Estonian Journal of Ecology最新文献

{"title":"Dominant cyanobacterial genera in Lake Peipsi (Estonia/Russia): effect of weather and nutrients in summer months","authors":"R. Laugaste, K. Panksep, M. Haldna","doi":"10.3176/ECO.2013.4.01","DOIUrl":"https://doi.org/10.3176/ECO.2013.4.01","url":null,"abstract":"Hydrochemical and phytoplankton data from L. Peipsi (3555 km 2 , mean depth 7.1 m) for July-September 1997-2011 (two lake basins) and for August 2003-2011 (three lake basins) were analysed. Our aim was to explain the impact of nutrient content and weather factors on the composition and species dominance of cyanobacteria. The share of cyanobacteria was on average 64% of the total biomass, maximum values amounted to 93% and 38 g m -3 in the areas of open water. Close to the lake shores these values reached 99% and 100 g m -3 in some cases. The most prevalent taxa affecting cyanobacterial biomass were Gloeotrichia echinulata in the littoral areas and Microcystis species in the open water. Principal component analysis placed all dominant genera (Aphanizomenon, Anabaena, Gloeotrichia, and Microcystis) separately from each other. Stepwise multiple analysis showed G. echinulata to be fairly independent of nutrients and related to the days with water temperature over 22 °C. The biomass of the genus Microcystis was found to have evidently the strongest positive connections with phosphorus and also with iron, as well as with all potentially toxic (vacuolated) forms of cyanobacteria. The other group of cyanobacteria, mainly small-celled colonial forms (Aphanocapsa, Aphanothece, Cyanodictyon, etc), constituted on average up to a fourth of the cyanobacterial biomass; its biomass showed a reasonably positive correlation with nitrogen and a negative correlation with water level. In summer, the succession of cyanobacterial genera in the lake started with Anabaena, then Gloeotrichia appeared (in the larger and deeper moderately eutrophic northern part of the lake), followed by Microcystis and Aphanizomenon.","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131488993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of the Abundance of Microfungi on the Barley Grain Grown as Pure and Mixed Crops in Central and North Estonia","authors":"Elina Akk, H. Lõiveke, L. Edesi, M. Kütt, E. Lauringson, V. Kastanje","doi":"10.3176/ECO.2013.4.03","DOIUrl":"https://doi.org/10.3176/ECO.2013.4.03","url":null,"abstract":"For centuries barley has been an important food crop for mankind. It is important to produce crops that are of good quality and safe to human and animal organisms. However, pathogenic fungi in cereals cause health problems both to humans and animals. In Estonia the microbiological quality of cereals has been studied to identify ”Fusarium” species in feed cereals. Still, the relationship between the agro-ecological conditions and the total abundance of moulds and yeasts on grain has been studied little in Estonia. In 2009 and 2010, we carried out field trials in the experimental station of the Estonian Research Institute of Agriculture in North Estonia (59°18'N, 24°39'E) and in the experimental station of Olustvere School of Service and Rural Economics in Central Estonia (58°33'N, 25°34'E). The variants of the experiment were barley in pure crops with added ammonium nitrate 120 kgN ha^(-1), barley in pure crops with added ammonium nitrate 60 kgN ha^(-1), barley in pure crops with no added ammonium nitrate, and barley.pea mixed crop. After harvesting, the grain was dried to 14% of moisture and grain samples were taken from each trial variant. The abundance of moulds, yeasts, and ”Fusarium” spp. was determined in grain samples using the dilution method. The impact of the levels of nitrogen, location of the trial site, and year (weather conditions) on the abundance of moulds, yeasts, and ”Fusarium” spp. was studied. The common genera of moulds identified were ”Cladosporium, Acremonium”, and ”Fusarium”. According to our results, yeasts were the most common fungi on barley grains. In North Estonia the abundance of moulds was lower compared to Central Estonia. The abundance of fungi was not affected by different levels of nitrogen or whether barley had been grown as a pure crop or a barley.pea mix. The weather conditions had the greatest impact on the abundance of microfungi.","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121053188","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Occurrence of Cladocera and the genetic diversity of Daphnia cucullata in the pelagic zone of Latvian salmonid lakes","authors":"Aija Brakovska, Jana Paidere, Renāte Škute, N. Škute, A. Skute","doi":"10.3176/ECO.2013.4.02","DOIUrl":"https://doi.org/10.3176/ECO.2013.4.02","url":null,"abstract":"INTRODUCTION Lakes are significant resources for the development of any area. They are especially important for the development of human settlements, tourism and recreation, fisheries, and other industries. About 40% of all lakes in Latvia are located in Latgale in the Augszeme Highland. According