Drying and rewetting of forest floors: dynamics of soluble phosphorus, microbial biomass-phosphorus, and the composition of microbial communities

The stoichiometric ratios of elements in microorganisms play an important role in biogeochemical cycling and evaluating the nutritional limits of microbial growth, but the effects of thinning treatment on the stoichiometric ratio of carbon, nitrogen, and phosphorus in microorganisms remain unclear. We conducted research in a Larix principis-rupprechtti Mayr. plantation to determine the main factors driving microbial carbon (C): nitrogen (N): phosphorus (P) stoichiometry following thinning and the underlying mechanisms of these effects. The plantation study varied in thinning intensity from 0% tree removal (control), 15% tree reduction (high density plantation, HDP), 35% tree reduction (medium density plantation, MDP), and 50% tree reduction (low density plantation, LDP). Our results indicated that medium density plantation significantly increased litter layer biomass, soil temperature, and other soil properties (e.g., soil moisture and nutrient contents). Understory vegetation diversity (i.e., shrub layer and herb layer) was highest in the medium density plantation. Meanwhile, thinning had a great influence on the biomass of microbial communities. For example, the concentration of phospholipid fatty acids (PLFA) for bacteria and fungi in the medium density plantation (MDP) was significantly higher than in other thinning treatments. Combining Pearson correlation analysis, regression modeling, and stepwise regression demonstrated that the alteration of the microbial biomass carbon: nitrogen was primarily related to gram-positive bacteria, gram-negative bacteria, soil temperature, and soil available phosphorus. Variation in bacteria, actinomycetes, gram-positive bacteria, gram–negative bacteria, and soil total phosphorus was primarily associated with shifts in microbial biomass carbon: phosphorus. Moreover, changes in microbial biomass nitrogen: phosphorus were regulated by actinomycetes, gram-negative bacteria, and soil temperature. In conclusion, our research indicates that the stoichiometric ratios of elements in microorganisms could be influenced by thinning management, and emphasizes the importance of soil factors and microbial communities in driving soil microbial stoichiometry.

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Microbial Substrate Utilization and Vegetation Shifts in Boreal Forest Floors of Western Canada

Frontiers in Forests and Global Change ◽

10.3389/ffgc.2021.700751 ◽

2021 ◽

Vol 4 ◽

Author(s):

Emily Lloret ◽

Sylvie Quideau

Keyword(s):

Boreal Forest ◽

Microbial Communities ◽

Forest Floor ◽

Microbial Respiration ◽

Substrate Utilization ◽

Utilization Efficiency ◽

Western Canada ◽

Spruce Forest ◽

Vegetation Shifts ◽

Forest Floors

Boreal forest soils are highly susceptible to global warming, and in the next few decades, are expected to face large increases in temperature and transformative vegetation shifts. The entire boreal biome will migrate northward, and within the main boreal forest of Western Canada, deciduous trees will replace conifers. The main objective of our research was to assess how these vegetation shifts will affect functioning of soil microbial communities and ultimately the overall persistence of boreal soil carbon. In this study, aspen and spruce forest floors from the boreal mixedwood forest of Alberta were incubated in the laboratory for 67 days without (control) and with the addition of three distinct 13C labeled substrates (glucose, aspen leaves, and aspen roots). Our first objective was to compare aspen and spruce substrate utilization efficiency (SUE) in the case of a labile C source (13C-glucose). For our second objective, addition of aspen litter to spruce forest floor mimicked future vegetation shifts, and we tested how this would alter substrate use efficiency in the spruce forest floor compared to the aspen. Tracking of carbon utilization by microbial communities was accomplished using 13C-PLFA analysis, and 13C-CO2 measurements allowed quantification of the relative contribution of each added substrate to microbial respiration. Following glucose addition, the aspen community showed a greater 13C-PLFA enrichment than the spruce throughout the 67-day incubation. The spruce community respired a greater amount of 13C glucose, and it also had a much lower glucose utilization efficiency compared to the aspen. Following addition of aspen litter, in particular aspen leaves, the aspen community originally showed greater total 13C-PLFA enrichment, although gram positive phospholipid fatty acids (PLFAs) were significantly more enriched in the spruce community. While the spruce community respired a greater amount of the added 13C-leaves, both forest floor types showed comparable substrate utilization efficiencies by Day 67. These results indicate that a shift from spruce to aspen may lead to a greater loss of the aspen litter through microbial respiration, but that incorporation into microbial biomass and eventually into the more persistent soil carbon pool may not be affected.

