47 >> Следующая

Currently, due to the intensified processes of uncontrollable invasion of new species, the issue of "repackaging" of niches in communities and introduction of new species into aboriginal communities become really.
Diversity of communities is determined not only by internal interrelations and mutual relations of niches, but by conditions of environment as well. Factors and resources have their diversity that determines the biotic diversity and can also depend on biotic factors (position 5.1; 5.2). A principle (5.5) that diversity increase is related to stability of conditions in time is one of the widely spread pos-
96
Summary
tulates about connection medium conditions and biodiversity. The diversity and spatial heterogeneity are related, in opposite, by another manner: high diversity is supported by high spatial heterogeneity of environment (position 5.6; 5.7). Evaluation of environment diversity is much more complex because indexes have different dimensions.
Since estimation of the Shannon index values requires estimation of significance of system elements, its suggested to use method of medium diversity estimation based on the expert evaluation each factor portion in common factorial field. Issue of possibility to control biodiversity through change of roles of different medium factors is an important issue and requires additional research.
There is a principle (5.11) that biodiversity reaches lowest values under extreme conditions. Even though this environment evaluation is indistinct, the thesis is widely used, in some form, in environmental policy. Reduction of antropo-geneous pressure and contamination, are considered as "improvement" of a medium, removal from extreme conditions. According to this logic such "improvement" should lead to increase in diversity. Most likely, neither excessive stabilization of conditions, nor excessive heterogeneity of medium and complete absence of external disturbances facilitate achievement of maximum diversity of communities (position 5.12; 5.13; 5.14). Also, by no means the biggest primary production determines the highest diversity but rather some average values.
One of major issues of diversicology is the diversity restriction and factors of its limitation. What effect diversity decrease below admissible minimum or too high diversity or emerging of "bad" diversity would have on normal functioning of community? Apparently, it is necessary to proceed processes in biotic systems based on the principle of balance of variability and conservatism (position 5.23). Such approach requires not search for a way to reach maximum diversity but reveal of optimum diversity in ecosystems.
Outlined principles enable to suggest a variant of biodiversity modification model (fig. 5.1) in gradients of basic features of environment. The highest diversity of communities should be expected under conditions of intermediate numbers of resources abundance, external disturbances, temporary stability and spatial heterogeneity. The introduced hypotheses allow more well-founded approach to the problem of possibility to maintain high diversity level implementing various measures to "improve" the environment (fig. 5.2). The essence of such recommendations is, that the measures to "improve" medium should be carried out only up to the point of reaching maximum diversity, because further "improvement" would start to reduce diversity. Certainly, the establishment of such optimum is the main task of the applied diversicology.
Another important issue in application of biodiversity estimations is related to bioindication of environment quality. Due to the fact that structural and functional features of communities are formed in the defined accordance with habitat conditions, their modification might be an indicator of environment conditions modification (position 6.1; 6.5). Monitoring for taxonomic diversity that is based on a hypothesis that in communities under more favorable conditions the higher
97
Биоразнообразие и его оценка. Концептуальная диверсикология
number of large taxa is represented by large number of species and there is no large taxa with overwhelming prevalence of number of species can become one of possible approaches to evaluation of medium quality through diversity. Apart from taxonomical unit (genera, families, orders) itself, ecomorphological and trophic groupings can also be used as "large taxa".
The use of indexes of species diversity based on relative significance of species in community (position 6.5) has shown, that with increase of contamination diversity of communities decreases (position 6.6). However, there is also data on a unimodal character of species diversity modification in raising trophic level and contamination gradient. Diversity is low under oligotrophic conditions, in sufficiently clean or highly polluted environment. With the formalistic approach, such distribution makes evaluations of environment quality extremely complicated, as the values of diversity index could be the same under completely different conditions. It is necessary to take into account not only quantitative, but also qualitative values, as various conditions have various species represented. The structure of diversity itself should be also considered, what causes diversity decrease — abundance or evenness. And, perhapse, the most important — whether the diversity maximum corresponds to some optimum conditions, which would require total revision of the concept of bioindication.
Предыдущая << 1 .. 37 38 39 40 41 42 < 43 > 44 45 46 .. 47 >> Следующая

Реклама

c1c0fc952cf0704ad12d6af2ad3bf47e03017fed

Есть, чем поделиться? Отправьте
материал
нам
Авторские права © 2009 BooksShare.
Все права защищены.
Rambler's Top100

c1c0fc952cf0704ad12d6af2ad3bf47e03017fed