Biomass Of Different Groups Research Articles

Divergent vertical distributions of microbial biomass with soil depth among groups and land uses

Soil microbial biomass is key to improving the prediction of soil organic carbon (SOC) dynamics by modeling. However, the driving mechanism of microbial biomass of different groups with soil depth is poorly understood across sites. Here, we compiled the biomass of different microbial groups (i.e., fungi, bacteria, gram-positive bacteria G+, and gram-negative bacteria G-) from the surface to a soil depth of 1 m from 71 soil profiles across three continents. We found that the biomass of microbial groups all decreased with soil depth but at different magnitudes, while the relative abundance of microbial groups, except G-, was relatively stable along soil profiles. Soil fungal biomass had a shallower vertical distribution than bacteria, especially G+, with 89% fungi and 76% G+ in the top 10 cm soils. In addition, a greater proportion of microbial biomass (71–89%) compared to SOC (64%) was in the top 10 cm soils, suggesting that microbes and SOC exhibited different vertical distributions. The vertical distributions of microbial biomass of different groups were significantly correlated with SOC and clay content but not with climate, and these distributions were different among land uses, highlighting the great influences of edaphic factors on vertical distributions of microbial biomass. The relationship between microbial biomass and soil depth provides a feasible way to estimate microbial biomass at different soil depths, which can serve as a benchmark to improve the prediction of SOC dynamics of entire soil profile at large scales.

Phytoplankton of lakes in different types of landscape in Southern Karelia (Vendyurskaya group and Zaonezhye)

The phytoplankton of nine lakes located in different types of landscapes in the southern part of the Republic of Karelia was studied in spring and summer seasons of 20112012. In seven of the lakes phytoplankton was studied for the first time (lakes Gizhozero, Lelikozero, Myagrozero, Kondozero, Korytovo (Zaonezhsky Peninsula), lakes Koverjarvi, Rapsudozero (Vendyurskaya group). The highest species diversity in lakes of all types of landscapes was demonstrated by diatoms (20-42 % of the total number of species) and green algae (17-42 %). Each lake had its specific algal flora, and degree of their similarity measured by the S0rensen index was low. Quantitative indicators of phytoplankton in the lakes varied over a wide range of values. Phytoplankton abundance ranged within 5.8-1060.5 thousand cells/L (with an average of 160.1 ± 29.1), and biomass ranged from 0.010 to 1.374 g/m 3 (0.209 ± 0.04 g/m 3 on average). Data clustering using 26 variables showed different levels of relationship both between lakes and between their groups. It was found that the main factors influencing the total abundance and total biomass of phytoplankton, as well as the abundance and biomass of different groups of algae are the catchment area/water surface area ratio, total nitrogen and phosphorus, water catchment area, mineralization, lake surface area, pH and color. We obtained significant positive correlations (at a level of p < 0.05) between the structural indicators of phytoplankton and nutrients (total nitrogen and phosphorus).

Littoral species diversity and biomass: concordance among organismal groups and the effects of environmental variables

Biomass and species diversity (richness and evenness) of littoral organisms were explored in 27 sites in three basins of the large Lake Saimaa system in eastern Finland. The basins differed in degree of nutrient loading and trophic status. Six organismal groups, i.e., phytoplankton, periphyton, macrophytes, crustacean zooplankton, benthic macroinvertebrates and fish were studied. Factors affecting the biomass and diversity of these groups were explored by multiple stepwise regression analysis. The biomass of different groups was explained by the same variables, mainly nutrients, while diversity was associated with different environmental factors among the studied groups. The biomass of periphyton, phytoplankton, zooplankton, and fish correlated significantly with each other. There was also an apparent association between the biomass of macrophytes and that of benthic invertebrates. However, no significant correlations were found among the diversity of the studied groups. In accordance with previous studies, our results did not support the existence of species-rich hotspots or the possibility of using any surrogate taxon to reveal overall biodiversity. Thus, for conservation planning, biological surveys should include extensive collection of taxonomic groups and organisms at all trophic levels.

Estimation of the biomass of arbuscular mycorrhizal fungi in a linseed field

Linseed was grown in field plots included in a long-term P fertilisation experiment (0, 15 or 30 kg P ha −1 yr −1 for 20 yr). Two months before sowing, half of each plot was applied with dazomet to prevent the formation of arbuscular mycorrhiza (AM). The biomass of different groups of micro-organisms was estimated 28, 51 and 72 d after sowing based on amounts of certain fatty acids extracted from the soil. Dazomet application strongly suppressed colonisation of the linseed roots by AM fungi throughout the experiment. In plots with no dazomet application, root colonisation by the AM fungi increased from harvests 1 to 3 as judged both from microscopical estimates and from quantitative analysis of the AM fungal indicative fatty acid 16:1ω5. These methods also revealed that AM formation was reduced in P-fertilised plots. The phospholipid fatty acid (PLFA) 16:1ω5 decreased in dazomet-treated soil, and it was assumed that the PLFA 16:1ω5 remaining in treated soil originated from bacteria. The biomass of the extraradical AM mycelium could then be estimated by multiplying the difference in PLFA 16:1ω5 between dazomet treated and nontreated soils by a conversion factor. This calculation indicated that the biomass of the extraradical mycelium of AM fungi was about 10 times as high as the biomass of intraradical mycelium and that the extraradical mycelium constituted the largest fraction of the soil microbial biomass. Dazomet application also decreased the biomass of saprophytic fungi in the soil as indicated by the amount of PLFA 18:2ω6,9, while analyses of bacteria-specific fatty acids indicated that the bacterial biomass in the soil was not affected by either dazomet or P application.