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Soil microbial communities in the face of changing farming practices: A case study in an agricultural landscape in France

PLoS ONE ◽

10.1371/journal.pone.0252216 ◽

2021 ◽

Vol 16 (6) ◽

pp. e0252216

Author(s):

Laurie Dunn ◽

Christophe Lang ◽

Nicolas Marilleau ◽

Sébastien Terrat ◽

Luc Biju-Duval ◽

...

Keyword(s):

Microbial Biomass ◽

Soil Properties ◽

Microbial Communities ◽

Soil Microorganisms ◽

Soil Microbial Communities ◽

Partial Least Square ◽

Farming Practices ◽

Soil Microbial ◽

Bacterial Richness ◽

Over Time

According to biogeography studies, the abundance and richness of soil microorganisms vary across multiple spatial scales according to soil properties and farming practices. However, soil microorganisms also exhibit poorly understood temporal variations. This study aimed at better understanding how soil microbial communities respond to changes in farming practices at a landscape scale over time. A regular grid of 269 sites was set up across a 1,200 ha farming landscape, and soil samples were characterized for their molecular microbial biomass and bacterial richness at two dates (2011 and 2016). A mapping approach highlighted that spatial microbial patterns were stable over time, while abundance and richness levels were modified. The drivers of these changes were investigated though a PLS-PM (partial least square path-modeling) approach. Soil properties were stable over time, but farming practices changed. Molecular microbial biomass was mainly driven by soil resources, whereas bacterial richness depended on both farming practices and ecological parameters. Previous-crop and management effects and a temporal dependence of the microbial community on the historical farming management were also highlighted.

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Soil Microbial Biomass and Community Composition Relates to Poplar Genotypes and Environmental Conditions

Forests ◽

10.3390/f11030262 ◽

2020 ◽

Vol 11 (3) ◽

pp. 262 ◽

Cited By ~ 3

Author(s):

Leszek Karliński ◽

Sabine Ravnskov ◽

Maria Rudawska

Keyword(s):

Microbial Biomass ◽

Microbial Communities ◽

Community Composition ◽

Soil Depth ◽

Abiotic Factors ◽

Soil Conditions ◽

Main Role ◽

Site Factors ◽

Host Genotype ◽

The Impact

Poplars, known for their diversity, are trees that can develop symbiotic relationships with several groups of microorganisms. The genetic diversity of poplars and different abiotic factors influence the properties of the soil and may shape microbial communities. Our study aimed to analyse the impact of poplar genotype on the biomass and community composition of the microbiome of four poplar genotypes grown under different soil conditions and soil depths. Of the three study sites, established in the mid-1990s, one was near a copper smelter, whereas the two others were situated in unpolluted regions, but were differentiated according to the physicochemical traits of the soil. The whole-cell fatty acid analysis was used to determine the biomass and proportions of gram-positive, gram-negative and actinobacteria, arbuscular fungi (AMF), other soil fungi, and protozoa in the whole microbial community in the soil. The results showed that the biomass of microorganisms and their contributions to the community of organisms in the soil close to poplar roots were determined by both factors: the tree-host genotype and the soil environment. However, each group of microorganisms was influenced by these factors to a different degree. In general, the site effect played the main role in shaping the microbial biomass (excluding actinobacteria), whereas tree genotype determined the proportions of the fungal and bacterial groups in the microbial communities and the proportion of AMF in the fungal community. Bacterial biomass was influenced more by site factors, whereas fungal biomass more by tree genotype. With increasing soil depth, a decrease in the biomass of all microorganisms was observed; however, the proportions of the different microorganisms within the soil profile were the result of interactions between the host genotype and soil conditions. Despite the predominant impact of soil conditions, our results showed the important role of poplar genotype in shaping microorganism communities in the soil.

