Bulgarian Journal of Soil Science

5-19

Authors: Metodi Teoharov

In this article is presented stage development of Bulgarian Soil Science – from 1911 year until our days. Fonder of soil science of Bulgaria is Nikola Pushkarov. Nearly, with his life is finished the first stage (1947). Pushkarov developed the first cientific program of soils with basic tasks. Second stage of development (1947-1969) is stage of rapid development of soil science associated with the reorganization of agriculture in Bulgaria. Third stage (1969-1989) is stage of modernization of equipment, strengthening of international relations and recognition, advanced science servicing of agriculture. Fourth stage is stage of reforms, changes and integration into European research area.

26-32

Authors: Biser Hristov, Ekaterina Filcheva, Plamen Ivanov

This paper deals with the contents and composition of organic matter in soils with stagnic properties. Study on the content and composition of soil organic matter, shows that these soils have low content of organic carbon. Soil formation proceeds under influence of acid plant residues from forest and seasonal waterlogging caused by the surface stagnating waters. The total carbon content decreases sharply in subsurface horizons. The amount of fulvic acids (Cf) prevail over humic acids (Ch) and type of humus is humic-fulvic and fulvic.

51-63

Authors: Yovana Todorova, Ivaylo Yotinov, Stilyana Lincheva, Yana Topalova

Heavy metals are widespread pollutants with significant environment risk due to high toxicity and clear tendency for accumulation in different matrices – soils, sediments, biota. The main research objective of this work is to assess the impact of heavy metal pollution on key structural and functional parameters of microbial communities in sediments of river-dam sequence of small hydropower cascade Middle Iskar, Bulgaria. The content of heavy metals (As, Cd, Cu, Hg, Pb, Zn) was measured during the low water summer periods of 2012, 2013 and 2014. The evaluation of site quality and heavy metal pollution was done by use of one integrated index - Pollution Load Index and it was compared to total count of sediment microbiota and count of coliform bacteria, also with total dehydrogenase activity and index of phosphatase activity. The assessment of heavy metal pollution in river-dam sequence of cascade indicates the higher metal concentrations and high Pollution Load Index in dam sediments. At low level of pollution in river sites, the both structural and functional microbial parameters react to local variations of heavy metal concentrations and high negative correlation (r=-0.8÷-0.9) exists between variables. But in dam sites, the microbial community is more resistant to pollution and structural parameters react conservatively with long reaction time. The enzyme activities are more adaptive and sensitive indicators for different level of environmental impact in this case. The complex phosphatase and dehydrogenase activities have a high potential to be used as reliable parameters for precise assessment of hazardous sediment pollution in complicated ecological situations with cumulative impacts.

78-91

Authors: Mariyana Lyubenova

The paper deals with meta-analysis of 259 dendrochronological series of mountain trees – Bosnian pine, Norway spruce and beech from 14 locations in Bulgaria for eustress investigation. The chronologies were analyzed by the original SPPAM 2.0 application. The tree ring width sequences were approximated with polynomials with determination coefficients, R*R ≥ 0.45. The growth index (It – the ratio between measured and approximated value of tree ring width) was computed. Years with It less than the threshold values were considered as eustress ones. The four grade scales for assessment of frequency, duration and depth of eustress was proposed. For the studied tree species and locations, the obtained eustress periods are as follows, respectively for the Bosnian pine, Norway spruce and beech: 42 (K=9.1), 30 (K=3.4) and 37 (K=3) on average. The obtained eustress characteristics are respectively: Average Depth, Aav = 0.16, 0.26 and 0.28; Average Duration, Dav = 2, 2.5 and 2.3 years; and Average Frequency, Fav = 10, 33 and 34 years over 100 years. The risk for The stands of two studied locations of spruce and three locations of beech were established to be in some risk. They require further monitoring. The predominance of cold-dry and hot-wet years in total number of adverse climatic years (with eustress) for the Bosnian pine, as well as hot-dry and cold-wet years for spruce and beech stands was established. The influence of climatic types of years on the eustress appearance for tree years periods have also been investigated. Proposed holistic approach for meta-analyses of series (eustress identification in radial growth of stems) is convenient for the fast monitoring of forest communities state and for recognizing the stands under risk. The capability of approach allows expression of reactive functional types of trees (PFTs) as groups of trees with the similar behavior to the influence of climatic types of years, and with similar characteristics of eustress periods. These PFTs can support the development of different local, regional and global models. The originality of approach applied includes: meta-analysis, new software, characteristics, indixes and coefficients.