to the quality indicators, they are clean lakes with low trophic state indexes (Urtane, 1998; Latvijas ezeru, 2002). Salmonid fish lakes are one of the priority water bodies in Latvia. Latgale has a high percentage of lakes that fall into this category; however, there have not been any extensive ecological studies of these lakes in the region. In accordance with the Regulations of the Cabinet of Ministers No. 118, Appendix 2 of 2002 there are 26 salmonid lakes in Latvia. One salmonid species found in these lakes is vendace (Coregonus albula), which is a planktophagous fish. Vendace was found in 30 lakes of Latvia in the 1930s, in 11 lakes in the 1950s-1960s, and only in 5 lakes in the 1990s. This means that this economically important species is gradually disappearing from the Latvian lakes. Since 1995, vendace has been included into the Red Data Book of Latvia as rare species of the 3rd category. Vendace is also included in the lists of the specially protected species. Since vendace mainly feeds on zooplankton, we chose zooplankton as a major research object for our paper. Zooplankton (e.g. Cladocera) is an important feeding base for juvenile fish and planktophagous fishes such as salmonids (Hebert, 1982; Malone & McQueen, 1983; Pinel-Alloul, 1995; Cimdins, 2001; Wetzel, 2001; Chang & Hanazato, 2004) and plays an essential role in the transformation of substances and energy in water bodies. Zooplankton controls the number of bacteria and algae, contributing to the biological self-purification process of water. A zooplankton community is a dynamic system in which the species composition may change significantly during the season. Temporal changes of the zooplankton species found in temperate lakes are influenced by many factors, including temperature, food, competition, and predation (Hebert, 1982; Malone & McQueen, 1983; Dodson, 1984; Larsson & Dodson, 1993; Weider & Pijanowska, 1993; Pinel-Alloul, 1995; Cimdins, 2001; Wetzel, 2001; Chang & Hanazato, 2004; Harris et al., 2012). It is a well-known fact that zooplankton organisms are very sensitive to the biotic and abiotic influences, which lead to structural and functional changes on a polymorphism level (De Meester et al., 1995). This makes them good bioindicators for the evaluation of water quality and toxicity as well as for experimental purposes in ecology and genetics (Sloka, 1998; Dussart & Defaye, 2001). During our research (Brakovska & Skute, 2007, 2009; Brakovska & Paidere, 2012; Brakovska et al., 2012; Jurevics et al., 2012) we found that Daphnia cucullata is among dominants in the Cladoceran community of Latvian salmonid lakes. It forms also an important part of the vendace food (Viljanen, 1","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124826791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatial distribution of marine benthic habitats in the Estonian coastal sea, northeastern Baltic Sea","authors":"G. Martin, J. Kotta, T. Möller, K. Herkül","doi":"10.3176/ECO.2013.3.01","DOIUrl":"https://doi.org/10.3176/ECO.2013.3.01","url":null,"abstract":"INTRODUCTION Annex I of the Habitat Directive (Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora) defines the habitat types of higher importance and in need of conservation within Europe. Together with the Birds Directive this directive forms a solid base for the European nature conservation policy and the Natura 2000 network. In order to implement the requirements of the directive and to resolve the existing needs for local conservation purposes, a benthic habitat classification system EBHAB (Eastern Baltic marine benthic HABitats) was developed in the frame of the multinational EU LIFE project 'Marine Protected Areas in the Eastern Baltic Sea (Baltic MPAs)'. In the current study a detailed inventory of the EBHAB habitat classes was performed within six study areas covering the most valuable nearshore marine areas and including several protected areas, i.e. the Natura 2000 areas in the Estonian coastal range. In general, prior to this inventory the knowledge on the distribution of habitats and associated biota in the coastal areas was very poor including only a few publications each containing a handful sampling sites only (e.g. Martin, 2000; Kotta & Orav, 2001; Kotta et al., 2008, Kovtun et al., 2009). Moreover, the published background information was very scattered and owing to differences in methodologies there was no way to systematize such knowledge. Thus, there was a need to examine the species composition and identify typical communities within their environment. The current inventory allowed us for the first time (1) to summarize the range of large-scale variability of the studied habitats in terms of benthic biodiversity, species composition, and dominance structure; (2) to provide a knowledge base for follow-on biological and ecological studies; and (3) thus, to provide important information for managing our marine resources. MATERIAL AND METHODS Study area Altogether six areas representing various environmental