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Response of microbial biomass to air-drying and rewetting in soils and compost

Geoderma ◽

10.1016/s0016-7061(01)00095-7 ◽

2002 ◽

Vol 105 (1-2) ◽

pp. 111-124 ◽

Cited By ~ 33

Author(s):

C Mondini ◽

M Contin ◽

L Leita ◽

M De Nobili

Keyword(s):

Microbial Biomass ◽

Air Drying ◽

Drying And Rewetting

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Microbial biomass and C and N transformations in forest floors under European beech, sessile oak, Norway spruce and Douglas-fir at four temperate forest sites

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2009.02.004 ◽

2009 ◽

Vol 41 (4) ◽

pp. 831-839 ◽

Cited By ~ 34

Author(s):

S. Malchair ◽

M. Carnol

Keyword(s):

Microbial Biomass ◽

Norway Spruce ◽

Temperate Forest ◽

European Beech ◽

Douglas Fir ◽

N Transformations ◽

Sessile Oak ◽

Forest Sites ◽

C And N ◽

Forest Floors

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What controls microbial growth in tropical soils? The role of carbon and phosphorus.

10.5194/egusphere-egu2020-20992 ◽

2020 ◽

Author(s):

Christian Ranits ◽

Lucia Fuchslueger ◽

Leandro Van Langenhove ◽

Ivan Janssens ◽

Josep Peñuelas ◽

...

Keyword(s):

Microbial Biomass ◽

Microbial Communities ◽

Microbial Growth ◽

Microbial Respiration ◽

Tropical Soils ◽

Microbial Biomass C ◽

P Availability ◽

Respiration Activity ◽

Respiration Rates ◽

C And N

Tropical forest ecosystems are important components of global biogeochemical cycling. Many tropical rainforests grow in old and highly weathered soils, depleted in phosphorus (P) and net primary productivity in tropical forests is often limited by P availability. It is unclear, however, if heterotrophic microbial communities in tropical soils are also limited by P or rather by carbon (C). Elemental limitations of microorganisms in soil have often been approached by measurements of respiration rates in response to additions of nutrients or carbon. However, it has been argued lately, that microbial growth rather than respiration should be used to assess limitations.In this study we therefore ask the question whether the growth of heterotrophic microbial communities in tropical soil is limited by available phosphorus or by carbon. We collected soils from three sites along a topographic gradient (plateau, slope, bottom) differing in soil texture, total and available P concentrations from a well-studied, P-poor region in Nouragues, French Guiana. We incubated these soils in the laboratory with C in the form of cellulose, inorganic phosphorus and with a combination of both, and studied microbial growth by measuring the 18O incorporation from labelled water into microbial DNA. Moreover, we measured microbial respiration and determined microbial biomass C, N (nitrogen) and P.Our results demonstrate that, although microbial biomass C and N was similar in soil collected from all three topographic sites, soil respiration rates were significantly higher in soils from the plateau indicating a more active microbial community. Microbial C and N did not respond to cellulose and inorganic P additions, only microbial P increased significantly when P was added in all soils. Although microbial biomass C was not increased, C and P additions stimulated microbial respiration in clay rich plateau soils. In slope soils microbial communities initially only increased respiration activity in response to P additions, however at the end of the incubation also C showed significant differences in respiration activity, with strongest increases when C and P were added in combination. In sandier bottom soils microorganisms responded with increased activity to C addition, but also here respiration showed strongest increases in response to combined carbon and phosphorus additions. We will discuss these findings in relation to the pattern of gross growth rates in these soils and evaluate the stoichiometric limitations of microbial activity and turnover.

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