and climatic conditions in the northeastern Baltic Sea were studied in detail with the aim of classifying the observed benthic habitats according to the recently established EBHAB classes (Fig. 1). An overview of the study areas is given below. [FIGURE 1 OMITTED] Eastern and western Gulf of Finland areas The average depth of the Gulf of Finland is 37 m and the maximum depth 123 m. The coastal slope is quite steep and depths reach over 30 m in all bays of the study area. Sand, silt, or sandy clay bottoms dominate in deeper areas, boulders and stones prevail near the coast. The coastline is diverse and disjuncted by peninsulas, many small islands occur in the area. The eastern gulf receives runoff from a huge drainage area and the western gulf is a direct continuation of the Baltic Proper. Therefore the gulf has a permanent east-west gradient of salinity. The salinity range of the study area is 4.5-6.2. The area is strongly influenced by diffuse and point-source nutrie","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":" 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132095875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Factors affecting the re-vegetation of abandoned extracted peatlands in Estonia: a synthesis from field and greenhouse studies","authors":"Triin Triisberg, E. Karofeld, J. Paal","doi":"10.3176/ECO.2013.3.02","DOIUrl":"https://doi.org/10.3176/ECO.2013.3.02","url":null,"abstract":"Re-vegetation of extracted peatlands is a slow and sporadic process. The aim of our study was to clarify whether this process is affected by the distance from vegetated areas and propagules arrival or by the conditions for propagules germination and plant growth. Our analysis is based on three extracted peatlands in Estonia, abandoned 26-31 years ago. In all study areas vegetation was analysed on the gradient from a neighbouring vegetated area towards the central part of the peatland. In addition, peat blocks were collected from the marginal and central parts of the peatlands, held in favourable moisture conditions for seed germination in a greenhouse, and half of them were fertilized with a complex fertilizer. Our study showed the species pool to be present everywhere on abandoned extracted peatlands, but the germination was influenced by different factors such as water table, peat chemistry, etc. The species richness on extracted peatlands was higher close to the neighbouring vegetated areas and decreased towards the central part of the peatland, but for the peat blocks held in the greenhouse, the number of species was higher for the blocks collected from the central parts of the peatlands. The proximity of the vegetated area did not increase the number of species developed in the greenhouse whereas higher moisture and temperature conditions initiated the growth of many additional species not found on the extracted peatlands. Our study demonstrated that fertilization with a complex fertilizer did not have an overall influence on the number of species, indicating that the re-vegetation of extracted peatlands is more controlled by moisture conditions than by the availability of nutrients or propagules arrival.","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126655175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of railway lines in the distribution of alien plant species in the territory of Daugavpils City (Latvia)","authors":"S. Rutkovska, I. Pučka, P. Evarts-Bunders, Jana Paidere","doi":"10.3176/ECO.2013.3.03","DOIUrl":"https://doi.org/10.3176/ECO.2013.3.03","url":null,"abstract":"The study was performed based on an inventory of alien flora in Daugavpils City. During the field studies all the alien species were recorded applying a regular grid consisting of 344 quadrats of 500 m × 500 m. Data of the 84 quadrats that cover all railway lines in the city were analysed to identify relationships between the distribution of alien plants and the location of railway lines. First the obtained data were compared with the first flora inventory in the city, which was conducted from 1975 to 1983. Comparison of data of the previous inventory and those obtained by us showed that the number of the recorded alien taxa along railways differed: 95 and 38 taxa, respectively. Secondly, some factors affecting the distribution of alien species along railway lines were analysed. Obtained results indicate that the highest concentrations of alien plants occurred in areas where railways are crossing or are located close to the adjacent cultivated and abandoned allotments, areas of private houses or cemeteries. Railway management measures such as topsoil disturbance and application of herbicides were found to be important human-induced factors affecting the distribution of annual alien taxa. The results of geospatial and statistical analyses demonstrated that the geo- graphical distribution of alien species in general did not coincide with railway lines. However, the distribution of three species, i.e. Dracocephalum thymiflorum, Erysimum durum, and Lappula squarrosa, was associated only with railway lines, demonstrating the importance of railway infrastructure elements for the expansion of these species.","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124759910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Iron Forms and Peroxidase Activity in Forest Island Soils","authors":"L. Szajdak, T. Meysner","doi":"10.3176/ECO.2013.2.01","DOIUrl":"https://doi.org/10.3176/ECO.2013.2.01","url":null,"abstract":"Oxidation-reduction reactions play a key role in ecologically important biogeochemical processes in soil and influence soil chemical, biochemical, and biological properties. The objective of this study was to compare the effect of a forest island located on two kinds of soils on the concentrations of iron forms and peroxidase activity participating in oxidation-reduction processes. The investigations were carried out in the Agroecological Landscape Park in Turew (40 km south of Poznan, Western Polish Lowland, 16°45'E, 52°01'N). The subject of the study was a palace park, which can be considered as a forest island. Part of this forest island is located on mineral soil and another part on mineral-organic soil. Our results showed that the flow of groundwater was accompanied by an increase in peroxidase activity, total iron concentration, and Fe(II) and Fe(III) ions in the mineral soils in most periods of sampling. However, an increase of peroxidase activity and a decrease of total iron concentration and Fe(II) and Fe(III) ions accompanying the flow of groundwater were observed in the mineral-organic soils.","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127828340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Potential for fast chlorophyll a fluorescence measurement in bryophyte ecophysiology","authors":"L. Liepiņa, G. Ievinsh","doi":"10.3176/ECO.2013.2.05","DOIUrl":"https://doi.org/10.3176/ECO.2013.2.05","url":null,"abstract":"The aim of the study was to analyse if the measurement of fast fluorescence induction kinetics in bryophyte samples in field conditions could be used for characterizing the photochemistry of photosynthesis in bryophytes. Bryophyte samples were collected in five different habitats of the boreo-nemoral zone growing on various substrates. Twenty-four species were epigeic, six epilithic, ten epiphytic, three epixylic, and six semi-aquatic or aquatic. Extremely high variation was found for fluorescence parameters between bryophyte samples. Performance Index showed the highest variability, reaching 160% in the case of epiphytic bryophytes. There were statistically significant differences for mean values of Fv/Fm, RC/ABS, and Fv/F0 between epigeic and epiphytic bryophyte samples as well as between epiphytic and semi-aquatic & aquatic samples. For Performance Index, a significant difference was observed only between epiphytic and epigeic bryophytes. It was concluded that bryophytes display a low intensity of the photochemistry of photosynthesis even in relatively wet habitats. In general, measurement of fast fluorescence induction kinetics in field conditions could be a rapid and efficient tool to obtain quantitative data useful for ecophysiological studies.","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122819645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seed Dormancy and Germination of an Endangered Coastal Plant Eryngium Maritimum (Apiaceae)","authors":"J. Ņečajeva, G. Ievinsh","doi":"10.3176/ECO.2013.2.06","DOIUrl":"https://doi.org/10.3176/ECO.2013.2.06","url":null,"abstract":"INTRODUCTION Eryngium maritimum L. is a littoral species growing on sand dunes and shingle beaches. Although it is listed among the species widespread in western and southern Europe, overall its population is declining (Van der Maarel & Van der Maarel-Versluys, 1996). The species is included in the Red Data Book of Latvia (Fatare, 2003) and is protected in several other European countries. In northern Europe and in the Baltic Region it grows near the limits of its current area of distribution and therefore is at a greater risk of extinction because in small and isolated populations there is a risk of inbreeding depression. For example, in Eryngium alpinum partial self-incompatibility causes lower seed set in selfing plants and selfing negatively affects seed mass and germination (Gaudeul & Till-Bottraud, 2003). A survey of E. maritimum populations along the Skagerrak coast was conducted and the persistence prospects of this species were evaluated as low in these localities due to the small size and fragmentation of individual populations (Curle et al., 2007). Population surveys were also conducted in Poland and Lithuania (Olsauskas, 1996; Labuz, 2007). While in some cases the decline of E. maritimum is linked to habitat disturbance, a population can be threatened also due to limited generative reproduction, affected both by low seed production and low germination as well as high juvenile mortality (Curle et al., 2007; Aviziene et al., 2008). It was suggested also that a decrease of the physiological fitness of E. maritimum individuals in northern populations is associated with lower photosynthetic productivity due to high precipitation and low air temperature (Andersone et al., 2011). Seeds of the Apiaceae family are often morphologically or morphophysiologically dormant (Finch-Savage & Leubner-Metzger, 2006). Seeds with morphological dormancy have small, differentiated embryos that need time to develop before a seed can start to germinate (Baskin & Baskin, 2004). Morphophysiologically dormant seeds also have a physiological component of dormancy and therefore require a dormancy-breaking pretreatment. Depending on the type of the physiological component, different combinations and length of warm and cold stratification can be required (Baskin & Baskin, 2004). Preliminary research on E. martimum seeds (J. Necajeva, unpublished results) confirmed that seeds of this species have underdeveloped embryos at the time of maturation and seed dispersal and, in addition, seeds require dormancy-breaking treatment (cold stratification) to germinate. Other researchers also reported that cold stratification is necessary to break the dormancy of E. maritimum seeds (Walmsley & Davy, 1997; Curle et al., 2007). The results of previous studies probably give sufficient information to develop an effective method of germinating E. maritimum seeds. However, to our knowledge, there have not been any detailed studies of the physiology of the germination process in E. mari","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130010565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Organic Mulches on the Content of Organic Carbon in the Soil","authors":"K. Bajorienė, D. Jodaugienė, R. Pupalienė, A. Sinkevičienė","doi":"10.3176/ECO.2013.2.02","DOIUrl":"https://doi.org/10.3176/ECO.2013.2.02","url":null,"abstract":"INTRODUCTION The content of organic carbon has long been recognized as a key component of soil quality (Reeves, 1997), and thus maintenance of soil organic carbon (SOC) in cropland soils is a major determinant of the productivity and long-term stability of agricultural systems (Carter, 2002). Soil organic matter (SOM) is composed of plant, animal, and microbial residues at varying stages of decomposition and amorphous humic substances (Jenkinson et al., 1992). An increase in the total content of SOC in organic farming was established by Marinari et al. (2010). Natural organic mulch eventually breaks down and becomes a part of the soil and a source of plant nutrients (Sharma et al., 1998; Bond & Grundy, 2001; Gruber et al., 2008). Increasing the amount of SOC is regarded as the main advantage of organic mulch (Paustian et al., 1997; Saroa & Lal, 2003). The influence of mulch on soil agrochemical properties depends on the chemical composition of mulch. It is recommended that in ecological farming soil should be covered with composts, chopped straw, and other organic residues to provide crops with nutrients, especially nitrogen (Relf, 2009). During the mineralization process of the mulch small amounts of nutrients become available for plants. However, it is not a sufficient supply of plant nutrients. Organic mulch is a source of nutrients for soil microorganisms, and as a result of their activity organic residues used for mulching are decomposed to available plant nutrients and a very important substance in soil--humus (Blanchart et al., 2006). Different opinions on the influence of organic mulches on SOM exist. A significant increase of SOC was observed in plots mulched with organic mulches (Relf, 2009). However, Kukkonen et al. (2004) stated that peat mulch has no significant influence on the amount of SOC. Oats and vetch grown for green manure and sprayed on soil surface were found to increase the amount of SOC and nitrogen in the soil compared with green manure inserted into the soil (Yadav, 1995; Astier et al., 2006). Cadavid et al. (1998) registered an increase of SOC and a decrease of the soil pH in plots covered with grass mulch. According to Blanco-Canqui & Lal (2007), mulching with straw during 10 years increased SOC by 33%. This means that 2/3 of the applied wheat straw was not converted into SOC and most probably was lost as emissions of C[O.sub.2] and C[H.sub.4]. Mulching even has the potential of reducing greenhouse gas emissions from soil by increasing its SOM content (Mulumba & Lal, 2008; Jordan et al., 2010). Our hypothesis was that the influence of organic mulch of different chemical composition on SOC will be unequal. The aim of the investigation was to evaluate the effect of various organic mulches and different thicknesses of the mulch layer on the SOC content. MATERIALS AND METHODS The two-factor field experiment was carried out in the Pomological Garden of Aleksandras Stulginskis University (formerly Lithuanian University of A","PeriodicalId":262667,"journal":{"name":"Estonian Journal of Ecology","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125797270","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}